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Editor Work2003 Vol. 11, No. 1
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Abstract
The Baiyian landslides are located in the left bank of the western termination of the Three-Gorges Changjiang River. They are ancient landslides, old landslides, and young landslides formed by the strong incision of the river after the Chuan and Xia rivers joined up to form an unitfied Changjiang River. The bank-slopes composed of the Triassic mudstone and limestone have undergone a complex process,inclinding gradual unloading toppling collapse and sliding. It is clear that the stability of Baiyi an landslides is different, the ancient landslide to be stable, some parts of the old landslides are unstable due to the 145m～175m water level change of the Three-Gorges reservoir and the young landslides on the surface layer maybe unstable in sustaining rainstorm. Finally, the engineering suggestions of control on landslides are put forward in this paper.
The Baiyian landslides are located in the left bank of the western termination of the Three-Gorges Changjiang River. They are ancient landslides, old landslides, and young landslides formed by the strong incision of the river after the Chuan and Xia rivers joined up to form an unitfied Changjiang River. The bank-slopes composed of the Triassic mudstone and limestone have undergone a complex process,inclinding gradual unloading toppling collapse and sliding. It is clear that the stability of Baiyi an landslides is different, the ancient landslide to be stable, some parts of the old landslides are unstable due to the 145m～175m water level change of the Three-Gorges reservoir and the young landslides on the surface layer maybe unstable in sustaining rainstorm. Finally, the engineering suggestions of control on landslides are put forward in this paper.
2003, 11(1): 10-14.
The landslide triggered by engineering excavation depends not only by geological structure of the slope zone itself, but also by the processes between engineering excavation and geological structure effect, thus scientific engineering excavation can avert this type of geo-hazards. In the case study of landslide triggered by the excavation of deep trench for long-distance-gas pipe line on the down-dip slope of Cretaceous sandstone and the large-deformation of Lanzhou coal-gas pipe line caused by the excavation in west Lanzhou suburb on July 1st, 2001, the paper reveals the engineering excavation effect of interlayer shear zone and its control on slope stability, and then sums up the lesson in this type of geo-hazards. The authors proposed that, for prevention and reduction of this type of geo-hazards, the key measure is to firmly hold the idea that the engineering geological work must take overall situation into account and runs through the while process of the engineering project.
The landslide triggered by engineering excavation depends not only by geological structure of the slope zone itself, but also by the processes between engineering excavation and geological structure effect, thus scientific engineering excavation can avert this type of geo-hazards. In the case study of landslide triggered by the excavation of deep trench for long-distance-gas pipe line on the down-dip slope of Cretaceous sandstone and the large-deformation of Lanzhou coal-gas pipe line caused by the excavation in west Lanzhou suburb on July 1st, 2001, the paper reveals the engineering excavation effect of interlayer shear zone and its control on slope stability, and then sums up the lesson in this type of geo-hazards. The authors proposed that, for prevention and reduction of this type of geo-hazards, the key measure is to firmly hold the idea that the engineering geological work must take overall situation into account and runs through the while process of the engineering project.
2003, 11(1): 15-24.
Maoping landslide, the largest ancient landslide in Geheyan reservoir area, with a volume of 23.5 million m3, is located on the left bank of Qingjang River at 66 km upstream of Geheyan dam. Since the reservoir impounding started in April 1993, the slide was reactivated and slowly deformed. A village with 290 inhabitants had to be relocated. Since then the landslide has been in persistent deformation and upto now a maximum displacement of 2100 mm was recorded. On the basis of investigation of the slides constituent structure and formation mechanism, the paper deals with an in-depth study of the deformation characteristics and induced mechanism of the ladnslide through comprehensive analysis of the observation data in 10 or more years and a prediction is made on its development tendency.
