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2012, 20(6): 903-908.
Water resistance is one of the most important factors which affect the speed of the fording landslide when it enters water at a high speed. The experiment system is designed. It includes movement apparatus, sensor apparatus, speed control apparatus and transmission apparatus. Six blocks with different areas of water attaining surface are selected to carry out experiments. Each block moves in water at five different speeds. They are 0.5ms-1、0.8ms-1、1.0ms-1、1.5ms-1 and 1.8ms-1. The correlation between Incremental pressure head and moving speed is analyzed by experiment method. The pressure head model is established to the resistance of water attaining surface when blokes move in water. As for the curved-surface sliding model of fording landslide, the forces of sliding masses both in water and above water are calculated. The kinetics equation and kinematics equation are used to calculate landslide speeds. At last, the speed model of fording landslide is put forward by slice method when landslide moves along a curved slip surface. The paper takes the Dayantang landslide that was located on the north side of Qing River and occurred on June 15, 2007 as an example. The speeds of landslide with water resistance acting on water attaining surface are compared with those of landslide without water resistance. The influences on the landslide speed from the water resistance are quantitatively analyzed.
Water resistance is one of the most important factors which affect the speed of the fording landslide when it enters water at a high speed. The experiment system is designed. It includes movement apparatus, sensor apparatus, speed control apparatus and transmission apparatus. Six blocks with different areas of water attaining surface are selected to carry out experiments. Each block moves in water at five different speeds. They are 0.5ms-1、0.8ms-1、1.0ms-1、1.5ms-1 and 1.8ms-1. The correlation between Incremental pressure head and moving speed is analyzed by experiment method. The pressure head model is established to the resistance of water attaining surface when blokes move in water. As for the curved-surface sliding model of fording landslide, the forces of sliding masses both in water and above water are calculated. The kinetics equation and kinematics equation are used to calculate landslide speeds. At last, the speed model of fording landslide is put forward by slice method when landslide moves along a curved slip surface. The paper takes the Dayantang landslide that was located on the north side of Qing River and occurred on June 15, 2007 as an example. The speeds of landslide with water resistance acting on water attaining surface are compared with those of landslide without water resistance. The influences on the landslide speed from the water resistance are quantitatively analyzed.
2012, 20(6): 909-915.
This paper presents an impulsive wave formula calculating system. It is based on geohazard impulsive wave formula and local head loss theory. . It takes into account on varied impulsive effect generated by varied landslides, decaying difference on varied region, frictional head loss and local head loss. It adopts many topography parameters. So its result is strongly objective. This paper takes impulsive wave generated by Gongjiafang for example and analyzes the impulsive wave. The results are close to the results of field investigation. The biggest impulsive wave height is 33.15 m. It is concluded that in the rapidly decaying area, the impulse wave has an average decrease of 4 m in wave amplitude within the distance of 100 m. While in the mildly decaying area, that figure is change to 0.11 m. Also it is found that there is an amplified decaying effect when the wave propagates from gorge to strath.
This paper presents an impulsive wave formula calculating system. It is based on geohazard impulsive wave formula and local head loss theory. . It takes into account on varied impulsive effect generated by varied landslides, decaying difference on varied region, frictional head loss and local head loss. It adopts many topography parameters. So its result is strongly objective. This paper takes impulsive wave generated by Gongjiafang for example and analyzes the impulsive wave. The results are close to the results of field investigation. The biggest impulsive wave height is 33.15 m. It is concluded that in the rapidly decaying area, the impulse wave has an average decrease of 4 m in wave amplitude within the distance of 100 m. While in the mildly decaying area, that figure is change to 0.11 m. Also it is found that there is an amplified decaying effect when the wave propagates from gorge to strath.
2012, 20(6): 916-925.
Radiation slices method has more advantage than other slice methods in dividing slices. But currently the radiation slices method applies only to the type of circular sliding surface. The method using radiation slices to calculate factor of safety (FOS) is not as completion as those of other slices methods. This paper presents a radiation slices-division mode for arbitrary curved slip surface. Radiation soil slice is taken as a uni. Direction of the inter-shear force uses two different types of the directions based on the previous results. Then the strict balance equation of force and torque is established. The formula of FOS for the general assumption of inter-force is deduced. When using the inter-force assumptions of Sarma and M-P method, their applicability to the radiation slices method is studied. At the same time, in order to broaden the use of M-P method in the radiation slices method, two new inter-force assumptions are put forward based on the inter-force relationship of M-P method by analyzing the inter-force relationship between radiation slice and vertical slice. When the sliding surface (including circular and arbitrary curve) is fixed and the number of slices is different, this article researches the feasibility of above-mentioned methods and through comparing and analyzing some examples. The results show the follows. (1) When the direction of inter-shear force is the first case of direction, the inter-force assumptions of Sarma method and the three kinds of M-P methods could be all applied to the radiation slice method for analyzing slope stability. (2) The two new kinds of inter-force assumptions based on M-P method have better improvement in convergence of calculated results than the traditional inter-force assumption of M-P method. (3) In the radiation slice method, arbitrary sliding has more applicability than the circular sliding surface.
Radiation slices method has more advantage than other slice methods in dividing slices. But currently the radiation slices method applies only to the type of circular sliding surface. The method using radiation slices to calculate factor of safety (FOS) is not as completion as those of other slices methods. This paper presents a radiation slices-division mode for arbitrary curved slip surface. Radiation soil slice is taken as a uni. Direction of the inter-shear force uses two different types of the directions based on the previous results. Then the strict balance equation of force and torque is established. The formula of FOS for the general assumption of inter-force is deduced. When using the inter-force assumptions of Sarma and M-P method, their applicability to the radiation slices method is studied. At the same time, in order to broaden the use of M-P method in the radiation slices method, two new inter-force assumptions are put forward based on the inter-force relationship of M-P method by analyzing the inter-force relationship between radiation slice and vertical slice. When the sliding surface (including circular and arbitrary curve) is fixed and the number of slices is different, this article researches the feasibility of above-mentioned methods and through comparing and analyzing some examples. The results show the follows. (1) When the direction of inter-shear force is the first case of direction, the inter-force assumptions of Sarma method and the three kinds of M-P methods could be all applied to the radiation slice method for analyzing slope stability. (2) The two new kinds of inter-force assumptions based on M-P method have better improvement in convergence of calculated results than the traditional inter-force assumption of M-P method. (3) In the radiation slice method, arbitrary sliding has more applicability than the circular sliding surface.
