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Editor Work2010 Vol. 18, No. 4
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2010, 18(4): 437-444.
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The reason of giant debris flow triggering was obtained by field investigation and analysis on the debris flow formation conditions: heavy rainfall happened in the upstream of Sanyanyu Gully and Luojiayu Gully.The recorded rainfall was 77.3mm in one hour from 23 to 24 oclock, August 7, 2010. The heavy rain caused powerful flash flood in the catchments,which destroyed several natural dams and prevention dams in the two gullies. Then the giant debris flows were formed. The debris flows were high density viscous debris flows. The total volume of debris flows and the volume of sediment in debris flows were estimated at 144.2104m3 and 97.7104m3, respectively. The large boulder involving in debris flows moved with powerful impact force and destroyed more than 5500 houses in depositional fans. The debris flows produced a dam with 550m in length, 70m in width, and 10m in height in Bailongjiang River. The dam blocked the river and formed a lake with 3km in length and half of Zhouqu city was inundated. As of August 18, 2010, the debris flows claimed 1287 death, with further 457 listed as missing. The tendency of debris flow development was obtained by a preliminary analysis of the initiation conditions of debris flows: （1) The debris flows will be triggered if there is a heavy rainfall in the upstream of debris flows gullies recently, but the scale of debris flows will be less than the scale of debris flows on August 7, 2010; （2) The debris flows will be triggered if there is a heavy rainfall in the upstream of debris flows gullies in a few years, the scale of debris flows will be a little bit less than the scale of debris flows on August 7, 2010; （3) The scale of debris flows 20 years later will be the same as the scale of debris flows before Wenchuan Earthquake if there is no more earthquake effect this area and a event of large scale debris flow has happened in these gullies.
The reason of giant debris flow triggering was obtained by field investigation and analysis on the debris flow formation conditions: heavy rainfall happened in the upstream of Sanyanyu Gully and Luojiayu Gully.The recorded rainfall was 77.3mm in one hour from 23 to 24 oclock, August 7, 2010. The heavy rain caused powerful flash flood in the catchments,which destroyed several natural dams and prevention dams in the two gullies. Then the giant debris flows were formed. The debris flows were high density viscous debris flows. The total volume of debris flows and the volume of sediment in debris flows were estimated at 144.2104m3 and 97.7104m3, respectively. The large boulder involving in debris flows moved with powerful impact force and destroyed more than 5500 houses in depositional fans. The debris flows produced a dam with 550m in length, 70m in width, and 10m in height in Bailongjiang River. The dam blocked the river and formed a lake with 3km in length and half of Zhouqu city was inundated. As of August 18, 2010, the debris flows claimed 1287 death, with further 457 listed as missing. The tendency of debris flow development was obtained by a preliminary analysis of the initiation conditions of debris flows: （1) The debris flows will be triggered if there is a heavy rainfall in the upstream of debris flows gullies recently, but the scale of debris flows will be less than the scale of debris flows on August 7, 2010; （2) The debris flows will be triggered if there is a heavy rainfall in the upstream of debris flows gullies in a few years, the scale of debris flows will be a little bit less than the scale of debris flows on August 7, 2010; （3) The scale of debris flows 20 years later will be the same as the scale of debris flows before Wenchuan Earthquake if there is no more earthquake effect this area and a event of large scale debris flow has happened in these gullies.
2010, 18(4): 445-454.
On June 28， 2010，due to sudden heavy rainfall，a high speed and long runout rockslidedebris flow occurred at Dazhai in Guanling of Guizhou Province. Its runout distance was about 1.5km.Its rock debris volume was about 174.9 M m3.Its destroyed two villages and resulted 99 fatalities.The landslide was located at the coalrelated sedimentary rock strata area.This rock system commonly presents in southwestern China.The upper strata are limestone and dolomite.The middle strata are sandstone with gentle dipangles.The lower strata are mainly shale and mudstone and have coal seams in local regions.The strata forming the mountains have a special geological structure with hard rocks at upper portion and soft rocks at lower portion and a hydrogeological structure with upper rich groundwater aquifer and lower impermeable beds，which can easily form landslide hazards.From the site topography，the hillside slopes are steeper at the upper portion and gentler in the lower portion.The topography looks like a shoeshaped geometry. The upper steep slopes can easily occur slope instability and the middle and lower gentle and wide slope valleys offer the kinematic conditions for landslide debris to flow long distance. Transformation of the larger potential energy into kinetic energy can easily form rockslidedebris flows with high speed and long runout distance.
The heavy rainfall on June 27and 28 were the main factor triggering the major disaster.The rainfall was up to 310mm and exceeded the records over the last 60 years.Analysis indicates that the runoff in valley streams were two times more than those during usual rainfall at the region.The large runoff water formed static groundwater pressure and seepage pressure in joints and fossils of the sandstones at the landslide source zone，which led the landslide to occur.Secondly，the runoff was formed in stream valleys，which became a layer of saturated water bed for the rock debris to flow long distance.As a result，the runout distance and speed of the rock debris flow was evidently increased. The findings of this investigation are useful to reduce and mitigate the disasters of such high speed and long runout rockslides and debris flows，the occurrences of which seem to have been increasing in recent years in China due to extremely heavy rainfall events.
