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Editor Work2014 Vol. 22, No. 3
Previous Issue
2014, 22(3): 355-360.
Abstract
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This paper investigates the sensitive factors of the average speed of debris flows and coupling relationship of the influence factors with the data of debris flows in Jiangjia gully. The BPANN and SVM are proposed for building predictive model of average velocity of debris flows. Prediction accuracy and scope of application of the two models are compared. Analysis is done on various factors for their sensitivities to average speed of debris flows with the default factor method. A prediction model for debris flows is established and verified. The results show that the prediction accuracy of the SVM model is better than that of the BPANN model in the validation phase. The extrapolating ability and predicting capability have been validated by using the support vector machine prediction model,and the SVM model is more suitable for its prediction of debris flow. Channel slope and the thickness of the unstable layer are the main sensitive factors affecting average velocity of debris flows. The interaction amongst various factors formed coupling relationship under the complicated condition. The relationship model of average speed of debris flows established base upon channel slope,and the thickness of the unstable layer can well express quantitatively the response relationship between debris flows dynamic and various factors with sufficient high accuracy. It is an accurate scientific basis for prevention of debris flow.
This paper investigates the sensitive factors of the average speed of debris flows and coupling relationship of the influence factors with the data of debris flows in Jiangjia gully. The BPANN and SVM are proposed for building predictive model of average velocity of debris flows. Prediction accuracy and scope of application of the two models are compared. Analysis is done on various factors for their sensitivities to average speed of debris flows with the default factor method. A prediction model for debris flows is established and verified. The results show that the prediction accuracy of the SVM model is better than that of the BPANN model in the validation phase. The extrapolating ability and predicting capability have been validated by using the support vector machine prediction model,and the SVM model is more suitable for its prediction of debris flow. Channel slope and the thickness of the unstable layer are the main sensitive factors affecting average velocity of debris flows. The interaction amongst various factors formed coupling relationship under the complicated condition. The relationship model of average speed of debris flows established base upon channel slope,and the thickness of the unstable layer can well express quantitatively the response relationship between debris flows dynamic and various factors with sufficient high accuracy. It is an accurate scientific basis for prevention of debris flow.
2014, 22(3): 361-365.
Based on detailed field geology survey, this paper examines the Cimodi ancient landslide in Yalongjiang River and evaluates its stability. The macro geological conditions are obtained from the aspects of topography and geomorphology, historical earthquake records and material structure and other geological conditions. A conclusion is obtained that in natural state, the ancient landslide is stable and the slope stability is up to original sliding soil and rock mass interface and potential sliding interface in the slope body. Refer to the inversion analysis of the morphological changes of ancient landslide before and after, according to the energy method, landslide kinematics and Scheideg-gar hypothesis, this paper determines four key landslide motion parameters: landslide radius r, equivalent slope degree ,integrated dynamic friction angle and trailing gap Hm. The max landslide speed Vmax can be calculated with landslide motion equation. Specially, there are two methods to value the trailing gap Hm: One method is considered that the tailing gap point can stop movement when the max landslide speed Vmax occurs and the Hm of Vmax is the vertical distance of trailing gap point before and after the sliding movement. The other method is considered that the tailing gap point can keep moving together with the slope body and slow down after the occurrence of the Vmax. Therefore the Hm of Vmax, which is less than the vertical distance of trailing gap point before and after the sliding movement, could be solved by circular arc sliding surface hypothesis and sliding movement formula. Finally, this paper suggests that ancient landslide is a high speed landslide and the max landslide speed Vmax value should be 13.50ms-1～21.20ms-1. It discusses the characteristics of geology condition of the ancient landslide with high speed. It is a meaningful reference to those unstable slopes in similar engineering geology background in the area nearby Cimodi ancient landslide.
Based on detailed field geology survey, this paper examines the Cimodi ancient landslide in Yalongjiang River and evaluates its stability. The macro geological conditions are obtained from the aspects of topography and geomorphology, historical earthquake records and material structure and other geological conditions. A conclusion is obtained that in natural state, the ancient landslide is stable and the slope stability is up to original sliding soil and rock mass interface and potential sliding interface in the slope body. Refer to the inversion analysis of the morphological changes of ancient landslide before and after, according to the energy method, landslide kinematics and Scheideg-gar hypothesis, this paper determines four key landslide motion parameters: landslide radius r, equivalent slope degree ,integrated dynamic friction angle and trailing gap Hm. The max landslide speed Vmax can be calculated with landslide motion equation. Specially, there are two methods to value the trailing gap Hm: One method is considered that the tailing gap point can stop movement when the max landslide speed Vmax occurs and the Hm of Vmax is the vertical distance of trailing gap point before and after the sliding movement. The other method is considered that the tailing gap point can keep moving together with the slope body and slow down after the occurrence of the Vmax. Therefore the Hm of Vmax, which is less than the vertical distance of trailing gap point before and after the sliding movement, could be solved by circular arc sliding surface hypothesis and sliding movement formula. Finally, this paper suggests that ancient landslide is a high speed landslide and the max landslide speed Vmax value should be 13.50ms-1～21.20ms-1. It discusses the characteristics of geology condition of the ancient landslide with high speed. It is a meaningful reference to those unstable slopes in similar engineering geology background in the area nearby Cimodi ancient landslide.
2014, 22(3): 366-371.
The tunneling erosion is not only a unique mode of soil erosion,but also usually an important factor to the stability of the highway slopes of unsaturated loess in the loess plateau. Based on the developed program of the strength reduction FEM with matric suction,this paper comparatively studies the different cases of the unsaturated loess slope stabilities. The results reveal the possible different effects on the stability of unsaturated loess slope by erosion tunneling as well as matric suction. The results indicate that when their occurrence nears the slope crest,the tunnel erosions prefer to maintain the stability of the slope. On the contrary,when their occurrence nears the slope toe,the tunnel erosions prefer to reduce the stability of slope especially as the tunneling is serious. The results also indicate that the safety factor of the unsaturated loess slope increases and the potential sliding surface moves downward when the matric suction is considered,while the safety factor of the unsaturated loess slope decreases and the potential sliding surface moves upward when the matric suction is ignored.