2012, 20(6): 926-933.
This paper aims to quickly evaluate the stability of accumulation slope and adopt scientific preventive maintenance countermeasure. It considers the scientific matters of evaluation model and maneuverability of expressway slope maintenance. It summarizes the existing research achievements domestic and abroad about accumulation slope. It then sets up a reasonable accumulation slope stability evaluation index Fuzzy-AHP analysis model. This model is established on the basis of extensive field investigation of accumulation slope disturbed to several expressways in Hunan province. The stability gradation model for accumulation slope stability analysis has been established. The hierarchy model consists of two indexes layers: five main evaluation indexes and 17 basic examination indexes. They are (1) structural characteristics of deposit body (basement lithologic, contact surface character, content of gravel, the thickness of deposit soil, and cementation degree of deposit soil);(2) the section characteristics of accumulation slope (slope gradient, height of slope, the relationship of slope direction and rock stratum occurrence);(3) hydraulic characteristics (drainage system, rainfall, groundwater);(4) engineering protection and vegetation protection(protection structure, reinforcement structure, vegetation coverage)and, (5) other factors (slope failure history, seismic intensity, excavation method). Based on fuzzy math and analytic hierarchy process, the weight of every index is obtained by making use of analytic hierarchy process. The fuzzy math method is used to calculation the relative membership degree vector and to make a comprehensive evaluation of accumulation slope stability. Thus the slope stability classification can be determined. Finally, the application to an engineering example verifies the accuracy and the rationality of the model. Its result is reliable. The results show that the application of this model can make evaluation of accumulation slope stability more scientific, more reasonable, more corresponded to expressway slope engineering practice. This method is simple and feasible. The result is reliable, and has certain superiority to conventional mechanics analysis method. It can provide scientific basis for slope of expressway maintenance decision-making.
This paper aims to quickly evaluate the stability of accumulation slope and adopt scientific preventive maintenance countermeasure. It considers the scientific matters of evaluation model and maneuverability of expressway slope maintenance. It summarizes the existing research achievements domestic and abroad about accumulation slope. It then sets up a reasonable accumulation slope stability evaluation index Fuzzy-AHP analysis model. This model is established on the basis of extensive field investigation of accumulation slope disturbed to several expressways in Hunan province. The stability gradation model for accumulation slope stability analysis has been established. The hierarchy model consists of two indexes layers: five main evaluation indexes and 17 basic examination indexes. They are (1) structural characteristics of deposit body (basement lithologic, contact surface character, content of gravel, the thickness of deposit soil, and cementation degree of deposit soil);(2) the section characteristics of accumulation slope (slope gradient, height of slope, the relationship of slope direction and rock stratum occurrence);(3) hydraulic characteristics (drainage system, rainfall, groundwater);(4) engineering protection and vegetation protection(protection structure, reinforcement structure, vegetation coverage)and, (5) other factors (slope failure history, seismic intensity, excavation method). Based on fuzzy math and analytic hierarchy process, the weight of every index is obtained by making use of analytic hierarchy process. The fuzzy math method is used to calculation the relative membership degree vector and to make a comprehensive evaluation of accumulation slope stability. Thus the slope stability classification can be determined. Finally, the application to an engineering example verifies the accuracy and the rationality of the model. Its result is reliable. The results show that the application of this model can make evaluation of accumulation slope stability more scientific, more reasonable, more corresponded to expressway slope engineering practice. This method is simple and feasible. The result is reliable, and has certain superiority to conventional mechanics analysis method. It can provide scientific basis for slope of expressway maintenance decision-making.
2012, 20(6): 934-939.
The wetting-drying effect of expansive soils plays an important role in slope stability analysis. This paper uses the field monitoring data of moisture contents of expansive soil slope and the calculation results of atmospheric influence depth at Nanling region. It then determines the wetting-drying circulate amplitudes of laboratory experiments. Laboratory tests on the soil strength are performed to discuss on the wetting-drying effect of expansive soil. Furthermore, the stability of expansive soil slope is studied taking into account the wetting-drying effect. The results show that the cohesion of expansive soil decreases with increasing number of cycles and its impact is especially obvious during the first and second cycles. After that, it reaches to a constant state. However, the friction angle keeps a stable value with little influence of the wetting-drying effect. It is also found that the value and cyclic number of the constant state reduce with increase of amplitude of variation of water content. As wetting-drying cycles cause irreversible damages to soil intergranular links, the shear strength reduction of expansive soil is the result of micro-structural degradation. Furthermore, the slope stability and safe factor decrease with increasing number of cycles and the stability analysis method with considering the wetting-drying effect is more in line with the practical engineering.
The wetting-drying effect of expansive soils plays an important role in slope stability analysis. This paper uses the field monitoring data of moisture contents of expansive soil slope and the calculation results of atmospheric influence depth at Nanling region. It then determines the wetting-drying circulate amplitudes of laboratory experiments. Laboratory tests on the soil strength are performed to discuss on the wetting-drying effect of expansive soil. Furthermore, the stability of expansive soil slope is studied taking into account the wetting-drying effect. The results show that the cohesion of expansive soil decreases with increasing number of cycles and its impact is especially obvious during the first and second cycles. After that, it reaches to a constant state. However, the friction angle keeps a stable value with little influence of the wetting-drying effect. It is also found that the value and cyclic number of the constant state reduce with increase of amplitude of variation of water content. As wetting-drying cycles cause irreversible damages to soil intergranular links, the shear strength reduction of expansive soil is the result of micro-structural degradation. Furthermore, the slope stability and safe factor decrease with increasing number of cycles and the stability analysis method with considering the wetting-drying effect is more in line with the practical engineering.