On June 28， 2010，due to sudden heavy rainfall，a high speed and long runout rockslidedebris flow occurred at Dazhai in Guanling of Guizhou Province. Its runout distance was about 1.5km.Its rock debris volume was about 174.9 M m3.Its destroyed two villages and resulted 99 fatalities.The landslide was located at the coalrelated sedimentary rock strata area.This rock system commonly presents in southwestern China.The upper strata are limestone and dolomite.The middle strata are sandstone with gentle dipangles.The lower strata are mainly shale and mudstone and have coal seams in local regions.The strata forming the mountains have a special geological structure with hard rocks at upper portion and soft rocks at lower portion and a hydrogeological structure with upper rich groundwater aquifer and lower impermeable beds，which can easily form landslide hazards.From the site topography，the hillside slopes are steeper at the upper portion and gentler in the lower portion.The topography looks like a shoeshaped geometry. The upper steep slopes can easily occur slope instability and the middle and lower gentle and wide slope valleys offer the kinematic conditions for landslide debris to flow long distance. Transformation of the larger potential energy into kinetic energy can easily form rockslidedebris flows with high speed and long runout distance.
The heavy rainfall on June 27and 28 were the main factor triggering the major disaster.The rainfall was up to 310mm and exceeded the records over the last 60 years.Analysis indicates that the runoff in valley streams were two times more than those during usual rainfall at the region.The large runoff water formed static groundwater pressure and seepage pressure in joints and fossils of the sandstones at the landslide source zone，which led the landslide to occur.Secondly，the runoff was formed in stream valleys，which became a layer of saturated water bed for the rock debris to flow long distance.As a result，the runout distance and speed of the rock debris flow was evidently increased. The findings of this investigation are useful to reduce and mitigate the disasters of such high speed and long runout rockslides and debris flows，the occurrences of which seem to have been increasing in recent years in China due to extremely heavy rainfall events.
The deeply seated and 11.068 km long Yuanliangshan tunnel is a key project of the railway from Chongqing to Huaihua. The tunnel goes cross the Yuanliangshan syncline,a NESW trending tightly folded syncline,and cuts numerous NWNWW striking transverse faults. The core of the syncline composes of Permian and Lower Triassic carbonate rock strata,and the soluble rock terrain is enveloped on all sides by underlying Devonian and Silurian shale. The length of the tunnel drifted through the soluble carbonate rock mass is 2,2 km. On the ground surface,there are a lot of karstic depressions,dolines and sinkholes. Numerous karstic springs emerge out from the tips of the transverse faults on both wings of the syncline,where the carbonate rock strata contacts with the underlying shale. The elevations of the springs are usually higher than 850～900 m above the mean sea level. These elevations are regarded as the local discharge base level of the underground karstic water. The tunnel is situated at 400 to 450 m under this base level. During the drifting of the tunnel,three infilled huge karstic caves(Nos. 1#, 2#,and 3#)were exposed near by the axis,at the axis and at the east wing of the syncline,respectively. Water gushing and sand boiling hazards occurred many times while drifting through the sand infilled cave No. 2#. An unexpected and seldom observed blasting and shooting extrusion of clayey soil hazard occurred when the clayey soil infilled cave No.3# was just exposed．
Through comprehensive analysis of the abundant data gathered during the construction of the tunnel,it is tentatively concluded: (1)an open primitive channel for the deep circulation of karstic water has been provided by the intersection of the two transverse faults(f7 and f9)with the longitudinal tension cracks nearby the axis,the bed separation void at the core of the syncline,and an interstratal shearing zone at the east wing of the syncline. A reversesiphonic circulation of karstic water was impelled by the potential difference between the underground water levels of the two transverse faults; (2)strong water conductive faults and cracks developed into caves through longtime differential dissolution and the water in these channels transformed into pipe flow; (3)by longtime strongly dissolution and erosion(and for the cave No.2 also roof collapse),the longitudinal tension crack,the bed separation void and the interstrated shearing zone were transformed into huge karstic caves; (4)caves were infilled due to the changing of hydrologic condition．
The deeply seated and 11.068 km long Yuanliangshan tunnel is a key project of the railway from Chongqing to Huaihua. The tunnel goes cross the Yuanliangshan syncline,a NESW trending tightly folded syncline,and cuts numerous NWNWW striking transverse faults. The core of the syncline composes of Permian and Lower Triassic carbonate rock strata,and the soluble rock terrain is enveloped on all sides by underlying Devonian and Silurian shale. The length of the tunnel drifted through the soluble carbonate rock mass is 2,2 km. On the ground surface,there are a lot of karstic depressions,dolines and sinkholes. Numerous karstic springs emerge out from the tips of the transverse faults on both wings of the syncline,where the carbonate rock strata contacts with the underlying shale. The elevations of the springs are usually higher than 850～900 m above the mean sea level. These elevations are regarded as the local discharge base level of the underground karstic water. The tunnel is situated at 400 to 450 m under this base level. During the drifting of the tunnel,three infilled huge karstic caves(Nos. 1#, 2#,and 3#)were exposed near by the axis,at the axis and at the east wing of the syncline,respectively. Water gushing and sand boiling hazards occurred many times while drifting through the sand infilled cave No. 2#. An unexpected and seldom observed blasting and shooting extrusion of clayey soil hazard occurred when the clayey soil infilled cave No.3# was just exposed．
Through comprehensive analysis of the abundant data gathered during the construction of the tunnel,it is tentatively concluded: (1)an open primitive channel for the deep circulation of karstic water has been provided by the intersection of the two transverse faults(f7 and f9)with the longitudinal tension cracks nearby the axis,the bed separation void at the core of the syncline,and an interstratal shearing zone at the east wing of the syncline. A reversesiphonic circulation of karstic water was impelled by the potential difference between the underground water levels of the two transverse faults; (2)strong water conductive faults and cracks developed into caves through longtime differential dissolution and the water in these channels transformed into pipe flow; (3)by longtime strongly dissolution and erosion(and for the cave No.2 also roof collapse),the longitudinal tension crack,the bed separation void and the interstrated shearing zone were transformed into huge karstic caves; (4)caves were infilled due to the changing of hydrologic condition．
2010, 18(4): 470-476.
