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Editor Work2010 Vol. 18, No. 1
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Wenchuan Earthquake produced abundant debris left behind on the hillside slopes. The debris would later serve as the source materials for rainfallinduced debris flow hazard. On 24th September 2008,a total of 72 debris flows were triggered by heavy rainfall in the central part of the epicenter region affected by the Wenchuan Earthquake. The Beichuan County in the central epicenter region is chosen for analyzing the change of debris flow source area after the earthquake and also following a rainstorm. Significant differences after the earthquake are noticed in producing a large amount of landslides for debris flow occurrence. Interpretations of aerial photographs and SPOT images as well as field investigations are used to identify landslide occurrences in the debris flow watershed for exploring the initial conditions triggering debris flows. Comparison of the aerial photographs taken on 18th May 2008(after the 512 Wenchuan earthquake) with the SPOT 5 images taken on 14th October 2008(after the rainstorm event on 24th September 2008)indicates that the landslide area in eight debris flow watersheds increased from 1537104 m2 to 1912104 m2 during that period of time. Measurement of the SPOT images reveals that the loose sediment areas on the channel beds had further expanded to 97104 m2 after the rainstorm. The present results show the Wenchuan Earthquake affected area is particularly susceptible to debris flow occurrence after heavy rainfall events．
Wenchuan Earthquake produced abundant debris left behind on the hillside slopes. The debris would later serve as the source materials for rainfallinduced debris flow hazard. On 24th September 2008,a total of 72 debris flows were triggered by heavy rainfall in the central part of the epicenter region affected by the Wenchuan Earthquake. The Beichuan County in the central epicenter region is chosen for analyzing the change of debris flow source area after the earthquake and also following a rainstorm. Significant differences after the earthquake are noticed in producing a large amount of landslides for debris flow occurrence. Interpretations of aerial photographs and SPOT images as well as field investigations are used to identify landslide occurrences in the debris flow watershed for exploring the initial conditions triggering debris flows. Comparison of the aerial photographs taken on 18th May 2008(after the 512 Wenchuan earthquake) with the SPOT 5 images taken on 14th October 2008(after the rainstorm event on 24th September 2008)indicates that the landslide area in eight debris flow watersheds increased from 1537104 m2 to 1912104 m2 during that period of time. Measurement of the SPOT images reveals that the loose sediment areas on the channel beds had further expanded to 97104 m2 after the rainstorm. The present results show the Wenchuan Earthquake affected area is particularly susceptible to debris flow occurrence after heavy rainfall events．
This paper is based on investigations of the landslides induced by Wenchuan Earthquake and collection and analysis of the related data. It presents the statistical relations between the earthquakeinduced landslides and other factors including earthquake parameters,geological and geomorphological factors. The results show that: (1)the landslides caused by Wenchuan earthquake mainly occurred in the Ⅶ～Ⅺ intensity districts,there were rather fewer landslides in the Ⅵ and below intensity districts; (2)the earthquakeinduced landslides mainly occurred in the area 300 km from the epicenter,and intensively distributed in the area 200 km from the epicenter; (3)the slopes with the dip angle of 30～50,especially 30～40,are very easy to slide during Wenchuan Earthquake; (4)the earthquakeinduced landslides mainly distributed in the elevation range of 600～1500m,especially 600～1000 m; (5)soft rocks such as mudstone,shale,schist and so on,are the easiest to slide during Wenchuan Earthquake; the combination of soft and hard rocks is secondary to slide; and hard rocks such as granite and carbonate rocks are not easy to slide; only a few old landslides were reactivated by Wenchuan Earthquake.
This paper is based on investigations of the landslides induced by Wenchuan Earthquake and collection and analysis of the related data. It presents the statistical relations between the earthquakeinduced landslides and other factors including earthquake parameters,geological and geomorphological factors. The results show that: (1)the landslides caused by Wenchuan earthquake mainly occurred in the Ⅶ～Ⅺ intensity districts,there were rather fewer landslides in the Ⅵ and below intensity districts; (2)the earthquakeinduced landslides mainly occurred in the area 300 km from the epicenter,and intensively distributed in the area 200 km from the epicenter; (3)the slopes with the dip angle of 30～50,especially 30～40,are very easy to slide during Wenchuan Earthquake; (4)the earthquakeinduced landslides mainly distributed in the elevation range of 600～1500m,especially 600～1000 m; (5)soft rocks such as mudstone,shale,schist and so on,are the easiest to slide during Wenchuan Earthquake; the combination of soft and hard rocks is secondary to slide; and hard rocks such as granite and carbonate rocks are not easy to slide; only a few old landslides were reactivated by Wenchuan Earthquake.
