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Editor Work2011 Vol. 19, No. 1
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2011, 19(1): 1-5.
Abstract
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The meta-synthesis approach,initiated by Prof.Qian Xuesen,is suggested to be accepted for solution making in the engineering geology system.An integration of multiple source knowledge,including experience,deduction and measurement evidence,constitutes the essential core of the proposed approach.Its basic principle is to integrate and merge the conclusions obtained in the different sources of knowledge or information.The integral agreement may support a rational solution,surmounted normal knowledge and standard.A practical example of slope stability evaluation is given in this paper for site selection of water pumping station.The decision was reached making a breakthrough over the conventional engineering solution.
The meta-synthesis approach,initiated by Prof.Qian Xuesen,is suggested to be accepted for solution making in the engineering geology system.An integration of multiple source knowledge,including experience,deduction and measurement evidence,constitutes the essential core of the proposed approach.Its basic principle is to integrate and merge the conclusions obtained in the different sources of knowledge or information.The integral agreement may support a rational solution,surmounted normal knowledge and standard.A practical example of slope stability evaluation is given in this paper for site selection of water pumping station.The decision was reached making a breakthrough over the conventional engineering solution.
2011, 19(1): 6-10.
This paper summarizes and defiene the structure technology terms and concepts.They are used for investigations and study of rocky slopes at present. The notion of slope mass based on the stability evaluation of slope is put forward. Then, a classification system of slope mass structure was summarized and put forward. This system is based the rocky slope investigations in the field of Chinese hydropower project in recent years. It includes the controlling structural plane and potential deformation and instability model. With this system, rocky slopes could be divided into four main types and nine subtypes. The four main types include bedded slope mass structure, middle-steep joints (or joints surfaces) controlling slope mass structure, wedge-shaped slope mass structure, and homogeneous slope mass structure. This kind of slope mass structure notion and classification system has directive significance to qualitative evaluation for the stability of complex rocky slope, the selection of calculation method, the determination of boundary condition, and the establishment of scheme controlling stability.
This paper summarizes and defiene the structure technology terms and concepts.They are used for investigations and study of rocky slopes at present. The notion of slope mass based on the stability evaluation of slope is put forward. Then, a classification system of slope mass structure was summarized and put forward. This system is based the rocky slope investigations in the field of Chinese hydropower project in recent years. It includes the controlling structural plane and potential deformation and instability model. With this system, rocky slopes could be divided into four main types and nine subtypes. The four main types include bedded slope mass structure, middle-steep joints (or joints surfaces) controlling slope mass structure, wedge-shaped slope mass structure, and homogeneous slope mass structure. This kind of slope mass structure notion and classification system has directive significance to qualitative evaluation for the stability of complex rocky slope, the selection of calculation method, the determination of boundary condition, and the establishment of scheme controlling stability.
APPLICATION OF PITCH RULES OF DISCONTINUITIES TO EXCAVATION SURFACE FOR ROCK SLOPE STRUCTURE MAPPING
2011, 19(1): 11-20.
In theory,the extension of a discontinuity trace in revealing detailed map of the excavated surface by rock slope design must be in accordance with the pitch of the intersecting line of discontinuity and excavated surface on the latter.Grasping the pitch regularity and manipulating the appropriate sketch technique maybe not only make the trace map coincide with the in-site actual situation,but also increase drawing efficiency and data quality,without no avail of the accurate analysis for slope structure model.In view of this,by means of in-site observation and conclusion,relationships between discontinuity and slope surface and properties of discontinuities traces are analyzed.Based on formulas to express pitch rules,the discriminance of pitching by features triangle,which is inferred from both attitudes of discontinuity and slope surface,is proposed.Meanwhile,nomograph to determine pitch of discontinuity trace is drawn up.Under the proper condition,checking and concluding one of essentials of attitude by other one is discussed.Practical application of pitch regularity to a particular case,the trace of which is difficult to draw,is illustrated.
In theory,the extension of a discontinuity trace in revealing detailed map of the excavated surface by rock slope design must be in accordance with the pitch of the intersecting line of discontinuity and excavated surface on the latter.Grasping the pitch regularity and manipulating the appropriate sketch technique maybe not only make the trace map coincide with the in-site actual situation,but also increase drawing efficiency and data quality,without no avail of the accurate analysis for slope structure model.In view of this,by means of in-site observation and conclusion,relationships between discontinuity and slope surface and properties of discontinuities traces are analyzed.Based on formulas to express pitch rules,the discriminance of pitching by features triangle,which is inferred from both attitudes of discontinuity and slope surface,is proposed.Meanwhile,nomograph to determine pitch of discontinuity trace is drawn up.Under the proper condition,checking and concluding one of essentials of attitude by other one is discussed.Practical application of pitch regularity to a particular case,the trace of which is difficult to draw,is illustrated.
2011, 19(1): 21-28.
