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Editor Work2011 Vol. 19, No. 3
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2011, 19(3): 289-296.
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A concept of Extreme Geo-Disaster and Risk is proposed in this paper.Extreme geo-disasters are considered to be geo-events of most low probability in the earth recent evolution.However,low probability of natural event does not mean that it will happen only in the far future,and it does not exclude that such geo-disasters may happen in relatively near future within our or next generations.Strong earthquake Ms 8.0 on 12th May, 2008 in Wenchuan,China,which caused large amount of fatalities and structure damage,showed the typical characteristics of an extreme natural disaster.It once again rang a tocsin to warning human society.It is a question,if human would forget it,when it passed and the terrible situation changed.Therefore,the author appeals that engineering geologists have to pay attention to and deal with such extreme disasters and risks.Scientific recognition of the level of natural dynamic forces responsible for extreme disaster provides an essential basis in the disaster prediction,and this should be one of the essential objectives of engineering geology.Regional study of geo-sphere dynamic processes may help in aiming at this purpose.To assess the potential risk an approach of impact area estimation is important and further analysis of relationship between the damaging effect and vulnerability damaged objects gives an assessed level of disaster risk.In the strategy of risk management a kind of precaution measure and warning should be focused instead of merely engineering protection.Social awareness and preparedness are equally important in the extreme risk mitigation.Accordingly a series of strategic measures may be worked out for the disaster reduction,which are different from that of normal safety design standard and mainly consist of non-engineering measures.In the progress of science and technology the human capability in reduction and management of extreme natural disaster should be much updated in the near future.
A concept of Extreme Geo-Disaster and Risk is proposed in this paper.Extreme geo-disasters are considered to be geo-events of most low probability in the earth recent evolution.However,low probability of natural event does not mean that it will happen only in the far future,and it does not exclude that such geo-disasters may happen in relatively near future within our or next generations.Strong earthquake Ms 8.0 on 12th May, 2008 in Wenchuan,China,which caused large amount of fatalities and structure damage,showed the typical characteristics of an extreme natural disaster.It once again rang a tocsin to warning human society.It is a question,if human would forget it,when it passed and the terrible situation changed.Therefore,the author appeals that engineering geologists have to pay attention to and deal with such extreme disasters and risks.Scientific recognition of the level of natural dynamic forces responsible for extreme disaster provides an essential basis in the disaster prediction,and this should be one of the essential objectives of engineering geology.Regional study of geo-sphere dynamic processes may help in aiming at this purpose.To assess the potential risk an approach of impact area estimation is important and further analysis of relationship between the damaging effect and vulnerability damaged objects gives an assessed level of disaster risk.In the strategy of risk management a kind of precaution measure and warning should be focused instead of merely engineering protection.Social awareness and preparedness are equally important in the extreme risk mitigation.Accordingly a series of strategic measures may be worked out for the disaster reduction,which are different from that of normal safety design standard and mainly consist of non-engineering measures.In the progress of science and technology the human capability in reduction and management of extreme natural disaster should be much updated in the near future.
2011, 19(3): 297-303.
A maritime construction is usually a slender line in the ocean.It is usual to see just its narrow surface strip and not analyse the large amount of submerged material the latter is supporting.Without doubt,it is the ground to which a notable load is transmitted in an environment subjected to periodic,alternating stresses,dynamic forces which the sea's media constitute. Both an outer and inner maritime construction works in a complex fashion.A granular solid(breakwater)breathes with the incident wave flow,dissipating part of the wave energy between its gaps.The backflow tries to extract the different items from the solid block,setting a balance between effective and neutral tensions that follow Terzaghui's principle. On some occasions,fluidification of the armour layer has caused the breakwater to collapse(Sines,Portugal,February 1978).On others,siphoning or liquefaction of sand supporting monoliths(vertical breakwaters)lead them to destruction or collapse(New Barcelona Harbour Mouth,Spain,November 2001). This is why the ground-force-structure interaction is a complicated analysis with joint design tools still in an incipient state. The purpose of this article is to describe two singular failures in inner maritime constructions in Spain deriving from ground problems(Malaga,July 2004and Barcelona,January 2007).They occurred recently and the causes are the subject of reflection and analysis.
A maritime construction is usually a slender line in the ocean.It is usual to see just its narrow surface strip and not analyse the large amount of submerged material the latter is supporting.Without doubt,it is the ground to which a notable load is transmitted in an environment subjected to periodic,alternating stresses,dynamic forces which the sea's media constitute. Both an outer and inner maritime construction works in a complex fashion.A granular solid(breakwater)breathes with the incident wave flow,dissipating part of the wave energy between its gaps.The backflow tries to extract the different items from the solid block,setting a balance between effective and neutral tensions that follow Terzaghui's principle. On some occasions,fluidification of the armour layer has caused the breakwater to collapse(Sines,Portugal,February 1978).On others,siphoning or liquefaction of sand supporting monoliths(vertical breakwaters)lead them to destruction or collapse(New Barcelona Harbour Mouth,Spain,November 2001). This is why the ground-force-structure interaction is a complicated analysis with joint design tools still in an incipient state. The purpose of this article is to describe two singular failures in inner maritime constructions in Spain deriving from ground problems(Malaga,July 2004and Barcelona,January 2007).They occurred recently and the causes are the subject of reflection and analysis.
2011, 19(3): 304-316.
This paper introduces the principles of engineering geological dynamics of rockmass(EGDR).It points out that the mission of EGDR is to reveal the law of interaction between rockmass and geo-dynamic factors.EGDR basically studies the following aspects: the dynamic origin and features of the material and structure of rockmass,the crustal-dynamical environment of rockmass,the dynamic behaviour and process of rockmass,and the principle of geohazard prevention for rock engineering.The basic viewpoints of EGDR includes the following subjects.(a)The geo-dynamic genesis which means rockmass and its geological features are the results of crustal dynamic process.(b)Dynamic interaction that means the engineering behaviour of rockmass is the reflection of the interplay between rockmass and the geo-environment.(c) The point of process adjustment that infers the basic approach for engineering geohazard prevention is to adjust the interacting process between rockmass and the geodynamical environment.The following aspects have been described in details under the framework of geo-dynamics: (1)the dynamic genesis and geological features of rockmass,(2)the features of geo-dynamical environment of rockmass,(3)the fundamental mechanical behaviour of rockmass,(4)the features and behaviours of rockmass under high crustalstress,(5)the dynamic reaction of rockmass,and (6) the reaction of ground water in rockmass.
