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1
2018, 26(6): 1534-1551.
Abstract
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A large-scale landslide occurred in Baige village, at the border between Tibet Autonomous Region and Sichuan Province, on October 11, 2018. The sliding mass detached from a high-elevation mountain ridge, then dammed the Jinsha River impounding a barrier lake. This initial lake drained naturally. Afterwards, on November 3, a second landslide involved with a large mass of loose material from the first event blocked the river again, inducing a 50 m high dam and a barrier lake with a capacity of 500 million cubic meters. In order to alleviate the dangers of potential dam-breach flood, the artificial spillway was constructed allowing controlled breaching until November 13. However, downstream flooding still cause a major loss of property and damage, covering a large area of Sichuan Province and Yunnan Province. Extensive on-site investigation, combined with historical satellite images interpretation, InSAR monitoring, UAV aerial photography and ground deformation monitoring techniques, was conducted in this paper, to analyze the historical deformation of the study area and the evolutional characteristics of these two events. Based on that, the emergency measurements after each event have been developed, and the implementation of spillway was secured by monitoring and early-warning work at site. The successive landslides damming the Jinsha River presents a good example to study the emergency response and mitigation plan for similar cases in the future.
A large-scale landslide occurred in Baige village, at the border between Tibet Autonomous Region and Sichuan Province, on October 11, 2018. The sliding mass detached from a high-elevation mountain ridge, then dammed the Jinsha River impounding a barrier lake. This initial lake drained naturally. Afterwards, on November 3, a second landslide involved with a large mass of loose material from the first event blocked the river again, inducing a 50 m high dam and a barrier lake with a capacity of 500 million cubic meters. In order to alleviate the dangers of potential dam-breach flood, the artificial spillway was constructed allowing controlled breaching until November 13. However, downstream flooding still cause a major loss of property and damage, covering a large area of Sichuan Province and Yunnan Province. Extensive on-site investigation, combined with historical satellite images interpretation, InSAR monitoring, UAV aerial photography and ground deformation monitoring techniques, was conducted in this paper, to analyze the historical deformation of the study area and the evolutional characteristics of these two events. Based on that, the emergency measurements after each event have been developed, and the implementation of spillway was secured by monitoring and early-warning work at site. The successive landslides damming the Jinsha River presents a good example to study the emergency response and mitigation plan for similar cases in the future.
2
2018, 26(2): 340-347.
Wenchuan earthquake induced a large amount of geological disasters such as landslides and collapses. Besides, the earthquake also caused a lot of the loose and broken rock mass. Those loose rock mass can produce large amounts of secondary geological disasters under the rainfall and other factors, which has great danger. Therefore, it has very important practical significance for geological disaster susceptibility evaluation of Wenchuan country. Based on GIS raster data model, this paper selects nine factors including elevation, gradient, slope direction, relief amplitude, gully density, the engineering rock group, fault, drainage and roads. It adopts the information, logistic and information-logistic coupling models for assessment of geological hazards. The results show that the coupling model is more reasonable and has higher precision. High and very high susceptibility of geological hazard areas are concentrated in the water extension area and fault concentration area. Susceptibility partition map of the calculation results is consistent with the actual situation of the study area and can play an important reference role in the geological hazard risk assessment.
Wenchuan earthquake induced a large amount of geological disasters such as landslides and collapses. Besides, the earthquake also caused a lot of the loose and broken rock mass. Those loose rock mass can produce large amounts of secondary geological disasters under the rainfall and other factors, which has great danger. Therefore, it has very important practical significance for geological disaster susceptibility evaluation of Wenchuan country. Based on GIS raster data model, this paper selects nine factors including elevation, gradient, slope direction, relief amplitude, gully density, the engineering rock group, fault, drainage and roads. It adopts the information, logistic and information-logistic coupling models for assessment of geological hazards. The results show that the coupling model is more reasonable and has higher precision. High and very high susceptibility of geological hazard areas are concentrated in the water extension area and fault concentration area. Susceptibility partition map of the calculation results is consistent with the actual situation of the study area and can play an important reference role in the geological hazard risk assessment.
3
2018, 26(1): 223-240.
A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×104 m3 moved down and scraped the original loose deposits and finally formed deposits of 82.3×104 m3, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.
A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×104 m3 moved down and scraped the original loose deposits and finally formed deposits of 82.3×104 m3, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.
4
2018, 26(1): 112-128.
Expansive soil is considered as a problematic soil in engineering, because it usually results in various engineering geological problems and disasters. According to the published results on the engineering geological characteristics of expansive soil in recent years, the advances on swelling-shrinkage behavior, desiccation cracking, overconsolidation, strength, permeability and microstructure of expansive soil were summarized, and the following main knowledge was obtained. (1)The swelling-shrinking characteristics are mainly related to the fraction of expansive clay minerals, hydro-mechanical boundary conditions and initial state. Irreversible volumetric deformation would occur when the expansive soil is subjected to wetting-drying cycles. Until now, there is still not a uniform viewpoint on the intrinsic mechanism on swelling-shrinking behavior. (2)Desiccation cracking is one of the salient features to distinguish expansive soil from other soils. The presence of cracks in soil can significantly undermine the overall structure of the soil, greatly weaken the mechanical properties and lead to many engineering geological problems directly or indirectly. The formation of desiccation cracks is related to expansive soil mineral composition, microstructure and the development of internal stress during drying. (3)Overconsolidation makes expansive soil has a greater structural strength and horizontal stress. Stress-release cracks are easy to occur when the expansive soil slope is excavated, which can damage the overall structure of the soil and promote landslide.(4)In terms of strength, most of studies focused on the effect of wetting-drying cycles. Generally, the strength decreases gradually with increasing wetting-drying cycles and eventually reaches stabilization. The wetting-drying cycle induced presence of cracks and microstructure arrangement are the two factors responsible for the corresponding strength changes. (5)The hydraulic conductivity is largely controlled by cracks. It is therefore important to consider the crack effect when performing permeability test in laboratory.(6)Microstructure of the expansive soil reflects the formation conditions and stress history. It is a fundamental factor controlling the macro-physical and mechanical behavior. Microstructure analysis is also the important way and theoretical basis to explore the intrinsic mechanisms of the observed macroscopic properties. Furthermore, as for as expansive soil engineering treatment technology, this article focused on the physical treatment technology for embankment filled with expansive soil and flexible supporting technology for expansive soil cut slope. Based on the above understanding and current research shortages in this field, some important research topics that should be well investigated in future were proposed, including anisotropic behavior of swelling-shrinking, mechanism of the desiccation cracking, quantitative relationship between geometrical parameters of cracks and the indicators of macro engineering properties, the coupling of macro-micro mechanical model and the hydro-mechanical response characteristics of expansive soil under multi-field coupling condition, et al.