At 14：28(Beijing time)of May 12, 2008,a catastrophic earthquake with surface wave magnitude of 80 struck Sichuan province of China. Tens of thousands of landslides were triggered by this earthquake over a broad area. A total of 48007 landslides were interpreted from aerial photographs and multisource remote sensing imageries,verified by field check. A spatial database,including landslides and associated controlling parameters which may have influence on the occurrence of landslides,was developed and analyzed using geographical information system(GIS)technology. The eight factors that influence landslide occurrence,including seismic intensity,lithology,slope angle,faults,elevation,slope aspect,drainages and roads were created in raster data format base on GIS platform. The landslide susceptibility index of all ranks in each impact factor was calculated,using the certainty factor analysis method. Earthquakeinduced landslide susceptibility areas of 16 impact factor combination categories were analyzed and mapped one after another,using the GIS raster analysis methods. The susceptibility result of the highest AUC(Area Under Curve)was used to create susceptibility map by using Natural Breaks law. The resulting susceptibility map showed five classes of landslide susceptibility,ie.〖KG-*5〗,extremely high,high,moderate,low,and extremely low. The validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide distributions. The area with extremely high and high susceptibility accounts for about 1169046 km2, 2402% of the study area,includes landslide areas of 52484 km2, 7373% of all landslide areas. The susceptibility success accuracy was up to 82107% in the form of AUC．
At 14：28(Beijing time)of May 12, 2008,a catastrophic earthquake with surface wave magnitude of 80 struck Sichuan province of China. Tens of thousands of landslides were triggered by this earthquake over a broad area. A total of 48007 landslides were interpreted from aerial photographs and multisource remote sensing imageries,verified by field check. A spatial database,including landslides and associated controlling parameters which may have influence on the occurrence of landslides,was developed and analyzed using geographical information system(GIS)technology. The eight factors that influence landslide occurrence,including seismic intensity,lithology,slope angle,faults,elevation,slope aspect,drainages and roads were created in raster data format base on GIS platform. The landslide susceptibility index of all ranks in each impact factor was calculated,using the certainty factor analysis method. Earthquakeinduced landslide susceptibility areas of 16 impact factor combination categories were analyzed and mapped one after another,using the GIS raster analysis methods. The susceptibility result of the highest AUC(Area Under Curve)was used to create susceptibility map by using Natural Breaks law. The resulting susceptibility map showed five classes of landslide susceptibility,ie.〖KG-*5〗,extremely high,high,moderate,low,and extremely low. The validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide distributions. The area with extremely high and high susceptibility accounts for about 1169046 km2, 2402% of the study area,includes landslide areas of 52484 km2, 7373% of all landslide areas. The susceptibility success accuracy was up to 82107% in the form of AUC．
2010, 18(1)
From May 13 to 27, 2009,the seismic responses of a slope during four aftershocks of the 2008 Wenchuan Earthquake were monitored with the 941B ultralowfrequency vibrometer and G01 generalpurpose instrument. The slope located at Wei Ganliang in Qingchuang county. The microseismic monitoring shows that relative to the 805 m elevation at the Wei Ganliang Mountain,the measured peak accelerations of ground motion at the 875 m elevation in the horizontal EW direction and vertical direction had the tendency of reduction. However,the measured peack accelerations in the horizontal NS direction had a significant multiplier effect. The magnification was up to 7 to 8 times. The main frequency of the amplitude spectrum focused on the low frequency range between 20 and 40 Hz. Analysis shows that the epicenter located on the north side of the NEE striking QingchuanPingwu fault. Along the direction of seismic wave propagation,the slope has significant an amplification effect．
From May 13 to 27, 2009,the seismic responses of a slope during four aftershocks of the 2008 Wenchuan Earthquake were monitored with the 941B ultralowfrequency vibrometer and G01 generalpurpose instrument. The slope located at Wei Ganliang in Qingchuang county. The microseismic monitoring shows that relative to the 805 m elevation at the Wei Ganliang Mountain,the measured peak accelerations of ground motion at the 875 m elevation in the horizontal EW direction and vertical direction had the tendency of reduction. However,the measured peack accelerations in the horizontal NS direction had a significant multiplier effect. The magnification was up to 7 to 8 times. The main frequency of the amplitude spectrum focused on the low frequency range between 20 and 40 Hz. Analysis shows that the epicenter located on the north side of the NEE striking QingchuanPingwu fault. Along the direction of seismic wave propagation,the slope has significant an amplification effect．
Identification of landslidingsurface is the crucial problem of landslide investigation and research. It is also important for landslide stability and construction design. The basic type of landslidingsurface is categorized to rock surface,sediment surface,and soil surface. The geological characters of landslidingsurface can be classified as smooth friction surface,striation,mudding zone and diamond shearing wedge with directional range. Based on this classification,it is generated that the main methods for landslidingsurface identification contains mechanical analysis,field geology judgment,site exploration,displacement monitoring and geophysical detection. Applicability of these methods is also discussed in the paper．