Maoping landslide, the largest ancient landslide in Geheyan reservoir area, with a volume of 23.5 million m3, is located on the left bank of Qingjang River at 66 km upstream of Geheyan dam. Since the reservoir impounding started in April 1993, the slide was reactivated and slowly deformed. A village with 290 inhabitants had to be relocated. Since then the landslide has been in persistent deformation and upto now a maximum displacement of 2100 mm was recorded. On the basis of investigation of the slides constituent structure and formation mechanism, the paper deals with an in-depth study of the deformation characteristics and induced mechanism of the ladnslide through comprehensive analysis of the observation data in 10 or more years and a prediction is made on its development tendency.
2003, 11(1): 25-29.
Using a theory of critical slip field, which has been further modified to be adequate the sea embankment on soft soils, and considering the case history of a sea embankment landslide, a series of critical slip fields have been determined incombination with different c , and values of fills. The computed location of thecritical slip field is coincident nearly with the actual failure surface. Based on numerical modeling, the mechanism for landslide is analyzed an the stabilization measures are proposed. The result of analysis shows that the theory of critical slip field is rather effective for slope stability analysis and is deserved to be applied to practical problems such as those on soft soils.
Using a theory of critical slip field, which has been further modified to be adequate the sea embankment on soft soils, and considering the case history of a sea embankment landslide, a series of critical slip fields have been determined incombination with different c , and values of fills. The computed location of thecritical slip field is coincident nearly with the actual failure surface. Based on numerical modeling, the mechanism for landslide is analyzed an the stabilization measures are proposed. The result of analysis shows that the theory of critical slip field is rather effective for slope stability analysis and is deserved to be applied to practical problems such as those on soft soils.
2003, 11(1): 30-35.
Based on analyzing the property of suction between loess grains and the micro-process of loess subsidence, the relation between the motive force or resistance for sliding of microstructural units with water content and soil pressure are discussed. A theory of synthetic effect of microstructure and generalized suction on the formation of loess subsidence is put forward. The relations between loess subsidence with water content, pressure or depth of soils are theoratically analyzed, and the inherent regularity of loess subsidence is open out. The motive force and resistance for structural reconstruction are caused by effects of gradual loss of generalized suction in small pores and gradual increase of absorption suction in larger pores after soil absorbing water. In this paper, it is thought that the process of subsidence is just a dynamic course of counteaction process between microstructre reconstructing motive force and resistance. Lastly, the basic conditions for subsidence and primary factors affecting subsidence are talked over. This study should be of theoretical significance in quantitative research of loess subsidence.
Based on analyzing the property of suction between loess grains and the micro-process of loess subsidence, the relation between the motive force or resistance for sliding of microstructural units with water content and soil pressure are discussed. A theory of synthetic effect of microstructure and generalized suction on the formation of loess subsidence is put forward. The relations between loess subsidence with water content, pressure or depth of soils are theoratically analyzed, and the inherent regularity of loess subsidence is open out. The motive force and resistance for structural reconstruction are caused by effects of gradual loss of generalized suction in small pores and gradual increase of absorption suction in larger pores after soil absorbing water. In this paper, it is thought that the process of subsidence is just a dynamic course of counteaction process between microstructre reconstructing motive force and resistance. Lastly, the basic conditions for subsidence and primary factors affecting subsidence are talked over. This study should be of theoretical significance in quantitative research of loess subsidence.
2003, 11(1): 36-43.
Nansha Islands have abundant natural resources, but there exist complex geoengineering conditions and frequent geological hazards.It is important and essential to survey and evaluate the engineering geoenvironment. On the basis of analyzing geological structure, active faults, volcanoes and earthquakes, and conbinination with the hydrodynamic conditions, the engineering geoenvironment in Nansha area is divided into 5 zones: southern continental shelf zone, western continental slope zone, Nansha trough zone, Liyuetan shoal zone and coral reef zone and the engineering-geological features in each zone are also analyzed. A fuzzy mathematic method is used to qualitatively assess the engineering geoenvironmental on Nansha Islands. the evaluation result is more objective and reasonable and provides a basis support of engineering geoenvironment for planning of resource development in Nansha Islands area.