2012, 20(6): 940-954.
The Jiufengershan landslide with the volume of 4107m3 is one of the huge landslides induced by the 1999 Taiwan Chi-Chi Earthquake. The collapse mechanism of this landslide may be shear out or buckling, which is an argument need to be further. This paper demonstrates that there might be different failure mechanisms that could happen in the landslide block at a reasonable friction coefficient of 0.05 by the 3-D models. Taking toe particles into account, the collapse mechanism is dominated by buckling with short run-out distance in the southern section. On the other hand, the mechanism is dominated by shear out with long run-out distance in the northern section. Thus, the mechanisms of large landslides are probably not unitary, and complex failure mechanisms might be existed due to the complex topographic features. Our result suggests that, in addition to the property of the landslide and the tectonics, the geomorphologic conditions and the geometric features of the landslide face can also play an important role in the occurrence and landsliding process of earthquake-triggered landslide.
The Jiufengershan landslide with the volume of 4107m3 is one of the huge landslides induced by the 1999 Taiwan Chi-Chi Earthquake. The collapse mechanism of this landslide may be shear out or buckling, which is an argument need to be further. This paper demonstrates that there might be different failure mechanisms that could happen in the landslide block at a reasonable friction coefficient of 0.05 by the 3-D models. Taking toe particles into account, the collapse mechanism is dominated by buckling with short run-out distance in the southern section. On the other hand, the mechanism is dominated by shear out with long run-out distance in the northern section. Thus, the mechanisms of large landslides are probably not unitary, and complex failure mechanisms might be existed due to the complex topographic features. Our result suggests that, in addition to the property of the landslide and the tectonics, the geomorphologic conditions and the geometric features of the landslide face can also play an important role in the occurrence and landsliding process of earthquake-triggered landslide.
2012, 20(6): 955-970.
Tanggudong landslide and Yuri accumulation body are situated at 1.5km downstream from the middle dam site of Lenggu hydropower station in the Yalong River Valley, Yajiang county, Sichuan Province. They can be a potential hazard to the safety of the planning dam. Based on local geological structure, this study establishes the inner link between Yuri accumulation characteristics and the formation process of the Tanggudong landslide. The formation process of Tanggudong landslide are found out through analysis of the Yuri accumulation body characteristics. The evolution process of the bank slope in this valley and its periodic characteristics are established. The result shows that as different individuals in the same local geological structure, Tanggudong landslide and Yuri accumulation body have some inevitable connection during the process of evolution, representing classic products of different evolutionary stages.
Tanggudong landslide and Yuri accumulation body are situated at 1.5km downstream from the middle dam site of Lenggu hydropower station in the Yalong River Valley, Yajiang county, Sichuan Province. They can be a potential hazard to the safety of the planning dam. Based on local geological structure, this study establishes the inner link between Yuri accumulation characteristics and the formation process of the Tanggudong landslide. The formation process of Tanggudong landslide are found out through analysis of the Yuri accumulation body characteristics. The evolution process of the bank slope in this valley and its periodic characteristics are established. The result shows that as different individuals in the same local geological structure, Tanggudong landslide and Yuri accumulation body have some inevitable connection during the process of evolution, representing classic products of different evolutionary stages.
2012, 20(6): 971-978.
The Milin county along Yarlungzangbo river is closed to the Indian plate with the Eurasian plate collision zones, where the tectonic movement is intense and the seismic activity is frequent. So debris flow are widely distributed. This paper uses the remote sensing and field investigation and examines 34 debris flow gullies which have an integrated deposit fan. Using geographical information system and remote sensing software, the paper analyses the basic parameters of the basin such as basin relief and the volume source. The regression analysis on the maximum length and width runout and their topographical factors is conducted using the software Mat lab. It is found that the maximum length and width runout have an obvious index correlation with the basin relief and the volume source. Based on the found single factor regular, the predicting model on evaluating the debris flow's hazardous range is established. This model absorbs the previous model advantages, distinguishes the risk range by less factors and saves time. It can be better and faster against the disaster.
The Milin county along Yarlungzangbo river is closed to the Indian plate with the Eurasian plate collision zones, where the tectonic movement is intense and the seismic activity is frequent. So debris flow are widely distributed. This paper uses the remote sensing and field investigation and examines 34 debris flow gullies which have an integrated deposit fan. Using geographical information system and remote sensing software, the paper analyses the basic parameters of the basin such as basin relief and the volume source. The regression analysis on the maximum length and width runout and their topographical factors is conducted using the software Mat lab. It is found that the maximum length and width runout have an obvious index correlation with the basin relief and the volume source. Based on the found single factor regular, the predicting model on evaluating the debris flow's hazardous range is established. This model absorbs the previous model advantages, distinguishes the risk range by less factors and saves time. It can be better and faster against the disaster.
2012, 20(6): 979-985.
Ground fissures are defects on earth's surface caused by endogenetic agents, external agents and human activities. Under these adverse geological conditions, ground fissures must have some effects to site earthquake response. This paper aims at providing research and engineering assessment on site seismic effects of ground fissures. A finite element numerical analysis is made to study the ground motion effects of ground fissures in Xi'an city. The influence characteristics and influence scope to peak ground acceleration and response spectrum are obtained. The results of analysis provide a reference to engineering structures' seismic resistance and hazards avoidance.