Largescale and super largescale rock landslides are not only huge in size and range,but also mostly located in mountains and valleys. Usually,site exploration can be used to determine landslide slip zone location and shape accurately. However,with extremely difficult terrain conditions and mostly at the preliminary study stage,the landslides slip surface location could not be determined accurately because of lacking of exploration data and thus strength parameters are hard to get also. This paper used the initial geological conditions for the formation of large rock landslide. They include terrain conditions,topography,lithology,structural conditions,river morphology,slope body structure and deformation damage structure,combined with slide morphological characteristics after its formation,used feedback approach and analyzed large rock landslide slip surface location and morphological characteristics. Based on the information of the location of the landslide slip surface,this paper analyzed and calculated normal stress(compressive stress)generated on the slip surface by the weight of the rock body covered the slip surface. Based on the acquired slip zone soil samples,using normal stress generated on the slip surface by landslide body weight force,this paper conducted matching laboratory tests using principle of gravity compaction to get the corresponding physical indicators on various areas. This paper also conducted matching lab tests of strength,and got strength parameters,and established the slidezone soil void ratio,water content relationship with friction coefficient and cohesion. With the relationship established from tests,combined with gravity compaction tests result of the water content at different parts,this paper analyzed and studied the slip surface strength parameters. Transfer coefficient and Morgenstern law were used to calculate the stability of landslide coefficient under natural condition,and calculated values greater than 12,which accorded with current distortion trends of landslides．
Largescale rockslides，Slide surface，The principle of gravity pressure density the principle of structure regenerate and intensity regenerate，Slide surface intensity parameters
Largescale and super largescale rock landslides are not only huge in size and range,but also mostly located in mountains and valleys. Usually,site exploration can be used to determine landslide slip zone location and shape accurately. However,with extremely difficult terrain conditions and mostly at the preliminary study stage,the landslides slip surface location could not be determined accurately because of lacking of exploration data and thus strength parameters are hard to get also. This paper used the initial geological conditions for the formation of large rock landslide. They include terrain conditions,topography,lithology,structural conditions,river morphology,slope body structure and deformation damage structure,combined with slide morphological characteristics after its formation,used feedback approach and analyzed large rock landslide slip surface location and morphological characteristics. Based on the information of the location of the landslide slip surface,this paper analyzed and calculated normal stress(compressive stress)generated on the slip surface by the weight of the rock body covered the slip surface. Based on the acquired slip zone soil samples,using normal stress generated on the slip surface by landslide body weight force,this paper conducted matching laboratory tests using principle of gravity compaction to get the corresponding physical indicators on various areas. This paper also conducted matching lab tests of strength,and got strength parameters,and established the slidezone soil void ratio,water content relationship with friction coefficient and cohesion. With the relationship established from tests,combined with gravity compaction tests result of the water content at different parts,this paper analyzed and studied the slip surface strength parameters. Transfer coefficient and Morgenstern law were used to calculate the stability of landslide coefficient under natural condition,and calculated values greater than 12,which accorded with current distortion trends of landslides．
Largescale rockslides，Slide surface，The principle of gravity pressure density the principle of structure regenerate and intensity regenerate，Slide surface intensity parameters
2010, 18(4): 477-482.
This paper deals with a special antislid pile whose head is further reinforced and stabilized with bars abchored in soil. Due to the existence of anchor bars,the internal forces and the pile anchoring depth can be greatly reduced. However,the method of calculation is not yet perfect and need a certain amount of engineering experience. The experimental study is very necessary. This paper presents the model test results of earth force in the side of antislide pile of anchor bars. There are three groups of the tests. The loads are on the back side of the slope in two groups. The other one has itsload just behind the pile by jack. In order to get the force of the soil,some earthpressure boxes are put to get the earth pressure on side of the piles. The part of the maximum pressure of the earth pressure is mainly focused under the slip line before the pile and is found by the test. The earth pressure before the pile is got by the test. According with the result of the test,the anchoring depth of the triangle and echelon shapes of the anti pressure is computed and compared the result with what got from the test.
This paper deals with a special antislid pile whose head is further reinforced and stabilized with bars abchored in soil. Due to the existence of anchor bars,the internal forces and the pile anchoring depth can be greatly reduced. However,the method of calculation is not yet perfect and need a certain amount of engineering experience. The experimental study is very necessary. This paper presents the model test results of earth force in the side of antislide pile of anchor bars. There are three groups of the tests. The loads are on the back side of the slope in two groups. The other one has itsload just behind the pile by jack. In order to get the force of the soil,some earthpressure boxes are put to get the earth pressure on side of the piles. The part of the maximum pressure of the earth pressure is mainly focused under the slip line before the pile and is found by the test. The earth pressure before the pile is got by the test. According with the result of the test,the anchoring depth of the triangle and echelon shapes of the anti pressure is computed and compared the result with what got from the test.
2010, 18(4): 483-489.
The complex antislide piles whose shapes like П or h have been applied to many slope protections. But it is difficult for many traditional methods to calculate the internal force of the pile,because the pile structures are statically indeterminate,the load distributions which acts on the piles are unkwown and the interaction between soil and pile is complicated. Its a feasible way for calculating the internal force of complex antislide pile using strength reduction finite element method. The assumed structure type and load distributoin are not necessary. So the results got with the method are authentic normally. In this paper,a complex antislide pile,whose shape likes П,located in a tunnel entrance slope was taken as a example. In the base of studying the slope stability,the pile internal force was calculated using the strength reduction finite element method. The interaction relationship between pile and soil and engineering control effect were evaluated. The results show that its an effective way using the strength reduction finite element method for calculating the pile internal force. Some results have reference values for protection design．
The complex antislide piles whose shapes like П or h have been applied to many slope protections. But it is difficult for many traditional methods to calculate the internal force of the pile,because the pile structures are statically indeterminate,the load distributions which acts on the piles are unkwown and the interaction between soil and pile is complicated. Its a feasible way for calculating the internal force of complex antislide pile using strength reduction finite element method. The assumed structure type and load distributoin are not necessary. So the results got with the method are authentic normally. In this paper,a complex antislide pile,whose shape likes П,located in a tunnel entrance slope was taken as a example. In the base of studying the slope stability,the pile internal force was calculated using the strength reduction finite element method. The interaction relationship between pile and soil and engineering control effect were evaluated. The results show that its an effective way using the strength reduction finite element method for calculating the pile internal force. Some results have reference values for protection design．
2010, 18(4): 490-496.