This paper introduces the principles of engineering geological dynamics of rockmass(EGDR).It points out that the mission of EGDR is to reveal the law of interaction between rockmass and geo-dynamic factors.EGDR basically studies the following aspects: the dynamic origin and features of the material and structure of rockmass,the crustal-dynamical environment of rockmass,the dynamic behaviour and process of rockmass,and the principle of geohazard prevention for rock engineering.The basic viewpoints of EGDR includes the following subjects.(a)The geo-dynamic genesis which means rockmass and its geological features are the results of crustal dynamic process.(b)Dynamic interaction that means the engineering behaviour of rockmass is the reflection of the interplay between rockmass and the geo-environment.(c) The point of process adjustment that infers the basic approach for engineering geohazard prevention is to adjust the interacting process between rockmass and the geodynamical environment.The following aspects have been described in details under the framework of geo-dynamics: (1)the dynamic genesis and geological features of rockmass,(2)the features of geo-dynamical environment of rockmass,(3)the fundamental mechanical behaviour of rockmass,(4)the features and behaviours of rockmass under high crustalstress,(5)the dynamic reaction of rockmass,and (6) the reaction of ground water in rockmass.
2011, 19(3): 317-322.
Macroscopic fractures of rocks are strongly linked to their microstructures and micro-defects.It is one of difficult problems of rock fracture mechanics to establish more intuitive relationship between rock microscopic mechanism and macro rupture.This paper uses the sericite phyllite and siliceous plate phyllite of Middle Devonian series on upriver of Jinsha River as the research object.The micro-rupture properties of rock are judged and the relation between the form and mechanism of phyllite micro-rupture and mineral component is revealed through scanning electronic microscope and mechanical tests.The sericite phyllite shows micro-scratch micro-fracture fracture which is a typical micro-brittle shear.The forms of micro-fracture have both pull-off rupture caused by intergranular fracture and the micro-shear rupture,belonging to the micro-fracture mechanism of the coexistence of the tension and shear fracture.The physical meaning of rock fracture is analyzed with the combination of mechanic characteristics of macroscopic fracture.The evidence is acquired to establish the link between rock micro-rupture mechanism and macroscopic fracture analysis.
Macroscopic fractures of rocks are strongly linked to their microstructures and micro-defects.It is one of difficult problems of rock fracture mechanics to establish more intuitive relationship between rock microscopic mechanism and macro rupture.This paper uses the sericite phyllite and siliceous plate phyllite of Middle Devonian series on upriver of Jinsha River as the research object.The micro-rupture properties of rock are judged and the relation between the form and mechanism of phyllite micro-rupture and mineral component is revealed through scanning electronic microscope and mechanical tests.The sericite phyllite shows micro-scratch micro-fracture fracture which is a typical micro-brittle shear.The forms of micro-fracture have both pull-off rupture caused by intergranular fracture and the micro-shear rupture,belonging to the micro-fracture mechanism of the coexistence of the tension and shear fracture.The physical meaning of rock fracture is analyzed with the combination of mechanic characteristics of macroscopic fracture.The evidence is acquired to establish the link between rock micro-rupture mechanism and macroscopic fracture analysis.
2011, 19(3): 323-331.
Small-scale physical modeling is an effective method for examining structural and geotechnical problems.However,the stress of a small-scale physical model under gravity is much lower than those in its prototype.In addition,the nonlinearity of the prototype materials is also not easily to be represented in the small-scale physical model.So,a regular small-scale physical model can hardly reproduce the behavior of its prototype.One way to resolve these difficulties is to raise the self-weight of the small-scale physical models up to its prototype.The most convenient tool to increase the self-weight stress is the so-called geotechnical centrifuge.This paper presents a state of the art review of relevant literatures and materials on geotechnical centrifuge technologies in China.It summarizes the geotechnical centrifuge modelling projects that have done up to now in China.According to level of research and applications,the development history of centrifuge technology in China can be divided into three phases.This paper illustrates applications and situation of research by each phase and introduces the development course of instruments,test techniques and data acquisition.in conclusion,some unsolved problems in centrifuge research in China have been pointed out.Outlook on centrifuge research and work is presented.
Small-scale physical modeling is an effective method for examining structural and geotechnical problems.However,the stress of a small-scale physical model under gravity is much lower than those in its prototype.In addition,the nonlinearity of the prototype materials is also not easily to be represented in the small-scale physical model.So,a regular small-scale physical model can hardly reproduce the behavior of its prototype.One way to resolve these difficulties is to raise the self-weight of the small-scale physical models up to its prototype.The most convenient tool to increase the self-weight stress is the so-called geotechnical centrifuge.This paper presents a state of the art review of relevant literatures and materials on geotechnical centrifuge technologies in China.It summarizes the geotechnical centrifuge modelling projects that have done up to now in China.According to level of research and applications,the development history of centrifuge technology in China can be divided into three phases.This paper illustrates applications and situation of research by each phase and introduces the development course of instruments,test techniques and data acquisition.in conclusion,some unsolved problems in centrifuge research in China have been pointed out.Outlook on centrifuge research and work is presented.
2011, 19(3): 332-337.