Ground fissures are defects on earth's surface caused by endogenetic agents, external agents and human activities. Under these adverse geological conditions, ground fissures must have some effects to site earthquake response. This paper aims at providing research and engineering assessment on site seismic effects of ground fissures. A finite element numerical analysis is made to study the ground motion effects of ground fissures in Xi'an city. The influence characteristics and influence scope to peak ground acceleration and response spectrum are obtained. The results of analysis provide a reference to engineering structures' seismic resistance and hazards avoidance.
2012, 20(6): 986-991.
This paper aims to effectively prevent rock burst accidents occurs because of the roof caving with the old roof periodic weighting in fully-mechanized sublevel caving mining face.It uses the mining examples of fully-mechanized sublevel caving mining in 1305 working face of Dongtan mine and adopts a new generation SOS microseism monitoring and measuring system.The system was made in Poland Mining Research Institute.It was developed to full time monitoring and measuring on the working face since the beginning of working face interconnection.The paper analyzes statistically the micro earthquake events,incident frequency and event total energy periodic changes.Thus it deduces the old roof fracture periodicity.Afterwards,it proves the accuracy of the system through theoretical calculations.The results show that there is a corresponding relationship between the working face periodic weighting and event total energy periodic changing. Before the strong micro-seismic activity occurred,there would be a weak seismic activity period and the weak seismic activity would play energy accumulation role to the strong seismic occurred.Releasing of the total energy in periodic weighting fluctuates in a certain range fluctuations,but the instability of fluctuation changes enhanced.The conclusion has certain actual significance for the working face safety mining and preventing the occurrence of mining-induced earthquakes.
This paper aims to effectively prevent rock burst accidents occurs because of the roof caving with the old roof periodic weighting in fully-mechanized sublevel caving mining face.It uses the mining examples of fully-mechanized sublevel caving mining in 1305 working face of Dongtan mine and adopts a new generation SOS microseism monitoring and measuring system.The system was made in Poland Mining Research Institute.It was developed to full time monitoring and measuring on the working face since the beginning of working face interconnection.The paper analyzes statistically the micro earthquake events,incident frequency and event total energy periodic changes.Thus it deduces the old roof fracture periodicity.Afterwards,it proves the accuracy of the system through theoretical calculations.The results show that there is a corresponding relationship between the working face periodic weighting and event total energy periodic changing. Before the strong micro-seismic activity occurred,there would be a weak seismic activity period and the weak seismic activity would play energy accumulation role to the strong seismic occurred.Releasing of the total energy in periodic weighting fluctuates in a certain range fluctuations,but the instability of fluctuation changes enhanced.The conclusion has certain actual significance for the working face safety mining and preventing the occurrence of mining-induced earthquakes.
2012, 20(6): 992-997.
It is technically feasible to carry out the intercepting underflow and artesian diversion project to utilize the abundant groundwater resource in the arid and semi-arid alluvial plain areas. But few instances or reports have been put into effect. The establishment of intercepting underflow project can extremely easily cause immersion and ecological environment deterioration. In this paper, the intercepting underflow and diversion project in Jia County is taken as an example to discuss the reasonability of the utilization scheme in the aspect of the environment effect. Based on the investigation and evaluation of ground water resource, the prediction of immersion scope of study area during the dry season is presented by three-dimensional numerical simulation method. Based on comprehensive analysis of the hydro-geological condition in the study area, the immersion scope is examined by the analogy method. The preliminary study on water pollution is conducted with influencing factor analysis method. The prediction of seepage deformation of base is performed using analytical method. The results show that it is not proper to conduct the intercepting underflow and artesian diversion program due to the serious environment effects that can be caused by this scheme. Correspondingly, new development programs and countermeasures are proposed to meet the water supply requirements and to avoid the environmental effects.
It is technically feasible to carry out the intercepting underflow and artesian diversion project to utilize the abundant groundwater resource in the arid and semi-arid alluvial plain areas. But few instances or reports have been put into effect. The establishment of intercepting underflow project can extremely easily cause immersion and ecological environment deterioration. In this paper, the intercepting underflow and diversion project in Jia County is taken as an example to discuss the reasonability of the utilization scheme in the aspect of the environment effect. Based on the investigation and evaluation of ground water resource, the prediction of immersion scope of study area during the dry season is presented by three-dimensional numerical simulation method. Based on comprehensive analysis of the hydro-geological condition in the study area, the immersion scope is examined by the analogy method. The preliminary study on water pollution is conducted with influencing factor analysis method. The prediction of seepage deformation of base is performed using analytical method. The results show that it is not proper to conduct the intercepting underflow and artesian diversion program due to the serious environment effects that can be caused by this scheme. Correspondingly, new development programs and countermeasures are proposed to meet the water supply requirements and to avoid the environmental effects.
2012, 20(6): 998-1006.
This paper mainly examines the characteristics of the multi-model grain size distribution of slip surface soils and fine-grained deposits of landslides. It uses the high-resolution laser grain size analyzer MS2000 in five typical sedimentary areas of China. Then It summarizes the characteristics between the discrepancies of different types of slip surface soils and landslide deposits. The characteristics have important theoretical and practical significances for understanding the formation of landslide mechanism. The test results show that: 1)There are at most four models(median size are 1m, 1~10m, 10~100m, 100~500m, respectively) that are superimposed to constitute of landslide slip surface soil and the deposits in the different types of sedimentary areas. The characteristics of multi-models grain size distribution are the fine, median and coarse grain of suspension and saltation.2)Different types of landslides slip surface soils and the deposits can have significantly different characteristics of grain size distribution.3)the grain size discrepancy of landslides slip surface soils and the deposits in the same area can be controlled by the formation and evolution of landslides themselves.
