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Editor Work2010 Vol. 18, No. 2
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2010, 18(2)
In order to analyze the intensity and influence of landslides triggered by the great Wenchuan earthquake,a central idea in this paper is to focus on the first 3 extreme landslide events among the first 10 landslides with the largest volume,the longest sliding runout,the most serious hazard and the largest landslidedammed lake. The followings are revealed: (1)the extreme landslides are mainly distributed along the Longmenshan central fault and in the areas with high intensity of Ⅹ-Ⅺ; the strong vibration force,the main propagation direction of earthquake and the NE expansion of seismic fault are the major reasons for the initiation of extreme landslide events; (2)generally,the first 10 landslides both have the largest volume and the longest sliding long runout,among them,the Daguangbao landslide,located at Anxian county,Mianzhu city,is the first one,with the volume of 742 million m3 and the sliding long runout of 35 km; the second one is the Wenjiagou landslide in Qingping county,Mianzhu city,with the volume of 150 million m3 and the sliding runout of 42 km. The above two landslides are all rare rapid and long runout landslides with high energy in the world; (3)the first 10 catastrophic landslides totally caused 3751 deaths,and over 100 deaths are due to individual event,with the maximum of 1600; (4)the first 10 landslidedammed lakes with potential risk had threatened the lives safety for hundreds of thousands of people; among them,the Tangjiashan dammed lake is the largest one,which had imperiled 03 million peoples life of Mianyang city; fortunately,timely measures such as artificial excavation had been taken for removing of potential risk．
In order to analyze the intensity and influence of landslides triggered by the great Wenchuan earthquake,a central idea in this paper is to focus on the first 3 extreme landslide events among the first 10 landslides with the largest volume,the longest sliding runout,the most serious hazard and the largest landslidedammed lake. The followings are revealed: (1)the extreme landslides are mainly distributed along the Longmenshan central fault and in the areas with high intensity of Ⅹ-Ⅺ; the strong vibration force,the main propagation direction of earthquake and the NE expansion of seismic fault are the major reasons for the initiation of extreme landslide events; (2)generally,the first 10 landslides both have the largest volume and the longest sliding long runout,among them,the Daguangbao landslide,located at Anxian county,Mianzhu city,is the first one,with the volume of 742 million m3 and the sliding long runout of 35 km; the second one is the Wenjiagou landslide in Qingping county,Mianzhu city,with the volume of 150 million m3 and the sliding runout of 42 km. The above two landslides are all rare rapid and long runout landslides with high energy in the world; (3)the first 10 catastrophic landslides totally caused 3751 deaths,and over 100 deaths are due to individual event,with the maximum of 1600; (4)the first 10 landslidedammed lakes with potential risk had threatened the lives safety for hundreds of thousands of people; among them,the Tangjiashan dammed lake is the largest one,which had imperiled 03 million peoples life of Mianyang city; fortunately,timely measures such as artificial excavation had been taken for removing of potential risk．
The highway from Yingxiu town to Wolong town is the nearest highway to the epicenter of Wenchuan Earthquake. The geohazards long and damage to the highway are the most serious. This paper presents a comprehensive investigation of the geological hazards due to the earthquake along the highway.Based on their characteristics,the geohazards are divided into four types.They are instability of highly weathered rockmass and soil on the upper part of the slopes,instability of rock mass cut by geological structural surface,landslides and debris flows. It analyzes the developmental law of geohazards along the highway. The geohazards show significant deviations between the two sides of the back range faults at the Longmen Mountain fault zone. The reasons are the seismic isolation effect of the deep fracture,scaling effect of the landforms,and geologic structures. The slope steepness and position of seismic instabilities have been studied via the analysis of 134 geological sections. The results show that the slope steepness of seismic instabilities are distributed within the range of from 33 to 84,mainly from 40 to 65. So,it can be concluded that the geohazards caused by the earthquake mainly took place on the road slopes steeper than 40. The failure zones caused by seismic force mainly distributed on the upside of the road slopes. The instability positions are mainly upon the parts with slope gradients more than 040.For the study of slope dynamic instability,four geologic structure models are put forward.They are rocksoil and strong weathered rock slopes,rock slopes with outward inclined structural plane,massive structure rock slopes and crushedrock soil slopes. It analyzes the type and characteristics of eachof the four geologic structure models.