Different types of discontinuities in deep rocks have different effects on the stabilities and water-sealed conditions of underground water-sealed oil storage caverns. So it is very important to identify different types of discontinuities in deep rocks and study the development of the discontinuities. This paper uses the results of drillhole image technique to study the issue in association with the project of underground water sealed oil storage caverns in Huangdao. The drillhole image characteristics of four types of discontinuity are analyzed from the aspects of the shape, width, color and interlace characteristics of the curve as well as the rock characteristics near the curve. The drillhole image in the drillhole ZK8 from 120 m above the sea level to 60m below the sea level is taken to identify different types of discontinuities in rocks and study the development of the discontinuities. Results obtained indicate follows: (1) The discontinuity characteristic of one classification is different from the others. So the development characteristics of the deep-discontinuities can be studied by different classifications according to the drillhole images. (2) The amount of tectonic joints and metamorphic differentiation discontinuities both becomes lower along the direction of depth. The metamorphic differentiation discontinuities only develop above the elevation of 30 m. Dike intrusion joints develop in local areas. Thus their influences to the stabilities of the caverns depend on their positions developed. Therefore, the development characteristics of discontinuities in deep rocks should be paid attention, which can be used for engineering construction.
Different types of discontinuities in deep rocks have different effects on the stabilities and water-sealed conditions of underground water-sealed oil storage caverns. So it is very important to identify different types of discontinuities in deep rocks and study the development of the discontinuities. This paper uses the results of drillhole image technique to study the issue in association with the project of underground water sealed oil storage caverns in Huangdao. The drillhole image characteristics of four types of discontinuity are analyzed from the aspects of the shape, width, color and interlace characteristics of the curve as well as the rock characteristics near the curve. The drillhole image in the drillhole ZK8 from 120 m above the sea level to 60m below the sea level is taken to identify different types of discontinuities in rocks and study the development of the discontinuities. Results obtained indicate follows: (1) The discontinuity characteristic of one classification is different from the others. So the development characteristics of the deep-discontinuities can be studied by different classifications according to the drillhole images. (2) The amount of tectonic joints and metamorphic differentiation discontinuities both becomes lower along the direction of depth. The metamorphic differentiation discontinuities only develop above the elevation of 30 m. Dike intrusion joints develop in local areas. Thus their influences to the stabilities of the caverns depend on their positions developed. Therefore, the development characteristics of discontinuities in deep rocks should be paid attention, which can be used for engineering construction.
2011, 19(3): 338-345.
Seepage into a tunnel system with granitic surrounding rock in an arid area is studied in this paper using logic-information method.Influential factors of seepage into the tunnels are analyzed and eleven factors are selected.Seriousness of seepage is divided into four grades based on the characteristics of seepage into the tunnels.The logic-information method is established to predict and evaluate seepage into the tunnels on the site.Weights of influential factors are calculated.According to the weights of influential factors,it can be concluded that lithology,landform and fracture characteristics of the surrounding granitic rock influenced the seepage into the tunnels clearly.And the site is divided into several different zones and the probability of seepage in each zone is evaluated.
Seepage into a tunnel system with granitic surrounding rock in an arid area is studied in this paper using logic-information method.Influential factors of seepage into the tunnels are analyzed and eleven factors are selected.Seriousness of seepage is divided into four grades based on the characteristics of seepage into the tunnels.The logic-information method is established to predict and evaluate seepage into the tunnels on the site.Weights of influential factors are calculated.According to the weights of influential factors,it can be concluded that lithology,landform and fracture characteristics of the surrounding granitic rock influenced the seepage into the tunnels clearly.And the site is divided into several different zones and the probability of seepage in each zone is evaluated.
2011, 19(3): 346-351.
As an important technological measure, comprehensive prediction in geology can solve many engineering geological problems and reduce the risk of construction in tunneling. But present comprehensive prediction is simply focused on quantity. In order to make comprehensive prediction more effective,a method to identify common adverse geological body is generalized by geo-analysis. Geological defect that may exist in front of face is preliminary determined by this method. Based on the principles of Analytic Hierarchy Process(AHP),factors that effect prediction measures are quantified, and the weight is given to each of them. Then two levels comprehensive appraisal index system are established. All of them is to research the suitability of different prediction methods in a particular engineering geological condition, and to optimize the best ones. The main results are as fallows. Prediction methods are optimized by geo-analysis method and AHP, which are used for qualitative and quantitative respectively. Arbitrary of choosing geophysical exploration measures is eliminated in the comprehensive prediction. The comprehensive forecast technical system is established. Aiming at the F2 Fault of Zijinshan Tunnel, a karst river is predicted successfully at ZK221+960 by using this system. It's verified that the AHP based comprehensive prediction is practicality and feasibility.
As an important technological measure, comprehensive prediction in geology can solve many engineering geological problems and reduce the risk of construction in tunneling. But present comprehensive prediction is simply focused on quantity. In order to make comprehensive prediction more effective,a method to identify common adverse geological body is generalized by geo-analysis. Geological defect that may exist in front of face is preliminary determined by this method. Based on the principles of Analytic Hierarchy Process(AHP),factors that effect prediction measures are quantified, and the weight is given to each of them. Then two levels comprehensive appraisal index system are established. All of them is to research the suitability of different prediction methods in a particular engineering geological condition, and to optimize the best ones. The main results are as fallows. Prediction methods are optimized by geo-analysis method and AHP, which are used for qualitative and quantitative respectively. Arbitrary of choosing geophysical exploration measures is eliminated in the comprehensive prediction. The comprehensive forecast technical system is established. Aiming at the F2 Fault of Zijinshan Tunnel, a karst river is predicted successfully at ZK221+960 by using this system. It's verified that the AHP based comprehensive prediction is practicality and feasibility.
2011, 19(3): 352-358.
Based on the rule of stress wave propagation,the characters of the stress waves propagating in rock slopes with horizontal strata layers are analyzed.A new model about the stress waves propagating in this type of slopes is proposed.The effect of structural plane in dynamic responses of the slopes under periodical compressive load is examined with UDEC.It is revealed that the structural plane plays an important role.Under the action of low frequency compressive waves,the vertical peak ground velocity of slope crest (near sloping surface)is also larger than that of a homogeneous slope at the same position.This effect is more obvious as the slope height increases.Under the action of high frequency compressive waves,the vertical peak ground velocity of slope crest is larger than that of a homogeneous slope at the same position.However,it is less than that of a homogenous slope at positions far away from the sloping surfaces.And the value of the vertical peak ground velocity varies in period from model right to left.The numerical results are conductive to reveal the characteristics of fatigue behavior and failure mechanisms of different kinds of rock slopes.