This paper mainly examines the characteristics of the multi-model grain size distribution of slip surface soils and fine-grained deposits of landslides. It uses the high-resolution laser grain size analyzer MS2000 in five typical sedimentary areas of China. Then It summarizes the characteristics between the discrepancies of different types of slip surface soils and landslide deposits. The characteristics have important theoretical and practical significances for understanding the formation of landslide mechanism. The test results show that: 1)There are at most four models(median size are 1m, 1~10m, 10~100m, 100~500m, respectively) that are superimposed to constitute of landslide slip surface soil and the deposits in the different types of sedimentary areas. The characteristics of multi-models grain size distribution are the fine, median and coarse grain of suspension and saltation.2)Different types of landslides slip surface soils and the deposits can have significantly different characteristics of grain size distribution.3)the grain size discrepancy of landslides slip surface soils and the deposits in the same area can be controlled by the formation and evolution of landslides themselves.
2012, 20(6): 1007-1012.
The Masangshao tunnel passes through a section with complicated geological condition. The ground is rich in karst and underground water, and has many faults and fractured zones. In the process of construction, a comprehensive geological prediction was adopted. It included the TSP203, geologic radar, regular geologic analysis and advance horizontal boring. They verify and supplement one another. The paper compares the geological prediction of Masangshao tunnel with the information revealed after excavation. This comparison shows the accuracy of comprehensive geological prediction. The above-mentioned practice has certain lessons and guiding significance to geological prediction of similar projects.
The Masangshao tunnel passes through a section with complicated geological condition. The ground is rich in karst and underground water, and has many faults and fractured zones. In the process of construction, a comprehensive geological prediction was adopted. It included the TSP203, geologic radar, regular geologic analysis and advance horizontal boring. They verify and supplement one another. The paper compares the geological prediction of Masangshao tunnel with the information revealed after excavation. This comparison shows the accuracy of comprehensive geological prediction. The above-mentioned practice has certain lessons and guiding significance to geological prediction of similar projects.
2012, 20(6): 1013-1019.
Rock deformation and failure can be regarded as the process of energy dissipation and release. This paper conducts the laboratory test on rocks s samples from Xirangpo banks of Badong town. The rock energy dissipation characteristics of the middle triassi badong formation are analyzed. Furthermore, the paper analyzes the laws of rock energy and discusses the strength characteristics and the failure regularity of bank slope. The paper indicates the follows. (1) By compression test, failure mode of rock can be divided into four categories. The wedge shear and tensile failure modes have the largest energy consumption rates. The mode of shear failure along weakness face owns the smallest one. (2) the hardness of rock can be characterized by energy of external load input before peak, rock failure and damage energy and unit length of the crack energy consumption rate. The hardness distributes unevenly vertically. The internal part of rock is easy to occur bedding slip under tectonic effects. (3) High strength rock usually performance brittle failure. The failure energy consumption speed is fast before the damage. Hard rock slopes normally concentrate a large number of elastic energy which is much larger than the required energy for rock failure in destruction stage, leading to severe sliding. (4) At the areas of mineral composition changes in rocks, the indicators of rock energy analysis have shown apparent fluctuation. Strength of lime rock is relative higher than clay rock. The results can provide an important reference for interpreting the mechanics character of rock and failure mode of landslides in Badong town.
Rock deformation and failure can be regarded as the process of energy dissipation and release. This paper conducts the laboratory test on rocks s samples from Xirangpo banks of Badong town. The rock energy dissipation characteristics of the middle triassi badong formation are analyzed. Furthermore, the paper analyzes the laws of rock energy and discusses the strength characteristics and the failure regularity of bank slope. The paper indicates the follows. (1) By compression test, failure mode of rock can be divided into four categories. The wedge shear and tensile failure modes have the largest energy consumption rates. The mode of shear failure along weakness face owns the smallest one. (2) the hardness of rock can be characterized by energy of external load input before peak, rock failure and damage energy and unit length of the crack energy consumption rate. The hardness distributes unevenly vertically. The internal part of rock is easy to occur bedding slip under tectonic effects. (3) High strength rock usually performance brittle failure. The failure energy consumption speed is fast before the damage. Hard rock slopes normally concentrate a large number of elastic energy which is much larger than the required energy for rock failure in destruction stage, leading to severe sliding. (4) At the areas of mineral composition changes in rocks, the indicators of rock energy analysis have shown apparent fluctuation. Strength of lime rock is relative higher than clay rock. The results can provide an important reference for interpreting the mechanics character of rock and failure mode of landslides in Badong town.
2012, 20(6): 1020-1027.
Tension-shear failure is one common type of rock instability in rock slope engineering and rock tunneling engineering. Based on engineering geological conditions, this paper analyzes the conditions that generate tension-shear stress state. It summarizes the current experiment methods of rock tension-shear research, constitutive equations and failure criterions. It points out the shortcomings of rock tension-shear research. Finally, it proposes the following research trends: (1) develop the standard tension-shear testing equipment for special experimental studies on rock; (2) do tension and shear experiments on more types of rock and more quantities of rock to study constitutive equations and failure criterions of different rock types; (3) strengthen the numerical simulation work of rock tension-shear tests and confirmed by each other.
Tension-shear failure is one common type of rock instability in rock slope engineering and rock tunneling engineering. Based on engineering geological conditions, this paper analyzes the conditions that generate tension-shear stress state. It summarizes the current experiment methods of rock tension-shear research, constitutive equations and failure criterions. It points out the shortcomings of rock tension-shear research. Finally, it proposes the following research trends: (1) develop the standard tension-shear testing equipment for special experimental studies on rock; (2) do tension and shear experiments on more types of rock and more quantities of rock to study constitutive equations and failure criterions of different rock types; (3) strengthen the numerical simulation work of rock tension-shear tests and confirmed by each other.
2012, 20(6): 1028-1035.