Expansive soil is considered as a problematic soil in engineering, because it usually results in various engineering geological problems and disasters. According to the published results on the engineering geological characteristics of expansive soil in recent years, the advances on swelling-shrinkage behavior, desiccation cracking, overconsolidation, strength, permeability and microstructure of expansive soil were summarized, and the following main knowledge was obtained. (1)The swelling-shrinking characteristics are mainly related to the fraction of expansive clay minerals, hydro-mechanical boundary conditions and initial state. Irreversible volumetric deformation would occur when the expansive soil is subjected to wetting-drying cycles. Until now, there is still not a uniform viewpoint on the intrinsic mechanism on swelling-shrinking behavior. (2)Desiccation cracking is one of the salient features to distinguish expansive soil from other soils. The presence of cracks in soil can significantly undermine the overall structure of the soil, greatly weaken the mechanical properties and lead to many engineering geological problems directly or indirectly. The formation of desiccation cracks is related to expansive soil mineral composition, microstructure and the development of internal stress during drying. (3)Overconsolidation makes expansive soil has a greater structural strength and horizontal stress. Stress-release cracks are easy to occur when the expansive soil slope is excavated, which can damage the overall structure of the soil and promote landslide.(4)In terms of strength, most of studies focused on the effect of wetting-drying cycles. Generally, the strength decreases gradually with increasing wetting-drying cycles and eventually reaches stabilization. The wetting-drying cycle induced presence of cracks and microstructure arrangement are the two factors responsible for the corresponding strength changes. (5)The hydraulic conductivity is largely controlled by cracks. It is therefore important to consider the crack effect when performing permeability test in laboratory.(6)Microstructure of the expansive soil reflects the formation conditions and stress history. It is a fundamental factor controlling the macro-physical and mechanical behavior. Microstructure analysis is also the important way and theoretical basis to explore the intrinsic mechanisms of the observed macroscopic properties. Furthermore, as for as expansive soil engineering treatment technology, this article focused on the physical treatment technology for embankment filled with expansive soil and flexible supporting technology for expansive soil cut slope. Based on the above understanding and current research shortages in this field, some important research topics that should be well investigated in future were proposed, including anisotropic behavior of swelling-shrinking, mechanism of the desiccation cracking, quantitative relationship between geometrical parameters of cracks and the indicators of macro engineering properties, the coupling of macro-micro mechanical model and the hydro-mechanical response characteristics of expansive soil under multi-field coupling condition, et al.
5
2018, 26(6): 1648-1656.
In the northwest, a lot of multi-stage high slopes with loess have been encountered in the construction of basic engineering. Slope engineering belongs to permanent project. So it is unavoidable to meet the conditions of rainfall. Under rainfall infiltration, the degree of saturation and mass of soil slope increase, which can further cause the change of slope matric suction and effective stress. As a result, the stability of the slope can be greatly influenced. In this paper, the coupling calculation model of seepage field and stress field is established. It considers the changes of the matrix suction as the rain water infiltration at the different depths of the slope body. Then, the stability of the multi-stage high slope with loess under the condition of rainfall infiltration can be analyzed. Then, according to an actual engineering and using the PLAXIS 3D geotechnical finite element software, the calculation model of slope stability is established. By setting the variation function of rainfall with the time and boundary condition, the stability calculation of multi-stage high slope with loess is carried out under the condition of rainfall infiltration. And then, The numerical calculation results are compared with the theoretical calculation results. According to the numerical calculation results, the changes of the deformation, matrix suction, effective stress, potential slip surface and safety factor of the multi-stage high slope with loess under the condition of rainfall infiltration are obtained. And the stability of the multi-stage high slope with loess under the condition of rainfall infiltration are analyzed. The study results can provide some guidance for the design of the multi-stage high slope with loess under the rainfall infiltration.
In the northwest, a lot of multi-stage high slopes with loess have been encountered in the construction of basic engineering. Slope engineering belongs to permanent project. So it is unavoidable to meet the conditions of rainfall. Under rainfall infiltration, the degree of saturation and mass of soil slope increase, which can further cause the change of slope matric suction and effective stress. As a result, the stability of the slope can be greatly influenced. In this paper, the coupling calculation model of seepage field and stress field is established. It considers the changes of the matrix suction as the rain water infiltration at the different depths of the slope body. Then, the stability of the multi-stage high slope with loess under the condition of rainfall infiltration can be analyzed. Then, according to an actual engineering and using the PLAXIS 3D geotechnical finite element software, the calculation model of slope stability is established. By setting the variation function of rainfall with the time and boundary condition, the stability calculation of multi-stage high slope with loess is carried out under the condition of rainfall infiltration. And then, The numerical calculation results are compared with the theoretical calculation results. According to the numerical calculation results, the changes of the deformation, matrix suction, effective stress, potential slip surface and safety factor of the multi-stage high slope with loess under the condition of rainfall infiltration are obtained. And the stability of the multi-stage high slope with loess under the condition of rainfall infiltration are analyzed. The study results can provide some guidance for the design of the multi-stage high slope with loess under the rainfall infiltration.
6
2018, 26(2): 528-539.