Based on the rule of stress wave propagation,the characters of the stress waves propagating in rock slopes with horizontal strata layers are analyzed.A new model about the stress waves propagating in this type of slopes is proposed.The effect of structural plane in dynamic responses of the slopes under periodical compressive load is examined with UDEC.It is revealed that the structural plane plays an important role.Under the action of low frequency compressive waves,the vertical peak ground velocity of slope crest (near sloping surface)is also larger than that of a homogeneous slope at the same position.This effect is more obvious as the slope height increases.Under the action of high frequency compressive waves,the vertical peak ground velocity of slope crest is larger than that of a homogeneous slope at the same position.However,it is less than that of a homogenous slope at positions far away from the sloping surfaces.And the value of the vertical peak ground velocity varies in period from model right to left.The numerical results are conductive to reveal the characteristics of fatigue behavior and failure mechanisms of different kinds of rock slopes.
ANALYSIS OF FACTORS AFFECTING DISTRIBUTION OF LANDSLIDE THRUST FORCE FOR DOUBLE-ROW ANTI-SLIDE PILES
2011, 19(3): 359-363.
This paper takes the basic form of double-row cantilever beam anti-slide piles without joist as the model.Based on structural analysis theory,it presents the equations for calculating the transferring push force and the distribution between the double-row piles..It further uses the Hongshibao landslide as a case study for analyzing the double-row pile static row spacing,the section size of back and front piles,and the soil elasticity modulus between piles.It examines their influences to the thrust force distribution.Conclusions from the examination are obtained as follows: (1)When either the rigidity of the back pile increases or the rigidity of the front piles decreases,the extrusion interacting force between the soil and the two-row piles decreases,A2/A1 decreases along with it.Otherwise A2/A1 increases.(2)When the row distance b increases,A1 decreases,A2 decreases gradually when b=3 to 10m; A2 increases when b=10 to 21m. (3)When increases the elasticity coefficient between piles,A2 increases.(4)Along with the increases of the section high of the front piles,both A1 and A2 increases gradually; along with the increases of the section high of the back piles,both A1and A2 decreases gradually.
This paper takes the basic form of double-row cantilever beam anti-slide piles without joist as the model.Based on structural analysis theory,it presents the equations for calculating the transferring push force and the distribution between the double-row piles..It further uses the Hongshibao landslide as a case study for analyzing the double-row pile static row spacing,the section size of back and front piles,and the soil elasticity modulus between piles.It examines their influences to the thrust force distribution.Conclusions from the examination are obtained as follows: (1)When either the rigidity of the back pile increases or the rigidity of the front piles decreases,the extrusion interacting force between the soil and the two-row piles decreases,A2/A1 decreases along with it.Otherwise A2/A1 increases.(2)When the row distance b increases,A1 decreases,A2 decreases gradually when b=3 to 10m; A2 increases when b=10 to 21m. (3)When increases the elasticity coefficient between piles,A2 increases.(4)Along with the increases of the section high of the front piles,both A1 and A2 increases gradually; along with the increases of the section high of the back piles,both A1and A2 decreases gradually.
2011, 19(3): 364-369.
In order to keep the safety construction TBM tunneling and avoid surface settlement and failure accidents at the TBM Portal areas,This paper carries out studies on how to determine the length of longitudinal reinforcement scopes and establish a new stability model for sandy stratum for the portal areas.It analyzes and summarizes the limitations of existed theoretical models.It refines some existing conclusions.It further presents a new load equivalent and sliding failure models based on strength and stability theories.The new theoretical models can better reflect the mechanical characteristics and deformation modes of actual cases and have a good stratum adaptability.Meanwhile,in order to certify its rationality of improved strength model,the two strength models have been put into use for calculating one actual engineering stratum reinforcement of TBM portal areas.Sensitivity analysis on the main influence factors of existed and new improved models have also been made.The conclusions are: when the diameter of shield tunnel is small,the deviation of calculation results of existed and the new models are small.But as the diameter of shield tunnel is continuously increasing,the deviation of existed model is bigger,which may cause serious accidents if the existing models are applied into actual engineering.So,for large diameter shield tunnel engineering,especially when the diameter is lager than 10meters,the new improved model will be better for designing and quantifying the longitudinal reinforcement scopes.It has the big significant for engineering construction.The load equivalent model presented in this paper gives a new analyzing and computing method for studying load asymmetric problem based on strength theory.It also provides a good reference for similar problems.
In order to keep the safety construction TBM tunneling and avoid surface settlement and failure accidents at the TBM Portal areas,This paper carries out studies on how to determine the length of longitudinal reinforcement scopes and establish a new stability model for sandy stratum for the portal areas.It analyzes and summarizes the limitations of existed theoretical models.It refines some existing conclusions.It further presents a new load equivalent and sliding failure models based on strength and stability theories.The new theoretical models can better reflect the mechanical characteristics and deformation modes of actual cases and have a good stratum adaptability.Meanwhile,in order to certify its rationality of improved strength model,the two strength models have been put into use for calculating one actual engineering stratum reinforcement of TBM portal areas.Sensitivity analysis on the main influence factors of existed and new improved models have also been made.The conclusions are: when the diameter of shield tunnel is small,the deviation of calculation results of existed and the new models are small.But as the diameter of shield tunnel is continuously increasing,the deviation of existed model is bigger,which may cause serious accidents if the existing models are applied into actual engineering.So,for large diameter shield tunnel engineering,especially when the diameter is lager than 10meters,the new improved model will be better for designing and quantifying the longitudinal reinforcement scopes.It has the big significant for engineering construction.The load equivalent model presented in this paper gives a new analyzing and computing method for studying load asymmetric problem based on strength theory.It also provides a good reference for similar problems.