The highway from Yingxiu town to Wolong town is the nearest highway to the epicenter of Wenchuan Earthquake. The geohazards long and damage to the highway are the most serious. This paper presents a comprehensive investigation of the geological hazards due to the earthquake along the highway.Based on their characteristics,the geohazards are divided into four types.They are instability of highly weathered rockmass and soil on the upper part of the slopes,instability of rock mass cut by geological structural surface,landslides and debris flows. It analyzes the developmental law of geohazards along the highway. The geohazards show significant deviations between the two sides of the back range faults at the Longmen Mountain fault zone. The reasons are the seismic isolation effect of the deep fracture,scaling effect of the landforms,and geologic structures. The slope steepness and position of seismic instabilities have been studied via the analysis of 134 geological sections. The results show that the slope steepness of seismic instabilities are distributed within the range of from 33 to 84,mainly from 40 to 65. So,it can be concluded that the geohazards caused by the earthquake mainly took place on the road slopes steeper than 40. The failure zones caused by seismic force mainly distributed on the upside of the road slopes. The instability positions are mainly upon the parts with slope gradients more than 040.For the study of slope dynamic instability,four geologic structure models are put forward.They are rocksoil and strong weathered rock slopes,rock slopes with outward inclined structural plane,massive structure rock slopes and crushedrock soil slopes. It analyzes the type and characteristics of eachof the four geologic structure models.
〖JP2〗On 12th May, 2008,the M80 Wenchuan Earthquake induced a rockslidesturzstrom at Wenjiagou valley in Qingping County,Mianzhu City,Sichuan Province,P. R. China. The field survey indicated that the height of rockslide source area is 455 m,the thickness is 20～30 m,and the rockslide mass that the initial volume is 2750107 m3 slipped. The rockslidemass slipped among the bedding surface,and the total motion distance is 4022 m in horizontal,and 1443 m in vertical. The rockslide mass left 5107m3 debris in the valley. The distance between rockslide source area and seismogenic fault named YingxiuBeichuan Fault,is only 36 km. The rockslide is located in the faults footwall. The earthquake intensity of rockslide source area is XI. The disaster event formed a complete chain of earthquakeinduced geohazards and killed 48 local people. The preliminary analysis showed that rockslide startup speed was very high. The process and position of the transformation of rockslide to sturzstrom is clear. The accompanied air cushion effect and front airblast effect,the sturzstrommass motion processing were complex. In this event,it is authors opinion that long duration strong earthquake is the immediate cause of very high startup speed of slipping mass. And that the mass crashed into a hill in the valley caused rockslide mass transformed into sturzstrom.
〖JP2〗On 12th May, 2008,the M80 Wenchuan Earthquake induced a rockslidesturzstrom at Wenjiagou valley in Qingping County,Mianzhu City,Sichuan Province,P. R. China. The field survey indicated that the height of rockslide source area is 455 m,the thickness is 20～30 m,and the rockslide mass that the initial volume is 2750107 m3 slipped. The rockslidemass slipped among the bedding surface,and the total motion distance is 4022 m in horizontal,and 1443 m in vertical. The rockslide mass left 5107m3 debris in the valley. The distance between rockslide source area and seismogenic fault named YingxiuBeichuan Fault,is only 36 km. The rockslide is located in the faults footwall. The earthquake intensity of rockslide source area is XI. The disaster event formed a complete chain of earthquakeinduced geohazards and killed 48 local people. The preliminary analysis showed that rockslide startup speed was very high. The process and position of the transformation of rockslide to sturzstrom is clear. The accompanied air cushion effect and front airblast effect,the sturzstrommass motion processing were complex. In this event,it is authors opinion that long duration strong earthquake is the immediate cause of very high startup speed of slipping mass. And that the mass crashed into a hill in the valley caused rockslide mass transformed into sturzstrom.