This paper uses the 5 12 Wenchuan earthquake as the background. It attempts to clarify scientifically and rationally the genetic mechanism of ruptures in the soil slope(including the overlay slope)under the dynamic loading of the earthquake. The aspect is examined systematically through vibration machine simulation test which belongs to the physical simulation method.The test results show the deformation and failure under the loading of earthquake have a certain correlation with the slope external structure.Stress mainly concentrated in the slope-shape turning zones,where damage can be made easily.The instability and failure Under the condition of vibration,soil slope show an general instability and failure mode that the slope collapses completely and results its debris piled at the slope toe area. Although this study reveals some regularities, the question about the dynamic response of soil slopes still needs further study.
This paper uses the 5 12 Wenchuan earthquake as the background. It attempts to clarify scientifically and rationally the genetic mechanism of ruptures in the soil slope(including the overlay slope)under the dynamic loading of the earthquake. The aspect is examined systematically through vibration machine simulation test which belongs to the physical simulation method.The test results show the deformation and failure under the loading of earthquake have a certain correlation with the slope external structure.Stress mainly concentrated in the slope-shape turning zones,where damage can be made easily.The instability and failure Under the condition of vibration,soil slope show an general instability and failure mode that the slope collapses completely and results its debris piled at the slope toe area. Although this study reveals some regularities, the question about the dynamic response of soil slopes still needs further study.
2011, 19(1): 29-36.
This paper is based on the method of random angle generating curve sliding surface. It analyses the stability of slopes comprising different soils under the action of seepage. It changes the value of the selected parameters to search for critical sliding surface. When considering the effect of seepage, the slope soil is modelled as three situations of slice divisions. Mechanical analysis is conduced to derive the formula of buoyancy and penetration of slices in simplified Janbu method. At the same time, in order to apply to computer programming, it made a reasonable simplification for the actual flow field. Through cooperating and analysing examples, it shows that both the minimum factor of safety and the most critical sliding surface obtained by this method are very close or quite similar to the results of the existing methods, which shows the correctness of this method. Secondly, the minimum factor of safety calculated by using non-circular sliding surface method is significantly smaller than that by using circular sliding surface method,which recommends that the non-circular sliding surface method be adopted under action of seepage. Thirdly it analyses the state of slopes by using ratio of height of water level and height of slope as the parameter for two homogeneous slopes under different water levels. The results show that with increase of groundwater level, factor of safety of slopes was sharply declined. So effect of seepage is an important factor for occurring of slope instability. Setting of drainage facilities on slopes should be paid special attention in engineering practice.
This paper is based on the method of random angle generating curve sliding surface. It analyses the stability of slopes comprising different soils under the action of seepage. It changes the value of the selected parameters to search for critical sliding surface. When considering the effect of seepage, the slope soil is modelled as three situations of slice divisions. Mechanical analysis is conduced to derive the formula of buoyancy and penetration of slices in simplified Janbu method. At the same time, in order to apply to computer programming, it made a reasonable simplification for the actual flow field. Through cooperating and analysing examples, it shows that both the minimum factor of safety and the most critical sliding surface obtained by this method are very close or quite similar to the results of the existing methods, which shows the correctness of this method. Secondly, the minimum factor of safety calculated by using non-circular sliding surface method is significantly smaller than that by using circular sliding surface method,which recommends that the non-circular sliding surface method be adopted under action of seepage. Thirdly it analyses the state of slopes by using ratio of height of water level and height of slope as the parameter for two homogeneous slopes under different water levels. The results show that with increase of groundwater level, factor of safety of slopes was sharply declined. So effect of seepage is an important factor for occurring of slope instability. Setting of drainage facilities on slopes should be paid special attention in engineering practice.
2011, 19(1): 37-42.
Spalling hazard affects the surface stability and its appearance. Conclusions can be made by investigating the spalling hazard in loess slopes on Huanglin-Yan'an expressway in Shaanxi province, with the assistance of theoretical analysis. The development state of spalling hazard is related with the factors including layer and lithology, geographic and geomorphic conditions, geological structure, the style of slope and its angle value. This paper establishes the classification criteria of spalling hazard in loess slope after combined with topological engineering method and the appraise of spalling hazard in loess slopes. The spalling hazard development state is represented by the correlation function. The calculation method for Matter-Element correlation degree is put forward. The method has a very important role in loess area for investigation and treatment of loess apalling hazard in loess slopes.
Spalling hazard affects the surface stability and its appearance. Conclusions can be made by investigating the spalling hazard in loess slopes on Huanglin-Yan'an expressway in Shaanxi province, with the assistance of theoretical analysis. The development state of spalling hazard is related with the factors including layer and lithology, geographic and geomorphic conditions, geological structure, the style of slope and its angle value. This paper establishes the classification criteria of spalling hazard in loess slope after combined with topological engineering method and the appraise of spalling hazard in loess slopes. The spalling hazard development state is represented by the correlation function. The calculation method for Matter-Element correlation degree is put forward. The method has a very important role in loess area for investigation and treatment of loess apalling hazard in loess slopes.