2011, 19(3): 370-375.
On May 20, 2010,the hidden potential geological hazard was found at the back hill of Qishan in Yongtai County of Fujian Province.Many group openings and fissures of 35cm to 80cm long were found at the lower part of the hill side.Huge collapses were happening continuously.The size of the sliding rock mass is about 80000m3. The risk of subsequent landslides is high.Any such landslide could cause disasters to the 2565 local residents and approximate 538million properties below the hillside slope. This paper presents the detailed investigation on the basic characteristics of the slip mass and preliminary analysis of the disaster causes.The investigation is based on the massive geologic investigation into the site of the disaster.It includes in-situ measurement,monitoring and other methods.The results indicate that the relatively prominent terrain condition of the source area and the characteristics of the geotechnical mass are the fundamental conditions for the occurring of the slope instability and potential huge landslides.The saturated surcharge of the rainfall,and the rainfalls infiltrating and softening effect along the joint fissures directly caused the slope instabilities and the potential landslides.Moreover,the paper sets forth some urgent remedial advice and unloading measures according to the features of the landslides.Finally,the monitoring results are analyzed and can used to direct the unloading construction.Therefore,the safety of the construction and the lives and property were all guaranteed.The successful case provides scientific evidences to direct urgent handling of geological disasters that would happen in Fujian littoral area.
On May 20, 2010,the hidden potential geological hazard was found at the back hill of Qishan in Yongtai County of Fujian Province.Many group openings and fissures of 35cm to 80cm long were found at the lower part of the hill side.Huge collapses were happening continuously.The size of the sliding rock mass is about 80000m3. The risk of subsequent landslides is high.Any such landslide could cause disasters to the 2565 local residents and approximate 538million properties below the hillside slope. This paper presents the detailed investigation on the basic characteristics of the slip mass and preliminary analysis of the disaster causes.The investigation is based on the massive geologic investigation into the site of the disaster.It includes in-situ measurement,monitoring and other methods.The results indicate that the relatively prominent terrain condition of the source area and the characteristics of the geotechnical mass are the fundamental conditions for the occurring of the slope instability and potential huge landslides.The saturated surcharge of the rainfall,and the rainfalls infiltrating and softening effect along the joint fissures directly caused the slope instabilities and the potential landslides.Moreover,the paper sets forth some urgent remedial advice and unloading measures according to the features of the landslides.Finally,the monitoring results are analyzed and can used to direct the unloading construction.Therefore,the safety of the construction and the lives and property were all guaranteed.The successful case provides scientific evidences to direct urgent handling of geological disasters that would happen in Fujian littoral area.
2011, 19(3): 376-380.
Debris flow is an important earth surface process to the geologic environment evolution in Mo-xi river basin.Investigation of the formation and evolution of the debris flow stream can provide useful basic data for the research of geologic environment evolution in Mo-xi river basin since the Quaternary.Based on the topographical statistic data of 51 debris flow gullies,the distribution of debris flows in Moxi river basin shows an asymmetric character obviously.There are fractal phenomenon and self-similarity among the debris flow numbers and the channel length,channel gradient and catchments area.Finally,this paper discusses the debris flow nonlinear evolution character and its response to the environment.This result can provide basic data for debris flow hazard prevention and risk control in Moxi river basin.
Debris flow is an important earth surface process to the geologic environment evolution in Mo-xi river basin.Investigation of the formation and evolution of the debris flow stream can provide useful basic data for the research of geologic environment evolution in Mo-xi river basin since the Quaternary.Based on the topographical statistic data of 51 debris flow gullies,the distribution of debris flows in Moxi river basin shows an asymmetric character obviously.There are fractal phenomenon and self-similarity among the debris flow numbers and the channel length,channel gradient and catchments area.Finally,this paper discusses the debris flow nonlinear evolution character and its response to the environment.This result can provide basic data for debris flow hazard prevention and risk control in Moxi river basin.
2011, 19(3): 381-387.
On the basis of the investigation and the statistics on site,this paper studies the distribution characters of the whole and different volume groups' rockfall of more than 200 blocks along the bended valley at Donghekou in Qinchuan town.The rockfalls happened during the 2008 Wenchuan Earthquake.The concept of rock blocks interception rate are given on the basis of statistical information.Then,the interception effect of the turning point and the rock blocks' distribution in the valley are analysed quantitatively from the point of the rock block number and the rock block volume.The conclusions are given as follows: the valley bend has the positive effect on controlling the following of the rockfall blocks; the larger the rock block,the bigger possibility intercepted at the point.From the view of the number,the bend turning point near the rockfall resource intercepted more rock blocks than that near the foot of the mountain.The method and the conclusions give the support to research bended valley and its turning point controlling the migration of the rockfall deposits,and also give some reference for preventing the rockfall hazards.
On the basis of the investigation and the statistics on site,this paper studies the distribution characters of the whole and different volume groups' rockfall of more than 200 blocks along the bended valley at Donghekou in Qinchuan town.The rockfalls happened during the 2008 Wenchuan Earthquake.The concept of rock blocks interception rate are given on the basis of statistical information.Then,the interception effect of the turning point and the rock blocks' distribution in the valley are analysed quantitatively from the point of the rock block number and the rock block volume.The conclusions are given as follows: the valley bend has the positive effect on controlling the following of the rockfall blocks; the larger the rock block,the bigger possibility intercepted at the point.From the view of the number,the bend turning point near the rockfall resource intercepted more rock blocks than that near the foot of the mountain.The method and the conclusions give the support to research bended valley and its turning point controlling the migration of the rockfall deposits,and also give some reference for preventing the rockfall hazards.
2011, 19(3): 388-396.