Two dimensional numerical particle flow code(PFC2D) is an important method to study the crack propagation characteristics of cracked rock. In review of related literatures, it is analyzed and summarized as follows:the current PFC2D simulation methods are summarized in three aspects of particle contact constitutive model, microparameters calibration and simulation method of crack. According to the current research, the PFC2D simulation of crack propagation characteristics is summarized focusing on the single cracked, intermittent double cracked rock under different loading methods. On this basis, the shortcomings of the current research are pointed out as follows. The fracture toughness of PFC2D model is not in line with the actual value of rock. Simulation results of parallel-bond model and test results of rock are different. There are differences between real crack and simulation crack. Combined with the existing shortcomings in the study, the corresponding solutions are put forward and are expected to contribute to the development of PFC2D simulation methods for cracked rocks.
Two dimensional numerical particle flow code(PFC2D) is an important method to study the crack propagation characteristics of cracked rock. In review of related literatures, it is analyzed and summarized as follows:the current PFC2D simulation methods are summarized in three aspects of particle contact constitutive model, microparameters calibration and simulation method of crack. According to the current research, the PFC2D simulation of crack propagation characteristics is summarized focusing on the single cracked, intermittent double cracked rock under different loading methods. On this basis, the shortcomings of the current research are pointed out as follows. The fracture toughness of PFC2D model is not in line with the actual value of rock. Simulation results of parallel-bond model and test results of rock are different. There are differences between real crack and simulation crack. Combined with the existing shortcomings in the study, the corresponding solutions are put forward and are expected to contribute to the development of PFC2D simulation methods for cracked rocks.
7
2018, 26(5): 1203-1210.
This paper takes the Kunming road underground utility tunnel crossing through f3 ground fissure in Xi'an city, China as research object. The deformation and force characteristics of underground segmented utility tunnel is analysed with finite element numerical simulationmethod. The results show that the vertical settlement deformation at the roof of underground utility tunnel exhibits reverse-S shape as a whole, and increases with the settlement of the hanging wall of ground fissure increasing. The longitudinal deformation of underground utility tunnel can be divided into three deformation sections:warping deformation section at the hanging wall of ground fissure, differential settlement section, and integral deformation section at the footwall of ground fissure. Under the action of ground fissure with a vertical dislocation 50 cm in the design life of 100 years, the horizontal displacement peak value of utility tunnel roof appears in the position of ground fissure zone. The maximum values are 4.1 cm on roof and 3.2 cm on the floor of utility tunnel. The joints between utility segmented tunnels is easy to pull apart and be damaged and should be reinforced. Nearby the ground fissure zone, the contact pressure between the utility tunnel floor and soil stratum decreases to 0 at the hanging wall with the increase of vertical dislocation of ground fissure and underground utility tunnel floor appears disengaging phenomenon. Grouting holes should be reserved convenient to grouting treatment, But the contact pressure between underground utility tunnel roof and soil stratum has an increase trend. The strain of the underground utility tunnel roof and floor exceeds the limit of the concrete strain when settlement of the hanging wall of ground fissure reaches 20 cm. Therefore, the deformation and failure mode of the underground utility tunnel is mainly tensile failure under the action of ground fissure. The research can provide a scientific basis for engineering design of underground utility tunnel crossing ground fissure zone in Xi'an city and other developed areas of ground fissure.
This paper takes the Kunming road underground utility tunnel crossing through f3 ground fissure in Xi'an city, China as research object. The deformation and force characteristics of underground segmented utility tunnel is analysed with finite element numerical simulationmethod. The results show that the vertical settlement deformation at the roof of underground utility tunnel exhibits reverse-S shape as a whole, and increases with the settlement of the hanging wall of ground fissure increasing. The longitudinal deformation of underground utility tunnel can be divided into three deformation sections:warping deformation section at the hanging wall of ground fissure, differential settlement section, and integral deformation section at the footwall of ground fissure. Under the action of ground fissure with a vertical dislocation 50 cm in the design life of 100 years, the horizontal displacement peak value of utility tunnel roof appears in the position of ground fissure zone. The maximum values are 4.1 cm on roof and 3.2 cm on the floor of utility tunnel. The joints between utility segmented tunnels is easy to pull apart and be damaged and should be reinforced. Nearby the ground fissure zone, the contact pressure between the utility tunnel floor and soil stratum decreases to 0 at the hanging wall with the increase of vertical dislocation of ground fissure and underground utility tunnel floor appears disengaging phenomenon. Grouting holes should be reserved convenient to grouting treatment, But the contact pressure between underground utility tunnel roof and soil stratum has an increase trend. The strain of the underground utility tunnel roof and floor exceeds the limit of the concrete strain when settlement of the hanging wall of ground fissure reaches 20 cm. Therefore, the deformation and failure mode of the underground utility tunnel is mainly tensile failure under the action of ground fissure. The research can provide a scientific basis for engineering design of underground utility tunnel crossing ground fissure zone in Xi'an city and other developed areas of ground fissure.
8
2018, 26(4): 1064-1077.
With the acceleration of the urbanization process and the rapid development of industrial production, soil heavy metal pollution is increasing seriously, which is causing serious harm to the ecological environment. Biochar is a solid material containing high fractions of aromatic functional groups and carbon. It is produced through thermal degradation under anoxic or oxygen-limited conditions. It attracts extensive attention because of significant effect in the remediation of soil contaminated with heavy metals. Based on the recent research achievements on biochar remediate heavy metals contaminated soil at home and abroad, the advances of some important aspects on, the research current situation and progress are summarized from several important aspects. They include production and properties of biochar, remediation effect and influencing factors and adsorption mechanism. The follows are shown. (1)Biochar has the advantages of low prices, high efficiency, soil improvement and friendly environment. (2)The physicochemical properties of biochar are affected by biomass materials and pyrolysis temperatures. Activation, magnetization, oxidation and digestion can improve the properties of biochar and efficiency of remediation. (3)The effect of biochar on heavy metal mobility and bioavailability includes two aspects:immobilizing heavy metals to reduce bioavailability or mobilizing heavy metals to increase bioavailability. The latter can be modified to reduce the mobility and bioavailability of heavy metals. (4)The effect of biochar on soil solidification is general, combining with other solidifying materials to improve the mechanical properties of solidified soil. (5)The effect remediation mechanism of biochar immobilized heavy metals is ranked as follows:precipitation > complexation > electrostatic interaction and ion exchange > physical adsorption. Finally, on account of research status in this field, some important research emphases and directions in the future are proposed. They mainly include establishing a uniform classification criterion of biochar, exploring the efficiency of biochar on multi-heavy metals pollution, illustrating the mechanism and contribution rate of adsorbing heavy metals by biochar, expanding the research scale, and carrying out solidification experiment and mechanical property research based on biochar.