2011, 19(1): 43-51.
Landslide risk management has become one of the most important methods for landslide mitigation in the world. However, it starts relatively late and it is still in the initial stage in China (Hong Kong is an exceptional). The concept and techniques of landslide risk management widely used internationally have not been well implemented in the project of landslide investigation in China. This paper takes the project of landslide investigation at Baota district in Yanan city deployed by the land resources survey as an example. It analyzes the problem when doing the project about geohazards investigation, and the differences among the and the idea of risk management according to the guidelines for landslide susceptibility hazard and risk zoning for land use planning issued by JTC-1[1] and some new references. The landslide investigation implemented in China is medium scale and the investigation accuracy includes high, medium and low. A technical route and working thought about loess landslide investigation and mapping based on GIS, DEM, RS and ground survey is proposed. The study covers the four aspects including the landslide investigation and risk mapping at the scale of 1∶50000 and 1∶10000, the landslide investigation and risk mapping in villages, the important infrastructures and the representative landslides.The paper summarizes the loess landslide investigation and risk mapping methods at Baota district in Yanan city.
Landslide risk management has become one of the most important methods for landslide mitigation in the world. However, it starts relatively late and it is still in the initial stage in China (Hong Kong is an exceptional). The concept and techniques of landslide risk management widely used internationally have not been well implemented in the project of landslide investigation in China. This paper takes the project of landslide investigation at Baota district in Yanan city deployed by the land resources survey as an example. It analyzes the problem when doing the project about geohazards investigation, and the differences among the and the idea of risk management according to the guidelines for landslide susceptibility hazard and risk zoning for land use planning issued by JTC-1[1] and some new references. The landslide investigation implemented in China is medium scale and the investigation accuracy includes high, medium and low. A technical route and working thought about loess landslide investigation and mapping based on GIS, DEM, RS and ground survey is proposed. The study covers the four aspects including the landslide investigation and risk mapping at the scale of 1∶50000 and 1∶10000, the landslide investigation and risk mapping in villages, the important infrastructures and the representative landslides.The paper summarizes the loess landslide investigation and risk mapping methods at Baota district in Yanan city.
2011, 19(1): 52-58.
Based on materials of field investigation and geological hazard situation inspection after wenchuan earthquake,in this paper,from the aspects of geological hazard case and dangerous case,the author analyze case distribution,type,grade of geo-hazard triggered by Wenchuan earthquake. Furthermore the author give an evaluation of geo-hazard triggered by Wenchuan earthquake in shaanxi province compared with in Sichuan and Gansu province,in the end trend of geo-hazard in shaanxi province is predicted preliminary. Wenchuan earthquake causes geological hazard of 302 cases in Shaanxi province. The distribution of those geological hazard is chiefly in Baoji City,Hanzhong City,Xianyang City and Shangluo City,those geological hazard lead to two people dead and 13 injuries and great direct economic loss. Geological hazard case type is mainly landslide,which proportion is 85.7% in the whole of the geological hazard case type proportion. Geo-hazard case grade is mainly small grade of geological hazard,however middle grade of geological hazard lead to main direct economic loss. Geological hazard-causing object is mainly settlement and secondly institution and schools. Geological hazard danger cases caused by Wenchuan earthquake is chiefly in Hanzhong City,Baoji City,Xianyang City and Ankang City. Geological hazard danger case type is mainly landslide. and geological hazard danger case grade is mainly small grade. Geological hazard causing object is mainly settlement and secondly institution and schools also. The geological hazard case and danger cases have the following five characteristics:First,geological hazard and danger case mainly distributes the extension of Longmenshan Mountain geological structure,and the distribution of danger cases is more widely than the distribution of geological hazard. Second,geological hazard case type is mainly landslides. Third,geological hazard-causing object is mainly institution and schools,which is also prevention and control emphasis of geological hazard in the future. Fourth,small grade of geological hazard cases is the largest in all hazard cases. Fifth,relation of geological hazards in scale and geological hazard grade is the U shaped relationship. Damage caused in Shaanxi province by Wenchuan earthquake is relatively light than which of Sichuan and Gansu province.Shaanxi province is one of serious provinces in geological hazard,so the frequency of geological hazards could be increased in the future. Two suggestions of deepening research of geological hazard are taken out,one is to further enhance the analysis of geological structure and earthquake and geological hazard,and two is strengthening the rule and characteristics of the geological hazard.