Nansha Islands have abundant natural resources, but there exist complex geoengineering conditions and frequent geological hazards.It is important and essential to survey and evaluate the engineering geoenvironment. On the basis of analyzing geological structure, active faults, volcanoes and earthquakes, and conbinination with the hydrodynamic conditions, the engineering geoenvironment in Nansha area is divided into 5 zones: southern continental shelf zone, western continental slope zone, Nansha trough zone, Liyuetan shoal zone and coral reef zone and the engineering-geological features in each zone are also analyzed. A fuzzy mathematic method is used to qualitatively assess the engineering geoenvironmental on Nansha Islands. the evaluation result is more objective and reasonable and provides a basis support of engineering geoenvironment for planning of resource development in Nansha Islands area.
2003, 11(1): 44-48.
Five indices of the medium conditions, occurence background, and engineering factors of rocks, such as uniaxial compressive strength, rock quality distribution, coal mass strength, groundwater status, and monthly advance of working face are used in establishing, the dynamical evaluation model of the roof stability with artificial neural network(ANN). The subzone of roof stability is forecasted from data of working face advance of 40m, 60m, 80m and 100m per month, respectively. The result of ANN analysis of 5 indeces shows the factors effecting on the roof stability in a sequence from high to low degree are rock quality distribution, groundwater status, rock uniaxial compressive strength, coal mass strength and face advance. The measures for controlling different types of roof stability are suggested pertinently according to above results.
Five indices of the medium conditions, occurence background, and engineering factors of rocks, such as uniaxial compressive strength, rock quality distribution, coal mass strength, groundwater status, and monthly advance of working face are used in establishing, the dynamical evaluation model of the roof stability with artificial neural network(ANN). The subzone of roof stability is forecasted from data of working face advance of 40m, 60m, 80m and 100m per month, respectively. The result of ANN analysis of 5 indeces shows the factors effecting on the roof stability in a sequence from high to low degree are rock quality distribution, groundwater status, rock uniaxial compressive strength, coal mass strength and face advance. The measures for controlling different types of roof stability are suggested pertinently according to above results.
2003, 11(1): 49-53.
With the development of economy in coastal areas of Southeast China, the problem of land lacking becomes prominent. A technique for land with dredge fill is a new way to solve the problem. In order to reduce time of consolidation of dredge fill, we made a sedimentation test of dredge fill and tried to find a method for consolidating the dredge fill while dredging. During the test it was found that the result of consolidation with mixed cement with lime is better than that only with cement. Comparing the engineering geological properties of soil samples and analyzing the structure of soil samples and other results of physical and chemical tests, we found the causes for different of consolidation results, so we can provide a more economical method to consolidate foundation of dredger fill.
With the development of economy in coastal areas of Southeast China, the problem of land lacking becomes prominent. A technique for land with dredge fill is a new way to solve the problem. In order to reduce time of consolidation of dredge fill, we made a sedimentation test of dredge fill and tried to find a method for consolidating the dredge fill while dredging. During the test it was found that the result of consolidation with mixed cement with lime is better than that only with cement. Comparing the engineering geological properties of soil samples and analyzing the structure of soil samples and other results of physical and chemical tests, we found the causes for different of consolidation results, so we can provide a more economical method to consolidate foundation of dredger fill.
2003, 11(1): 54-57.
The residual strength of soft clayey rocks is studied and analized in this paper, and the variatuion trend of the strength of these rocks is obtained by modeling the conditions for softening of the rocks due to long-term inundation, and the regularity of strength variation of these ricks is discussed.
The residual strength of soft clayey rocks is studied and analized in this paper, and the variatuion trend of the strength of these rocks is obtained by modeling the conditions for softening of the rocks due to long-term inundation, and the regularity of strength variation of these ricks is discussed.
2003, 11(1): 58-63.