This paper investigates the collapsible loess foundation with contrast experiments on foundation treatment by dynamic consolidation. Five combination schemes are adopted and consist of different tamping energies(8000kNm, 6500kNm and 3000kNm) and different grid spacing(1.6D, 2D and 2.5D) and different bottom areas(5m2, 7m2).Before and after the experiment, a series of in-situ and laboratory tests are performed. They include standard penetration tests, static touch tests, static load tests and permeability test. Through these tests, the influence of the dynamic consolidation on the soil properties including dry density, bearing capacity, compressibility, collapsibility and permeability is analyzed. The effective depth of improvement of each project is different according to the choosing of construction technics and parameters of the dynamic consolidation. Influence of vibration caused by dynamic consolidation to adjacent buildings is analyzed, which make an example for analogic engineering construction in the future.
This paper investigates the collapsible loess foundation with contrast experiments on foundation treatment by dynamic consolidation. Five combination schemes are adopted and consist of different tamping energies(8000kNm, 6500kNm and 3000kNm) and different grid spacing(1.6D, 2D and 2.5D) and different bottom areas(5m2, 7m2).Before and after the experiment, a series of in-situ and laboratory tests are performed. They include standard penetration tests, static touch tests, static load tests and permeability test. Through these tests, the influence of the dynamic consolidation on the soil properties including dry density, bearing capacity, compressibility, collapsibility and permeability is analyzed. The effective depth of improvement of each project is different according to the choosing of construction technics and parameters of the dynamic consolidation. Influence of vibration caused by dynamic consolidation to adjacent buildings is analyzed, which make an example for analogic engineering construction in the future.
2012, 20(6): 1036-1041.
In plateau lacustrine, the modulus of compression of soft clay is low. Sometimes, equivalent compression modulus in the range of the effective depth of foundation settlement analysis can be less than 2.5MPa. The empirical settlement coefficient exceeds the range of standard. The settlement is too large. This paper uses the three-point method, the hyperbolic curve, the Asaoka method to fit final settlement. The results are compared with the foundation settlement calculated with the layer-wise summation method. Six empirical settlement coefficients are obtained. The paper analyzes the equivalent compression modulus and points out the fitting curve equation. The range of equivalent compression modulus is 2.05~4.15MPa. Meanwhile, this paper points out the suggested value for the empirical settlement coefficient They are in the range of equivalent compression modulus 1.5~4.15MPa. It makes up the weaknesses of empirical settlement coefficient that in plateau lacustrine.
In plateau lacustrine, the modulus of compression of soft clay is low. Sometimes, equivalent compression modulus in the range of the effective depth of foundation settlement analysis can be less than 2.5MPa. The empirical settlement coefficient exceeds the range of standard. The settlement is too large. This paper uses the three-point method, the hyperbolic curve, the Asaoka method to fit final settlement. The results are compared with the foundation settlement calculated with the layer-wise summation method. Six empirical settlement coefficients are obtained. The paper analyzes the equivalent compression modulus and points out the fitting curve equation. The range of equivalent compression modulus is 2.05~4.15MPa. Meanwhile, this paper points out the suggested value for the empirical settlement coefficient They are in the range of equivalent compression modulus 1.5~4.15MPa. It makes up the weaknesses of empirical settlement coefficient that in plateau lacustrine.
2012, 20(6): 1042-1049.
In the process of vacuum preloading consolidation, soft foundation is consolidated by powerful vacuum suction. A kind of soft clay has many fine particles that would be flowed to drain pipes with vacuum. The plastic pipes would be surrounded with clay. Then they would be formed with mud membrane. Through laboratory test, the course of drainage consolidation is simulated. It is aimed that the laws of particle migration can be resolved with the proposed approach. Test results confirm that the consolidation conditions affect the fine particle migration phenomenon. At the gravitational compaction consolidation stage, the fine particles are influenced by boundary conditions and seepage paths. However, at the pressure consolidation stage, the fine particles are influenced by the additional loading generated vertical pressure. Therefore, the tendency of particle migration is no more than weak. And The distribution of fine particles is changed from vertical gershgorim band to horizontal gershgorim band. Furthermore, the mass ratio of silt and clay is primary defined as aggregate clay ratio. It reflects the status of migration process. The aggregate clay ratio is considered as the indicator of migration. Data analysis results show that the indicator can effectively reflect the degree of consolidation. With the continuing process of consolidation drainage, the aggregate clay ratio is increasing gradually. It reflects indirectly the strength of high clay dredger fill. In the consolidation process, aggregate clay ratio is increased as the drainage velocity is changed lower.
In the process of vacuum preloading consolidation, soft foundation is consolidated by powerful vacuum suction. A kind of soft clay has many fine particles that would be flowed to drain pipes with vacuum. The plastic pipes would be surrounded with clay. Then they would be formed with mud membrane. Through laboratory test, the course of drainage consolidation is simulated. It is aimed that the laws of particle migration can be resolved with the proposed approach. Test results confirm that the consolidation conditions affect the fine particle migration phenomenon. At the gravitational compaction consolidation stage, the fine particles are influenced by boundary conditions and seepage paths. However, at the pressure consolidation stage, the fine particles are influenced by the additional loading generated vertical pressure. Therefore, the tendency of particle migration is no more than weak. And The distribution of fine particles is changed from vertical gershgorim band to horizontal gershgorim band. Furthermore, the mass ratio of silt and clay is primary defined as aggregate clay ratio. It reflects the status of migration process. The aggregate clay ratio is considered as the indicator of migration. Data analysis results show that the indicator can effectively reflect the degree of consolidation. With the continuing process of consolidation drainage, the aggregate clay ratio is increasing gradually. It reflects indirectly the strength of high clay dredger fill. In the consolidation process, aggregate clay ratio is increased as the drainage velocity is changed lower.
2012, 20(6): 1050-1056.