Based on materials of field investigation and geological hazard situation inspection after wenchuan earthquake,in this paper,from the aspects of geological hazard case and dangerous case,the author analyze case distribution,type,grade of geo-hazard triggered by Wenchuan earthquake. Furthermore the author give an evaluation of geo-hazard triggered by Wenchuan earthquake in shaanxi province compared with in Sichuan and Gansu province,in the end trend of geo-hazard in shaanxi province is predicted preliminary. Wenchuan earthquake causes geological hazard of 302 cases in Shaanxi province. The distribution of those geological hazard is chiefly in Baoji City,Hanzhong City,Xianyang City and Shangluo City,those geological hazard lead to two people dead and 13 injuries and great direct economic loss. Geological hazard case type is mainly landslide,which proportion is 85.7% in the whole of the geological hazard case type proportion. Geo-hazard case grade is mainly small grade of geological hazard,however middle grade of geological hazard lead to main direct economic loss. Geological hazard-causing object is mainly settlement and secondly institution and schools. Geological hazard danger cases caused by Wenchuan earthquake is chiefly in Hanzhong City,Baoji City,Xianyang City and Ankang City. Geological hazard danger case type is mainly landslide. and geological hazard danger case grade is mainly small grade. Geological hazard causing object is mainly settlement and secondly institution and schools also. The geological hazard case and danger cases have the following five characteristics:First,geological hazard and danger case mainly distributes the extension of Longmenshan Mountain geological structure,and the distribution of danger cases is more widely than the distribution of geological hazard. Second,geological hazard case type is mainly landslides. Third,geological hazard-causing object is mainly institution and schools,which is also prevention and control emphasis of geological hazard in the future. Fourth,small grade of geological hazard cases is the largest in all hazard cases. Fifth,relation of geological hazards in scale and geological hazard grade is the U shaped relationship. Damage caused in Shaanxi province by Wenchuan earthquake is relatively light than which of Sichuan and Gansu province.Shaanxi province is one of serious provinces in geological hazard,so the frequency of geological hazards could be increased in the future. Two suggestions of deepening research of geological hazard are taken out,one is to further enhance the analysis of geological structure and earthquake and geological hazard,and two is strengthening the rule and characteristics of the geological hazard.
2011, 19(1): 59-64.
Based on the creep test data of the slipped zone soils of the Gushubao landslide and experience theory,a new empirical-creep model has been developed. The hyperbolic function is adopted for shear stress-strain behavior and the Morgan Mercer Florin function for strain-time behavior.Parameters of this creep model are presented in this paper by using of the / versus curve and genetic algorithm.Fitting results show that the predicted results are in reasonable agreement with the experimental data. The correlation coefficients of the fitting curves are all above 0.96,which indicates that this creep model can effectively reflect the creep characteristics of the slipped zone soils of Gushubao landslide.
Based on the creep test data of the slipped zone soils of the Gushubao landslide and experience theory,a new empirical-creep model has been developed. The hyperbolic function is adopted for shear stress-strain behavior and the Morgan Mercer Florin function for strain-time behavior.Parameters of this creep model are presented in this paper by using of the / versus curve and genetic algorithm.Fitting results show that the predicted results are in reasonable agreement with the experimental data. The correlation coefficients of the fitting curves are all above 0.96,which indicates that this creep model can effectively reflect the creep characteristics of the slipped zone soils of Gushubao landslide.
2011, 19(1): 65-69.
The distribution characteristics of weak intercalations and the development characteristics of landslides sliding zone in rock mass of the third Member of Badong Formation in new county-site town of Badong are studied in this paper. The results show that the sliding zone of landslides which developed in the third Member of Badong Formation corresponded to the sedimentary interlayers in the original rock. The intercalated dislocation caused by tectonic process in the interlayers evolved to landslides sliding zone by groundwater sliming effect. This effect is shown as the gravels with intercalated mud or the clay with intercalated gravels. The analysis shows that the deep-seated deformation in Huangtupo landslide and Zhaoshuling landslide were related to the broken rocks caused by the secondary fold and interbeded cleavage. The difference between the two landslide structure lied in the interlayer density in the original rock mass.
The distribution characteristics of weak intercalations and the development characteristics of landslides sliding zone in rock mass of the third Member of Badong Formation in new county-site town of Badong are studied in this paper. The results show that the sliding zone of landslides which developed in the third Member of Badong Formation corresponded to the sedimentary interlayers in the original rock. The intercalated dislocation caused by tectonic process in the interlayers evolved to landslides sliding zone by groundwater sliming effect. This effect is shown as the gravels with intercalated mud or the clay with intercalated gravels. The analysis shows that the deep-seated deformation in Huangtupo landslide and Zhaoshuling landslide were related to the broken rocks caused by the secondary fold and interbeded cleavage. The difference between the two landslide structure lied in the interlayer density in the original rock mass.
2011, 19(1): 70-75.