The tunneling erosion is not only a unique mode of soil erosion,but also usually an important factor to the stability of the highway slopes of unsaturated loess in the loess plateau. Based on the developed program of the strength reduction FEM with matric suction,this paper comparatively studies the different cases of the unsaturated loess slope stabilities. The results reveal the possible different effects on the stability of unsaturated loess slope by erosion tunneling as well as matric suction. The results indicate that when their occurrence nears the slope crest,the tunnel erosions prefer to maintain the stability of the slope. On the contrary,when their occurrence nears the slope toe,the tunnel erosions prefer to reduce the stability of slope especially as the tunneling is serious. The results also indicate that the safety factor of the unsaturated loess slope increases and the potential sliding surface moves downward when the matric suction is considered,while the safety factor of the unsaturated loess slope decreases and the potential sliding surface moves upward when the matric suction is ignored.
2014, 22(3): 372-378.
Eight natural limit-state loess high slopes are measured in Xixian-Lishi area of Shanxi province. Then the geologic models are built. Meanwhile,soil test data of 592 groups soil samples from investigation reports of the engineering geology are collected,counting the physical and mechanical parameters of loess in study area according to chronologic age. Soil test data of 9 sites along Linxian-Lishi road are selected. The parameters c, are statistically analyzed for the variability of loess simultaneously. The coefficient of variation for the value of strength parameters c, are combined,carrying out the simulation of reliability by Monte-Carlo method. The results show that the stability coefficients of these slopes are between 0.96 and 1.14. The probability of failure are between 33.0% and 61.8%.The natural analogy method is used to analyze two natural limit-state loess high slopes with the heights of 50.5m and 80.8m,respectively. The analysis shows that for the slope of 50.5m high if the design requires the probability of failure no more than 10%,the slope ratio should not be more than 1:1.81 under the average combination of variation coefficient(COVc=0.66,COV=0.28). For the slope of 81.8m height if the design requires the probability of failure no more than 10%,the slope ratio should not be more than 1:1.94 under the same combination of variation coefficient.
Eight natural limit-state loess high slopes are measured in Xixian-Lishi area of Shanxi province. Then the geologic models are built. Meanwhile,soil test data of 592 groups soil samples from investigation reports of the engineering geology are collected,counting the physical and mechanical parameters of loess in study area according to chronologic age. Soil test data of 9 sites along Linxian-Lishi road are selected. The parameters c, are statistically analyzed for the variability of loess simultaneously. The coefficient of variation for the value of strength parameters c, are combined,carrying out the simulation of reliability by Monte-Carlo method. The results show that the stability coefficients of these slopes are between 0.96 and 1.14. The probability of failure are between 33.0% and 61.8%.The natural analogy method is used to analyze two natural limit-state loess high slopes with the heights of 50.5m and 80.8m,respectively. The analysis shows that for the slope of 50.5m high if the design requires the probability of failure no more than 10%,the slope ratio should not be more than 1:1.81 under the average combination of variation coefficient(COVc=0.66,COV=0.28). For the slope of 81.8m height if the design requires the probability of failure no more than 10%,the slope ratio should not be more than 1:1.94 under the same combination of variation coefficient.
2014, 22(3): 379-385.
This paper is based on the predecessors' research and is aided with investigation and prospection at field. It analyzes the distribution regularity and development background of landslides at the edge of the loess table lands from Baoji to Changxing. It proves the following five points. (1)The scales of the landslides decrease gradually from super large to large and middle,even small.(2)Landslides are at these sites where Ⅲ terrace or both Ⅲ and Ⅱ terrace disappeared.(3)Development of landslides mainly has three periods: early stage of late Pleistocene epoch,early stage of Holocene epoch and last stage of Holocene epoch.(4)The eastward tilting movement with activity difference of the lithosphere in the west of Weihe river basin resulted in the physiognomy pattern of tablelands with distinct altitude differences. Then it controlled the development regular change of scales of the landslides. The northward movement of Weihe river and intense riverside eroding induced the concentrated development of landslides at the edge of the tablelands in different periods.(5)The intense human engineering movements are the main inducing factor of new landslides or revival of old landslides in late stage of Holocene.
This paper is based on the predecessors' research and is aided with investigation and prospection at field. It analyzes the distribution regularity and development background of landslides at the edge of the loess table lands from Baoji to Changxing. It proves the following five points. (1)The scales of the landslides decrease gradually from super large to large and middle,even small.(2)Landslides are at these sites where Ⅲ terrace or both Ⅲ and Ⅱ terrace disappeared.(3)Development of landslides mainly has three periods: early stage of late Pleistocene epoch,early stage of Holocene epoch and last stage of Holocene epoch.(4)The eastward tilting movement with activity difference of the lithosphere in the west of Weihe river basin resulted in the physiognomy pattern of tablelands with distinct altitude differences. Then it controlled the development regular change of scales of the landslides. The northward movement of Weihe river and intense riverside eroding induced the concentrated development of landslides at the edge of the tablelands in different periods.(5)The intense human engineering movements are the main inducing factor of new landslides or revival of old landslides in late stage of Holocene.
2014, 22(3): 386-395.
The Guanyinping landslide turned up evident deformation. There were two possible cause factors. One is the first-stage impoundment of Xiangjiaba hydropower station and the other is the rebuilding construction of the the 307 provincial road whose cutting and filling project had just been finished. The real cause triggering the landslide deformation remains to be controversial between the reservoir impoundment and the construction of the rebuilt road. Based on the landslide deformation behaviors and the results of in-situ monitoring, the deformation mechanism of the landslide is discussed specifically in this paper. In order to analyze the stability of the landslide, a 2D model is developed by using the finite element numerical simulation. The factors of safety under various operational conditions are calculated through shear strength reduction method. The result shows the following three points:(1)Construction of the rebuilt road and the rising of reservoir water level are both against the whole stability of the landslide, especially the rising of reservoir water level;(2)After the construction of the rebuilt road and the first-stage impoundment, the landslide is in the critical stable state. Supposing no reinforcement measure is taken, the factor of safety reduces continually under the second-stage impoundment and the normal impoundment;(3)The treatment measure of cutting slope and unloading is presented. The factor of safety can meet the requirements of norms under the second-stage impoundment and the normal impoundment after being controlled. The relevant conclusions and methods proposed can provide the references for the treatment for the similar landslides.