With the acceleration of the urbanization process and the rapid development of industrial production, soil heavy metal pollution is increasing seriously, which is causing serious harm to the ecological environment. Biochar is a solid material containing high fractions of aromatic functional groups and carbon. It is produced through thermal degradation under anoxic or oxygen-limited conditions. It attracts extensive attention because of significant effect in the remediation of soil contaminated with heavy metals. Based on the recent research achievements on biochar remediate heavy metals contaminated soil at home and abroad, the advances of some important aspects on, the research current situation and progress are summarized from several important aspects. They include production and properties of biochar, remediation effect and influencing factors and adsorption mechanism. The follows are shown. (1)Biochar has the advantages of low prices, high efficiency, soil improvement and friendly environment. (2)The physicochemical properties of biochar are affected by biomass materials and pyrolysis temperatures. Activation, magnetization, oxidation and digestion can improve the properties of biochar and efficiency of remediation. (3)The effect of biochar on heavy metal mobility and bioavailability includes two aspects:immobilizing heavy metals to reduce bioavailability or mobilizing heavy metals to increase bioavailability. The latter can be modified to reduce the mobility and bioavailability of heavy metals. (4)The effect of biochar on soil solidification is general, combining with other solidifying materials to improve the mechanical properties of solidified soil. (5)The effect remediation mechanism of biochar immobilized heavy metals is ranked as follows:precipitation > complexation > electrostatic interaction and ion exchange > physical adsorption. Finally, on account of research status in this field, some important research emphases and directions in the future are proposed. They mainly include establishing a uniform classification criterion of biochar, exploring the efficiency of biochar on multi-heavy metals pollution, illustrating the mechanism and contribution rate of adsorbing heavy metals by biochar, expanding the research scale, and carrying out solidification experiment and mechanical property research based on biochar.
9
2018, 26(5): 1170-1177.
The instability of loess slope is one of the engineering problems that urgently need to be solved in geotechnical engineering. Firstly, the loess slope in Northern Shaanxi is selected as the research object. Four field simulated rainfall experiments under the condition of rain intensity are carried out. The boundary conditions of the slope are improved by digging the isolation groove on both sides of the slope. The changes of the depth of the water immersion and the soil moisture content of the soil under different rainfall intensity conditions are measured. Then, we analyze the rainfall infiltration process and slope stress variation characteristics under different rain intensity conditions, and compare the differences between different infiltration laws under different rain intensity conditions. The test results show that the rule is as follows. The deepest infiltration is at slope toe. The second is at slope crest. The last is at slope middle surface. The infiltration rate is the fastest at slope crest, followed by the slope toe, and the last at the middle slope. The rainfall infiltration capacity gradually weakens as the depth increases. The volumetric water content and earth pressure change amplitude of the measuring point at the same buried depth become larger with the increase of rain intensity. The time is shortened for the abrupt change of water content and soil pressure. The effect of the scour is more obvious. Finally, the seepage analysis based on Geo-studio software verifies the correctness of the field test results and clarifies the influence of rain intensity on rainfall infiltration of loess slope.
The instability of loess slope is one of the engineering problems that urgently need to be solved in geotechnical engineering. Firstly, the loess slope in Northern Shaanxi is selected as the research object. Four field simulated rainfall experiments under the condition of rain intensity are carried out. The boundary conditions of the slope are improved by digging the isolation groove on both sides of the slope. The changes of the depth of the water immersion and the soil moisture content of the soil under different rainfall intensity conditions are measured. Then, we analyze the rainfall infiltration process and slope stress variation characteristics under different rain intensity conditions, and compare the differences between different infiltration laws under different rain intensity conditions. The test results show that the rule is as follows. The deepest infiltration is at slope toe. The second is at slope crest. The last is at slope middle surface. The infiltration rate is the fastest at slope crest, followed by the slope toe, and the last at the middle slope. The rainfall infiltration capacity gradually weakens as the depth increases. The volumetric water content and earth pressure change amplitude of the measuring point at the same buried depth become larger with the increase of rain intensity. The time is shortened for the abrupt change of water content and soil pressure. The effect of the scour is more obvious. Finally, the seepage analysis based on Geo-studio software verifies the correctness of the field test results and clarifies the influence of rain intensity on rainfall infiltration of loess slope.
10
2018, 26(6): 1638-1647.
The weak intercalation forms a sliding zone after long-term geological evolution and plays an important role in controlling the stability of massive layered rockslides. In order to determine the formation process of the sliding zone, we take the Jiweishan Landslide as an example and analyze the developmental regularities of the weak intercalation. The weak intercalation can be divided into three stages including the original soft rock, the interlayer shear zone and the sliding zone. In addition, we have comparatively studied the evolutionary characteristics of weak intercalation through the laboratory test of the physical properties, physicochemical properties, and physical mechanics properties. As a result, from the view of the mineral composition, the mean value of the clay mineral content is increased from 4.4% to 16.9%. From the view of the physical properties and the microstructure, the density is decreased from 5% to 6%, and the porosity is increased by 108%. It reflects the decreased density and loose structure due to long-term evolution. From the view of the physicochemical properties, the total content of exchangeable salt is the highest in the original soft rock, followed by the sliding zone, whereas the interlayer shear zone exhibited the lowest value. The organic matter content is gradually increased in the alkalescence evolutionary environment. From the view of the shear creep strength, the internal friction angle is decreased from 57.58°to 29.63°, and the cohesion decreased from 585 kPa to 96 kPa. Based on these data, we analyze the change of the residual sliding thrust of the main section of the Jiweishan Landslide driving block. The residual sliding thrust increases with a decrease in the long-term strength parameter. When the internal friction angle φ < 25° and cohesion c < 129 kPa, the residual sliding thrust of the driving block is greater than zero, and then the driving block is sliding. The conclusions provide an important reference for the study of the development and mechanism of layered rockslides controlled by weak intercalations.