Identification of landslidingsurface is the crucial problem of landslide investigation and research. It is also important for landslide stability and construction design. The basic type of landslidingsurface is categorized to rock surface,sediment surface,and soil surface. The geological characters of landslidingsurface can be classified as smooth friction surface,striation,mudding zone and diamond shearing wedge with directional range. Based on this classification,it is generated that the main methods for landslidingsurface identification contains mechanical analysis,field geology judgment,site exploration,displacement monitoring and geophysical detection. Applicability of these methods is also discussed in the paper．
The coupling mechanism between landslide and climate change is one of the hot topics in the landslide study in recent years.This paper studies the paleolandslides and present landslides that occurred in the upper Yellow River since latePleistocene. The characteristics of spatial and temporal distribution of the landslide and the coupling relationship between landslide active periods and climate changes and the climate changedriven mechanism of landslide are analyzed in detail. It is found that: (1)the landslide development is closely related to the climate changes. Most landslides are developed in warm and wet periods such as the marine oxygen isotopic odd stages. Rapid and continuous climatic fluctuation periods usually are also the highfrequency active periods of landslide. (2)There are 205 landslides distributed from Liujia Gorge to Longyang Gorge in the main stream of upper Yellow River. The total volume of residual deposits is 781108 m3. There are 15 superlarge landslides located the main steam,which accounts for 73% of the total landslides. 3)There are three active periods of Paleolandslides and debris flows in the region from Longyang Gorge to Liujia Gorge of Yellow River. Landslides in the first active stage have the OSL age of 18～21 kaBP. Their volume is more than 5108 m3. They are developed on the 3rd～4th fluvial terraces of Yellow River. Landslides in the 2nd active stage have the OSL age of 4～9 kaBP. Their volume is between 1～5108 m3. They are developed on the 2nd fluvial terraces of Yellow River. The present landslides are in the 3rd active stage. Their volume is between 05～1107m3. They are developed on the 1st fluvial terraces of Yellow River. The study shows that the Gonghe tectonic movement caused the region uplift and in turn strong downcutting erosion occurred along the river to form 300～600m steep slopes. In addition,the rapid climatic fluctuation in the LGM induced the landslide development in the first stage. During the 3～8 ka BP. of Holocene Optimal,strong monsoonal rainfall and a large of melted snow and ice converged into Yellow River,which led the landslide development of the second stage. The present landslides were mainly trigged by the human activities．
The coupling mechanism between landslide and climate change is one of the hot topics in the landslide study in recent years.This paper studies the paleolandslides and present landslides that occurred in the upper Yellow River since latePleistocene. The characteristics of spatial and temporal distribution of the landslide and the coupling relationship between landslide active periods and climate changes and the climate changedriven mechanism of landslide are analyzed in detail. It is found that: (1)the landslide development is closely related to the climate changes. Most landslides are developed in warm and wet periods such as the marine oxygen isotopic odd stages. Rapid and continuous climatic fluctuation periods usually are also the highfrequency active periods of landslide. (2)There are 205 landslides distributed from Liujia Gorge to Longyang Gorge in the main stream of upper Yellow River. The total volume of residual deposits is 781108 m3. There are 15 superlarge landslides located the main steam,which accounts for 73% of the total landslides. 3)There are three active periods of Paleolandslides and debris flows in the region from Longyang Gorge to Liujia Gorge of Yellow River. Landslides in the first active stage have the OSL age of 18～21 kaBP. Their volume is more than 5108 m3. They are developed on the 3rd～4th fluvial terraces of Yellow River. Landslides in the 2nd active stage have the OSL age of 4～9 kaBP. Their volume is between 1～5108 m3. They are developed on the 2nd fluvial terraces of Yellow River. The present landslides are in the 3rd active stage. Their volume is between 05～1107m3. They are developed on the 1st fluvial terraces of Yellow River. The study shows that the Gonghe tectonic movement caused the region uplift and in turn strong downcutting erosion occurred along the river to form 300～600m steep slopes. In addition,the rapid climatic fluctuation in the LGM induced the landslide development in the first stage. During the 3～8 ka BP. of Holocene Optimal,strong monsoonal rainfall and a large of melted snow and ice converged into Yellow River,which led the landslide development of the second stage. The present landslides were mainly trigged by the human activities．
2010, 18(1)
his paper examines three huge rockslides triggered by reservoir in the world They are the Vaint landslide in Italy, the Tangyanguang landslide in Hunan province of China and the Qianjiangping landslide in Three Gorges Reservoir of Central China. They have many similarities in geological conditions, triggering mechanism and deformation characteristics. The paper finds that the reservoir water flouting, slip surface soak softening and their coupling are the triggering causes. The paper proposes a landslide space prediction model. It is based on the geological structure included the following six essential factors: bedding slope structure, chair shape slope, soft inter-layers, slide out space, soft intercalation exposure at the toe, and deep and thick weathered rock mass. with the former four factors are the necessary conditions and the later two are selective. The main landslide deformation characteristics for short term are the formation of discontinued tensile cracks at the crown and the small collapse at the toe. The landslide deformation characteristics for near slide are the cracks at the crown continued and have closing tendency. The deep rockmass displacement orientation becomes upward. The creep v-t curve tangent is nearly upright. The creep speed is 20～30 cm per day.