Recently,as investigated,the ground fissure in Qingxu of Shanxi province is one of the most active fissures in Fenwei Basin. It has caused serious damages to surface infrastructures such as roads and buildings.In order to monitor the deformation of the Qingxu fissure and to deduce its cause,this paper uses the differential SAR interferometry technique(D-InSAR).In order to mitigate the temporal decorrelation over the farm region, two scenes of Envisat ASAR data with only 70 days intervals in 2007 are selected and used to generated surface deformation results.Firstly, a subsidence of cone shape is detected as an ellipsoid with 2km long axis located in the south of Qingxu fissure. Then two profiles paralleling to the fissure and eight profiles normal to the fissure are taken to analyze the spatial characteristics of the fissure. It is found that the main deformation area is located in the south of the fissure. The maximum influence width is up to 100 m. Besides, it is found that the activity of ground fissure in different areas is greatly different. The maximum land subsidence difference crossing the ground fissure is up to 5 cm. Finally, the Jiaocheng fault is deduced to control the location of Qingxu fissure. The great land subsidence is the main sake for unusual activity of Qingxu fissure.
Recently,as investigated,the ground fissure in Qingxu of Shanxi province is one of the most active fissures in Fenwei Basin. It has caused serious damages to surface infrastructures such as roads and buildings.In order to monitor the deformation of the Qingxu fissure and to deduce its cause,this paper uses the differential SAR interferometry technique(D-InSAR).In order to mitigate the temporal decorrelation over the farm region, two scenes of Envisat ASAR data with only 70 days intervals in 2007 are selected and used to generated surface deformation results.Firstly, a subsidence of cone shape is detected as an ellipsoid with 2km long axis located in the south of Qingxu fissure. Then two profiles paralleling to the fissure and eight profiles normal to the fissure are taken to analyze the spatial characteristics of the fissure. It is found that the main deformation area is located in the south of the fissure. The maximum influence width is up to 100 m. Besides, it is found that the activity of ground fissure in different areas is greatly different. The maximum land subsidence difference crossing the ground fissure is up to 5 cm. Finally, the Jiaocheng fault is deduced to control the location of Qingxu fissure. The great land subsidence is the main sake for unusual activity of Qingxu fissure.
2011, 19(1): 76-82.
This paper presents our investigation on landslide monitoring over last many years.Based on the results of other studies,the paper introduces the system of landslide monitoring. It can monitor geological environments,induced factors and process factor. The induced and process factor are more important in landslide monitoring.The techniques of rain-infiltration-displacement is applied to the landslide monitoring engineering at Hekou sugar refinery factory. The automatic monitoring system can make remote data collection,data transfer,data warehousing. According to the real-time monitoring data,it is concluded that the depth of infiltration was 7 m when the daily rainfall was 67 mm. The depth was more than 7 m and less than 12 m when the 10 daily rainfall was 110 mm. The speed of infiltration was found to 0.53 m d-1 from 0 m to 7 m and was 0.29 m d-1 from 7 m to 12 m in depth.
This paper presents our investigation on landslide monitoring over last many years.Based on the results of other studies,the paper introduces the system of landslide monitoring. It can monitor geological environments,induced factors and process factor. The induced and process factor are more important in landslide monitoring.The techniques of rain-infiltration-displacement is applied to the landslide monitoring engineering at Hekou sugar refinery factory. The automatic monitoring system can make remote data collection,data transfer,data warehousing. According to the real-time monitoring data,it is concluded that the depth of infiltration was 7 m when the daily rainfall was 67 mm. The depth was more than 7 m and less than 12 m when the 10 daily rainfall was 110 mm. The speed of infiltration was found to 0.53 m d-1 from 0 m to 7 m and was 0.29 m d-1 from 7 m to 12 m in depth.
2011, 19(1): 88-92.
A new data mining method of Support Vector Machines(SVM)is applied on the classification of rock mass in tunnels.SVM is a novel powerful leaning method that based on Statistical Learning Theory.SVM can solve small-sample learning problems better than neural network. Parameters including rock layer thickness,rock mass structure,inlay condition,weathering condition,groundwater characteristic,joint condition,hammer knocking sound and ground stress,are chose as the judge factors.Data samples from Niba Mountain tunnel are used to train the SVM with different kernels. The mapping relationship between judge factors and rock mass classes is used. The SVM can discriminate and provide class-unknown data samples of rock mass. Result of the classification shows that SVM with polynomial kernel has a high accuracy when it is used to classify the rock mass.So this is an intelligent classification of rock mass method that can be applied to classify rock mass in tunnels.
A new data mining method of Support Vector Machines(SVM)is applied on the classification of rock mass in tunnels.SVM is a novel powerful leaning method that based on Statistical Learning Theory.SVM can solve small-sample learning problems better than neural network. Parameters including rock layer thickness,rock mass structure,inlay condition,weathering condition,groundwater characteristic,joint condition,hammer knocking sound and ground stress,are chose as the judge factors.Data samples from Niba Mountain tunnel are used to train the SVM with different kernels. The mapping relationship between judge factors and rock mass classes is used. The SVM can discriminate and provide class-unknown data samples of rock mass. Result of the classification shows that SVM with polynomial kernel has a high accuracy when it is used to classify the rock mass.So this is an intelligent classification of rock mass method that can be applied to classify rock mass in tunnels.
2011, 19(1): 93-98.