Lots of cutting slopes were developed in building along the highway from Yichang to Badong, where the ground was covered by the residual unsaturated red clay. The soil strength fell sharply under rainfall, which caused a large number of cutting slopes to lose stability. Currently there was little experimental study in strength and deformation characteristics of Badong unsaturated red clay. To investigate the effect of matrix suction to the shear strength of red clay, the soil-water characteristic curve and triaxial strength test of the red soil were conducted. The triaxial shear test was conducted by using GDS triaxial system with double pressure chamber. The results show that the matrix suction has a major influence on soil strength. When the matrix suction is controlled, the soil strength has a nonlinear growth with the matrix suction increasing; the matrix suction gets lower as the soil water content increases. That's to say, the strength characteristics of Badong unsaturated red clay can get worse with soil water content increasing. Finally, the shear strength formula of Badong unsaturated red clay was fitted. The research results can be used for engineering practice in this region.
Lots of cutting slopes were developed in building along the highway from Yichang to Badong, where the ground was covered by the residual unsaturated red clay. The soil strength fell sharply under rainfall, which caused a large number of cutting slopes to lose stability. Currently there was little experimental study in strength and deformation characteristics of Badong unsaturated red clay. To investigate the effect of matrix suction to the shear strength of red clay, the soil-water characteristic curve and triaxial strength test of the red soil were conducted. The triaxial shear test was conducted by using GDS triaxial system with double pressure chamber. The results show that the matrix suction has a major influence on soil strength. When the matrix suction is controlled, the soil strength has a nonlinear growth with the matrix suction increasing; the matrix suction gets lower as the soil water content increases. That's to say, the strength characteristics of Badong unsaturated red clay can get worse with soil water content increasing. Finally, the shear strength formula of Badong unsaturated red clay was fitted. The research results can be used for engineering practice in this region.
2012, 20(6): 1057-1063.
the foundation of a 2300MW pithead's power plant in southwest of Shandong province is located in alluvial layers of the Yellow River. The engineering properties of the strata are poor. The low foundation strength can't meet the needs of the key structures and buildings of the power plant. According to the geological conditions, foundation treatment has been conducted by high-strength pre-stressed concrete pipe. In the case study, we test the pile body with low strain integrity testing methods, determine the vertical ultimate bearing capacity of single pile using two methods such as high strain tests and static load tests, and contrast the advantages/disadvantages and affecting factors. Then we conclude the following three results.(1)Testing results by high strain CAPWAP method after fitting agree well with that by the vertical static load of a single pile. So it is likely to enhance the accuracy and reliability of high strain test results by optimizing the pile and soil parameters.(2)When it is not allowed for in-situ static load test, high strain tests can be used as a supplement means to the load test for pile foundation.(3)When we get more reliable high strain test results, some adjustments can be made for the design scheme according to standard method based on rigorous calculation.
the foundation of a 2300MW pithead's power plant in southwest of Shandong province is located in alluvial layers of the Yellow River. The engineering properties of the strata are poor. The low foundation strength can't meet the needs of the key structures and buildings of the power plant. According to the geological conditions, foundation treatment has been conducted by high-strength pre-stressed concrete pipe. In the case study, we test the pile body with low strain integrity testing methods, determine the vertical ultimate bearing capacity of single pile using two methods such as high strain tests and static load tests, and contrast the advantages/disadvantages and affecting factors. Then we conclude the following three results.(1)Testing results by high strain CAPWAP method after fitting agree well with that by the vertical static load of a single pile. So it is likely to enhance the accuracy and reliability of high strain test results by optimizing the pile and soil parameters.(2)When it is not allowed for in-situ static load test, high strain tests can be used as a supplement means to the load test for pile foundation.(3)When we get more reliable high strain test results, some adjustments can be made for the design scheme according to standard method based on rigorous calculation.
2012, 20(6): 1064-1070.
The physical and mechanical properties of loess at different regions in China have significant differences. Based on the data from ordinary triaxial test of Yan'an Q2 loess under different confining pressures and misture contents, this paper establishes the constitutive model of triaxial statistical damage for Yan'an Q2 loess by introducing rock statistical damage theory in the damage constitutive model of Yan'an Q2 loess. In the meantime, the paper considers the effect of damage threshold on Yan'an Q2 loess damage variable as well. In addition, the parameters in damage constructive equation are calculated by linear regression on the test results. The experiment and analysis present that in semilogarithmic coordinates, the initial damage point is the peak inflection point of triaxial stress-strain curve of Yan'an Q2 loess. The corresponding value of damage point is also the damage stress threshold. The Yan'an Q2 loess cannot damage and the stress and strain can be in linear elastic relationship when applied stress is less than damage threshold. Conversely, Yan'an Q2 loess can begin to damage. And the damage of Yan'an Q2 loess can enlarge with the increase of applied stress. Finally, statistical damage curve shows good agreements with test curve. This paper indicates that with the consideration of damage threshold, loess statistical damage constitutive model can better reflect the characteristics of Yan'an Q2 loess deformation and failure, with a reference for geotechnical engineering design in the loess plateau.
The physical and mechanical properties of loess at different regions in China have significant differences. Based on the data from ordinary triaxial test of Yan'an Q2 loess under different confining pressures and misture contents, this paper establishes the constitutive model of triaxial statistical damage for Yan'an Q2 loess by introducing rock statistical damage theory in the damage constitutive model of Yan'an Q2 loess. In the meantime, the paper considers the effect of damage threshold on Yan'an Q2 loess damage variable as well. In addition, the parameters in damage constructive equation are calculated by linear regression on the test results. The experiment and analysis present that in semilogarithmic coordinates, the initial damage point is the peak inflection point of triaxial stress-strain curve of Yan'an Q2 loess. The corresponding value of damage point is also the damage stress threshold. The Yan'an Q2 loess cannot damage and the stress and strain can be in linear elastic relationship when applied stress is less than damage threshold. Conversely, Yan'an Q2 loess can begin to damage. And the damage of Yan'an Q2 loess can enlarge with the increase of applied stress. Finally, statistical damage curve shows good agreements with test curve. This paper indicates that with the consideration of damage threshold, loess statistical damage constitutive model can better reflect the characteristics of Yan'an Q2 loess deformation and failure, with a reference for geotechnical engineering design in the loess plateau.