The 512 Wenchuan Earthquake induced a lot of landslidesStudy areas of this paper are several severest disaster counties including Wenchuan，Beichuan，Qingchuan，Anxian，Pingwu，Maoxian，Jiangyou，Pengzhou，Shifang，Mianzhu etcUnder detailed field investigation，distribution and spatial characteristics of typical high speed landslides under the condition of strong earthquakes are analyzed comprehensivelyHigh speed landslides were all located along the Longmen Shan fault zone，and especially controlled by the Beichuan Yingxiu Fault which is one of the three sub faults of Longmen Shan faultThere is also another distribution characteristic that high speed landslides were all along the water systemsActive structures have macroscopic control to landslides while water systems have local effect to themFurthermore some spatial characteristics of high speed landslides such as slippage，the distances between the front and the back edge of landslides，height of the landslide shear crack are analyzed in this paper．
The 512 Wenchuan Earthquake induced a lot of landslidesStudy areas of this paper are several severest disaster counties including Wenchuan，Beichuan，Qingchuan，Anxian，Pingwu，Maoxian，Jiangyou，Pengzhou，Shifang，Mianzhu etcUnder detailed field investigation，distribution and spatial characteristics of typical high speed landslides under the condition of strong earthquakes are analyzed comprehensivelyHigh speed landslides were all located along the Longmen Shan fault zone，and especially controlled by the Beichuan Yingxiu Fault which is one of the three sub faults of Longmen Shan faultThere is also another distribution characteristic that high speed landslides were all along the water systemsActive structures have macroscopic control to landslides while water systems have local effect to themFurthermore some spatial characteristics of high speed landslides such as slippage，the distances between the front and the back edge of landslides，height of the landslide shear crack are analyzed in this paper．
2010, 18(4): 497-506.
In the viewpoint of seismic engineering,the horizontal seismic force is the decisive factor that leads to rocksoil mass destruction,while the vertical seismic forces are negligible. In view of huge destruction of the slopes and constructions caused by vertical seismic force in Wenchuan Earthquake,this paper conducted a numerical simulation research on the horizontal and vertical response law of the vertical acceleration in the slope with different heights and slope angle under the influence of the Pwave with different cycles and amplitude by use of FLAC finite difference software. The results showed that when the slope height is low,the acceleration,less than half of the slope height,increases with the height,while more than half of the slope height,it remains unchanged. When the slope height increases,the acceleration changes with a regularity,and the acceleration in the peak of the slope is bigger than any other parts in the slope. The bigger the slope angle and the greater the vibration acceleration enlargement ranges.The vibration acceleration increases as the amplitude increases. They have significant linear relations.The vibration acceleration on the slope increases as the cycle gradually decreases.
In the viewpoint of seismic engineering,the horizontal seismic force is the decisive factor that leads to rocksoil mass destruction,while the vertical seismic forces are negligible. In view of huge destruction of the slopes and constructions caused by vertical seismic force in Wenchuan Earthquake,this paper conducted a numerical simulation research on the horizontal and vertical response law of the vertical acceleration in the slope with different heights and slope angle under the influence of the Pwave with different cycles and amplitude by use of FLAC finite difference software. The results showed that when the slope height is low,the acceleration,less than half of the slope height,increases with the height,while more than half of the slope height,it remains unchanged. When the slope height increases,the acceleration changes with a regularity,and the acceleration in the peak of the slope is bigger than any other parts in the slope. The bigger the slope angle and the greater the vibration acceleration enlargement ranges.The vibration acceleration increases as the amplitude increases. They have significant linear relations.The vibration acceleration on the slope increases as the cycle gradually decreases.
2010, 18(4): 507-515.
Slope in material depots for hydropower station construction is generally characterized by great height and great slope angle. Considering its usage,this type of slope is usually designed as temporary slope with,therefore,temporary supporting scheme. Due to the rapid unloading caused by rock exploration,large deformation and failure happen frequently within such slope. Two slopes in material depots for the construction of Pubugou hydropower station in Sichuan Province,China,were taken as examples in this study. The supporting scheme were of dynamic design,that is,the design of supporting work was kept updated according to the monitoring of deformation in the progress of rock exploration. This paper concludes the dynamic design method and flowchart employed for these two slopes and puts forward a practical methodology for stability evaluation and supporting work design for such slopes. Firstly,three engineering geological problems about the selected slopes are summarized: （1)overall instability controlled by particular combination of weak discontinuities； （2)block instability； and（3)instability of cataclastic rock masses. Secondly,the overall slope stability is evaluated followed by local stability evaluation on the basis of dynamic investigation of rock mass during excavation. Dynamic design for slope supporting works during rock exploration obeys a general rule,ensuring overall stability,controlling local distortion and paying attention to potential instable zone. The instable zones,which could be determined and delineated by qualitative analysis were designed and constructed prior to others. Rules for the design of supporting works and standard for construction are stipulated for the blocks and cataclastic rock masses susceptible to deforming during rock exploration. To ensure security of construction and reduce the cost for slope supporting,the excavation scheme was adjusted from time to time for potential distortion zone. The practice in slopes at Pubugou hydropower station shows that the proposed method can fasten excavation of high slope and reduce the cost for slope stabilization.