Weathered rock mass often contain weak zones. The weak zones reduce the mechanical strength of rock mass substantially.To locate and describe the weak zones,drillholes are employed to take rock samples. But,because of reason of economic and construction period,the number of drillholes is limited and the weak zones cannot be located accurately and efficiently. This causes problems in accurately analyzing mechanical properties of rock mass. This kind of problems can induce instability of rock mass in slopes and foundations. This paper introduces a new method to detect and characterize weak zones in weathered rock mass. This method applies Drilling Process Monitoring system(DPM)to monitor the full drilling processes for installation of soil nails,tiebacks,anti-slide piles and so on. Without taking samples,the weak zones can be detected and characterized with the analysis of DPMdata. The case study shows that this method can efficiently and quickly detect and characterize the weak zones in weathered rock mass. This method can be useful to better investigate weathered rock mass for design and construction.
Weathered rock mass often contain weak zones. The weak zones reduce the mechanical strength of rock mass substantially.To locate and describe the weak zones,drillholes are employed to take rock samples. But,because of reason of economic and construction period,the number of drillholes is limited and the weak zones cannot be located accurately and efficiently. This causes problems in accurately analyzing mechanical properties of rock mass. This kind of problems can induce instability of rock mass in slopes and foundations. This paper introduces a new method to detect and characterize weak zones in weathered rock mass. This method applies Drilling Process Monitoring system(DPM)to monitor the full drilling processes for installation of soil nails,tiebacks,anti-slide piles and so on. Without taking samples,the weak zones can be detected and characterized with the analysis of DPMdata. The case study shows that this method can efficiently and quickly detect and characterize the weak zones in weathered rock mass. This method can be useful to better investigate weathered rock mass for design and construction.
2011, 19(1): 99-102.
Deformation modulus of the weak rock zone has a great significance on the project construction. It is difficult for the current deformation test methods to characterize deformation modulus of the in-situ weak rock zone, which results in conservative values. In this paper, on the basis of theory of elasticity, analytical solution of deformation modulus of underlain weak rock belts is deduced. A new evaluation method of deformation modulus of weak rock zone is established. On the basis of field test and finite element inversion, it is shown that the calculation method is reasonably practicable between the results of numerical simulation and experiment calculation. It can greatly improve the test results that are conventionally and directly carried out on weak rock zone.
Deformation modulus of the weak rock zone has a great significance on the project construction. It is difficult for the current deformation test methods to characterize deformation modulus of the in-situ weak rock zone, which results in conservative values. In this paper, on the basis of theory of elasticity, analytical solution of deformation modulus of underlain weak rock belts is deduced. A new evaluation method of deformation modulus of weak rock zone is established. On the basis of field test and finite element inversion, it is shown that the calculation method is reasonably practicable between the results of numerical simulation and experiment calculation. It can greatly improve the test results that are conventionally and directly carried out on weak rock zone.
2011, 19(1): 103-108.
Ground settlements due to construction of underground tunnels crossing existing structures are an important issue. It is often encountered in the development of underground traffic and high speed railways lines. This paper investigates the ground settlement standards and methods caused by tunnel excavation. According to the different characteristics of roads,railways,tunnels and buildings,and including different construction characteristics,excavation areas,depths and engineering geological conditions,different existing structures have different control measures and recommended standards.So,the current standards of ground settlements are unreasonable in tunnels crossing,because the characteristics of the existing structure,geological conditions and construction features may not be taken into account in the ground settlement standards.
Ground settlements due to construction of underground tunnels crossing existing structures are an important issue. It is often encountered in the development of underground traffic and high speed railways lines. This paper investigates the ground settlement standards and methods caused by tunnel excavation. According to the different characteristics of roads,railways,tunnels and buildings,and including different construction characteristics,excavation areas,depths and engineering geological conditions,different existing structures have different control measures and recommended standards.So,the current standards of ground settlements are unreasonable in tunnels crossing,because the characteristics of the existing structure,geological conditions and construction features may not be taken into account in the ground settlement standards.
2011, 19(1): 109-115.
Rock-filled embankment has become a general type of road embankment in mountain area. But, there is a lack of the study about its stability in the condition of seismicity.There is a time of seismic vibrancy since Wenchuang earthquake in China. So it is necessary to carry study about highway embankment stability in high seismic region.This paper studies the stability and deformation of high rock-fill embankment which is under the conditions of nature,immersion and seismicity from K112+908.16 to K113+675 along Ya-Lu high way.The findings include the following. Reinforcing the embankment lateral constraints and reducing its lateral deformation are the precondition of a stable embankment and no road tensile openings under traffic loads. In the condition of water immersion,the embankment stability has a little change. But the action of wave scouring should be paid attention.In the condition of VIII degree earthquake intensity,the embankment would be fail by the way of pure aside slide. The slide plane would be the interface between embankment and foundation soil.So it will be effective to improve the ability of resisting seismicity that the strength of interface is enhanced.It is an effective measure to improve the embankment strength and reduce deformation that the degree of compaction is enlarged.But it is not better and better as the degree of compaction becomes bigger.There is a necessary study about the relation between the degree of compaction and bearing capacity of foundation soil.