his paper examines three huge rockslides triggered by reservoir in the world They are the Vaint landslide in Italy, the Tangyanguang landslide in Hunan province of China and the Qianjiangping landslide in Three Gorges Reservoir of Central China. They have many similarities in geological conditions, triggering mechanism and deformation characteristics. The paper finds that the reservoir water flouting, slip surface soak softening and their coupling are the triggering causes. The paper proposes a landslide space prediction model. It is based on the geological structure included the following six essential factors: bedding slope structure, chair shape slope, soft inter-layers, slide out space, soft intercalation exposure at the toe, and deep and thick weathered rock mass. with the former four factors are the necessary conditions and the later two are selective. The main landslide deformation characteristics for short term are the formation of discontinued tensile cracks at the crown and the small collapse at the toe. The landslide deformation characteristics for near slide are the cracks at the crown continued and have closing tendency. The deep rockmass displacement orientation becomes upward. The creep v-t curve tangent is nearly upright. The creep speed is 20～30 cm per day.
The K492 landslide on Chengyu railway has been worsening from its first deformation in 1998. The phenomenon of road base deformation and ground crack can often be seen in rainy season. With the change of groundwater level and the water level in Yangtze River, the landslide is still in the deformation of stage. Its formation and development is mainly due to the pore water pressure in the slope. This paper determines the factors of safety associated with the landslide in different water levels. The results indicate that its instability is at the major flood level. At the same time, it is calculated the factor of safety according to the changes of water level, the development of fissures and the crack -water level. The landslide of complex water-bearing accumulation horizon should be controlled in a comprehensive way of retaining structures and drainage.
The K492 landslide on Chengyu railway has been worsening from its first deformation in 1998. The phenomenon of road base deformation and ground crack can often be seen in rainy season. With the change of groundwater level and the water level in Yangtze River, the landslide is still in the deformation of stage. Its formation and development is mainly due to the pore water pressure in the slope. This paper determines the factors of safety associated with the landslide in different water levels. The results indicate that its instability is at the major flood level. At the same time, it is calculated the factor of safety according to the changes of water level, the development of fissures and the crack -water level. The landslide of complex water-bearing accumulation horizon should be controlled in a comprehensive way of retaining structures and drainage.
A group of huge ancient landslides locates at Zhangmu port to the south of Himalayas. The slope terrain of the landslides is steep. The regional tectonic movement is strong. Seismic activity is frequent. Rainfall is very abundant. The lower of stratum forming the landslides is biotite plagiogneiss schist of Sinian period. The upper is eluvial deposits,colluvial deposits and deluvial materials of Quaternary period. In recent years,some of the ancient landslides moves acutely as a result of rapid town construction and development. The ground movement has caused damage of many town buildings. It is estimated that properties of about 8 hundred million RMB and 8000 local people are being threatened by the landslides. The systematic deformation characters and patterns of the landslides are examined with the superficial crack monitoring,superficial displacement monitoring and deep borehole displacement monitoring. The results of the monitoring indicate that two ancient landslides may be stable. Rainfall and human activities triggered the revival of Xiaofangdui landslide. This Xiaofangdui landslide is at the stage of creep and extrusion. Its landslide deformation has a slowly rising tendency．
A group of huge ancient landslides locates at Zhangmu port to the south of Himalayas. The slope terrain of the landslides is steep. The regional tectonic movement is strong. Seismic activity is frequent. Rainfall is very abundant. The lower of stratum forming the landslides is biotite plagiogneiss schist of Sinian period. The upper is eluvial deposits,colluvial deposits and deluvial materials of Quaternary period. In recent years,some of the ancient landslides moves acutely as a result of rapid town construction and development. The ground movement has caused damage of many town buildings. It is estimated that properties of about 8 hundred million RMB and 8000 local people are being threatened by the landslides. The systematic deformation characters and patterns of the landslides are examined with the superficial crack monitoring,superficial displacement monitoring and deep borehole displacement monitoring. The results of the monitoring indicate that two ancient landslides may be stable. Rainfall and human activities triggered the revival of Xiaofangdui landslide. This Xiaofangdui landslide is at the stage of creep and extrusion. Its landslide deformation has a slowly rising tendency．
The steady state strength (i.e., residual strength) plays a major role in the flow sliding mechanism of loess landslides. The evaluation of residual strength requires a better understanding of undrained saturated loess behavior. The steady strength of saturated loess is examined using stresscontrolled undrained consolidation triaxial test. Two typical stress-strain behaviors of saturated loess are steady state behavior and quasi-steady state. The majority situations exhibit steady state behavior. Only loose loess exhibits quasi-steady state behavior. According to the test results, steady state line and steady state strength line of saturated loess are established. These lines can be used to analyze the mechanism of flow slide. It can use the angle of internal friction and cohesion to describe the steady state behavior of saturated loess. The meaning of these parameters is discussed. The difference of irrigation-induced landslides of loess and seismically-induced landslides of loess is analyzed. If the landslides induced by earthquake, the steady state strength (residual strength) plays a major role. If the landslides induced by irrigation, the peak strength plays a major role.