The Guanyinping landslide turned up evident deformation. There were two possible cause factors. One is the first-stage impoundment of Xiangjiaba hydropower station and the other is the rebuilding construction of the the 307 provincial road whose cutting and filling project had just been finished. The real cause triggering the landslide deformation remains to be controversial between the reservoir impoundment and the construction of the rebuilt road. Based on the landslide deformation behaviors and the results of in-situ monitoring, the deformation mechanism of the landslide is discussed specifically in this paper. In order to analyze the stability of the landslide, a 2D model is developed by using the finite element numerical simulation. The factors of safety under various operational conditions are calculated through shear strength reduction method. The result shows the following three points:(1)Construction of the rebuilt road and the rising of reservoir water level are both against the whole stability of the landslide, especially the rising of reservoir water level;(2)After the construction of the rebuilt road and the first-stage impoundment, the landslide is in the critical stable state. Supposing no reinforcement measure is taken, the factor of safety reduces continually under the second-stage impoundment and the normal impoundment;(3)The treatment measure of cutting slope and unloading is presented. The factor of safety can meet the requirements of norms under the second-stage impoundment and the normal impoundment after being controlled. The relevant conclusions and methods proposed can provide the references for the treatment for the similar landslides.
2014, 22(3): 396-404.
A large-scale landslide disaster of about 3.1 million m3 happened in Darong village of Siyang town,Cengong country on June 29,2012. Darong landslide is in the accumulation zone of ancient landslide. Based on the analysis of failure characteristics and geological prototype of landslide,the failure mode is qualitatively judged as creep sliding-fracturing-traction sliding. Under the action of unreasonable artificial filled soil in landslide promoter region and heavy rainfall,the base of slope had creep deformation and became unstable,which weakened the supporting force in the base of slope of the main slide area. Consequently,sliding and instability happened in the lower part of the main slide area,which thus induced the upper right side of the main slide to be gradually unstable. Slip zone is located in highly weathered bedrock underlying. The left side of the main body slipped to west,and the right one slipped to southwest. Based on coupled numerical analysis of stress field and seepage field,the instability process and generation mechanism of the landslide are reappeared. The study on formation mechanism of Darong landslide provides an important reference for analogous landslide analysis and identification in western mountains.
A large-scale landslide disaster of about 3.1 million m3 happened in Darong village of Siyang town,Cengong country on June 29,2012. Darong landslide is in the accumulation zone of ancient landslide. Based on the analysis of failure characteristics and geological prototype of landslide,the failure mode is qualitatively judged as creep sliding-fracturing-traction sliding. Under the action of unreasonable artificial filled soil in landslide promoter region and heavy rainfall,the base of slope had creep deformation and became unstable,which weakened the supporting force in the base of slope of the main slide area. Consequently,sliding and instability happened in the lower part of the main slide area,which thus induced the upper right side of the main slide to be gradually unstable. Slip zone is located in highly weathered bedrock underlying. The left side of the main body slipped to west,and the right one slipped to southwest. Based on coupled numerical analysis of stress field and seepage field,the instability process and generation mechanism of the landslide are reappeared. The study on formation mechanism of Darong landslide provides an important reference for analogous landslide analysis and identification in western mountains.
2014, 22(3): 405-411.
Automatic integration and analysis of multi-source monitoring data are the important foundation of the geo-hazard monitoring and early warning. This paper examines the problems and difficulties in the integration of monitor data of geo-hazard and tries to realize the automation of the geo-hazard monitoring. This paper combines the actual project requirements,develops a set of software entitledIntegration of Monitor Data of Geo-hazard System.This software integrates the data structure standard and abnormal data processing technology. This system has an advanced storage concept and introduces it in geo-hazard monitoring work with the aid of system service technology. It can automatically process and integrate the real-time monitoring data. The realization comes true on the monitoring data platform seamlessly integrate data of various monitoring instrument. It finally achieves the goal of fully automatic monitoring of geo-hazard warning.
Automatic integration and analysis of multi-source monitoring data are the important foundation of the geo-hazard monitoring and early warning. This paper examines the problems and difficulties in the integration of monitor data of geo-hazard and tries to realize the automation of the geo-hazard monitoring. This paper combines the actual project requirements,develops a set of software entitledIntegration of Monitor Data of Geo-hazard System.This software integrates the data structure standard and abnormal data processing technology. This system has an advanced storage concept and introduces it in geo-hazard monitoring work with the aid of system service technology. It can automatically process and integrate the real-time monitoring data. The realization comes true on the monitoring data platform seamlessly integrate data of various monitoring instrument. It finally achieves the goal of fully automatic monitoring of geo-hazard warning.
2014, 22(3): 412-420.
The impact of collapse or colluvial gravitational load may induce deformation and instability of landslide. On the basis of ascertaining slope structure,this paper applies the 3DEC discrete element numerical simulation method to simulating the mechanism,the scale of buckling mode,destruction and movement by the collapse of high and steep slope under the action of underground mining overall process. It especially analyzes deeply the interaction effect of slope after instability and landslide. The results show that the process of collapse by underground mining can disturb the underground mining slope and can produce a massive collapse. The rolling stones by collapse can have a strong impact on landslide. The generated colluvial deposits can have a gravitational load on landslide. The creep deformation of landside is mainly caused by the impact of colluvial gravitational load from the analysis of the monitoring data and the field of information collection. And landside has a tendency to continue to deformation. In rain season,the landslide deformation rate can be increased and become a risk of potential sliding mass. The corresponding protection work is necessary.
The impact of collapse or colluvial gravitational load may induce deformation and instability of landslide. On the basis of ascertaining slope structure,this paper applies the 3DEC discrete element numerical simulation method to simulating the mechanism,the scale of buckling mode,destruction and movement by the collapse of high and steep slope under the action of underground mining overall process. It especially analyzes deeply the interaction effect of slope after instability and landslide. The results show that the process of collapse by underground mining can disturb the underground mining slope and can produce a massive collapse. The rolling stones by collapse can have a strong impact on landslide. The generated colluvial deposits can have a gravitational load on landslide. The creep deformation of landside is mainly caused by the impact of colluvial gravitational load from the analysis of the monitoring data and the field of information collection. And landside has a tendency to continue to deformation. In rain season,the landslide deformation rate can be increased and become a risk of potential sliding mass. The corresponding protection work is necessary.