A landslide forecast model is mainly used to forecast occurrence time of a landslide. But for model researchers and decisionmakers,an important issue is the model forecast effect. The author proposed a fitting effect index(including posterior index,model fitting efficiency index and RMS error),an experiment forecast effect index(experiment forecast index and related coefficient index),and an establishment quality testing model of landslide forecast. Using gray GM(1, 1)mathematical model,the three exponential smoothing model and time series model fit and experiment forecast the monitoring data of Lianziya dangerous rock body. Prediction results showed that integrated indicators GM(1, 1)is the highest value among the three kinds models. So the landslide using GM(1, 1)to predict is recommended. Through a comprehensive analysis of the model,the author not only analyzes the simulation results,but also a direct comparison fitting results between the models,and provides the adequate basis for the establishment a good model. These show that landslide prediction model for quality testing is an effective and practical method．
A landslide forecast model is mainly used to forecast occurrence time of a landslide. But for model researchers and decisionmakers,an important issue is the model forecast effect. The author proposed a fitting effect index(including posterior index,model fitting efficiency index and RMS error),an experiment forecast effect index(experiment forecast index and related coefficient index),and an establishment quality testing model of landslide forecast. Using gray GM(1, 1)mathematical model,the three exponential smoothing model and time series model fit and experiment forecast the monitoring data of Lianziya dangerous rock body. Prediction results showed that integrated indicators GM(1, 1)is the highest value among the three kinds models. So the landslide using GM(1, 1)to predict is recommended. Through a comprehensive analysis of the model,the author not only analyzes the simulation results,but also a direct comparison fitting results between the models,and provides the adequate basis for the establishment a good model. These show that landslide prediction model for quality testing is an effective and practical method．
Estimating the activity of faults is not only the basis to predict earthquake and to reduce geological disasters,but also is the core issue of urban engineering design. Based on fuzzy and grey characteristics in assessment of fault activity,a fuzzy-grey model of assessment is proposed in the frame work of fuzzy mathematical theory associated with grey system. This paper establishes the fuzzy integrate assessment model and decides a trapezoidal membership function using the fuzzy mathematics. The power of each factor is decided with the principle that the relative value of activity symbol is larger,the power is greater. This model is applied to the assessment of fault activity in Xian area. The result shows that the activity of LintongChangan fault is the strongest and that of YuxiaTieluzi fault is the weakest.
Estimating the activity of faults is not only the basis to predict earthquake and to reduce geological disasters,but also is the core issue of urban engineering design. Based on fuzzy and grey characteristics in assessment of fault activity,a fuzzy-grey model of assessment is proposed in the frame work of fuzzy mathematical theory associated with grey system. This paper establishes the fuzzy integrate assessment model and decides a trapezoidal membership function using the fuzzy mathematics. The power of each factor is decided with the principle that the relative value of activity symbol is larger,the power is greater. This model is applied to the assessment of fault activity in Xian area. The result shows that the activity of LintongChangan fault is the strongest and that of YuxiaTieluzi fault is the weakest.
Based on the the brittle failure theory of multiple locked patches along a seismogenic fault presented recently by us,the possibility of that the strong earthquake will occur in DatongYanggaoZhangbei area is analysed. It is shown that a destructive earthquake with a magnitude of more than 65 in this area will possibly occur.
Based on the the brittle failure theory of multiple locked patches along a seismogenic fault presented recently by us,the possibility of that the strong earthquake will occur in DatongYanggaoZhangbei area is analysed. It is shown that a destructive earthquake with a magnitude of more than 65 in this area will possibly occur.
2010, 18(2)
There is a large number of geological disasters along the Bomi section of SichuanTibet Highway, in southeast Tibet region. The main source material of the geological disasters is loose deposits which are made by rock weathering. The topography and geological conditions are in favor of rock weathering, because of the uplift of QinghaiTibet Plateau. The difference in temperature change is another important factor for rock weathering. Compare with field observation and experiment of cylindrical rock samples, freezethaw plays a major role in the weathering of rocks in the region.
There is a large number of geological disasters along the Bomi section of SichuanTibet Highway, in southeast Tibet region. The main source material of the geological disasters is loose deposits which are made by rock weathering. The topography and geological conditions are in favor of rock weathering, because of the uplift of QinghaiTibet Plateau. The difference in temperature change is another important factor for rock weathering. Compare with field observation and experiment of cylindrical rock samples, freezethaw plays a major role in the weathering of rocks in the region.
2010, 18(2)
The Jingshiyu is located at a glacis in Taishan Mountain in Shandong Province,where a total of 2799 Chinese characters for the Buddhisms book entitled The Vajracchedika Prajnaparamita Sutra were written by caving on biotite quartzdiorite. Because of the long term natural weathering,freezing and scour,there are only 1069 characters left.The view of the site and measurement shows that the multilayer sheetlike peeling on the diorite glacis is one of the main causes which has been destroying the cut in rock Chinese characters. Sheetlike exfoliation has reached the 5th layers. Each layer has a thickness of 05～08 cm. The geometric characteristics of multilayer sheetlike exfoliation is examined. A weathering model is put forward for the multilayer sheetlike exfoliation at the site. The model includes the process that the rock bulged firstly,then flaked off directly,or flaked off after the sheetlike due to bulging spreading through the rock.