The weak intercalation forms a sliding zone after long-term geological evolution and plays an important role in controlling the stability of massive layered rockslides. In order to determine the formation process of the sliding zone, we take the Jiweishan Landslide as an example and analyze the developmental regularities of the weak intercalation. The weak intercalation can be divided into three stages including the original soft rock, the interlayer shear zone and the sliding zone. In addition, we have comparatively studied the evolutionary characteristics of weak intercalation through the laboratory test of the physical properties, physicochemical properties, and physical mechanics properties. As a result, from the view of the mineral composition, the mean value of the clay mineral content is increased from 4.4% to 16.9%. From the view of the physical properties and the microstructure, the density is decreased from 5% to 6%, and the porosity is increased by 108%. It reflects the decreased density and loose structure due to long-term evolution. From the view of the physicochemical properties, the total content of exchangeable salt is the highest in the original soft rock, followed by the sliding zone, whereas the interlayer shear zone exhibited the lowest value. The organic matter content is gradually increased in the alkalescence evolutionary environment. From the view of the shear creep strength, the internal friction angle is decreased from 57.58°to 29.63°, and the cohesion decreased from 585 kPa to 96 kPa. Based on these data, we analyze the change of the residual sliding thrust of the main section of the Jiweishan Landslide driving block. The residual sliding thrust increases with a decrease in the long-term strength parameter. When the internal friction angle φ < 25° and cohesion c < 129 kPa, the residual sliding thrust of the driving block is greater than zero, and then the driving block is sliding. The conclusions provide an important reference for the study of the development and mechanism of layered rockslides controlled by weak intercalations.
11
2018, 26(6): 1552-1561.
We used Landsat and other high-moderate space resolution images to analysis the glacial retreat in the recent 40 years of Sedongpu Basin, and combed the eight times debris flow blocking Yarlung Zangbo river incidents of Sedongpu Basin after 2014. Combined with the radar and meteorological data, we analyzed the reasons of frequent collapse disasters occurred in the basin. Then we found the following factors. First, the "steep-gentle-relative steep" ladder terrain is the foundation of the frequent occurrence of the debris flows in Sedongpu Basin. Second, the debris flow always block the channel at a large extent. Third, there are lots of crevasses in the glacier trailing edge. Fourth, earthquake and abundant rainfalls also lead to the frequent debris flow of Sedongpu Basin. Combined the above factors, we speculate the glacier avalanche induced debris flow(GAIDF) of Sedongpu Basin will happen frequently for a long time with typical periodicity. So, we suggested to establish a long-time monitoring and warning system for the Yarlung Zangbo Grand Canyon in order to provide effective support to the emergency work of Sedongpu Basin glacier debrisflow.
We used Landsat and other high-moderate space resolution images to analysis the glacial retreat in the recent 40 years of Sedongpu Basin, and combed the eight times debris flow blocking Yarlung Zangbo river incidents of Sedongpu Basin after 2014. Combined with the radar and meteorological data, we analyzed the reasons of frequent collapse disasters occurred in the basin. Then we found the following factors. First, the "steep-gentle-relative steep" ladder terrain is the foundation of the frequent occurrence of the debris flows in Sedongpu Basin. Second, the debris flow always block the channel at a large extent. Third, there are lots of crevasses in the glacier trailing edge. Fourth, earthquake and abundant rainfalls also lead to the frequent debris flow of Sedongpu Basin. Combined the above factors, we speculate the glacier avalanche induced debris flow(GAIDF) of Sedongpu Basin will happen frequently for a long time with typical periodicity. So, we suggested to establish a long-time monitoring and warning system for the Yarlung Zangbo Grand Canyon in order to provide effective support to the emergency work of Sedongpu Basin glacier debrisflow.
12
2018, 26(3): 758-766.
Based on the differences in pore structure characteristics between marine and continental shale in China, Weiyuan marine shale(1#), Jiao Shiba marine shale(2#), Yaoqu tuff(4#) and Yaoqu continental shale(5# and 6#)were selected to study the pore structure characteristics using cold field emission scanning microscopy(FE-SEM) and nuclear magnetic resonance(NMR). Nuclear magnetic resonance cryoporometry(NMRC)was employed to represent nano-scale pore structure. This method can be extended to microns measurement combining nuclear magnetic resonance relaxation analysis to detect in detail the pore structure of shales under the different aperture scales. The smaller the test temperature gradient is, the finer the result of pore distribution is. Test results show decreasing porosity from sample 5#, 2#, 6#, and 1# to sample 4#. NMRC, low field nuclear magnetic resonance(LFNMR), mercury intrusion porosimetry(MIP) and gas adsorption(GA)methods show good agreement of pore size distribution in their respective scope of application. Hence, the pore structure of the reservoir shale can be evaluated more accurately by combining NMRC, LFNMR with GA and MIP. Thus the nano-pores of continental shale(5# Yaoqu shale) are clearly better developed and will more likely have a higher commercial exploitation value than those of marine shale.
Based on the differences in pore structure characteristics between marine and continental shale in China, Weiyuan marine shale(1#), Jiao Shiba marine shale(2#), Yaoqu tuff(4#) and Yaoqu continental shale(5# and 6#)were selected to study the pore structure characteristics using cold field emission scanning microscopy(FE-SEM) and nuclear magnetic resonance(NMR). Nuclear magnetic resonance cryoporometry(NMRC)was employed to represent nano-scale pore structure. This method can be extended to microns measurement combining nuclear magnetic resonance relaxation analysis to detect in detail the pore structure of shales under the different aperture scales. The smaller the test temperature gradient is, the finer the result of pore distribution is. Test results show decreasing porosity from sample 5#, 2#, 6#, and 1# to sample 4#. NMRC, low field nuclear magnetic resonance(LFNMR), mercury intrusion porosimetry(MIP) and gas adsorption(GA)methods show good agreement of pore size distribution in their respective scope of application. Hence, the pore structure of the reservoir shale can be evaluated more accurately by combining NMRC, LFNMR with GA and MIP. Thus the nano-pores of continental shale(5# Yaoqu shale) are clearly better developed and will more likely have a higher commercial exploitation value than those of marine shale.