Regional geo-hazard susceptibility assessment is the basis for early warning of geo-hazards.To develop assessment methods of geo-hazard susceptibility in Qinling Mountain area,the distribution and the main influencing factors of geo-hazards in Fengxian county,Shaanxi province are comprehensively analyzed based on the geo-hazard investigation and mapping of 1 :50000 scale.With GIS and information model,the geo-hazard susceptibility evaluation of the whole area of Fengxian County is carried out.According to the result,the distribution of geo-hazard is mainly affected by river erosion,vegetation coverage and human activities.The whole area can be divided into four categories: the high grade area,which covers 190.3km2,accounting for 6.0% of the total study area; the medium grade area,which covers 642.0km2,accounting for 20.1%; the low grade area,which is measured 1314.5km2,taking up for 41.2%; and the stable area that is measured 1040.1km2,taking up for 32.6%.The results can provide a basis for construction layout and geo-hazard prevention and reduction in Fengxian County and also provide the guideline for geo-hazard susceptibility zonation in other counties of Qinling Mountain area.
Regional geo-hazard susceptibility assessment is the basis for early warning of geo-hazards.To develop assessment methods of geo-hazard susceptibility in Qinling Mountain area,the distribution and the main influencing factors of geo-hazards in Fengxian county,Shaanxi province are comprehensively analyzed based on the geo-hazard investigation and mapping of 1 :50000 scale.With GIS and information model,the geo-hazard susceptibility evaluation of the whole area of Fengxian County is carried out.According to the result,the distribution of geo-hazard is mainly affected by river erosion,vegetation coverage and human activities.The whole area can be divided into four categories: the high grade area,which covers 190.3km2,accounting for 6.0% of the total study area; the medium grade area,which covers 642.0km2,accounting for 20.1%; the low grade area,which is measured 1314.5km2,taking up for 41.2%; and the stable area that is measured 1040.1km2,taking up for 32.6%.The results can provide a basis for construction layout and geo-hazard prevention and reduction in Fengxian County and also provide the guideline for geo-hazard susceptibility zonation in other counties of Qinling Mountain area.
2011, 19(3): 397-403.
Unstable rock blocks are one of the geological natural hazard sources and can have a great influence on human life and engineering activities.The investigation of the unstable rock blocks,the evaluation of their stability and thier prevention measure are difficult tasks.The Nanmenwan unstable rocks have 20 blocks.The controlling design for the unstable rock blocks is very difficult for their complex geological characteristics.In this paper,in order to treat the unstable rock blocks,a stability evaluation criterion for unstable rock blocks at Nanmenwan is established on the basis of the study for the W6 unstable rock block with stereographic projection method.At the same time,the stability zone division at Nanmenwan is carried by the analysis of rock fractures development.At last,the control measures for unstable rock are also proposed for a guiding significance for the project.
Unstable rock blocks are one of the geological natural hazard sources and can have a great influence on human life and engineering activities.The investigation of the unstable rock blocks,the evaluation of their stability and thier prevention measure are difficult tasks.The Nanmenwan unstable rocks have 20 blocks.The controlling design for the unstable rock blocks is very difficult for their complex geological characteristics.In this paper,in order to treat the unstable rock blocks,a stability evaluation criterion for unstable rock blocks at Nanmenwan is established on the basis of the study for the W6 unstable rock block with stereographic projection method.At the same time,the stability zone division at Nanmenwan is carried by the analysis of rock fractures development.At last,the control measures for unstable rock are also proposed for a guiding significance for the project.
SLIDING CHARACTERISTICS OF HIGH-SPEED AND LONG RUN-OUT GIANT ROCKSLIDE LANDSLIDE AT WENJIAGOU STREAM
2011, 19(3): 404-408.
Wenjiagou landslide is a giant rockslide with high-speed and long run-out.It was triggered by the 2008 Wenchuan earthquake.But its sliding characteristic is unclear so far.This paper presents a study on the sliding characteristic of this rockslide.It is based on the field investigation and is combined with remote sensing interpretation.The conclusions are as follows: The slip mass started diversity from source area,scraped rock-soil body of slope surface at the slope area,and then glided or flied into Wenjia gully,continued to downslide along the gully,meanwhile scraped the both valley side slopes.The rock mass occurred five times large-scale collisions with the bank slopes,disintegrated into debris gradually.The debris began to slow down and accumulate in large-scale after the third collision.Finally some sediments reached the valley mouth.The results show that,the hilly terrain is the controlling factor of sliding and accumulation of slip mass,climb,toss,overtopping of slip mass when it crashed into a hill.The disintegration into debris of slip mass and the formation of air blast were the concrete manifestation of high-speed travel.The collision was the main way leading to the disintegration of debris in the whole process.
Wenjiagou landslide is a giant rockslide with high-speed and long run-out.It was triggered by the 2008 Wenchuan earthquake.But its sliding characteristic is unclear so far.This paper presents a study on the sliding characteristic of this rockslide.It is based on the field investigation and is combined with remote sensing interpretation.The conclusions are as follows: The slip mass started diversity from source area,scraped rock-soil body of slope surface at the slope area,and then glided or flied into Wenjia gully,continued to downslide along the gully,meanwhile scraped the both valley side slopes.The rock mass occurred five times large-scale collisions with the bank slopes,disintegrated into debris gradually.The debris began to slow down and accumulate in large-scale after the third collision.Finally some sediments reached the valley mouth.The results show that,the hilly terrain is the controlling factor of sliding and accumulation of slip mass,climb,toss,overtopping of slip mass when it crashed into a hill.The disintegration into debris of slip mass and the formation of air blast were the concrete manifestation of high-speed travel.The collision was the main way leading to the disintegration of debris in the whole process.
2011, 19(3): 409-416.