The Jingshiyu is located at a glacis in Taishan Mountain in Shandong Province,where a total of 2799 Chinese characters for the Buddhisms book entitled The Vajracchedika Prajnaparamita Sutra were written by caving on biotite quartzdiorite. Because of the long term natural weathering,freezing and scour,there are only 1069 characters left.The view of the site and measurement shows that the multilayer sheetlike peeling on the diorite glacis is one of the main causes which has been destroying the cut in rock Chinese characters. Sheetlike exfoliation has reached the 5th layers. Each layer has a thickness of 05～08 cm. The geometric characteristics of multilayer sheetlike exfoliation is examined. A weathering model is put forward for the multilayer sheetlike exfoliation at the site. The model includes the process that the rock bulged firstly,then flaked off directly,or flaked off after the sheetlike due to bulging spreading through the rock.
Injecting the CO2 into deep underground formations with the appropriate closure for isolated storage has been recognized as a possible effective technical approach in reducing CO2 emissions. The sand lens reservoir trap has a good structure and reservoir properties for the storage. The sand lens reservoirs with depletion of oil and gas are better CO2 geological storage boxes. Based on the pennyshaped crack model and the hydraulic fracturing principle，the sand lens reservoir of horizontal occurrence is simplified as a type-I pennyshaped crack of the cap rock. It is due to the fact that the thickness and horizontal distribution length of the reservoir are much smaller than the global cap rock scale. The cap rock fracture resistance of the storage box is analyzed from the view of rock fracture mechanics. The stress intensity factor of the pennyshaped crack tip (corresponding to the tip of sand lens reservoir) for the cap rock is calculated by the superposition principle. And then the fracture mechanics criteria (K=KIC) and the critical effective compressive stress criteria (P=PC) are concluded as the basic principle to evaluate the fracture resistance of the cap rock of the sand lens reservoir. The findings in the paper can provide a new way for the evaluation of cap rock fracture resistance capability of sand lens reservoir.
Injecting the CO2 into deep underground formations with the appropriate closure for isolated storage has been recognized as a possible effective technical approach in reducing CO2 emissions. The sand lens reservoir trap has a good structure and reservoir properties for the storage. The sand lens reservoirs with depletion of oil and gas are better CO2 geological storage boxes. Based on the pennyshaped crack model and the hydraulic fracturing principle，the sand lens reservoir of horizontal occurrence is simplified as a type-I pennyshaped crack of the cap rock. It is due to the fact that the thickness and horizontal distribution length of the reservoir are much smaller than the global cap rock scale. The cap rock fracture resistance of the storage box is analyzed from the view of rock fracture mechanics. The stress intensity factor of the pennyshaped crack tip (corresponding to the tip of sand lens reservoir) for the cap rock is calculated by the superposition principle. And then the fracture mechanics criteria (K=KIC) and the critical effective compressive stress criteria (P=PC) are concluded as the basic principle to evaluate the fracture resistance of the cap rock of the sand lens reservoir. The findings in the paper can provide a new way for the evaluation of cap rock fracture resistance capability of sand lens reservoir.
2010, 18(2)
The research of angle by shear failure is a hot topic and key point in engineering geology, and the conventional analytic solutions are MohrCoulomb solution and Roscoe solution. Consider the fact that the macrofailure is controlled by the distribution probability of those microfailures in samples, A failure probability model is introduced to analyze the rock and soil shearing failure angle, and then a Mohr circle of failure probability is given out on the base of a found that the principal axis of failure probability is the equal of the principal stress axis. Moreover, an analyses about the relation between microfailure probability and MohrCoulomb failure criterion is carried out, and Its found that MohrCoulomb criterion is a statistical result of large number microfailures in the failure progress and the Weibull model is only a special case of the distribution probability of failures, and so the failure model based on probability can accord with the failure criterions admirably．
The research of angle by shear failure is a hot topic and key point in engineering geology, and the conventional analytic solutions are MohrCoulomb solution and Roscoe solution. Consider the fact that the macrofailure is controlled by the distribution probability of those microfailures in samples, A failure probability model is introduced to analyze the rock and soil shearing failure angle, and then a Mohr circle of failure probability is given out on the base of a found that the principal axis of failure probability is the equal of the principal stress axis. Moreover, an analyses about the relation between microfailure probability and MohrCoulomb failure criterion is carried out, and Its found that MohrCoulomb criterion is a statistical result of large number microfailures in the failure progress and the Weibull model is only a special case of the distribution probability of failures, and so the failure model based on probability can accord with the failure criterions admirably．