Rock-filled embankment has become a general type of road embankment in mountain area. But, there is a lack of the study about its stability in the condition of seismicity.There is a time of seismic vibrancy since Wenchuang earthquake in China. So it is necessary to carry study about highway embankment stability in high seismic region.This paper studies the stability and deformation of high rock-fill embankment which is under the conditions of nature,immersion and seismicity from K112+908.16 to K113+675 along Ya-Lu high way.The findings include the following. Reinforcing the embankment lateral constraints and reducing its lateral deformation are the precondition of a stable embankment and no road tensile openings under traffic loads. In the condition of water immersion,the embankment stability has a little change. But the action of wave scouring should be paid attention.In the condition of VIII degree earthquake intensity,the embankment would be fail by the way of pure aside slide. The slide plane would be the interface between embankment and foundation soil.So it will be effective to improve the ability of resisting seismicity that the strength of interface is enhanced.It is an effective measure to improve the embankment strength and reduce deformation that the degree of compaction is enlarged.But it is not better and better as the degree of compaction becomes bigger.There is a necessary study about the relation between the degree of compaction and bearing capacity of foundation soil.
2011, 19(1): 116-121.
According to the typical loess in Shuozhou in Shanxi province,tests on its compaction characteristics,shear strength characteristics and disintegration are carried out. The original loess and three improved loess soils are used in the tests. The three loess soils are improved with lime and fly-ash,lime and cement,cement and fly-ash,respectively. The best improved soil plan is brought out.The improve soil is used in the filling engineering of elevator shaft in a pit.The result of numerical simulation indicates that it is feasible to use the improved loess of lime and fly-ash in the engineering project.The test results indicate that the compact hybrid structure is formed by fly ash and loess.The compact hybrid structure is formed by fly ash and loess.The activity of fly ash is activated as a result of the lime mixing.A series of hydration reaction of silicates prompt the intensity of loess and the physical and mechanical properties of improved loess are improved noticeably.
According to the typical loess in Shuozhou in Shanxi province,tests on its compaction characteristics,shear strength characteristics and disintegration are carried out. The original loess and three improved loess soils are used in the tests. The three loess soils are improved with lime and fly-ash,lime and cement,cement and fly-ash,respectively. The best improved soil plan is brought out.The improve soil is used in the filling engineering of elevator shaft in a pit.The result of numerical simulation indicates that it is feasible to use the improved loess of lime and fly-ash in the engineering project.The test results indicate that the compact hybrid structure is formed by fly ash and loess.The compact hybrid structure is formed by fly ash and loess.The activity of fly ash is activated as a result of the lime mixing.A series of hydration reaction of silicates prompt the intensity of loess and the physical and mechanical properties of improved loess are improved noticeably.
2011, 19(1): 122-128.
The stability of dam would reduce after rock dissolution occurs at the dam base.Taking a project for example,this paper analyzes the uneven settlement of dam at different dissolution degrees of dam base rock mass. The paper uses a three-dimensional numerical analysis. The result of calculation can show the following findings: the maximum displacement on dam top will be 10 cm if a strong dissolution occurs at dam base. The maximum displacement on dam top will be 5.5 cm if a middling dissolution occurs at dam base. The maximum displacement on dam top will be 4 cm if a slight dissolution occurs at dam base.The more serious of dam base dissolution,the more serious degree of uneven settlement in dam.At the same degree of dissolution,uneven settlements of the dam heel will be of the most serious,uneven settlement of the dam top will be of middle serious,uneven settlement of the dam toe will be of slight.
The stability of dam would reduce after rock dissolution occurs at the dam base.Taking a project for example,this paper analyzes the uneven settlement of dam at different dissolution degrees of dam base rock mass. The paper uses a three-dimensional numerical analysis. The result of calculation can show the following findings: the maximum displacement on dam top will be 10 cm if a strong dissolution occurs at dam base. The maximum displacement on dam top will be 5.5 cm if a middling dissolution occurs at dam base. The maximum displacement on dam top will be 4 cm if a slight dissolution occurs at dam base.The more serious of dam base dissolution,the more serious degree of uneven settlement in dam.At the same degree of dissolution,uneven settlements of the dam heel will be of the most serious,uneven settlement of the dam top will be of middle serious,uneven settlement of the dam toe will be of slight.
2011, 19(1): 129-136.