The Guanyinyan Hydropower Station locates in the upper reaches of Jinsha River.The dam type is a combination of concrete gravity dam and core rockfill dam.The stratum in the dam site is middle Shedian group of Jurassic.The lithology is mainly the calcareous ferruginous cemented conglomerate and the quartz sandstone.The main components of conglomerate are cryptite and biolithite.The large cystic cavities or holes are formed by corroded calcareous ferruginous under groundwater.The corroded calcareous cement in sandstone displays sand-like or sugar-like.So it affects the stability of dam foundation.On the basis of analyzing geological conditions and hydro-geological conditions in the right bank of the station,this paper investigates the groundwater-dynamic simulation,water-soluble element statistics and corrosion experiment of sampling for rock corrosion rules.It is found that the rock and tectonic control play a leading role for the rock corrosion.The solute reaction is developed intensely along strike direction of joints and fractures,because of local-groundwater with quick circle and rapid flow rate.Not only the agglutination of the sandy and gravelly rock is calcareous,but also 30％ ~50％of the gravel is calcareous.So the dissolubility of the rock is strong.The fresh rock surface is easily corroded,and the corrosion rate is fast.The research results can serve as the foundation for antiskid,distortion and seepage stability evaluation.They also provide background information for the study to erosion-dissolution of rock with groundwater after impounded water.
The Guanyinyan Hydropower Station locates in the upper reaches of Jinsha River.The dam type is a combination of concrete gravity dam and core rockfill dam.The stratum in the dam site is middle Shedian group of Jurassic.The lithology is mainly the calcareous ferruginous cemented conglomerate and the quartz sandstone.The main components of conglomerate are cryptite and biolithite.The large cystic cavities or holes are formed by corroded calcareous ferruginous under groundwater.The corroded calcareous cement in sandstone displays sand-like or sugar-like.So it affects the stability of dam foundation.On the basis of analyzing geological conditions and hydro-geological conditions in the right bank of the station,this paper investigates the groundwater-dynamic simulation,water-soluble element statistics and corrosion experiment of sampling for rock corrosion rules.It is found that the rock and tectonic control play a leading role for the rock corrosion.The solute reaction is developed intensely along strike direction of joints and fractures,because of local-groundwater with quick circle and rapid flow rate.Not only the agglutination of the sandy and gravelly rock is calcareous,but also 30％ ~50％of the gravel is calcareous.So the dissolubility of the rock is strong.The fresh rock surface is easily corroded,and the corrosion rate is fast.The research results can serve as the foundation for antiskid,distortion and seepage stability evaluation.They also provide background information for the study to erosion-dissolution of rock with groundwater after impounded water.
2011, 19(3): 417-427.
The link segment of Qinggangzui Bridge abutment and Gangzishang Tunnel portal in Yalu Expressway will be built on the ice deposit fan on the right bank of the Dadu River.Because of the water storage of Pubugou Hydropower Station,about a quarter in front of the bank slope will be underwater.The main geotechnical material impacting the entire slope is the ice deposits composed by upper-middle PleistoceneIce ice sediments and ice water sediments.Under the action of water,their physical and mechanical properties and strength will be significantly changed.Their engineering behavior will be weakened.Thus the bank slope stability and the abutment arrangement will be affected.It can be foreseen that the water from the external conditions will play an important role and the reservoir bank reconstruction will generally control the bank slope stability.In this paper,the reservoir bank slope in Yalu Expressway is discussed because Gangzishang Tunnel portal is to be constructed on the slope.Through the slope engineering geological conditions,rock and soil structure and mechanical properties,the analysis of factors affecting slope,the water impact on the banks as well as the slope stability are mainly discussed.The used methods are Cacho,Two Sections(Multiple),Limit-equilibrium for the analysis of the water impact on the reservoir bank and to predict recycling width.Forecasting results from the three methods all show that different parts of the slope will have bank collapse in different degrees after the Pubugou Power Station is impounded.According to the structural characteristics of the reservoir bank slope and the three methods of application conditions,this paper puts forward an integrated prediction method that different forecasting methods need to adopt at different sections of the reservoir bank slope.The Two Sections(Multiple)method is used to forecast the underwater bank slope.For the slope upon water,the calculation results of Cacho method and Limit-equilibrium method are comprehensively considered.The results can also be used for stability analysis of similar reservoir bank slopes.
The link segment of Qinggangzui Bridge abutment and Gangzishang Tunnel portal in Yalu Expressway will be built on the ice deposit fan on the right bank of the Dadu River.Because of the water storage of Pubugou Hydropower Station,about a quarter in front of the bank slope will be underwater.The main geotechnical material impacting the entire slope is the ice deposits composed by upper-middle PleistoceneIce ice sediments and ice water sediments.Under the action of water,their physical and mechanical properties and strength will be significantly changed.Their engineering behavior will be weakened.Thus the bank slope stability and the abutment arrangement will be affected.It can be foreseen that the water from the external conditions will play an important role and the reservoir bank reconstruction will generally control the bank slope stability.In this paper,the reservoir bank slope in Yalu Expressway is discussed because Gangzishang Tunnel portal is to be constructed on the slope.Through the slope engineering geological conditions,rock and soil structure and mechanical properties,the analysis of factors affecting slope,the water impact on the banks as well as the slope stability are mainly discussed.The used methods are Cacho,Two Sections(Multiple),Limit-equilibrium for the analysis of the water impact on the reservoir bank and to predict recycling width.Forecasting results from the three methods all show that different parts of the slope will have bank collapse in different degrees after the Pubugou Power Station is impounded.According to the structural characteristics of the reservoir bank slope and the three methods of application conditions,this paper puts forward an integrated prediction method that different forecasting methods need to adopt at different sections of the reservoir bank slope.The Two Sections(Multiple)method is used to forecast the underwater bank slope.For the slope upon water,the calculation results of Cacho method and Limit-equilibrium method are comprehensively considered.The results can also be used for stability analysis of similar reservoir bank slopes.
2011, 19(3): 428-432.