2012, 20(6): 1071-1077.
Chemical improvement of loess is an important topic in the area of loess foundation engineering treatment. It has important theoretical value and good applied prospects in loess foundation treatment, loess hazard and control. Loess as filling material of roadbed, channel and slope engineering is frequently encountered in northwest and north of China. Loess and remolded loess possess many distinctive physical-mechanical properties that can lead to the improvement and development of various ground improvement techniques such as soil solidification and reinforcement. Loess must be improved. Otherwise it cannot be applied to engineering construction. In order to study the effects of loess solidified by chemical materials, a series of indoor experiments are conducted to analyze the properties of the raw loess of Taiyuan before and after treated by mixed with varying contents of new polymer-soil stabilizer(SH) and cement. The results of compressive strength, direct shear and permeability tests show that the engineering properties of the loess are improved by SH or cement. The strength and impermeability of solidified loess with chemical solidified materials are better than the raw loess. The properties of strength increased with the content of solidified agent, its density and curing time, but the permeability coefficients decreased. The suitable content of mixed SH or cement is about 10%.SH is a new polymer-stabilized agent of water-solubility. Because of its less dosage, cheap price, high strength, low permeability and no disintegrating effect on loess, SH is better than cement. SH can be taken into consideration according to practical situation.
Chemical improvement of loess is an important topic in the area of loess foundation engineering treatment. It has important theoretical value and good applied prospects in loess foundation treatment, loess hazard and control. Loess as filling material of roadbed, channel and slope engineering is frequently encountered in northwest and north of China. Loess and remolded loess possess many distinctive physical-mechanical properties that can lead to the improvement and development of various ground improvement techniques such as soil solidification and reinforcement. Loess must be improved. Otherwise it cannot be applied to engineering construction. In order to study the effects of loess solidified by chemical materials, a series of indoor experiments are conducted to analyze the properties of the raw loess of Taiyuan before and after treated by mixed with varying contents of new polymer-soil stabilizer(SH) and cement. The results of compressive strength, direct shear and permeability tests show that the engineering properties of the loess are improved by SH or cement. The strength and impermeability of solidified loess with chemical solidified materials are better than the raw loess. The properties of strength increased with the content of solidified agent, its density and curing time, but the permeability coefficients decreased. The suitable content of mixed SH or cement is about 10%.SH is a new polymer-stabilized agent of water-solubility. Because of its less dosage, cheap price, high strength, low permeability and no disintegrating effect on loess, SH is better than cement. SH can be taken into consideration according to practical situation.
2012, 20(6): 1078-1082.
Soluble carbonate rocks in karst or karst phenomena is a natural geological phenomenon. In South Southwest of China, the geological conditions of terrain are complex, and distribution of karst terrain is widely observed. It is difficulty to build highway road in these areas. The mode is approximately simplified by structural mechanics to quantitatively calculate the stability of the highway embankment in karst areas. It gives the relationship of stability between cave roof, span, and cover depth. It is a certain model. It has some reference value for stability analysis and evaluation of highway embankment in the future.
Soluble carbonate rocks in karst or karst phenomena is a natural geological phenomenon. In South Southwest of China, the geological conditions of terrain are complex, and distribution of karst terrain is widely observed. It is difficulty to build highway road in these areas. The mode is approximately simplified by structural mechanics to quantitatively calculate the stability of the highway embankment in karst areas. It gives the relationship of stability between cave roof, span, and cover depth. It is a certain model. It has some reference value for stability analysis and evaluation of highway embankment in the future.
2012, 20(6): 1087-1095.
In October 2012,the 9th National Congress of Engineering Geology was held in Qingdao city, Shandong Province. This paper is based on its published papers, its academic presentations, and the knowledge of the engineering geology discipline development in China. It analyzed and summarized new tendency and new characteristics of the discipline. The science and technique and the practical requirements of engineering geology have been developed rapidly due to the fast development of national economy in recent years. The engineering geology has demonstrated the following features: (1)Research areas have extended from inland to ocean, from mountain to city. Marine engineering geology and urban geo-engineering environment geology will become the important research areas in future.(2)Research scales have extended gradually from the middle scale of engineering to the macro scale of the Earth, to the mesoscale of mineral particles and crystal particles, and even to the micro scale of molecular and atomic structures.(3)Detecting and test instruments for engineering geology are being developed domestically, which is a change from the past practice of importing instruments from overseas. Those with proprietary intellectual property rights will play a leading role in this field. In the end, the further efforts in engineering geology are pointed out.
In October 2012,the 9th National Congress of Engineering Geology was held in Qingdao city, Shandong Province. This paper is based on its published papers, its academic presentations, and the knowledge of the engineering geology discipline development in China. It analyzed and summarized new tendency and new characteristics of the discipline. The science and technique and the practical requirements of engineering geology have been developed rapidly due to the fast development of national economy in recent years. The engineering geology has demonstrated the following features: (1)Research areas have extended from inland to ocean, from mountain to city. Marine engineering geology and urban geo-engineering environment geology will become the important research areas in future.(2)Research scales have extended gradually from the middle scale of engineering to the macro scale of the Earth, to the mesoscale of mineral particles and crystal particles, and even to the micro scale of molecular and atomic structures.(3)Detecting and test instruments for engineering geology are being developed domestically, which is a change from the past practice of importing instruments from overseas. Those with proprietary intellectual property rights will play a leading role in this field. In the end, the further efforts in engineering geology are pointed out.
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