2014, 22(3): 421-427.
Collapses and landslides in slopes with soft base are very common geologic disasters in southwestern mountain regions and the Three Gorges reservoir area of China. They are harmful. The upper hard rock weight,the weathering and water softening and the underlain by soft rock base can generate compression and horizontal plastic flow towards the free face. Therefore,the upper hard rock can generate tensile cracks. Ultimately they lead to collapses and landslides. A slope in Guizhou is examined. Its upper part has a height of about 150m and is a limestone cliffs. Its lower part has a thickness greater than150m and is a shale gentle slope. It is a typical slope of a gently inclined ramp within the weak base. This paper uses the finite element numerical simulation and bottom friction method of combining physical simulation. It analyses the slope of the body stress,deformation distribution and development process. Based on this model,the paper studies the weak base of slope and its deformation and failure mechanisms and provides the theoretical support for the weak base slope of geological disasters protection. The results show that the slope deformation and failure mechanisms dipping the base are of the three performance of a compressed plastic flow,tension crack and shear-cut.
Collapses and landslides in slopes with soft base are very common geologic disasters in southwestern mountain regions and the Three Gorges reservoir area of China. They are harmful. The upper hard rock weight,the weathering and water softening and the underlain by soft rock base can generate compression and horizontal plastic flow towards the free face. Therefore,the upper hard rock can generate tensile cracks. Ultimately they lead to collapses and landslides. A slope in Guizhou is examined. Its upper part has a height of about 150m and is a limestone cliffs. Its lower part has a thickness greater than150m and is a shale gentle slope. It is a typical slope of a gently inclined ramp within the weak base. This paper uses the finite element numerical simulation and bottom friction method of combining physical simulation. It analyses the slope of the body stress,deformation distribution and development process. Based on this model,the paper studies the weak base of slope and its deformation and failure mechanisms and provides the theoretical support for the weak base slope of geological disasters protection. The results show that the slope deformation and failure mechanisms dipping the base are of the three performance of a compressed plastic flow,tension crack and shear-cut.
2014, 22(3): 428-435.
The Jieniangping deformation body lies in the city of Duyun,Guizhou province. Considering the severe deformation and potential consequences caused by instability,we decided to monitor the deformation at this site. We based on the type of deformation monitoring and early warning index,and connected them with the domestic related project experience and landform condition in the region. We chose the GPS based automatic monitoring technology,and supplemented it with surface crack monitoring and rainfall monitoring. The structure and the design of automatic monitoring system is introduced in this paper. The multi-antenna technology is clearly described. We compared the GPS data with the surface crack and surface displacement monitoring data. To some extent,we further verified the applicability of GPS in the project. Since March 2013,the monitoring results of the system show that the largest monitoring point of the accumulative deformation and subsidence is located at G2. In addition,the direction of deformation of four monitoring concentrations in coal mining in the southwest,reflecting the deformation of slope is mainly related to the mountain bottom coal mining. The relationship between deformation and local rainfall is not obvious.
The Jieniangping deformation body lies in the city of Duyun,Guizhou province. Considering the severe deformation and potential consequences caused by instability,we decided to monitor the deformation at this site. We based on the type of deformation monitoring and early warning index,and connected them with the domestic related project experience and landform condition in the region. We chose the GPS based automatic monitoring technology,and supplemented it with surface crack monitoring and rainfall monitoring. The structure and the design of automatic monitoring system is introduced in this paper. The multi-antenna technology is clearly described. We compared the GPS data with the surface crack and surface displacement monitoring data. To some extent,we further verified the applicability of GPS in the project. Since March 2013,the monitoring results of the system show that the largest monitoring point of the accumulative deformation and subsidence is located at G2. In addition,the direction of deformation of four monitoring concentrations in coal mining in the southwest,reflecting the deformation of slope is mainly related to the mountain bottom coal mining. The relationship between deformation and local rainfall is not obvious.
2014, 22(3): 436-442.
The method of residents' self-mitigating of disasters is a basic form to control geohazards in the vast rural areas of China. At present,we always transfer the monitoring information with the method of step by step. Such information transfer is not in a timely manner. The experts may not get the first-hand data about the geohazards. So this paper proposes a design method and realization technology about the geohazards monitoring and early warning system by local people at rural areas. It analyzes the Android's Socket API technique and the communication conditions among the different internal network nodes. Then it designs the application software structure of the monitoring terminal based on smartphones in order to record the geohazards information. The system is supported by the public network server. It is designed a forwarding information mechanism based on TCP to realize the communication among the mobile phone,public network server and internal monitoring platform. It forwards the monitoring information with GPRS or VPN(Virtual Private Network).100mobile terminals are arranged in Guizhou Province. The results of actual application indicate that the system can conveniently transmit the geohazards information with the characteristics of security,efficiency and stability,which meets the actual requirements.
The method of residents' self-mitigating of disasters is a basic form to control geohazards in the vast rural areas of China. At present,we always transfer the monitoring information with the method of step by step. Such information transfer is not in a timely manner. The experts may not get the first-hand data about the geohazards. So this paper proposes a design method and realization technology about the geohazards monitoring and early warning system by local people at rural areas. It analyzes the Android's Socket API technique and the communication conditions among the different internal network nodes. Then it designs the application software structure of the monitoring terminal based on smartphones in order to record the geohazards information. The system is supported by the public network server. It is designed a forwarding information mechanism based on TCP to realize the communication among the mobile phone,public network server and internal monitoring platform. It forwards the monitoring information with GPRS or VPN(Virtual Private Network).100mobile terminals are arranged in Guizhou Province. The results of actual application indicate that the system can conveniently transmit the geohazards information with the characteristics of security,efficiency and stability,which meets the actual requirements.
2014, 22(3): 443-449.