High collapsibility of loess appears in sorth part of Ningxia. The research result show that the loess collapsibility is causted by pore microstructre, and close relation between granula metrical composition and cement types. Other factors affecting loess collapsibility are soil thickness permeability coefficient, and occurence depth. Other properties of loess are also explained herein. We obtain the detail information of the soil formed in different processes and environments. From these result we suggest a collapsibility mechnism of loess. Finaly some Measures to prevent and control loess deformation are discussed.
High collapsibility of loess appears in sorth part of Ningxia. The research result show that the loess collapsibility is causted by pore microstructre, and close relation between granula metrical composition and cement types. Other factors affecting loess collapsibility are soil thickness permeability coefficient, and occurence depth. Other properties of loess are also explained herein. We obtain the detail information of the soil formed in different processes and environments. From these result we suggest a collapsibility mechnism of loess. Finaly some Measures to prevent and control loess deformation are discussed.
2003, 11(1): 64-69.
The natural slope failures are often found after constructing mountain road due to cutting their foots. Taking the cut slope in Daganping as example, the Daganping clay was tested under the unloading stress-path on triaxial equipment forits, in order to quantify the parameters for stability analysis of the slope. A non-linear FEM for analysis of stability of the cut slope is established. The results provide a clear description of the extension of plastic zone in the slope during cutting and bracing. The location of slip surface is determined from the results by FEM. The variation of ground water table in the slope are monitored in field during seepage. The limit equilibrium method is used to calculate the safety factor of slope stability, and the stability is estimated from calculation results. According to the FEM results, the methods of slope treatment including a bracing system with retaining wall and a drainage system with a bunch of tree branches are presented. The observation shows that the result of the treatment is satisfactory in practice.
The natural slope failures are often found after constructing mountain road due to cutting their foots. Taking the cut slope in Daganping as example, the Daganping clay was tested under the unloading stress-path on triaxial equipment forits, in order to quantify the parameters for stability analysis of the slope. A non-linear FEM for analysis of stability of the cut slope is established. The results provide a clear description of the extension of plastic zone in the slope during cutting and bracing. The location of slip surface is determined from the results by FEM. The variation of ground water table in the slope are monitored in field during seepage. The limit equilibrium method is used to calculate the safety factor of slope stability, and the stability is estimated from calculation results. According to the FEM results, the methods of slope treatment including a bracing system with retaining wall and a drainage system with a bunch of tree branches are presented. The observation shows that the result of the treatment is satisfactory in practice.
2003, 11(1): 70-78.
Engineering-geological surveying and analysis Engineering-geological of Yingxian Wooden Tower foundation, made us to clarify the stration age and existence of fault. The engineering-physical properties and mechanical properties were determined by specimen analyses, standard penetration test, and static pressuer tests. Probing and getting the foundation structure and layering structure of the tower courtyard foundation were detected by tomography with surface electrode arrays.
Engineering-geological surveying and analysis Engineering-geological of Yingxian Wooden Tower foundation, made us to clarify the stration age and existence of fault. The engineering-physical properties and mechanical properties were determined by specimen analyses, standard penetration test, and static pressuer tests. Probing and getting the foundation structure and layering structure of the tower courtyard foundation were detected by tomography with surface electrode arrays.
2003, 11(1): 79-84.
Method of trigonometric series is one of methods widely used for syhthesizing artificial ground motion. However, the compution errors,which are similar to the classic baseline shift, are found in integrated acceleration time history. An analytic formula for calculating integrated velocity time history is deviated in detail, and compution errors are analyzed emphatically. The study proves that the strength envelope function will produce compution errors of integrated velocity time history, if there are non differentiable singular points in it. On this basis, a new modified method is put forward.
Method of trigonometric series is one of methods widely used for syhthesizing artificial ground motion. However, the compution errors,which are similar to the classic baseline shift, are found in integrated acceleration time history. An analytic formula for calculating integrated velocity time history is deviated in detail, and compution errors are analyzed emphatically. The study proves that the strength envelope function will produce compution errors of integrated velocity time history, if there are non differentiable singular points in it. On this basis, a new modified method is put forward.
2003, 11(1): 85-88.