2010, 18(2)
The deformation modulus(E),cohesion(c)and internal friction angle()are three basic mechanical parameters in the process of rock creep. They can gradually degrade with time and stress. This paper improves the present creep apparatus and develops a new manmade fivejointed uniaxial creep apparatus. The new apparatus can test five samples simultaneously under the different conditions for their mechanical parameters(E,c,and ). The degrading regularities of above three parameters of mudstone collected from Qinyuan coal mine plant in Baoji Shanxi are investigated in the process of creep with this new creep apparatus. The results show that the dependent variable values of E,c, and are degraded exponentially with the viscoplastic strain, as the independent variable. The failure values of E,c and are calculated. The paper analyzes the relationship of E,c, and with the viscoplastic strain. Three coupling functional equations are obtained for indicating the influence of E,c, and on the stress()and time(t), respectively. This paper lays a foundation for further establishment of unsteady mudstone constitutive model．
The deformation modulus(E),cohesion(c)and internal friction angle()are three basic mechanical parameters in the process of rock creep. They can gradually degrade with time and stress. This paper improves the present creep apparatus and develops a new manmade fivejointed uniaxial creep apparatus. The new apparatus can test five samples simultaneously under the different conditions for their mechanical parameters(E,c,and ). The degrading regularities of above three parameters of mudstone collected from Qinyuan coal mine plant in Baoji Shanxi are investigated in the process of creep with this new creep apparatus. The results show that the dependent variable values of E,c, and are degraded exponentially with the viscoplastic strain, as the independent variable. The failure values of E,c and are calculated. The paper analyzes the relationship of E,c, and with the viscoplastic strain. Three coupling functional equations are obtained for indicating the influence of E,c, and on the stress()and time(t), respectively. This paper lays a foundation for further establishment of unsteady mudstone constitutive model．
The maximum and minimum principles in the slope stability analysis,can be used to test the accuracy of the stability analysis model,and obtain the related condition used in improving the model. This paper uses the Simplified Threedimensional Sarma Method. It analyzes the variation of the stability factor caused by the direction of shearing force on the sliding surface .The results show that no matter what the distribution of the direction,when it changes,the corresponding stability factors has a great value. This just proves that the maximum principle in threedimensional slope stability analysis is applicable. At the same time,on the base of a rigorous determining method for the twodimensional potential sliding surface of slope,this paper builds an algorithm for determining the threedimensional potential sliding surface,and analyzes the effect of the parameters in the object function on the stability factor through the case in ZhangXings paper. The results show that twodimensional determining method is feasible,and it also proves that the minimum principle in the twodimensional slope stability analysis is met. But in the threedimensional slope stability,the results have some difference with the demand of the minimum principle for the threedimensional limit equilibrium method not taking into account the boundary conditions of threedimensional slope．
The maximum and minimum principles in the slope stability analysis,can be used to test the accuracy of the stability analysis model,and obtain the related condition used in improving the model. This paper uses the Simplified Threedimensional Sarma Method. It analyzes the variation of the stability factor caused by the direction of shearing force on the sliding surface .The results show that no matter what the distribution of the direction,when it changes,the corresponding stability factors has a great value. This just proves that the maximum principle in threedimensional slope stability analysis is applicable. At the same time,on the base of a rigorous determining method for the twodimensional potential sliding surface of slope,this paper builds an algorithm for determining the threedimensional potential sliding surface,and analyzes the effect of the parameters in the object function on the stability factor through the case in ZhangXings paper. The results show that twodimensional determining method is feasible,and it also proves that the minimum principle in the twodimensional slope stability analysis is met. But in the threedimensional slope stability,the results have some difference with the demand of the minimum principle for the threedimensional limit equilibrium method not taking into account the boundary conditions of threedimensional slope．
2010, 18(2)