Slope in material depots for hydropower station construction is generally characterized by great height and great slope angle. Considering its usage,this type of slope is usually designed as temporary slope with,therefore,temporary supporting scheme. Due to the rapid unloading caused by rock exploration,large deformation and failure happen frequently within such slope. Two slopes in material depots for the construction of Pubugou hydropower station in Sichuan Province,China,were taken as examples in this study. The supporting scheme were of dynamic design,that is,the design of supporting work was kept updated according to the monitoring of deformation in the progress of rock exploration. This paper concludes the dynamic design method and flowchart employed for these two slopes and puts forward a practical methodology for stability evaluation and supporting work design for such slopes. Firstly,three engineering geological problems about the selected slopes are summarized: （1)overall instability controlled by particular combination of weak discontinuities； （2)block instability； and（3)instability of cataclastic rock masses. Secondly,the overall slope stability is evaluated followed by local stability evaluation on the basis of dynamic investigation of rock mass during excavation. Dynamic design for slope supporting works during rock exploration obeys a general rule,ensuring overall stability,controlling local distortion and paying attention to potential instable zone. The instable zones,which could be determined and delineated by qualitative analysis were designed and constructed prior to others. Rules for the design of supporting works and standard for construction are stipulated for the blocks and cataclastic rock masses susceptible to deforming during rock exploration. To ensure security of construction and reduce the cost for slope supporting,the excavation scheme was adjusted from time to time for potential distortion zone. The practice in slopes at Pubugou hydropower station shows that the proposed method can fasten excavation of high slope and reduce the cost for slope stabilization.
2010, 18(4): 516-520.
Several cracks were found to occur on the slope face of the Laiwushan retaining wall. In order to understand the mechanism of deformation and failure mechanism,automatic monitoring instruments,including piezometers,tensiometers,moisture probes and inplace inclinometers were installed at the top of fill slope. The following findings can be observed based on the monitoring data of piezometers,moisture probes and tensiometers: rainfall infiltration has little influence on the fluctuation of the groundwater table,possibly because the groundwater table was deep； the response of pore pressure and volumetric water content at various depths in the fill was delayed,depending on the soil depth. The rainwater can infiltrate into a depth of over 3m,and a perched water table can be observed at the depth of 3m,resulting in reduction in shear strength of soil and potential shallow failure.
Several cracks were found to occur on the slope face of the Laiwushan retaining wall. In order to understand the mechanism of deformation and failure mechanism,automatic monitoring instruments,including piezometers,tensiometers,moisture probes and inplace inclinometers were installed at the top of fill slope. The following findings can be observed based on the monitoring data of piezometers,moisture probes and tensiometers: rainfall infiltration has little influence on the fluctuation of the groundwater table,possibly because the groundwater table was deep； the response of pore pressure and volumetric water content at various depths in the fill was delayed,depending on the soil depth. The rainwater can infiltrate into a depth of over 3m,and a perched water table can be observed at the depth of 3m,resulting in reduction in shear strength of soil and potential shallow failure.
2010, 18(4): 521-528.
The complex distribution and combination characteristics of rockmass structural planes determine the engineering geology and mechanics properties and affect the failure mode of the rockmass slope. The slope at the Lancangjiang bridge along the DaliRuili railway is located in the Lancangjiang tectonic belt,where seismic intensity is high,neotectonic movement is active, the external force and active hypabyssal and hypergene rebuilding process are also active. Therefore,the rock mass structure of the both sides of Lancang river are very complex. Based on plentiful geologic investigation data of the engineered slope at the Lancangjiang bridge, a statistical analysis are undertaken to examine the structural planes with fitting test by the way of chiSquare and KolmogorovSmirnov method. The results show that：(1)three preferred structure planes are in the right bank; (2)four preferred structure planes are in the left bank; (3)the occurrence of those preferred structure planes are confirming with normal distributions,respectively. Statistic models of the engineered slopes are constructed to analyze the failure modes based on the statistic results. The failure model of the right bank engineered slope is sliding and fracturing; and the failure model of the right bank slope is the local rock blocks lossing stability．
The complex distribution and combination characteristics of rockmass structural planes determine the engineering geology and mechanics properties and affect the failure mode of the rockmass slope. The slope at the Lancangjiang bridge along the DaliRuili railway is located in the Lancangjiang tectonic belt,where seismic intensity is high,neotectonic movement is active, the external force and active hypabyssal and hypergene rebuilding process are also active. Therefore,the rock mass structure of the both sides of Lancang river are very complex. Based on plentiful geologic investigation data of the engineered slope at the Lancangjiang bridge, a statistical analysis are undertaken to examine the structural planes with fitting test by the way of chiSquare and KolmogorovSmirnov method. The results show that：(1)three preferred structure planes are in the right bank; (2)four preferred structure planes are in the left bank; (3)the occurrence of those preferred structure planes are confirming with normal distributions,respectively. Statistic models of the engineered slopes are constructed to analyze the failure modes based on the statistic results. The failure model of the right bank engineered slope is sliding and fracturing; and the failure model of the right bank slope is the local rock blocks lossing stability．
2010, 18(4): 529-533.