Wangmo river valley in Guizhou province Wangmo county has complicated geological conditions and high topography fall,strong confluence,rich loose material and three main gullies. On the condition of strong rainfall,small debris-flows developed in channels can break out simultaneously and flow into the main gully,finally gather together in Wangmo river. The increased flow and sediment can easily induce great debris flow disaster,which means a great loss of life and property to the river dwellers and the downriver Wangmo County. A great debris flow disaster happened on Jun.6th,2006,which caused great loss to local residents. Based on field research,an automatic monitoring and warning system is constructed to decrease the harm. The system contains many functions including data collection,interpretation,transmission,analysis,decision,control and warning. The monitoring contents conclude rainfall,infrasound,water level and image. The field monitoring system is composed of rain gauge,level meter,infrasound alarm apparatus and video device. Thus warning threshold values and warning levels are drawn up on the basis of field research and data analysis. By data analysis,it is found the automation system can make effectively real-time dynamic monitoring and early warning of Wangmo river debris flow in Wangmo county,Guizhou province.
Wangmo river valley in Guizhou province Wangmo county has complicated geological conditions and high topography fall,strong confluence,rich loose material and three main gullies. On the condition of strong rainfall,small debris-flows developed in channels can break out simultaneously and flow into the main gully,finally gather together in Wangmo river. The increased flow and sediment can easily induce great debris flow disaster,which means a great loss of life and property to the river dwellers and the downriver Wangmo County. A great debris flow disaster happened on Jun.6th,2006,which caused great loss to local residents. Based on field research,an automatic monitoring and warning system is constructed to decrease the harm. The system contains many functions including data collection,interpretation,transmission,analysis,decision,control and warning. The monitoring contents conclude rainfall,infrasound,water level and image. The field monitoring system is composed of rain gauge,level meter,infrasound alarm apparatus and video device. Thus warning threshold values and warning levels are drawn up on the basis of field research and data analysis. By data analysis,it is found the automation system can make effectively real-time dynamic monitoring and early warning of Wangmo river debris flow in Wangmo county,Guizhou province.
2014, 22(3): 450-455.
Many debris flows were triggered in and around the Dayi area of the Guizhou province,China during a rainstorm in 2011. High-intensity short duration rainfall was the main triggering factor for these gully type debris flows. They are probably triggered by a runoff induced mechanism. A revised prediction model is introduced for this kind of gully type debris flows. The factors are related to the topography,geology and hydrology(rainfall),and the model is applied to the Wangmo river catchment. Regarding the geological factor,thesoft lithology and loose sediments in the channel are added to the list of the average firmness coefficient for the lithology. Also the chemical weathering is taken into account for the revised geological factor. Concerning the hydrological factor,a coefficient of variation of rainfall is introduced for the normalization of the rainfall factor. The prediction model for debris flows proposed in this paper,delivers three classes of the probability of debris flow occurrence. The model is successfully validated in debris flow gullies with the same initiation mechanism in other areas of southwest China. The generic character of the model is explained by the fact that its factors are based on the initiation mechanisms and the statistical analyses of an unique variety of local factors. The result provides a new way to predict the occurrence of debris flows initiated by a runoff induced mechanism.
Many debris flows were triggered in and around the Dayi area of the Guizhou province,China during a rainstorm in 2011. High-intensity short duration rainfall was the main triggering factor for these gully type debris flows. They are probably triggered by a runoff induced mechanism. A revised prediction model is introduced for this kind of gully type debris flows. The factors are related to the topography,geology and hydrology(rainfall),and the model is applied to the Wangmo river catchment. Regarding the geological factor,thesoft lithology and loose sediments in the channel are added to the list of the average firmness coefficient for the lithology. Also the chemical weathering is taken into account for the revised geological factor. Concerning the hydrological factor,a coefficient of variation of rainfall is introduced for the normalization of the rainfall factor. The prediction model for debris flows proposed in this paper,delivers three classes of the probability of debris flow occurrence. The model is successfully validated in debris flow gullies with the same initiation mechanism in other areas of southwest China. The generic character of the model is explained by the fact that its factors are based on the initiation mechanisms and the statistical analyses of an unique variety of local factors. The result provides a new way to predict the occurrence of debris flows initiated by a runoff induced mechanism.
2014, 22(3): 456-463.
The stability of a potential landslide involves the interaction and inter-coupling of multi-factors. So it is very difficult to evaluate the interaction relationship among the influencing factors quantitatively and determine weight considering multi-factors. Therefore according to other scholars' achievement and the principle of rock engineering system theory's matrix construction and decoding,a new potential landslide identification model is suggested based on improved BP network. Then,the arithmetic flow of coding interaction matrix and considering multi-factors determine weight are deduced. At last,the model is applied to identify potential soil landslides. The research results show that the parameters analysis of artificial neural network can be used not only to potential landslide identification but also to determine weight considering multi-factors.
The stability of a potential landslide involves the interaction and inter-coupling of multi-factors. So it is very difficult to evaluate the interaction relationship among the influencing factors quantitatively and determine weight considering multi-factors. Therefore according to other scholars' achievement and the principle of rock engineering system theory's matrix construction and decoding,a new potential landslide identification model is suggested based on improved BP network. Then,the arithmetic flow of coding interaction matrix and considering multi-factors determine weight are deduced. At last,the model is applied to identify potential soil landslides. The research results show that the parameters analysis of artificial neural network can be used not only to potential landslide identification but also to determine weight considering multi-factors.
2014, 22(3): 464-473.
This paper takes Kaiyang phosphorite rockfall in Guizhou for example. It analyzes the geological conditions,mining exploitation and failure characteristics. It then develops the process of rockfall deformation with anti-dip and top hard-bottom soft rock. The formation mechanism of this type rockfall is studied through numerical simulation and physical simulation. The results show that this rockfall is induced by specific geological background,dynamic conditions and predisposing factors. Especially,there is a long development process from occurrence to destroy. A rapid destruction form is presented finally. They are specifically deformation of the roof and floor rock in the mine area,appearance of cracks on the top of slope and development of cracks along the steep joints in the slope. There are three failure modes: crack-toppling,crack-slide and crack-shear. Therefore,the key about monitoring and prevention of geological disasters to this type rockfall is precursory information for enhancing early identification and warning.