The steady state strength (i.e., residual strength) plays a major role in the flow sliding mechanism of loess landslides. The evaluation of residual strength requires a better understanding of undrained saturated loess behavior. The steady strength of saturated loess is examined using stresscontrolled undrained consolidation triaxial test. Two typical stress-strain behaviors of saturated loess are steady state behavior and quasi-steady state. The majority situations exhibit steady state behavior. Only loose loess exhibits quasi-steady state behavior. According to the test results, steady state line and steady state strength line of saturated loess are established. These lines can be used to analyze the mechanism of flow slide. It can use the angle of internal friction and cohesion to describe the steady state behavior of saturated loess. The meaning of these parameters is discussed. The difference of irrigation-induced landslides of loess and seismically-induced landslides of loess is analyzed. If the landslides induced by earthquake, the steady state strength (residual strength) plays a major role. If the landslides induced by irrigation, the peak strength plays a major role.
The dam of the landslide debris barrier lake mainly consists of boulder and stony soil and it is more vulnerable to instability as the result of a rise in water level. The dambreak may cause huge economic property and life loss. Therefore the study of dambreak problem has important academic significance and application value. A highspeed giant landslide occurred in Yigong River in the Bomi,Tibet,on April 9, 2〖CS％0,0,0,0〗〖CS〗000.A landslide dam was formed suddenly with 2500 m long, 2500 m wide and 60 m high, 280～300 million m3 in volume. A debris barrier lake was formed. Taking the dambreak of Yigong barrier lake as an example,according to the continuity equation and NavierStokes equation,combining with standard turbulence model,and tracking the freesurface with VOF method,via computational fluid dynamics software Fluent,this paper analyzes the dambreak flood evolution in downstream river course and the velocity changes at different sites. The simulation results are consistent with the observed data. At the same time,it shows that the model can simply simulate the flood evolution in the river bend with complex terrain after dambreak. The study can provide the prevention of dambreak disaster in terms of downstream flooding.
The dam of the landslide debris barrier lake mainly consists of boulder and stony soil and it is more vulnerable to instability as the result of a rise in water level. The dambreak may cause huge economic property and life loss. Therefore the study of dambreak problem has important academic significance and application value. A highspeed giant landslide occurred in Yigong River in the Bomi,Tibet,on April 9, 2〖CS％0,0,0,0〗〖CS〗000.A landslide dam was formed suddenly with 2500 m long, 2500 m wide and 60 m high, 280～300 million m3 in volume. A debris barrier lake was formed. Taking the dambreak of Yigong barrier lake as an example,according to the continuity equation and NavierStokes equation,combining with standard turbulence model,and tracking the freesurface with VOF method,via computational fluid dynamics software Fluent,this paper analyzes the dambreak flood evolution in downstream river course and the velocity changes at different sites. The simulation results are consistent with the observed data. At the same time,it shows that the model can simply simulate the flood evolution in the river bend with complex terrain after dambreak. The study can provide the prevention of dambreak disaster in terms of downstream flooding.