13
2018, 26(4): 1008-1016.
This paper aims to achieve the automation monitoring of landslide surface deformation with a low-cost system. It proposes and adopts a high accurate real-time landslide monitoring system based on Beidou cloud. This system consists of Beidou monitoring receivers with the functions of wireless transmission, cloud storage and Ntrip protocol, the softwares of the efficient real-time data flow management, high-precision landslide deformation monitoring and positioning, and optimized design of the field operation solution. The results of practical application show that the real-time monitoring accuracy of Beidou short baseline is better than 2 mm, 3 mm and 3 mm for east, north, up compositions, respectively. It can meet the high precision requirements of real-time monitoring of landslide. This paper compares the long-term continuous monitoring results of the test landslide using the method mentioned above with the precision measurement results obtained by the automatic total station. The results show that the two methods are in good agreement with each other in the horizontal and elevation directions with better than 3 mm for difference, respectively.
This paper aims to achieve the automation monitoring of landslide surface deformation with a low-cost system. It proposes and adopts a high accurate real-time landslide monitoring system based on Beidou cloud. This system consists of Beidou monitoring receivers with the functions of wireless transmission, cloud storage and Ntrip protocol, the softwares of the efficient real-time data flow management, high-precision landslide deformation monitoring and positioning, and optimized design of the field operation solution. The results of practical application show that the real-time monitoring accuracy of Beidou short baseline is better than 2 mm, 3 mm and 3 mm for east, north, up compositions, respectively. It can meet the high precision requirements of real-time monitoring of landslide. This paper compares the long-term continuous monitoring results of the test landslide using the method mentioned above with the precision measurement results obtained by the automatic total station. The results show that the two methods are in good agreement with each other in the horizontal and elevation directions with better than 3 mm for difference, respectively.
14
2018, 26(5): 1113-1120.
In loess area, both artificial rainfall field test and in-situ observation under natural rainfall conditions suggest that the influence of surface water is limited to the top several meters, below which the variation of soil water content is little. Therefore, it is a controversy to fact that the surface water infiltration can induce loess landslides with deep seated failure surfaces. In this study, an in-situ observation test is undertaken in a thick loess layer for a period of one year from June 1st, 2015 to May 31st, 2016. Results show that water infiltration in the loess can be divided into three zones, namely, active, stable, and saturated zones. The active zone is influenced significantly by precipitation and evaporation events, where water flow is a transient behavior. The stable zone is characterized with a stable water content and steady seepage flow. The saturated zone is where groundwater exits, which can be drained in the forms of spring. In the long run, the hydraulic condition reaches an equilibrium state with a stable water content in the stable zone and stable ground water table level. However, this equilibrium state can be disturbed with a higher surface water infiltration, for example irrigation water and leakage from pipelines, which contributes to a new equilibrium state with higher stable water content in stable zone and higher GWT level. Loess landslides with deep seated failure surfaces may occur during the transitional process from the initial equilibrium state to the new equilibrium state. Yanlian deep loess landslide is taken as an example to illustrate the mechanism of surface water infiltration induced deep landslides. The hydraulic response to long-term surface drop water and its influence to slope stability are analyzed. Results highlight the close relationship between deep loess landslides and long-term surface water infiltration, which is easy to be neglected due to its slow flow rate.
In loess area, both artificial rainfall field test and in-situ observation under natural rainfall conditions suggest that the influence of surface water is limited to the top several meters, below which the variation of soil water content is little. Therefore, it is a controversy to fact that the surface water infiltration can induce loess landslides with deep seated failure surfaces. In this study, an in-situ observation test is undertaken in a thick loess layer for a period of one year from June 1st, 2015 to May 31st, 2016. Results show that water infiltration in the loess can be divided into three zones, namely, active, stable, and saturated zones. The active zone is influenced significantly by precipitation and evaporation events, where water flow is a transient behavior. The stable zone is characterized with a stable water content and steady seepage flow. The saturated zone is where groundwater exits, which can be drained in the forms of spring. In the long run, the hydraulic condition reaches an equilibrium state with a stable water content in the stable zone and stable ground water table level. However, this equilibrium state can be disturbed with a higher surface water infiltration, for example irrigation water and leakage from pipelines, which contributes to a new equilibrium state with higher stable water content in stable zone and higher GWT level. Loess landslides with deep seated failure surfaces may occur during the transitional process from the initial equilibrium state to the new equilibrium state. Yanlian deep loess landslide is taken as an example to illustrate the mechanism of surface water infiltration induced deep landslides. The hydraulic response to long-term surface drop water and its influence to slope stability are analyzed. Results highlight the close relationship between deep loess landslides and long-term surface water infiltration, which is easy to be neglected due to its slow flow rate.
15
2018, 26(3): 732-740.
Slope surface erosion due to rainfall is liable to cause soil erosion and landslide hazard, which is a difficult problem.This paper takes a loess slope as an example and puts forward a comprehensive protection method of ecological slope based on the concept of water reducing and drainage.In order to study on soil erosion law and evolution mechanism of slope under different factors, the simulation experiments were carried out with the self-developed slope rainfall simulator.It considers modifier content, lattice protective form, intensity, duration, aspect ratio on the effect of protection.Test results show that the loess slope surface erosion can be summarized as splash erosion, sheet erosion, gully erosion and landslides.With the increase of the modifier content, the corrosion resistance of the improved slope is enhanced, and the optimal dosage of the modifier is 3‰.Compared with the plain loess slope, rainfall intensity has little influence on improved slope with 3‰modifier.With the increase of rainfall duration, the improvement effect of the modifier is more obvious.Modifier and frame as well as their comprehensive utilization can effectively improve the slope resistance to rainfall erosion.When the slope gradient increases to a certain extent, the slope is prone to collapse suddenly due to the rainfall erosion, which needs to be emphasized.The modifier mainly makes the soil particles more compacted by flocculation, so as to improve the water holding capacity and corrosion resistance of loess.