The calculation of anchor cable antislide pile has not considered the interaction between the pile and the landside by the traditional methods. It only considers the pile above the slidesurface as static structure or finite statically indeterminate structure. Based on elastic foundation beam theory and considering deformation compatibility of the anchor cable and pile,this paper applies the initial parameter method to the calculation of anchor cable antislide pile. By selecting reasonable initial parameters as the unknown variable,this paper has deduced the calculation steps of the pile,including the tension force of anchor cable and internal forces of the pile. Applying this method to the treatment of bedding landslide controlling engineering in one project and comparing with the traditional method,this new method is shown to be safer and agrees well with the results using the traditional method．
The calculation of anchor cable antislide pile has not considered the interaction between the pile and the landside by the traditional methods. It only considers the pile above the slidesurface as static structure or finite statically indeterminate structure. Based on elastic foundation beam theory and considering deformation compatibility of the anchor cable and pile,this paper applies the initial parameter method to the calculation of anchor cable antislide pile. By selecting reasonable initial parameters as the unknown variable,this paper has deduced the calculation steps of the pile,including the tension force of anchor cable and internal forces of the pile. Applying this method to the treatment of bedding landslide controlling engineering in one project and comparing with the traditional method,this new method is shown to be safer and agrees well with the results using the traditional method．
Quantification of hydraulic conductivity and principal hydraulic directions of fractured rock mass is very important for its permeability. The hydraulic property of rock mass around geological repository of highlevel radioactive waste directly determines its safety in operation. The permeability property of rock mass around the 3# borehole in Beishan Area,Gansu Province is analyzed using the discrete fracture network model. The fracture transmissivity of the fluid flow model is calibrated via simulating the packer test process conducted in the depth range 1715～178m of the 3# borehole. The REV(Representative Element Volume)size and principal hydraulic conductivity of the rock mass near the 3# borehole are determined via performing the flow calculations based on the tranmissivity calibrated discrete fracture network model. It is found that the results are compared quite well with those obtained through the radial flow continuum porous media model．
Quantification of hydraulic conductivity and principal hydraulic directions of fractured rock mass is very important for its permeability. The hydraulic property of rock mass around geological repository of highlevel radioactive waste directly determines its safety in operation. The permeability property of rock mass around the 3# borehole in Beishan Area,Gansu Province is analyzed using the discrete fracture network model. The fracture transmissivity of the fluid flow model is calibrated via simulating the packer test process conducted in the depth range 1715～178m of the 3# borehole. The REV(Representative Element Volume)size and principal hydraulic conductivity of the rock mass near the 3# borehole are determined via performing the flow calculations based on the tranmissivity calibrated discrete fracture network model. It is found that the results are compared quite well with those obtained through the radial flow continuum porous media model．
The proposed ChinaRussia Crude Oil Pipeline runs through the permafrost area for about 500 km,across mountains,forests and wetlands with complicated frozenground engineering geological conditions. The maximum allowable thaw settlement of pipeline foundation soils is chosen as the assessment criterion. Using the meaning annual ground temperature and ice content of permafrost as the assessment indices,the permafrost along the pipeline route was classified into four types(according to10 and20℃): thermallystable permafrost and transitory cold permafrost,thawunstable warm permafrost（-10～-20℃）and extremely unstable warm permafrost（-10℃）. The recommended construction modes include conventional burial,insulated burial,drainage control,refill with nonfrostsusceptilble and/or thawstable soils,elevation,and even above ground bent/dike with or without drainage control. Using this assessment system,about 430km of permafrost of the pipeline route has been evaluated in detail. The assessment system is simple in criteria,and has resulted in appropriate and practical products.
The proposed ChinaRussia Crude Oil Pipeline runs through the permafrost area for about 500 km,across mountains,forests and wetlands with complicated frozenground engineering geological conditions. The maximum allowable thaw settlement of pipeline foundation soils is chosen as the assessment criterion. Using the meaning annual ground temperature and ice content of permafrost as the assessment indices,the permafrost along the pipeline route was classified into four types(according to10 and20℃): thermallystable permafrost and transitory cold permafrost,thawunstable warm permafrost（-10～-20℃）and extremely unstable warm permafrost（-10℃）. The recommended construction modes include conventional burial,insulated burial,drainage control,refill with nonfrostsusceptilble and/or thawstable soils,elevation,and even above ground bent/dike with or without drainage control. Using this assessment system,about 430km of permafrost of the pipeline route has been evaluated in detail. The assessment system is simple in criteria,and has resulted in appropriate and practical products.