Landslide risk research has target and hierarchy,not limited in one form and content. Current landslide risk research is scarce in the type classification and hierarchy comparison. Furthermore,its application range is unclear,too. With the landslide risk research development,its necessary to study the landslide risk research types and definitions based on the former studies. The results will be convenient for standardizing the contents and forms of landslide risk research. According to target classification method,here,landslide risk research is classified into five types: landslide risk appraisal and zoning,risk analysis,risk probability,risk assessment and risk management. Based on internal relationship among landslide risk types,hierarchical knowledge and practical application method are established. Among different landslide risk types,there is a hierarchical knowledge relationship. Although different levels have different functions,they support each other．
Landslide risk research has target and hierarchy,not limited in one form and content. Current landslide risk research is scarce in the type classification and hierarchy comparison. Furthermore,its application range is unclear,too. With the landslide risk research development,its necessary to study the landslide risk research types and definitions based on the former studies. The results will be convenient for standardizing the contents and forms of landslide risk research. According to target classification method,here,landslide risk research is classified into five types: landslide risk appraisal and zoning,risk analysis,risk probability,risk assessment and risk management. Based on internal relationship among landslide risk types,hierarchical knowledge and practical application method are established. Among different landslide risk types,there is a hierarchical knowledge relationship. Although different levels have different functions,they support each other．
2010, 18(1)
As located at the transition terrain between Tibet Plateau and Sichuan Basin,Luding county is typical of complex geological envirnonment and 127 debris flow gullies are distributed in this county with a formation density of 054 gully10km-2. On the basis of RS interpretation and field investigation,the forming,characteristics,damages,developing trend were discussed and corresponding prevention advices were put forward.(1)Complex geological,steep geomorphology and intense rainfall supply enough loose solid materials and advantageous potential and kinetic energy to debris flows. Whats more,an obvious powerlaw relationship is existed between the intraday rainfall and former sixday antecedent effective rainfall.(2)Debris flows are typical of groupoccurrence(including 2005-06-30 event, 2005-08-11 event and 2006-07-14 event)as occurrence space is concerned and nightoccurrence as occurrence time is concerned.(3)Burying,bursting,eroding and blocking consist of the main damage mode of debris flows and 74 residents had lost their lives because of debris flows in history.(4)Most debris gullies are at the forming stage and developing stage(113 gullies, 89%)and the annual period has been shorting from 20 years to less 10 years but the occurrence times have been increasing from 4 to 44 on the contrary.(5)Town debris flows,blocking of debris flows,scenic spot debris flows and ravine debris flows are four main prevention problems in Luding county and corresponding prevention advices were put forward including scientific planning,constructing of riskmitigation system,engineering,monitoring and warning.
As located at the transition terrain between Tibet Plateau and Sichuan Basin,Luding county is typical of complex geological envirnonment and 127 debris flow gullies are distributed in this county with a formation density of 054 gully10km-2. On the basis of RS interpretation and field investigation,the forming,characteristics,damages,developing trend were discussed and corresponding prevention advices were put forward.(1)Complex geological,steep geomorphology and intense rainfall supply enough loose solid materials and advantageous potential and kinetic energy to debris flows. Whats more,an obvious powerlaw relationship is existed between the intraday rainfall and former sixday antecedent effective rainfall.(2)Debris flows are typical of groupoccurrence(including 2005-06-30 event, 2005-08-11 event and 2006-07-14 event)as occurrence space is concerned and nightoccurrence as occurrence time is concerned.(3)Burying,bursting,eroding and blocking consist of the main damage mode of debris flows and 74 residents had lost their lives because of debris flows in history.(4)Most debris gullies are at the forming stage and developing stage(113 gullies, 89%)and the annual period has been shorting from 20 years to less 10 years but the occurrence times have been increasing from 4 to 44 on the contrary.(5)Town debris flows,blocking of debris flows,scenic spot debris flows and ravine debris flows are four main prevention problems in Luding county and corresponding prevention advices were put forward including scientific planning,constructing of riskmitigation system,engineering,monitoring and warning.
This paper aims at the characteristics of conceptual twophase resistance of debris flow. It uses the conceptual twophase resistance for a static analysis on accumulation state of debris flow. As a result,a formula for accumulation state of debris flow in general condition is presented. Furthermore,the characteristics of accumulation state of debris flow in different conditions are discussed. The analysis shows that it is reasonable to model the resistance term with the conceptual twophase resistance. It also indicates the complicated structure composition and reflects veritably the real accumulation state of debris flow. Under a given material condition,the conceptual twophase resistance term transforms into the resistance term of single material. The corresponding conclusion obtained is identical to the existing conclusion of analysis on a single material．
This paper aims at the characteristics of conceptual twophase resistance of debris flow. It uses the conceptual twophase resistance for a static analysis on accumulation state of debris flow. As a result,a formula for accumulation state of debris flow in general condition is presented. Furthermore,the characteristics of accumulation state of debris flow in different conditions are discussed. The analysis shows that it is reasonable to model the resistance term with the conceptual twophase resistance. It also indicates the complicated structure composition and reflects veritably the real accumulation state of debris flow. Under a given material condition,the conceptual twophase resistance term transforms into the resistance term of single material. The corresponding conclusion obtained is identical to the existing conclusion of analysis on a single material．