This paper takes Kaiyang phosphorite rockfall in Guizhou for example. It analyzes the geological conditions,mining exploitation and failure characteristics. It then develops the process of rockfall deformation with anti-dip and top hard-bottom soft rock. The formation mechanism of this type rockfall is studied through numerical simulation and physical simulation. The results show that this rockfall is induced by specific geological background,dynamic conditions and predisposing factors. Especially,there is a long development process from occurrence to destroy. A rapid destruction form is presented finally. They are specifically deformation of the roof and floor rock in the mine area,appearance of cracks on the top of slope and development of cracks along the steep joints in the slope. There are three failure modes: crack-toppling,crack-slide and crack-shear. Therefore,the key about monitoring and prevention of geological disasters to this type rockfall is precursory information for enhancing early identification and warning.
2014, 22(3): 474-481.
Landslides are the most common geohazards in mountainous terrains and can cause extraordinary landscape changes and destruction of people's lives and properties. So assessing landslide hazards is significant and can provide valuable information to planners,developers and engineers. This paper examines some landslides at a hilly area of western China,Guizhou province. The purpose is to generate a landslide susceptibility map using the weights of evidence. It is based on the GIS technology and combined with landslides inventory and environmental factors. The causal factors include lithology,tectonic,elevation,slope,aspect,relief,distance from road and distance from stream. The weight of each causal class is calculated in a GIS software ArcGIS 10. Then the landslide hazard index of each unit is produced and divided into four classes: very high hazard,high hazard,medium hazard and low hazard. Finally,a success rate curve is built to detect the capability rate of the method. The study area under the curve is 0.71.A hazard zonation map is produced and the predictive power of the map is tested on the basis of landslides inventory. The evaluation results are in line with the landslides distribution. The weights of evidence are effective to assess the landslides hazard in regional scale.
Landslides are the most common geohazards in mountainous terrains and can cause extraordinary landscape changes and destruction of people's lives and properties. So assessing landslide hazards is significant and can provide valuable information to planners,developers and engineers. This paper examines some landslides at a hilly area of western China,Guizhou province. The purpose is to generate a landslide susceptibility map using the weights of evidence. It is based on the GIS technology and combined with landslides inventory and environmental factors. The causal factors include lithology,tectonic,elevation,slope,aspect,relief,distance from road and distance from stream. The weight of each causal class is calculated in a GIS software ArcGIS 10. Then the landslide hazard index of each unit is produced and divided into four classes: very high hazard,high hazard,medium hazard and low hazard. Finally,a success rate curve is built to detect the capability rate of the method. The study area under the curve is 0.71.A hazard zonation map is produced and the predictive power of the map is tested on the basis of landslides inventory. The evaluation results are in line with the landslides distribution. The weights of evidence are effective to assess the landslides hazard in regional scale.
2014, 22(3): 482-488.
Small collapses had happened intermittently at Madaling,Duyun in Guizhou province since 2003. A large-scale landslide happened on May 18th,2006 due to continuous rainfall. The debris,caused by slump-mass,rolled by the water released from gob,scraped the residual slope wash of the gull,which forms the mud-rock flow. Such kind of geo-hazard,presenting as chain reaction,is composed of the collapse,landslide and secondary flow,and forms a disaster chain of collapse landslide and debris flow. This paper takes this Madaling geological disaster chain as the study object. It is based on the regional environmental geological survey and research of regularity of geological disaster chain. It takes rainfall,relative displacement,obliquity,osmotic pressure water head,mud level,infrasound as the monitoring indexes. Automatic monitoring stations are set up at trailing edge of collapse body and mouth of debris flow. It forms an automatic monitoring system by integrating automatic collection,wireless transmission,data gathering and analysis,decision-making and early warning. Indicated from the running state of monitoring system and monitoring results,it can reflect the deformation behavior of geological disaster chain better by live transmission of monitoring data,offer technical assistance for early warning of the disaster chain.
Small collapses had happened intermittently at Madaling,Duyun in Guizhou province since 2003. A large-scale landslide happened on May 18th,2006 due to continuous rainfall. The debris,caused by slump-mass,rolled by the water released from gob,scraped the residual slope wash of the gull,which forms the mud-rock flow. Such kind of geo-hazard,presenting as chain reaction,is composed of the collapse,landslide and secondary flow,and forms a disaster chain of collapse landslide and debris flow. This paper takes this Madaling geological disaster chain as the study object. It is based on the regional environmental geological survey and research of regularity of geological disaster chain. It takes rainfall,relative displacement,obliquity,osmotic pressure water head,mud level,infrasound as the monitoring indexes. Automatic monitoring stations are set up at trailing edge of collapse body and mouth of debris flow. It forms an automatic monitoring system by integrating automatic collection,wireless transmission,data gathering and analysis,decision-making and early warning. Indicated from the running state of monitoring system and monitoring results,it can reflect the deformation behavior of geological disaster chain better by live transmission of monitoring data,offer technical assistance for early warning of the disaster chain.
2014, 22(3): 489-497.
Division of primary-secondary consolidation is one of the key problems of prediction and analysis foundation deformation of soft soil correctly and taking effective engineering measures. A series of one dimensional compression secondary consolidation tests and three-dimensional secondary consolidation tests are performed by using unidirectional consolidation apparatus and triaxial shear apparatus for the typical soft soil in Tianjin. Load,pore ratio and pore water pressure,volume strain and time relationship are obtained. The test results show that: the division point of primary-secondary consolidation should be before the pore water pressure dissipation completely. A new method according to the strain rate and strain curve to differentiate the primary and secondary consolidation is founded. And the new method is suitable for all kinds of load. Primary consolidation time is prolonged along with increasing sample height while shortened along with the strengthening of drainage condition. With the increase of the load level,primary consolidation time is prolonged. When the load is less than the structure yield stress,the division of the primary-secondary consolidation is less affected by load ratio. While the load is greater than the structure yield stress,the primary consolidation time is prolonged along with the increase of load ratio. The ratio of the primary consolidation strain and the total strain after preloading is increased 30.7%than that of no preloading. The ratio increases along with the increase of the preloading load.