Slope interlayered by sand rock，mud rock and macker in Qianfuyan Formation In the Middle Jurassic generated deformation，such as cracks，relaxation，and creeping along soft discontinuitiesEngineering geology groups of rock masses of Qianfuyan Formation in the Middle Jurassic was divided into group of thin layer mudstone and thin layer sandstone，group of thickbedded sandstone with middle layer sandstone and thin layer mudstone interlayerAccording to detailed study of rock mass structure，soft interlayer was confirmed as key discontinuity for slope stability，and then the stability of superficial slope in cataclastic texture rock mass and blocks combined by discontinuities were analyzed，which indicated that superficial slope stability was worse，and the stability of large scale block was betterThe result accorded with the deformation of slope．
Slope interlayered by sand rock，mud rock and macker in Qianfuyan Formation In the Middle Jurassic generated deformation，such as cracks，relaxation，and creeping along soft discontinuitiesEngineering geology groups of rock masses of Qianfuyan Formation in the Middle Jurassic was divided into group of thin layer mudstone and thin layer sandstone，group of thickbedded sandstone with middle layer sandstone and thin layer mudstone interlayerAccording to detailed study of rock mass structure，soft interlayer was confirmed as key discontinuity for slope stability，and then the stability of superficial slope in cataclastic texture rock mass and blocks combined by discontinuities were analyzed，which indicated that superficial slope stability was worse，and the stability of large scale block was betterThe result accorded with the deformation of slope．
2010, 18(4): 534-537.
This paper presents the triaxial test results of mudstone from the foundation of the Nanjing third bridge on Yangtse River. It is found that the failure pressure,the plastic deformation and the residual strength of the mudstone after subversion increase as the confining pressure increases. Then,it studies and analyses the relation between the damage soften parameters and the confining pressure,when the strength of rocks microunit is of the Weibull distribution and the strength of rocks microunit conformed to the MohrCoulomb strength criterion. Connecting with the stressstrain full procedure curves,the initial damage characteristic is discussed. The results indicate that the relation of logarithm of pressure and confining pressure of initial damage is linear. By studying on the relation between damage variable and main stress,it is found the relation of damage variable and main stress submits to a hyperbola model. The hyperbola model can be transformed into a linear equation. So the model parameters can be gotten by regressive analysis based on the test results. The results indicate F0 increases as the confining pressure increases,but m declines,which reflects the brittleness tolerance of the mudstone declines as the confining pressure increases．
This paper presents the triaxial test results of mudstone from the foundation of the Nanjing third bridge on Yangtse River. It is found that the failure pressure,the plastic deformation and the residual strength of the mudstone after subversion increase as the confining pressure increases. Then,it studies and analyses the relation between the damage soften parameters and the confining pressure,when the strength of rocks microunit is of the Weibull distribution and the strength of rocks microunit conformed to the MohrCoulomb strength criterion. Connecting with the stressstrain full procedure curves,the initial damage characteristic is discussed. The results indicate that the relation of logarithm of pressure and confining pressure of initial damage is linear. By studying on the relation between damage variable and main stress,it is found the relation of damage variable and main stress submits to a hyperbola model. The hyperbola model can be transformed into a linear equation. So the model parameters can be gotten by regressive analysis based on the test results. The results indicate F0 increases as the confining pressure increases,but m declines,which reflects the brittleness tolerance of the mudstone declines as the confining pressure increases．
2010, 18(4): 538-542.
The bedrocks for a proposed large power station contain a set of river and lake facies sedimentary rocks. The rocks contain conglomerate,sandstone,siltstone and mudstone and have a variety of lithologies. Different rocks have different mass deformation parameters. Conventional deformation test can only get a single lithology of rock mass deformation modulus. The soft and hard interlayered rock mass has an integrated deformation modulus that is a function of the single rock mass deformation moduli,the rock bidding angles,and the rock layer thicknesss. How to assess the integrated deformation modulus is an important task. At first,the paper conducts a statistic analysis on the proportion of different lithologies at dam site and obtains that the thickness ratio of the sandstone,siltstone and mudstone are 6：2.5：1.5. According to the statistics,the test area containing sandstone,siltstone and mudstone along the dam axial is selected. The bearing plate size is defined to be 200 cm in length and 37 cm in width for the insitu test. At the same time,the bearing plate can cover the sandstone,siltstone and mudstone.
The plate can transfer the maximum applied load of 250 tons onto the underlain multilayered rocks. As a result,the integrated deformation of the bedrock can be determined. The experimental results show that for the weak weathered bedrock at the rock dam foundation,its integrated deformation modulus can be up to 7.0 GPa. This value meets the design requirements.
The bedrocks for a proposed large power station contain a set of river and lake facies sedimentary rocks. The rocks contain conglomerate,sandstone,siltstone and mudstone and have a variety of lithologies. Different rocks have different mass deformation parameters. Conventional deformation test can only get a single lithology of rock mass deformation modulus. The soft and hard interlayered rock mass has an integrated deformation modulus that is a function of the single rock mass deformation moduli,the rock bidding angles,and the rock layer thicknesss. How to assess the integrated deformation modulus is an important task. At first,the paper conducts a statistic analysis on the proportion of different lithologies at dam site and obtains that the thickness ratio of the sandstone,siltstone and mudstone are 6：2.5：1.5. According to the statistics,the test area containing sandstone,siltstone and mudstone along the dam axial is selected. The bearing plate size is defined to be 200 cm in length and 37 cm in width for the insitu test. At the same time,the bearing plate can cover the sandstone,siltstone and mudstone.
The plate can transfer the maximum applied load of 250 tons onto the underlain multilayered rocks. As a result,the integrated deformation of the bedrock can be determined. The experimental results show that for the weak weathered bedrock at the rock dam foundation,its integrated deformation modulus can be up to 7.0 GPa. This value meets the design requirements.
2010, 18(4): 543-547.