Slope surface erosion due to rainfall is liable to cause soil erosion and landslide hazard, which is a difficult problem.This paper takes a loess slope as an example and puts forward a comprehensive protection method of ecological slope based on the concept of water reducing and drainage.In order to study on soil erosion law and evolution mechanism of slope under different factors, the simulation experiments were carried out with the self-developed slope rainfall simulator.It considers modifier content, lattice protective form, intensity, duration, aspect ratio on the effect of protection.Test results show that the loess slope surface erosion can be summarized as splash erosion, sheet erosion, gully erosion and landslides.With the increase of the modifier content, the corrosion resistance of the improved slope is enhanced, and the optimal dosage of the modifier is 3‰.Compared with the plain loess slope, rainfall intensity has little influence on improved slope with 3‰modifier.With the increase of rainfall duration, the improvement effect of the modifier is more obvious.Modifier and frame as well as their comprehensive utilization can effectively improve the slope resistance to rainfall erosion.When the slope gradient increases to a certain extent, the slope is prone to collapse suddenly due to the rainfall erosion, which needs to be emphasized.The modifier mainly makes the soil particles more compacted by flocculation, so as to improve the water holding capacity and corrosion resistance of loess.
16
2018, 26(3): 749-757.
Relying on the counter-tilt slope of the right bank of dam site of Zha La hydropower station in Tibet, a slope physical model is established based on geological knowledge and similarity theory. A method of staged excavation is adopted to simulate the incised action of a valley, and the evolution process of toppling deformation of a toppling rock slope is studied. The development process of deformation and fracture after excavation shows that: The toppling deformation modes of counter-tilt slope are initial unloading rebound deformation, long-term gravity bending(fracture) deformation and creep deformation in the later stage. Through the analysis of the law of displacement, deformation rate and deformation acceleration: The toppling deformation process of counter-tilt slope can be divided into 3 evolution stages(the stage of toppling initiation, the stage of steady deformation and the stage of rapid destabilization) according to the deformation acceleration a. Each stage corresponds to the deformation characteristics of attenuation creep, steady creep and accelerated creep respectively. On this basis, the deformation acceleration a is used as the criterion of slope stability, and try to use a(deformation acceleration)≥a2(upper limit of steady-state creep) as a slope instability prediction criterion.
Relying on the counter-tilt slope of the right bank of dam site of Zha La hydropower station in Tibet, a slope physical model is established based on geological knowledge and similarity theory. A method of staged excavation is adopted to simulate the incised action of a valley, and the evolution process of toppling deformation of a toppling rock slope is studied. The development process of deformation and fracture after excavation shows that: The toppling deformation modes of counter-tilt slope are initial unloading rebound deformation, long-term gravity bending(fracture) deformation and creep deformation in the later stage. Through the analysis of the law of displacement, deformation rate and deformation acceleration: The toppling deformation process of counter-tilt slope can be divided into 3 evolution stages(the stage of toppling initiation, the stage of steady deformation and the stage of rapid destabilization) according to the deformation acceleration a. Each stage corresponds to the deformation characteristics of attenuation creep, steady creep and accelerated creep respectively. On this basis, the deformation acceleration a is used as the criterion of slope stability, and try to use a(deformation acceleration)≥a2(upper limit of steady-state creep) as a slope instability prediction criterion.
17
2018, 26(5): 1188-1195.
The Haiyuan MS8.5 earthquake on December 16, 1920, occurred at the loess plateau. It triggered a large number of landslides. The landslides directly caused a large number of casualties. In recent years, there have been some special studies on landslides triggered by the Haiyuan earthquake. However, most of these studies have limitations on their local study areas or individual landslides. There are few detailed and comprehensive results about landslides triggered by the earthquake. This situation has become an obstacle to understand the overall incidence and severity, spatial distribution law of the Haiyuan earthquake-triggered landslides. In this study, we carry out the visual interpretation of landslides in the high seismic intensity(Ⅸ-Ⅺ)areas of Haiyuan earthquake based on Google Earth platform, as well as analyze the relationship between landslides and several influence factors. Results show that the earthquake triggered at least 5384 landslides, which have a total landslide area of 218.78 km2. The highest density of landslides is located at the NW part of seismic intensity Ⅸ circle. Through analyzing the relationship between these landslides and topography, earthquake and geological factors, it is found that elevation 1700~2000 m registers the largest landslide number and density. Most landslides are concentrated in the slope angle range of 15°~25°whereas the number density of landslides increases with the increase of slope angle. The lower the slope position is, i.e., the closer to rivers, the greater the density of the landslides. The areas with Cenozoic strata underlying, especially the Quaternary loess covered areas, register most of the landslides and the high density of landslides. This study provides a scientific reference for exploring the law of the occurrence of seismic landslides and reduction and mitigation of earthquake-triggered landslides in loess area.
The Haiyuan MS8.5 earthquake on December 16, 1920, occurred at the loess plateau. It triggered a large number of landslides. The landslides directly caused a large number of casualties. In recent years, there have been some special studies on landslides triggered by the Haiyuan earthquake. However, most of these studies have limitations on their local study areas or individual landslides. There are few detailed and comprehensive results about landslides triggered by the earthquake. This situation has become an obstacle to understand the overall incidence and severity, spatial distribution law of the Haiyuan earthquake-triggered landslides. In this study, we carry out the visual interpretation of landslides in the high seismic intensity(Ⅸ-Ⅺ)areas of Haiyuan earthquake based on Google Earth platform, as well as analyze the relationship between landslides and several influence factors. Results show that the earthquake triggered at least 5384 landslides, which have a total landslide area of 218.78 km2. The highest density of landslides is located at the NW part of seismic intensity Ⅸ circle. Through analyzing the relationship between these landslides and topography, earthquake and geological factors, it is found that elevation 1700~2000 m registers the largest landslide number and density. Most landslides are concentrated in the slope angle range of 15°~25°whereas the number density of landslides increases with the increase of slope angle. The lower the slope position is, i.e., the closer to rivers, the greater the density of the landslides. The areas with Cenozoic strata underlying, especially the Quaternary loess covered areas, register most of the landslides and the high density of landslides. This study provides a scientific reference for exploring the law of the occurrence of seismic landslides and reduction and mitigation of earthquake-triggered landslides in loess area.
18
2018, 26(5): 1285-1291.