In order to guide construction and improve the safety and economy of construction,hydro-fracturing stress measurements have been conducted for Xizhouling tunnel of Zhejiang Province.It is found that the most important stress direction is the horizontal direction in the surveyed area.Within the measured depths,the maximum horizontal stress is of 10.57~19.39MPa.This stress level can be classified as middle to high level in this deep-seated tunnel.The dominant direction of the maximum horizontal stress is about N33W.The angle between the direction of the maximum horizontal stress and the direction of the tunnel axis is relatively small for this tunnel,and favorable to the stability of the tunnel and the surrounding rock mass.Based on the in-situ stress results and four distinguished methods( i.e. , Hoek method,Turchaninov method,Russenes method and engineering rock quality classification standard)rockbursts are forecasted during tunnel construction in the deep-seated tunnel conditions.The critical buried depth of rockburst is estimated.The results show that there are high possibilities of occurring weak and moderate rockbursts in this tunnel.The critical buried depth of rockburst is about 397m.In order to avoid the disadvantage conditions,reasonable excavation method and safety precautions should be adopted during the tunnel construction.
In order to guide construction and improve the safety and economy of construction,hydro-fracturing stress measurements have been conducted for Xizhouling tunnel of Zhejiang Province.It is found that the most important stress direction is the horizontal direction in the surveyed area.Within the measured depths,the maximum horizontal stress is of 10.57~19.39MPa.This stress level can be classified as middle to high level in this deep-seated tunnel.The dominant direction of the maximum horizontal stress is about N33W.The angle between the direction of the maximum horizontal stress and the direction of the tunnel axis is relatively small for this tunnel,and favorable to the stability of the tunnel and the surrounding rock mass.Based on the in-situ stress results and four distinguished methods( i.e. , Hoek method,Turchaninov method,Russenes method and engineering rock quality classification standard)rockbursts are forecasted during tunnel construction in the deep-seated tunnel conditions.The critical buried depth of rockburst is estimated.The results show that there are high possibilities of occurring weak and moderate rockbursts in this tunnel.The critical buried depth of rockburst is about 397m.In order to avoid the disadvantage conditions,reasonable excavation method and safety precautions should be adopted during the tunnel construction.
2011, 19(3): 433-439.
The distribution of land subsidence caused by both high-rise building loading and exploitation of groundwater is increasingly complex in urban area.This paper examines the land subsidence in Tanggu area.It considers the equilibrium condition,the elastic constitutive condition,the deformation compatibility condition of solid,and the continuity condition of water flow in soil consolidation.It then develops a three-dimensional land subsidence model for Tanggu area.The model is also based on the Biot's consolidation theory and takes into account both high-rise building loading and exploitation of groundwater.The finite element method is applied to the numerical calculation of the ground subsidence.The results indicate that there will be a considerable ground settlement in 3~4 years after construction of high-rise building.The settlement under the condition of both high-rise building loading and the exploitation of groundwater is lower than the sum settlement under he two single conditions.The model has a good convergence property and its computing results conform to actual data well.
The distribution of land subsidence caused by both high-rise building loading and exploitation of groundwater is increasingly complex in urban area.This paper examines the land subsidence in Tanggu area.It considers the equilibrium condition,the elastic constitutive condition,the deformation compatibility condition of solid,and the continuity condition of water flow in soil consolidation.It then develops a three-dimensional land subsidence model for Tanggu area.The model is also based on the Biot's consolidation theory and takes into account both high-rise building loading and exploitation of groundwater.The finite element method is applied to the numerical calculation of the ground subsidence.The results indicate that there will be a considerable ground settlement in 3~4 years after construction of high-rise building.The settlement under the condition of both high-rise building loading and the exploitation of groundwater is lower than the sum settlement under he two single conditions.The model has a good convergence property and its computing results conform to actual data well.
2011, 19(3): 440-446.
Road embankments in west coastal area of Bohai gulf are mainly fill embankment.The fill materials are mainly saline soil.When using saline soil for filling,it should be treated by modification and solidification to solve the weaker strength and stability due to the expansion,depression and serious water absorption of saline soil.More inorganic materials and fewer polymer materials are suitable for a reasonable construction budget.Some tests on saline soil with lime and saline soil with lime and SH agent are carried out.The tests include unconfined compression strength,tensile strength,triaxial shear strength,and CBR in laboratory,as well as degree of compaction,flattening degree,rebound deflection,CBR,and rebound modulus in-situ.The test purposes is to study the mechanical properties of solidified saline soils used for highway embankment fillings simultaneously.The test results indicate that (1)Mechanical indices of two solidified soils meet the requirements on highway fillings.The strength of saline soil with lime and SH agent is better than that of saline soil with lime.(2)SH agent brings about anti-water connection between soil particles,and forms lots of the wire-like connecting network in pores after drying.So anti-deformation and strength in air and water of the solidified soil are increased.(3)It is noted that compaction effort in-situ is well.The test results of the solidified soils are corresponding in the condition of laboratory and in-situ.The compaction and mechanical properties of saline soil with lime and SH agent satisfy the requirements of highway specification and are of a suitable treatment measure and have well using objective in the coastal area.
Road embankments in west coastal area of Bohai gulf are mainly fill embankment.The fill materials are mainly saline soil.When using saline soil for filling,it should be treated by modification and solidification to solve the weaker strength and stability due to the expansion,depression and serious water absorption of saline soil.More inorganic materials and fewer polymer materials are suitable for a reasonable construction budget.Some tests on saline soil with lime and saline soil with lime and SH agent are carried out.The tests include unconfined compression strength,tensile strength,triaxial shear strength,and CBR in laboratory,as well as degree of compaction,flattening degree,rebound deflection,CBR,and rebound modulus in-situ.The test purposes is to study the mechanical properties of solidified saline soils used for highway embankment fillings simultaneously.The test results indicate that (1)Mechanical indices of two solidified soils meet the requirements on highway fillings.The strength of saline soil with lime and SH agent is better than that of saline soil with lime.(2)SH agent brings about anti-water connection between soil particles,and forms lots of the wire-like connecting network in pores after drying.So anti-deformation and strength in air and water of the solidified soil are increased.(3)It is noted that compaction effort in-situ is well.The test results of the solidified soils are corresponding in the condition of laboratory and in-situ.The compaction and mechanical properties of saline soil with lime and SH agent satisfy the requirements of highway specification and are of a suitable treatment measure and have well using objective in the coastal area.
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