Nowadays in China the construction of infrastructure has been expedited. The methodologies to prevent destruction caused by expansive soil have been put in the frontier. Expansive soil is a kind of special regional clay which can be found in many places of China. Geological disasters caused by expansive soil happened in a more and more frequent trend. With the intention to bolster the resources recycling,and meanwhile alleviate the damages to be incurred by the expansive soil,a string of explorations has been undertaken in this paper. In the present study,a uniaxial compressive strength soil test is conducted. It studies the impact of wasted tire rubber powder content and water content for the mixture uniaxial compressive strength. The test results indicate the characteristics of the improved expensive soil shear strength. They confirm the assumption that wasted tire rubber powder can improve the expansive soil greatly. This finding opens up a new improving method to reduce the engineering disaster caused by expensive soil．
Nowadays in China the construction of infrastructure has been expedited. The methodologies to prevent destruction caused by expansive soil have been put in the frontier. Expansive soil is a kind of special regional clay which can be found in many places of China. Geological disasters caused by expansive soil happened in a more and more frequent trend. With the intention to bolster the resources recycling,and meanwhile alleviate the damages to be incurred by the expansive soil,a string of explorations has been undertaken in this paper. In the present study,a uniaxial compressive strength soil test is conducted. It studies the impact of wasted tire rubber powder content and water content for the mixture uniaxial compressive strength. The test results indicate the characteristics of the improved expensive soil shear strength. They confirm the assumption that wasted tire rubber powder can improve the expansive soil greatly. This finding opens up a new improving method to reduce the engineering disaster caused by expensive soil．
2010, 18(4): 548-553.
On the basis of disturbed state concept for saturated soils,a new expression form of coupled disturbing variable for unsaturated soils is defined in this paper,in which both of disturbance factors that external force and wetting are considered. Moreover,a new constitutive model of unsaturated intact soils is build up in accordance with homogenization theory for composites materials,and the evolution equation of the coupled disturbing variable is proposed. Comparing the calculation results of BBM and this model with the experimental results respectively,it can be seen clearly that this model can better simulate the mechanical properties of unsaturated intact loess. In addition,according to the analysis results of the influence of structural parameters on shear behavior,the degradation law of soil structure can be well described by the proposed evolution equation of coupled disturbing variable.
On the basis of disturbed state concept for saturated soils,a new expression form of coupled disturbing variable for unsaturated soils is defined in this paper,in which both of disturbance factors that external force and wetting are considered. Moreover,a new constitutive model of unsaturated intact soils is build up in accordance with homogenization theory for composites materials,and the evolution equation of the coupled disturbing variable is proposed. Comparing the calculation results of BBM and this model with the experimental results respectively,it can be seen clearly that this model can better simulate the mechanical properties of unsaturated intact loess. In addition,according to the analysis results of the influence of structural parameters on shear behavior,the degradation law of soil structure can be well described by the proposed evolution equation of coupled disturbing variable.
2010, 18(4): 554-558.
The developmental state of residual fissures in goaf is an important factor in the design of goaf filling and grouting. Under the conditions of multiple seam mining,this paper discusses the distribution of residual fissures in overlying stratum by means of simulated experiment of similar materials. The test results show that after the end of mining the distribution of residual fissures in goaf has obvious characteristics in different zones. From both sides to the middle of goaf,it can be divided into three zones: residual fissure zone,fissure compacted zone,and surface tensile fissure zone. The fissure rate of residual fissure zone generally varies from 19.54% to 45.27% while the fissure rate of fissure compacted zone varies from 9.28% to 19.33%. The developmental height of separated strata is decided by both mining width and total mining height. In both theory and practice,this study has the great importance in estimation of stability of construction site on the goaf,determining the range and depth of goaf management,reasonable arrangement of injected hole,as well as reasonable computation of grouting amount for single injected hole．
The developmental state of residual fissures in goaf is an important factor in the design of goaf filling and grouting. Under the conditions of multiple seam mining,this paper discusses the distribution of residual fissures in overlying stratum by means of simulated experiment of similar materials. The test results show that after the end of mining the distribution of residual fissures in goaf has obvious characteristics in different zones. From both sides to the middle of goaf,it can be divided into three zones: residual fissure zone,fissure compacted zone,and surface tensile fissure zone. The fissure rate of residual fissure zone generally varies from 19.54% to 45.27% while the fissure rate of fissure compacted zone varies from 9.28% to 19.33%. The developmental height of separated strata is decided by both mining width and total mining height. In both theory and practice,this study has the great importance in estimation of stability of construction site on the goaf,determining the range and depth of goaf management,reasonable arrangement of injected hole,as well as reasonable computation of grouting amount for single injected hole．
2010, 18(4): 559-565.
The research results of engineering mechanical properties on closely jointed basaltic mass were only reported in the open literature from the Basalt Waste Isolation Project in Handford,USA and the Baihetan hydropower project in China. The insitu tests of the closely jointed basaltic mass were summarized from similar projects at home and abroad. The developed plunging colonnade and multilevel structural planes of closely jointed basaltic mass in China were discussed. The deformable discrete element method was applied to the modeling of its 3 dimensional numerical model. Then the scale effect and anisotropy of the insitu tests were studied by numerical bearing plate test with different plate diameters. The results show that the cause is mainly due to scale effect of bearing plate tests. The anisotropy of insitu tests decreases as the diameter of bearing plate increases. The closely jointed basaltic mass can be regarded as an isotropic rock mass when the diameter of bearing plate is over 6 m. The results have some practical value in engineering on utilization and reconstruction of jointed basaltic mass．
The research results of engineering mechanical properties on closely jointed basaltic mass were only reported in the open literature from the Basalt Waste Isolation Project in Handford,USA and the Baihetan hydropower project in China. The insitu tests of the closely jointed basaltic mass were summarized from similar projects at home and abroad. The developed plunging colonnade and multilevel structural planes of closely jointed basaltic mass in China were discussed. The deformable discrete element method was applied to the modeling of its 3 dimensional numerical model. Then the scale effect and anisotropy of the insitu tests were studied by numerical bearing plate test with different plate diameters. The results show that the cause is mainly due to scale effect of bearing plate tests. The anisotropy of insitu tests decreases as the diameter of bearing plate increases. The closely jointed basaltic mass can be regarded as an isotropic rock mass when the diameter of bearing plate is over 6 m. The results have some practical value in engineering on utilization and reconstruction of jointed basaltic mass．
2010, 18(4): 566-574.