Division of primary-secondary consolidation is one of the key problems of prediction and analysis foundation deformation of soft soil correctly and taking effective engineering measures. A series of one dimensional compression secondary consolidation tests and three-dimensional secondary consolidation tests are performed by using unidirectional consolidation apparatus and triaxial shear apparatus for the typical soft soil in Tianjin. Load,pore ratio and pore water pressure,volume strain and time relationship are obtained. The test results show that: the division point of primary-secondary consolidation should be before the pore water pressure dissipation completely. A new method according to the strain rate and strain curve to differentiate the primary and secondary consolidation is founded. And the new method is suitable for all kinds of load. Primary consolidation time is prolonged along with increasing sample height while shortened along with the strengthening of drainage condition. With the increase of the load level,primary consolidation time is prolonged. When the load is less than the structure yield stress,the division of the primary-secondary consolidation is less affected by load ratio. While the load is greater than the structure yield stress,the primary consolidation time is prolonged along with the increase of load ratio. The ratio of the primary consolidation strain and the total strain after preloading is increased 30.7%than that of no preloading. The ratio increases along with the increase of the preloading load.
2014, 22(3): 498-506.
The analysis of some in-situ test means, such as self-boring pressure meter has revealed a phenomenon that the coefficient of lateral earth pressure at rest in natural soil strata is commonly on the high side. One of the reasons of the phenomenon is that the vertical stress estimated with the traditional theory is on the low side. For undisturbed sample had gone through the process of unloading and expanding, the gravity density of the soil tested in lab is no longer equal to that at the initial state in buried conditions before exploration and excavation. Influenced by the overburden pressure in initial state, the physical properties of soil should not be deviated from the compressible nature. So it is improper that the natural soil is identified in the idea of homogenization assumption. This paper takes technical measures, for example, adding 100kPa to the consolidation pressure in order to reform the analyzing model for compression test. It tries to build the mathematical model of the initial state of the soil with the conditions associated with the virgin compression, recompression and stress history of the soil body. Combined with case analysis, the recompression index proposed in experimental observation is not enough to reflect the expansion of samples. The physical meanings of minimum dry density and limit of liquidity may be the virgin compression of soil's characteristics of void ratio in loosest state. The compression index cannot give expression to the compressibility principle satisfactorily.
The analysis of some in-situ test means, such as self-boring pressure meter has revealed a phenomenon that the coefficient of lateral earth pressure at rest in natural soil strata is commonly on the high side. One of the reasons of the phenomenon is that the vertical stress estimated with the traditional theory is on the low side. For undisturbed sample had gone through the process of unloading and expanding, the gravity density of the soil tested in lab is no longer equal to that at the initial state in buried conditions before exploration and excavation. Influenced by the overburden pressure in initial state, the physical properties of soil should not be deviated from the compressible nature. So it is improper that the natural soil is identified in the idea of homogenization assumption. This paper takes technical measures, for example, adding 100kPa to the consolidation pressure in order to reform the analyzing model for compression test. It tries to build the mathematical model of the initial state of the soil with the conditions associated with the virgin compression, recompression and stress history of the soil body. Combined with case analysis, the recompression index proposed in experimental observation is not enough to reflect the expansion of samples. The physical meanings of minimum dry density and limit of liquidity may be the virgin compression of soil's characteristics of void ratio in loosest state. The compression index cannot give expression to the compressibility principle satisfactorily.
2014, 22(3): 507-514.
Permafrost has all kinds of rock and soil with ice under 0℃.Due to its complexity of physical and mechanical properties, problems are brought about for the design and construction of Qinghai Tibet power DC interconnection line project. Especially, the safe operation and stability of power grid within service life are affected by long-term shear strength of frozen soil because the soil properties, ice content and density are complex along the project. To solve these questions, the remolded samples are prepared. Three kinds of frozen soils(silty clay, silty and fine sand),three kinds of ice state(ice saturated, rich ice and muti ice state) at dense and loose conditions are sheared with fast rate by creep tests in laboratory under-2℃.The creep properties of different types of frozen soils are obtained. The long-term strength and its influence factors are predicted and analyzed. The results show that:(1)The load capacity of frozen soils increases in a short time with the increase of ice content; as loading time increases, creep deformation of frozen soils increases and the strength reduces because of the rheological properties of the ice; (2)The initial strength is higher as density and ice content increase; when time increases, intensity attenuation velocity is smaller as density reduces or ice content increases; (3)Variation of long term strength is not affected by the soil types, which shows that different kinds of frozen soils can be handled in the same way if only the long-term strength is considered during construction. The above results provide a basis for frozen soils foundation design, construction and operation of transmission line and reference experimental data for other engineering activities in Qinghai-Tibet area.
Permafrost has all kinds of rock and soil with ice under 0℃.Due to its complexity of physical and mechanical properties, problems are brought about for the design and construction of Qinghai Tibet power DC interconnection line project. Especially, the safe operation and stability of power grid within service life are affected by long-term shear strength of frozen soil because the soil properties, ice content and density are complex along the project. To solve these questions, the remolded samples are prepared. Three kinds of frozen soils(silty clay, silty and fine sand),three kinds of ice state(ice saturated, rich ice and muti ice state) at dense and loose conditions are sheared with fast rate by creep tests in laboratory under-2℃.The creep properties of different types of frozen soils are obtained. The long-term strength and its influence factors are predicted and analyzed. The results show that:(1)The load capacity of frozen soils increases in a short time with the increase of ice content; as loading time increases, creep deformation of frozen soils increases and the strength reduces because of the rheological properties of the ice; (2)The initial strength is higher as density and ice content increase; when time increases, intensity attenuation velocity is smaller as density reduces or ice content increases; (3)Variation of long term strength is not affected by the soil types, which shows that different kinds of frozen soils can be handled in the same way if only the long-term strength is considered during construction. The above results provide a basis for frozen soils foundation design, construction and operation of transmission line and reference experimental data for other engineering activities in Qinghai-Tibet area.
2014, 22(3): 515-521.
How to implement mining with water protection is a major research topic in ecologically fragile areas. Hydrogeology and engineering geology conditions exploration test and division index study are an important foundation and prerequisite for the implementation of water protected mining. This paper takes a typical mine of northern Shaanxi as an example. It is based on the exploration test. It includes the results of water pressure test before and after mining,indoor simulation of mining overburden rock deformation and failure process of permeability variation test. The results show that coal mining has a different impact on overlying rock mass permeability. The permeability of siltstone and mudstone is lesser and it can be used as a weak aquifuge. After mining,the bedrock permeability of the overall mobile belt appears varying degree of increase. The permeability coefficient increases about one order of magnitude. The red clay permeability variation is not obvious. Red clay can be used as key aquifuge before mining. According to water resources leakage,recharge and water level changes,the ecological fragile area is divided into four zones,i.e.,not influenced zone,zone of light water leakage,zone of normal water leakage and zone of serious water leakage. On the basis of the principle of water balance,the condition partition index of the four types calculation formula is derived. The application example is given.