In the Three-Gorges Reservoir area on Changjiang River, million people are mostly relocating from the previous sites backward to new sites, where geological conditions are complex, landslides and collapses were frequent. Thus, the geologic hazards could affect the safety of residents. Our government has paid great attention to the prevention and treatment of the geologic hazards in the reservoir area. After investigation and study for decades, at present stage an investment is made for large-scale prevention and treatment of geologic hazards. This paper deals with the characteristics of geologic hazards in the reservoir area, previous history of their prevention and controlling, the main issues in study at present stage and the main problems to be further studied.
In the Three-Gorges Reservoir area on Changjiang River, million people are mostly relocating from the previous sites backward to new sites, where geological conditions are complex, landslides and collapses were frequent. Thus, the geologic hazards could affect the safety of residents. Our government has paid great attention to the prevention and treatment of the geologic hazards in the reservoir area. After investigation and study for decades, at present stage an investment is made for large-scale prevention and treatment of geologic hazards. This paper deals with the characteristics of geologic hazards in the reservoir area, previous history of their prevention and controlling, the main issues in study at present stage and the main problems to be further studied.
2003, 11(1): 89-99.
A super high reinforced retaining wall 57 m high is analyzed in combination with waste soil rock disposal and enlargement of land use by filling in the Wushan county, an typical site of relocation of the Three Gorges. The FLAC is applied to simulating stress state, deformation and failure process. And the pressure distribution at the wall back, subsidence of plate and filling, and fabric belt tense force is studied by using centrifuge modeling, a model of three-step wall is setup. A complete program is suggested to remedy the damage wall.
A super high reinforced retaining wall 57 m high is analyzed in combination with waste soil rock disposal and enlargement of land use by filling in the Wushan county, an typical site of relocation of the Three Gorges. The FLAC is applied to simulating stress state, deformation and failure process. And the pressure distribution at the wall back, subsidence of plate and filling, and fabric belt tense force is studied by using centrifuge modeling, a model of three-step wall is setup. A complete program is suggested to remedy the damage wall.
2003, 11(1): 100-104.
The Sichuan-Tibet Highway was frequently destroyed and obstructed by geological hazards, such as debris flew, landslides, debacles, avalanche, etc, and due to for weak protection. Great changes have taken place after large investment for treating the hazards and recontruction the way, but there is no way to feasible treat some large-scale and complex hazards in the special environment. After investigating on the characteristics of the geological environment and hazards along the highway and summing up experience of hazards controlling and rebuilding for last years, the anthor in this paper gives some suggestions of approach, goal, and principles.
The Sichuan-Tibet Highway was frequently destroyed and obstructed by geological hazards, such as debris flew, landslides, debacles, avalanche, etc, and due to for weak protection. Great changes have taken place after large investment for treating the hazards and recontruction the way, but there is no way to feasible treat some large-scale and complex hazards in the special environment. After investigating on the characteristics of the geological environment and hazards along the highway and summing up experience of hazards controlling and rebuilding for last years, the anthor in this paper gives some suggestions of approach, goal, and principles.
2003, 11(1): 105-110.
The main engineering geological problems in Northwest China are summarized from the data given in Proceedings of 2002 Forum of Engineering Geological Problems in Northwest China and the topic lectures. The main engineering-geological problems include regional stability, active faults, specific rocks and soils, high slopes, and excavation of long and deep tunnels.
The main engineering geological problems in Northwest China are summarized from the data given in Proceedings of 2002 Forum of Engineering Geological Problems in Northwest China and the topic lectures. The main engineering-geological problems include regional stability, active faults, specific rocks and soils, high slopes, and excavation of long and deep tunnels.
2003, 11(1): 111-112.
The advantages of Hong Kong as a largest containers seaport in the world are elaborated and some matters needing attention to keep these advantages are also suggested in the paper.
The advantages of Hong Kong as a largest containers seaport in the world are elaborated and some matters needing attention to keep these advantages are also suggested in the paper.
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