The study of earthquakeinduced landslides is based on the collection of the recorded documents and knowledge of landslides. It becomes very important to manage all these documents efficiently in order to speed up the study in this subject. This paper introduces a database management system about earthquakeinduced landslides. The system has a userfriendly interface for easy operation and maintenance. It is believed that this system will be a powerful tool in further study about earthquakesinduced landslides．
The study of earthquakeinduced landslides is based on the collection of the recorded documents and knowledge of landslides. It becomes very important to manage all these documents efficiently in order to speed up the study in this subject. This paper introduces a database management system about earthquakeinduced landslides. The system has a userfriendly interface for easy operation and maintenance. It is believed that this system will be a powerful tool in further study about earthquakesinduced landslides．
2010, 18(1)
The critical slip surface is controlled by two aspects,one is the combination relation with rock mass discontinuity and slope,another aspect is the size and the lie of the load. The failure mechanism of highsteep slope intact rock is very complex,the search for critical slip surface is tedious. The shape and position of 3D critical slip surface of highsteep slope intact rock under load are analyzed based on the stress effect coefficient. The effects of influence factors on the shape and position of 3D critical slip surface are analyzed. Results show that the shape of critical slip surface of highsteep slope intact rock under load should be an irregular wedge body and mainly in front region of the foundation,and the side of wedge is related to the size of bridge foundation,slope and the distance of bridge foundation. The load strength has no effect on the shape of critical slip surface,and the distance of bridge foundation has an important effect on it. The range of critical slip line of highsteep slope intact rock under load increases with the size or distance of bridge foundation,and with the slope increased,the length of critical slip line decreases,the depth increases. The range of 3D critical slip surface on highsteep slope intact rock is determined as follow: Pw=08444L-05098+05759S+693716,Ph=01148L+0171B+11725+00733S-5719．
The critical slip surface is controlled by two aspects,one is the combination relation with rock mass discontinuity and slope,another aspect is the size and the lie of the load. The failure mechanism of highsteep slope intact rock is very complex,the search for critical slip surface is tedious. The shape and position of 3D critical slip surface of highsteep slope intact rock under load are analyzed based on the stress effect coefficient. The effects of influence factors on the shape and position of 3D critical slip surface are analyzed. Results show that the shape of critical slip surface of highsteep slope intact rock under load should be an irregular wedge body and mainly in front region of the foundation,and the side of wedge is related to the size of bridge foundation,slope and the distance of bridge foundation. The load strength has no effect on the shape of critical slip surface,and the distance of bridge foundation has an important effect on it. The range of critical slip line of highsteep slope intact rock under load increases with the size or distance of bridge foundation,and with the slope increased,the length of critical slip line decreases,the depth increases. The range of 3D critical slip surface on highsteep slope intact rock is determined as follow: Pw=08444L-05098+05759S+693716,Ph=01148L+0171B+11725+00733S-5719．
In a single hole with multipurposes,the evaluation ability of waterresistance and confirming progressive intrusion height can be put in practice during the process of geostresses tests with the insitu hydraulic fracturing method in mining working faces or roadways. Test results in practice show that the abilities of the waterresistances of mudrocks,fine sandstones,middle sandstones,limestones are from large to small. The progressive intrusion heights are from small to large. The abilities of the waterresistances of strata in the floor Nos. 11, 10, 7, 8 of the coal seams are from large to small. The strata stabilities in the floor Nos. 8, 11, 7, 10 of the coal seams are also from large to small. Geostress tests with the insitu hydraulic fracturing method indicate that the original geostress states are SH＞Sv＞Sh. The directions of the maximum horizontal stress are from NE to NEE in this area. The water inrush critical index evaluation shows that the water inrush possibility is higher as the coal extraction into the550m level. Preventive measures should be undertaken earlier．
In a single hole with multipurposes,the evaluation ability of waterresistance and confirming progressive intrusion height can be put in practice during the process of geostresses tests with the insitu hydraulic fracturing method in mining working faces or roadways. Test results in practice show that the abilities of the waterresistances of mudrocks,fine sandstones,middle sandstones,limestones are from large to small. The progressive intrusion heights are from small to large. The abilities of the waterresistances of strata in the floor Nos. 11, 10, 7, 8 of the coal seams are from large to small. The strata stabilities in the floor Nos. 8, 11, 7, 10 of the coal seams are also from large to small. Geostress tests with the insitu hydraulic fracturing method indicate that the original geostress states are SH＞Sv＞Sh. The directions of the maximum horizontal stress are from NE to NEE in this area. The water inrush critical index evaluation shows that the water inrush possibility is higher as the coal extraction into the550m level. Preventive measures should be undertaken earlier．
To enhance understanding of the mechanism of slope stability,this paper investigates some of the mechanical characteristics of the slope mass only subjected to its selfweight body force. It uses the FLAC numerical simulation software and similarity law. It studies the relationships between them and the related physical or mechanical parameters. At the ground surface,the principal stresses must be either parallel or normal to the topography in the absence of surface loads. As the depth increases,the principal stress directions approach either vertical or horizontal. There are tensile stress and compressive stress at the slope surface. And the tensile stress in the toe of a slope is also very high. These are some general characteristics for the distribution of stresses in a slope,shown both in this paper or some other articles. This paper emphasizes that when the angle of a slope increases linearly,the changing velocity of maximum tensile stress on the top of the slope behaves fastly,then slowly and then fastly. The tensile stress decreases linearly with the depth on a line from the top of the slope downward vertically to the inner of the slope. Under the condition of small deformation,the stress field does not depend on the Youngs modulus value. When meeting the similarity law,the magnitudes of displacement ratios at the corresponding points are square times of their sizes ratios of a slope. This paper complements to existing knowledge. It further offers a base for further studies on more complicated slopes. It is meaningful in both theory and practice．