Jiubao Tunnel,located between Wangquan county to Shangyi county of Hebei province,is the key and controlling works of the underconstructed ZhangjiakouJining Railway Line. The tunnel passes through the granulite and the biotite gneiss of the Upper Archen Era,where faults well developed faults and the rock mass is fractured. The geological conditions disclosed during tunneling were greatly different from those of the construction design drawing. The alteration ratio of the classification of tunnel surrounding rocks even reaches 80.3%. It was due to insufficient understanding to rock mass structure. The high alteration directly caused the occurrence of many geohazards such as squeezing,collapse,water inrush during tunneling. The paper takes the section of DK30+520～DK30+910 as the example and makes the comprehensive analysis to the key geological conditions of tunnel surrounding rock. The key conditions include geology,geotechnics,earth stress and underground water. It studies the special characteristics of rock mass structure and directs that the tunnel surrounding rock is complicatedly controlled by the fault fracture zones and the alternative outcropping of weak and hard engineering geological rock masses. It is the special rock mass structural characteristics that controls the deformation and collapse of tunnel. It also summarizes the rock mass structure types which are possibly encountered during tunnel construction. The research result on the rock mass structure of Jiubao Tunnel is helpful to the tunnel design change and construction in the metamorphic and greatly tectonic disturbed areas.
Jiubao Tunnel,located between Wangquan county to Shangyi county of Hebei province,is the key and controlling works of the underconstructed ZhangjiakouJining Railway Line. The tunnel passes through the granulite and the biotite gneiss of the Upper Archen Era,where faults well developed faults and the rock mass is fractured. The geological conditions disclosed during tunneling were greatly different from those of the construction design drawing. The alteration ratio of the classification of tunnel surrounding rocks even reaches 80.3%. It was due to insufficient understanding to rock mass structure. The high alteration directly caused the occurrence of many geohazards such as squeezing,collapse,water inrush during tunneling. The paper takes the section of DK30+520～DK30+910 as the example and makes the comprehensive analysis to the key geological conditions of tunnel surrounding rock. The key conditions include geology,geotechnics,earth stress and underground water. It studies the special characteristics of rock mass structure and directs that the tunnel surrounding rock is complicatedly controlled by the fault fracture zones and the alternative outcropping of weak and hard engineering geological rock masses. It is the special rock mass structural characteristics that controls the deformation and collapse of tunnel. It also summarizes the rock mass structure types which are possibly encountered during tunnel construction. The research result on the rock mass structure of Jiubao Tunnel is helpful to the tunnel design change and construction in the metamorphic and greatly tectonic disturbed areas.
2010, 18(4): 575-580.
This paper presents the insitu tests for improving saturated soft soil ground formed by hydraulic fill method. The wellpoint dewatering method and roller compaction method are used firstly in order to obtain initial bearing capacity. After this,the bearing capacity can be advanced obviously by dynamic compaction method. This new method is named as dynamic compaction method with predewatering in this paper. According to a large number of insitu test results,this paper studies the problems such as the affecting scopes of wellpoint dewatering,pore water pressure induced by dynamic compaction,deep settlements of soil layers. In the meantime,number of passes,number of drops per pass,duration time between various passes,and other factors are also discussed. The studies show that the bearing capacity of soft soil ground can be greatly increased using dynamic consolidation with predewatering method.
This paper presents the insitu tests for improving saturated soft soil ground formed by hydraulic fill method. The wellpoint dewatering method and roller compaction method are used firstly in order to obtain initial bearing capacity. After this,the bearing capacity can be advanced obviously by dynamic compaction method. This new method is named as dynamic compaction method with predewatering in this paper. According to a large number of insitu test results,this paper studies the problems such as the affecting scopes of wellpoint dewatering,pore water pressure induced by dynamic compaction,deep settlements of soil layers. In the meantime,number of passes,number of drops per pass,duration time between various passes,and other factors are also discussed. The studies show that the bearing capacity of soft soil ground can be greatly increased using dynamic consolidation with predewatering method.
2010, 18(4): 581-585.
This paper takes the Yuntaishan tunnel located in Lianyungang as an example. The lithology around the tunnel is single, which consists of a massive of hard granulite and a small amount of weak green schist. The intersection of the structural features releases blocks or wedges which can fall or slide from the surface of the tunnel excavation. This paper considers its discontinuity controlling model. The keyblock theory is used to optimize the design of the tunnel with Unwedge procedure, which includes the choice of hole shape,the trend of the tunnel,support parameters. Through the analysis and calculation,it is indicated that the key block theory is correct and efficient,which is significant to the further study of the optimization of tunnel design in low ground stress regions．
This paper takes the Yuntaishan tunnel located in Lianyungang as an example. The lithology around the tunnel is single, which consists of a massive of hard granulite and a small amount of weak green schist. The intersection of the structural features releases blocks or wedges which can fall or slide from the surface of the tunnel excavation. This paper considers its discontinuity controlling model. The keyblock theory is used to optimize the design of the tunnel with Unwedge procedure, which includes the choice of hole shape,the trend of the tunnel,support parameters. Through the analysis and calculation,it is indicated that the key block theory is correct and efficient,which is significant to the further study of the optimization of tunnel design in low ground stress regions．
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