Strength of rock mass is largely determined by the strength of structure planes in the rock mass. This is especially true to platy rock mass.It is significant to get the strength parameters of structure planes in the rock mass directly by in-situ test both for the stability analysis of rock mass and for engineering design.In order to understand the strength property of platy rock mass,in-situ tests for the strength of the structure plane in dolomite platy rock mass at Xiaoyouying in Fangshan District of Beijing are carried out.Traditional in-situ tests will result in a high cost,and bring more difficulties for the shear strength of rock mass.To get rid of the heavy reaction frame,according to the relationship between the attitude of platy planes and the direction of tectonic stress in the rock mass,three test rock blocks,laterally disconnected from their parent rock in different forms,are dug out vertically on the horizontal ground of the test site.Beside two parallel vertical free surfaces,a certain free room is left between test block and its parent rock.This room is just a reaction frame for loading,where a jack and steel pads can be put and horizontal test loads can be applied vertically to the free surface of the test block.This makes the test get rid of cumbersome reaction equipment totally.The state of the tectonic stress in the test block changes with the forms of block disconnection from its parent rock and the varied tectonic stresses in different states,adding upon the stresses caused by horizontal test loads,forms different normal and tangential stresses in the pre-concerted shear plane at last.By means of the test method explained above,and based on the data of the local tectonic stress in Beijing territory,a pretty good result has resulted from the in-situ test for the shear strength(c,)of platy planes in the dolomite platy rock mass at Xiaoyouying in Fangshan district of Beijing.The strength parameter will be a helpful reference for the design of extra high voltage network foundation and for the stability analysis of engineering rock masses in mountain areas with similar platy rock mass.
Strength of rock mass is largely determined by the strength of structure planes in the rock mass. This is especially true to platy rock mass.It is significant to get the strength parameters of structure planes in the rock mass directly by in-situ test both for the stability analysis of rock mass and for engineering design.In order to understand the strength property of platy rock mass,in-situ tests for the strength of the structure plane in dolomite platy rock mass at Xiaoyouying in Fangshan District of Beijing are carried out.Traditional in-situ tests will result in a high cost,and bring more difficulties for the shear strength of rock mass.To get rid of the heavy reaction frame,according to the relationship between the attitude of platy planes and the direction of tectonic stress in the rock mass,three test rock blocks,laterally disconnected from their parent rock in different forms,are dug out vertically on the horizontal ground of the test site.Beside two parallel vertical free surfaces,a certain free room is left between test block and its parent rock.This room is just a reaction frame for loading,where a jack and steel pads can be put and horizontal test loads can be applied vertically to the free surface of the test block.This makes the test get rid of cumbersome reaction equipment totally.The state of the tectonic stress in the test block changes with the forms of block disconnection from its parent rock and the varied tectonic stresses in different states,adding upon the stresses caused by horizontal test loads,forms different normal and tangential stresses in the pre-concerted shear plane at last.By means of the test method explained above,and based on the data of the local tectonic stress in Beijing territory,a pretty good result has resulted from the in-situ test for the shear strength(c,)of platy planes in the dolomite platy rock mass at Xiaoyouying in Fangshan district of Beijing.The strength parameter will be a helpful reference for the design of extra high voltage network foundation and for the stability analysis of engineering rock masses in mountain areas with similar platy rock mass.
2011, 19(1): 137-142.
In order to systematically study the temperature effect on the engineering properties of clayey soils,laboratory test was conducted to evaluate the relations between temperature and shear strength of unsaturated remodeling soil samples.Among three common types of clayey soils in Nanjing with different mineral composition,direct shear tests of soil samples in different moisture content and dry density have been done in the range of 5~50℃.The results indicate that the following. (1)the cohesive force change mainly and linearly with the temperature. (2) the shear strength of clayey soils with higher content of hydrophilic mineral is more sensitive to temperature change. (3)the cohesive force decrease with the temperature rise,showing thermal-softening on strength. (4) for clayey soils with lower content of hydrophilic mineral,when the moisture content is lower(w17%),the shear strength shows the thermo-hardening phenomenon,however it shows the thermal-softening phenomenon when the moisture content is higher(w22%),and the temperature effect on shear strength is more obvious when the dry density of sample is higher.Moreover,the mechanism of thermal softening and hardening of unsaturated clayey soils is analyzed.
In order to systematically study the temperature effect on the engineering properties of clayey soils,laboratory test was conducted to evaluate the relations between temperature and shear strength of unsaturated remodeling soil samples.Among three common types of clayey soils in Nanjing with different mineral composition,direct shear tests of soil samples in different moisture content and dry density have been done in the range of 5~50℃.The results indicate that the following. (1)the cohesive force change mainly and linearly with the temperature. (2) the shear strength of clayey soils with higher content of hydrophilic mineral is more sensitive to temperature change. (3)the cohesive force decrease with the temperature rise,showing thermal-softening on strength. (4) for clayey soils with lower content of hydrophilic mineral,when the moisture content is lower(w17%),the shear strength shows the thermo-hardening phenomenon,however it shows the thermal-softening phenomenon when the moisture content is higher(w22%),and the temperature effect on shear strength is more obvious when the dry density of sample is higher.Moreover,the mechanism of thermal softening and hardening of unsaturated clayey soils is analyzed.
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