2010, 18(2)
The construction of the underground petroleum and gas storage caverns in rock salt has become the direction of the energy reserve development. However,the study on the subsidence in the region of underground storage caverns is still in the state of exploration. Disasters induced by the subsidence happened from time to time. So it is necessary to investigate the subsidence in the region of underground storage caverns in rock salt.The investigation will provide reliable principles for the design and construction. This paper reports the authors literature reviews on the processes and the results in forecast of the subsidence in the region of underground storage caverns obtained by scholars in China and aboard. Three aspects are summarized as follows: 1)insitu monitoring: France,German,and American have established the insitu monitoring net successively,and got a large number of monitoring data; 2)theoretical calculation: the scholars in China introduced the random medium theory to the forecast of subsidence induced by the water mining in rock salt in the late 20th century,which provided a new theoretic basis for the forecast of the subsidence in the region of underground storages; 3)numerical simulation: the scholars in Europe made use of FLAC2D program to simulate the ground stability in the region of the storages in rock salt,and the scholar in China made use of the forecasting model established on the basis of new probability integral 3D model to simulate the subsidence successfully. Besides,in order to control the ground deformation in the region of storages effectively,the pillar supported mining methods have been applied extensively in the construction of underground storages in rock salt in some foreign countries. At last,this paper puts forward that further studies will focuses on the time dependent ground deformation,revise the theoretic model properly,and improve the parameter choosing method with considering the in situ monitoring data. Consequently,it is expected to get more reliable and veracious forecasting result．
The construction of the underground petroleum and gas storage caverns in rock salt has become the direction of the energy reserve development. However,the study on the subsidence in the region of underground storage caverns is still in the state of exploration. Disasters induced by the subsidence happened from time to time. So it is necessary to investigate the subsidence in the region of underground storage caverns in rock salt.The investigation will provide reliable principles for the design and construction. This paper reports the authors literature reviews on the processes and the results in forecast of the subsidence in the region of underground storage caverns obtained by scholars in China and aboard. Three aspects are summarized as follows: 1)insitu monitoring: France,German,and American have established the insitu monitoring net successively,and got a large number of monitoring data; 2)theoretical calculation: the scholars in China introduced the random medium theory to the forecast of subsidence induced by the water mining in rock salt in the late 20th century,which provided a new theoretic basis for the forecast of the subsidence in the region of underground storages; 3)numerical simulation: the scholars in Europe made use of FLAC2D program to simulate the ground stability in the region of the storages in rock salt,and the scholar in China made use of the forecasting model established on the basis of new probability integral 3D model to simulate the subsidence successfully. Besides,in order to control the ground deformation in the region of storages effectively,the pillar supported mining methods have been applied extensively in the construction of underground storages in rock salt in some foreign countries. At last,this paper puts forward that further studies will focuses on the time dependent ground deformation,revise the theoretic model properly,and improve the parameter choosing method with considering the in situ monitoring data. Consequently,it is expected to get more reliable and veracious forecasting result．
Flooddischarging tunnel at Jinping First Stage Hydropower Station situates in marbles on right bank of Yalong River where complex geological structures condition appears and the cover depth is more than 100 m. It is clear whether there are key rock blocks on the excavation planes during excavation will sufficiently affect engineering safety. This paper bases on geological conditions in one part of central drift in the flooddischarging tunnel,and draws stochastic probability into key block theory. It studies the generation probability,volume and safety factors of these potential key blocks and obtains the following conclusions. The generation probability of key blocks shows an exponential distribution,on the condition that faults are extended freely. The probability will mainly determined by the length distribution of two joint sets. The relationship between volume of key blocks and trace length of main structural planes is direct ratio. But as trace length increases,the volume of blocks will approach to the maximum value which indicates the complete cut state. The safety factors of key blocks decrease with the growth of the main structuralplane trace length. It has a minimum value which shows the complete cut state. These are useful to offer effective reinforcement design and have important engineering values.
Flooddischarging tunnel at Jinping First Stage Hydropower Station situates in marbles on right bank of Yalong River where complex geological structures condition appears and the cover depth is more than 100 m. It is clear whether there are key rock blocks on the excavation planes during excavation will sufficiently affect engineering safety. This paper bases on geological conditions in one part of central drift in the flooddischarging tunnel,and draws stochastic probability into key block theory. It studies the generation probability,volume and safety factors of these potential key blocks and obtains the following conclusions. The generation probability of key blocks shows an exponential distribution,on the condition that faults are extended freely. The probability will mainly determined by the length distribution of two joint sets. The relationship between volume of key blocks and trace length of main structural planes is direct ratio. But as trace length increases,the volume of blocks will approach to the maximum value which indicates the complete cut state. The safety factors of key blocks decrease with the growth of the main structuralplane trace length. It has a minimum value which shows the complete cut state. These are useful to offer effective reinforcement design and have important engineering values.