How to implement mining with water protection is a major research topic in ecologically fragile areas. Hydrogeology and engineering geology conditions exploration test and division index study are an important foundation and prerequisite for the implementation of water protected mining. This paper takes a typical mine of northern Shaanxi as an example. It is based on the exploration test. It includes the results of water pressure test before and after mining,indoor simulation of mining overburden rock deformation and failure process of permeability variation test. The results show that coal mining has a different impact on overlying rock mass permeability. The permeability of siltstone and mudstone is lesser and it can be used as a weak aquifuge. After mining,the bedrock permeability of the overall mobile belt appears varying degree of increase. The permeability coefficient increases about one order of magnitude. The red clay permeability variation is not obvious. Red clay can be used as key aquifuge before mining. According to water resources leakage,recharge and water level changes,the ecological fragile area is divided into four zones,i.e.,not influenced zone,zone of light water leakage,zone of normal water leakage and zone of serious water leakage. On the basis of the principle of water balance,the condition partition index of the four types calculation formula is derived. The application example is given.
2014, 22(3): 522-530.
Measurement and analysis of the distribution of radon concentrations in soil air are an effective method to study the manifestations of geodynamic activity in the upper crust. Studying radon emanation is possible to reveal positions/activity of faults in the area,as well as to identify the recent movement intensity of fault blocks. The purpose of this paper is to determine a possible connection between anomalous radon values and the Huangcun fault at Qiaojiayao,where is currently exposing geothermal water in a limited area,with the temperature up to 34℃. Estimation of soil-radon activity is first carried out for faults in southeastern Lushi Basin,Henan Province. Four profile radon surveys are conducted at Huangcun fault that is overlain by Quaternary sediment in the southwest of the Lushi Basin. Radon concentrations are measured at 74 sites in an area about 1.2km2(6002000m) from July to August in 2013. The background and anomaly threshold values calculated are 7.12 kBqm-3 and 12.36 kBqm-3,respectively. Abnormal radon values,with peak signals of about 2～3 times higher than the background level,lead to the detection of a fractured zone,denoted as F2. The spatial variation of soil gas radon values are correlated with the activated Huangcun faults in the southwest of the Lushi Basin. The lower 222Rn activity is recorded on the main fault plane,while relatively higher 222Rn values is sampled a few tens of meters on the both sides of the fault,as a consequence of the dilution effect played by the soil(CO2)efflux. Radon concentrations highlight a decreasing gradient from south to north in the area. On moving further away from the main fault plane toward north,soil-gas activity decreases and becomes more stable. Higher soil 222Rn values are detected on the upthrown side of the Huangcun fault than on its downthrown side. This could be due to the greater structural instability of the downthrown side of the fault,and hence to its greater fracturing,which would result in a higher degree of radon dispersion and/or air dilution. The Qiaojiayao geothermal anomaly is located in the transition zone of radon concentrations between middle values and background values. Radon values illustrate a close relation with the activity of the Huangcun fault. The active fault zones and the associated fractures act as paths for radon migration. The data analysis suggests that the fault could be activated and transformed from a compress-shear to a normal fault. Such a fault is very likely extending down deeply,forming large conduits through which gases and heat move upwards. It may constitute the most important structural element concerning the formation of geothermal water near north of the fault at the Qiaojiayao village. The initial result shows that,the basement tectonic has multiple phrases of activities,and that the compressive-twisting faults in active region can be converted into regional tensional ones,controlling migration of hydrothermal fluids.
Measurement and analysis of the distribution of radon concentrations in soil air are an effective method to study the manifestations of geodynamic activity in the upper crust. Studying radon emanation is possible to reveal positions/activity of faults in the area,as well as to identify the recent movement intensity of fault blocks. The purpose of this paper is to determine a possible connection between anomalous radon values and the Huangcun fault at Qiaojiayao,where is currently exposing geothermal water in a limited area,with the temperature up to 34℃. Estimation of soil-radon activity is first carried out for faults in southeastern Lushi Basin,Henan Province. Four profile radon surveys are conducted at Huangcun fault that is overlain by Quaternary sediment in the southwest of the Lushi Basin. Radon concentrations are measured at 74 sites in an area about 1.2km2(6002000m) from July to August in 2013. The background and anomaly threshold values calculated are 7.12 kBqm-3 and 12.36 kBqm-3,respectively. Abnormal radon values,with peak signals of about 2～3 times higher than the background level,lead to the detection of a fractured zone,denoted as F2. The spatial variation of soil gas radon values are correlated with the activated Huangcun faults in the southwest of the Lushi Basin. The lower 222Rn activity is recorded on the main fault plane,while relatively higher 222Rn values is sampled a few tens of meters on the both sides of the fault,as a consequence of the dilution effect played by the soil(CO2)efflux. Radon concentrations highlight a decreasing gradient from south to north in the area. On moving further away from the main fault plane toward north,soil-gas activity decreases and becomes more stable. Higher soil 222Rn values are detected on the upthrown side of the Huangcun fault than on its downthrown side. This could be due to the greater structural instability of the downthrown side of the fault,and hence to its greater fracturing,which would result in a higher degree of radon dispersion and/or air dilution. The Qiaojiayao geothermal anomaly is located in the transition zone of radon concentrations between middle values and background values. Radon values illustrate a close relation with the activity of the Huangcun fault. The active fault zones and the associated fractures act as paths for radon migration. The data analysis suggests that the fault could be activated and transformed from a compress-shear to a normal fault. Such a fault is very likely extending down deeply,forming large conduits through which gases and heat move upwards. It may constitute the most important structural element concerning the formation of geothermal water near north of the fault at the Qiaojiayao village. The initial result shows that,the basement tectonic has multiple phrases of activities,and that the compressive-twisting faults in active region can be converted into regional tensional ones,controlling migration of hydrothermal fluids.
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