The typical silt in Wuhan is solidified with Ionic Soil Stabilizer(ISS). The plasticity index of soil with different mix proportions is obtained through the test of Atterberg limits. The compressive properties, microstructure, specific surface area, chemical composition, energy spectrum analysis and cation exchange test are carried out before and after the solidification of silt with ISS. The macroscopic and microscopic mechanism of the solidification of silt with ISS are studied. The test results show that the compressive strength of silt treated with ISS decreases and porosity decreases. Ionic Soil Stabilizer promotes aggregation and condensation of soil particles, aggregates obviously increase, specific surface area decreases, specific surface energy decreases, and soil structure is denser. There is no change in the chemical composition of the silt before and after solidification. Cation exchange reaction occurs between the ISS and the counter ion layer on the surface of the silt colloid particles. The K+ and Na+ ions in the diluents of the curing agent are captured and adsorbed by the silt. The Ca2+ and Mg2+ ions on the surface of clay particles are resolved, which makes the thickness of the diffusion layer thinner, the ξ potential decreased, and the clay colloid particles coalesced. ISS improves the strength and stability of the soil particles, so as to achieve the purpose of soil modification and solidification.
The typical silt in Wuhan is solidified with Ionic Soil Stabilizer(ISS). The plasticity index of soil with different mix proportions is obtained through the test of Atterberg limits. The compressive properties, microstructure, specific surface area, chemical composition, energy spectrum analysis and cation exchange test are carried out before and after the solidification of silt with ISS. The macroscopic and microscopic mechanism of the solidification of silt with ISS are studied. The test results show that the compressive strength of silt treated with ISS decreases and porosity decreases. Ionic Soil Stabilizer promotes aggregation and condensation of soil particles, aggregates obviously increase, specific surface area decreases, specific surface energy decreases, and soil structure is denser. There is no change in the chemical composition of the silt before and after solidification. Cation exchange reaction occurs between the ISS and the counter ion layer on the surface of the silt colloid particles. The K+ and Na+ ions in the diluents of the curing agent are captured and adsorbed by the silt. The Ca2+ and Mg2+ ions on the surface of clay particles are resolved, which makes the thickness of the diffusion layer thinner, the ξ potential decreased, and the clay colloid particles coalesced. ISS improves the strength and stability of the soil particles, so as to achieve the purpose of soil modification and solidification.
19
FULL SECTION MONITORING OF LAND SUBSIDENCE BOREHOLE USING DISTRIBUTED FIBER OPTIC SENSING TECHNIQUES
2018, 26(2): 356-364.
This paper introduces a full section monitoring of land subsidence borehole using distributed fiber optic sensing(DFOS)techniques, which can obtain data on multi-fields and multi-parameters and provide delicate monitoring of land subsidence. The concept of full section monitoring of borehole using DFOS is firstly introduced. The key techniques on the application of this method include the selections of cables and sensors, the backfill materials, the coupling of cables and soils and the installation of cables and sensors in boreholes. A system frame of the full section monitoring of borehole with DFOS is built. Finally, the whole process of full section monitoring with DFOS and its features are illustrated with a case in Shengze Town, Suzhou.
This paper introduces a full section monitoring of land subsidence borehole using distributed fiber optic sensing(DFOS)techniques, which can obtain data on multi-fields and multi-parameters and provide delicate monitoring of land subsidence. The concept of full section monitoring of borehole using DFOS is firstly introduced. The key techniques on the application of this method include the selections of cables and sensors, the backfill materials, the coupling of cables and soils and the installation of cables and sensors in boreholes. A system frame of the full section monitoring of borehole with DFOS is built. Finally, the whole process of full section monitoring with DFOS and its features are illustrated with a case in Shengze Town, Suzhou.
20
2018, 26(5): 1243-1249.
This paper takes the cement clay of different cement contents as the studied object. The samples of cement clay soil are used for nuclear magnetic resonance test to study the effect of cement content on the distribution of micro-pore. The samples are used for the variable water head penetration test to study the effect of cement content on permeability. On this basis, the paper investigates the microscopic mechanism of the effect of cement content on permeability. The study results show the follow. The permeability coefficient of cement-soil decreases as the cement content increases. It decreases intensely at cement content ranging from 4%to 12%, and decreases slowly at cement content ranging from 15%to 25%. There are three peaks in the T2 distribution curves of cement-soil, which correspond to small pores, medium pores and large pores, respectively. As the cement content increases, the total area of T2 distribution curve tends to decrease. At the stage of low cement content, the area of the second and third peaks diminishes obviously. But at the stage of high cement content, the area of the first peak diminishes obviously. Thus it can be seen that in the range of low cement content, the hydration of cement-soil is prior to block up large pores and medium pores, which makes the permeability coefficient decreases significantly with the increase of cement content. While in the range of high cement content, the area of small pores mainly declines with the increment of cement content. But that of large pores and medium pores has little difference, so the increase of cement content has little effect on the decrease of permeability coefficient of cement-soil.
This paper takes the cement clay of different cement contents as the studied object. The samples of cement clay soil are used for nuclear magnetic resonance test to study the effect of cement content on the distribution of micro-pore. The samples are used for the variable water head penetration test to study the effect of cement content on permeability. On this basis, the paper investigates the microscopic mechanism of the effect of cement content on permeability. The study results show the follow. The permeability coefficient of cement-soil decreases as the cement content increases. It decreases intensely at cement content ranging from 4%to 12%, and decreases slowly at cement content ranging from 15%to 25%. There are three peaks in the T2 distribution curves of cement-soil, which correspond to small pores, medium pores and large pores, respectively. As the cement content increases, the total area of T2 distribution curve tends to decrease. At the stage of low cement content, the area of the second and third peaks diminishes obviously. But at the stage of high cement content, the area of the first peak diminishes obviously. Thus it can be seen that in the range of low cement content, the hydration of cement-soil is prior to block up large pores and medium pores, which makes the permeability coefficient decreases significantly with the increase of cement content. While in the range of high cement content, the area of small pores mainly declines with the increment of cement content. But that of large pores and medium pores has little difference, so the increase of cement content has little effect on the decrease of permeability coefficient of cement-soil.
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