Jinping Ⅰ hydropower underground station which buries in a depth of 350m,locates in marble strata. Varies failure phenomena can be found in surrounding rock under high ground stress during excavation process. Based on detailed description of those phenomena,obvious regularities are concluded and described as follows: fracture in top arch of underground station and voltage transformation station downstream sidewall; buckling in top arch of bus bar line cavern and penstock downstream plat part. At last why the anchor over load is explained using numerical simulation results that the radial force is far over the rockmass strength．
Jinping Ⅰ hydropower underground station which buries in a depth of 350m,locates in marble strata. Varies failure phenomena can be found in surrounding rock under high ground stress during excavation process. Based on detailed description of those phenomena,obvious regularities are concluded and described as follows: fracture in top arch of underground station and voltage transformation station downstream sidewall; buckling in top arch of bus bar line cavern and penstock downstream plat part. At last why the anchor over load is explained using numerical simulation results that the radial force is far over the rockmass strength．
2010, 18(2)
Dalongtan hydropower station is located in one carbonate rock area. The karsts are controlled by lithologic characters and structural features as follows: 1)the lithology in the first member of Najinguan formation of Ordovician（O1n1）,the first layer of the second member of Najinguan formation(O1n2-1)and the second layer of the fourth member of the Cambrian(4-23m)are shale infiltrated limestone,band argillaceous limestone and band siliceous limestone respectively. The karts in these rocks are very weak and oppositely strong in other rock layers; 2)Karsts develop along the bedding surface and fault plane,which form karst canals. So the seepage mainly occurs along these karst faults. In antiseepage curtaindesigning,the design relies on the shale of 188 m depth and emphasizes the locations of the faults. Results of the longterm groundwater observation and analysis show that the efficiency of the antiseepage curtain is very good and there is no large seepage. Only at the sites where the faults pass,the amount of seepage may be somewhat larger. The achievement of the antiseepage curtaindesigning in Dalongtan hydropower station gives a good example and may provide significant reference for other projects
Dalongtan hydropower station is located in one carbonate rock area. The karsts are controlled by lithologic characters and structural features as follows: 1)the lithology in the first member of Najinguan formation of Ordovician（O1n1）,the first layer of the second member of Najinguan formation(O1n2-1)and the second layer of the fourth member of the Cambrian(4-23m)are shale infiltrated limestone,band argillaceous limestone and band siliceous limestone respectively. The karts in these rocks are very weak and oppositely strong in other rock layers; 2)Karsts develop along the bedding surface and fault plane,which form karst canals. So the seepage mainly occurs along these karst faults. In antiseepage curtaindesigning,the design relies on the shale of 188 m depth and emphasizes the locations of the faults. Results of the longterm groundwater observation and analysis show that the efficiency of the antiseepage curtain is very good and there is no large seepage. Only at the sites where the faults pass,the amount of seepage may be somewhat larger. The achievement of the antiseepage curtaindesigning in Dalongtan hydropower station gives a good example and may provide significant reference for other projects
2010, 18(2)
The control of settlementdeformation of shallow tunnel in soft rock during operation is a difficult task. The most basic content is to master the law of settlementdeformation induced by excavation. This paper presents the observation and analysis of the surface subsidence deformation at Longyan railway tunnel. The deformation of surface subsidence versus time is divided into three main phases: the initial settlement stage,the accelerated settlement stage and the decelerated settlement stage. Combining the results of sedimentation monitoring of the tunnel vault,the positive correlation of surface subsidence and sedimentation of the tunnel vault is concluded. The influenced ranges of the tunnel excavation in front of and behind of the work face are 15D and 3D respectively,where D is the tunnel span. The influenced ranges of traverse are 4D in both sides of the center line. The influenced ranges of the structures are 2D in both sides of the center line. Due to large ground and vault settlements were predicted,a whole section pregrouting was adopted to prevent the large settlements. Monitoring results indicate that the whole section pregrouting can reduce the ground and vault settlements effectively. Convergence reduction is not markable. The scheme achieved the aim of settlement reduction．
The control of settlementdeformation of shallow tunnel in soft rock during operation is a difficult task. The most basic content is to master the law of settlementdeformation induced by excavation. This paper presents the observation and analysis of the surface subsidence deformation at Longyan railway tunnel. The deformation of surface subsidence versus time is divided into three main phases: the initial settlement stage,the accelerated settlement stage and the decelerated settlement stage. Combining the results of sedimentation monitoring of the tunnel vault,the positive correlation of surface subsidence and sedimentation of the tunnel vault is concluded. The influenced ranges of the tunnel excavation in front of and behind of the work face are 15D and 3D respectively,where D is the tunnel span. The influenced ranges of traverse are 4D in both sides of the center line. The influenced ranges of the structures are 2D in both sides of the center line. Due to large ground and vault settlements were predicted,a whole section pregrouting was adopted to prevent the large settlements. Monitoring results indicate that the whole section pregrouting can reduce the ground and vault settlements effectively. Convergence reduction is not markable. The scheme achieved the aim of settlement reduction．
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