To enhance understanding of the mechanism of slope stability,this paper investigates some of the mechanical characteristics of the slope mass only subjected to its selfweight body force. It uses the FLAC numerical simulation software and similarity law. It studies the relationships between them and the related physical or mechanical parameters. At the ground surface,the principal stresses must be either parallel or normal to the topography in the absence of surface loads. As the depth increases,the principal stress directions approach either vertical or horizontal. There are tensile stress and compressive stress at the slope surface. And the tensile stress in the toe of a slope is also very high. These are some general characteristics for the distribution of stresses in a slope,shown both in this paper or some other articles. This paper emphasizes that when the angle of a slope increases linearly,the changing velocity of maximum tensile stress on the top of the slope behaves fastly,then slowly and then fastly. The tensile stress decreases linearly with the depth on a line from the top of the slope downward vertically to the inner of the slope. Under the condition of small deformation,the stress field does not depend on the Youngs modulus value. When meeting the similarity law,the magnitudes of displacement ratios at the corresponding points are square times of their sizes ratios of a slope. This paper complements to existing knowledge. It further offers a base for further studies on more complicated slopes. It is meaningful in both theory and practice．
Discontinuity of structuralplanes appearance is a complex research object; however,it has important an influence to the mechanical properties. At the present time,the study of incompletely backfilling of structuralplane is very poor. The adhesive friction theory is applied to research the changing course of structural plane,which is based on the analysis of incompletely backfilling．
Discontinuity of structuralplanes appearance is a complex research object; however,it has important an influence to the mechanical properties. At the present time,the study of incompletely backfilling of structuralplane is very poor. The adhesive friction theory is applied to research the changing course of structural plane,which is based on the analysis of incompletely backfilling．
The hydraulic conductivity function is the key parameter in the seepage analysis of unsaturated soil. Based on the foundational equation of fluid mechanics and the theory of probability and statistics,this paper proposes a theoretical model for saturated permeability function. This model can take the influence of soil structure into account. It is combined with the Mualeum(1976)relative permeability function model,together with the variation law of the structural parameters during deformation proposed by Assouline(2006). The influence of deformation on unsaturated permeability function is modeled. The paper compares the experimental results and some available models and the present model. The present model can improve the prediction precision without any increase of experimental workload. The necessities of applying statistic theory into soil mechanics is also discussed in the end of the paper.
The hydraulic conductivity function is the key parameter in the seepage analysis of unsaturated soil. Based on the foundational equation of fluid mechanics and the theory of probability and statistics,this paper proposes a theoretical model for saturated permeability function. This model can take the influence of soil structure into account. It is combined with the Mualeum(1976)relative permeability function model,together with the variation law of the structural parameters during deformation proposed by Assouline(2006). The influence of deformation on unsaturated permeability function is modeled. The paper compares the experimental results and some available models and the present model. The present model can improve the prediction precision without any increase of experimental workload. The necessities of applying statistic theory into soil mechanics is also discussed in the end of the paper.
During the last decades, a number of methods have been developed for the optimization of hydrologic model parameters. One frequently used method is the PEST method which is a LevenbergMarquardtbased optimization algorithm. As a nonlinear parameter estimator, the PEST method can exist independently of any particular models, can estimate parameters and/or excitations, and can carry out various predictive analysis tasks. Its model types cover a wide range. It is preferable to calibrate a MODFLOW model using the PEST method in many situations. However, for a largescale, highresolution or highcomplexity groundwater flow modeling, the parameter optimization requires massive computing time. In this study, the OpenMP programming paradigm is used to achieve the modest parallelism on a sharedmemory computer for the PEST method. Application of the parallel PEST method to Beishan area, Gansu province shows that the computing speed can be increased up to 3.7 times. The computing speed is defined as the ratio of the serial computing time and the parallel computing time. The parallel PEST parameter optimization method can be an useful and effective tool for large models.
During the last decades, a number of methods have been developed for the optimization of hydrologic model parameters. One frequently used method is the PEST method which is a LevenbergMarquardtbased optimization algorithm. As a nonlinear parameter estimator, the PEST method can exist independently of any particular models, can estimate parameters and/or excitations, and can carry out various predictive analysis tasks. Its model types cover a wide range. It is preferable to calibrate a MODFLOW model using the PEST method in many situations. However, for a largescale, highresolution or highcomplexity groundwater flow modeling, the parameter optimization requires massive computing time. In this study, the OpenMP programming paradigm is used to achieve the modest parallelism on a sharedmemory computer for the PEST method. Application of the parallel PEST method to Beishan area, Gansu province shows that the computing speed can be increased up to 3.7 times. The computing speed is defined as the ratio of the serial computing time and the parallel computing time. The parallel PEST parameter optimization method can be an useful and effective tool for large models.
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