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Editor Work2011 Vol. 19, No. 5
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2011, 19(5): 637-641.
Abstract
442KB
The surrounding rock zoning and analysis are the main basis to determine the roadway bolting and loose ground pressure.Displacement of surrounding rock is the main parameter for the design of coal mine tunnel cross section and the determination of distortion geostatic pressure.This paper adopts Hoek-Brown strength theory and limit equilibrium equation and carries out the elasto-plastic analysis of an idealized roadway surrounding rock with a unit lateral pressure coefficient.It derives the plastic zone radius,stress field and displacements of the surrounding rock.The results are further compared with the results determined from the widely used Fennner formula associated with the Mohr-Coulomb yield strength criterion.
The surrounding rock zoning and analysis are the main basis to determine the roadway bolting and loose ground pressure.Displacement of surrounding rock is the main parameter for the design of coal mine tunnel cross section and the determination of distortion geostatic pressure.This paper adopts Hoek-Brown strength theory and limit equilibrium equation and carries out the elasto-plastic analysis of an idealized roadway surrounding rock with a unit lateral pressure coefficient.It derives the plastic zone radius,stress field and displacements of the surrounding rock.The results are further compared with the results determined from the widely used Fennner formula associated with the Mohr-Coulomb yield strength criterion.
2011, 19(5): 642-647.
Deformation parameters of engineering rock mass are important necessary precondition for deformation calculation and stability analysis.So the reasonable selection on the deformation parameters is a focus and difficulty in geotechnical engineering.Because of size effect,the mechanical parameters would change with the research size of rock mass.Mechanical parameters from laboratory test,even from in-situ test can't exactly represent the characteristics of the engineering rock mass.In order to get mechanical parameters of the engineering rock mass that can be applied to practical engineering directly,the size effect of rock mass parameters and its mechanism of production need to be systemically studied.The size effect of rock mass deformation parameters is studied by multi-scale methods combined with specific engineering project.Deformation modulus with different sizes of rock mass are got from the experiments of laboratory test,in-situ plate load test,wave velocity test,numerical simulation and displacement back analysis.It is found that the rock mass deformation modulus decreases significantly as the rock mass size increases.When the tested rock mass size is larger than 30m,the deformation modulus of rock mass tends to be stable.Equations between deformation modulus and rock mass size are got with regression analysis.Then the macro-mechanical parameters and the REV scale are obtained.Finally,the mechanism of the size effect to rock mass deformation modulus is discussed.It shows the structural planes with different size within rock mass are the intrinsic cause for the mechanism.The REV scale of jointed rock mass is about 3 times of the length of the main structure.When the size is larger than the REV scale,the deformation modulus of rock mass would became a stable value.It is a new attempt to survey the macro parameters of rock mass by combination of multi-scale methods and statistics theory.The findings presented in this paper can provide a useful reference to the parameter determination of rock mass in geotechnique engineering and other similar projects.
Deformation parameters of engineering rock mass are important necessary precondition for deformation calculation and stability analysis.So the reasonable selection on the deformation parameters is a focus and difficulty in geotechnical engineering.Because of size effect,the mechanical parameters would change with the research size of rock mass.Mechanical parameters from laboratory test,even from in-situ test can't exactly represent the characteristics of the engineering rock mass.In order to get mechanical parameters of the engineering rock mass that can be applied to practical engineering directly,the size effect of rock mass parameters and its mechanism of production need to be systemically studied.The size effect of rock mass deformation parameters is studied by multi-scale methods combined with specific engineering project.Deformation modulus with different sizes of rock mass are got from the experiments of laboratory test,in-situ plate load test,wave velocity test,numerical simulation and displacement back analysis.It is found that the rock mass deformation modulus decreases significantly as the rock mass size increases.When the tested rock mass size is larger than 30m,the deformation modulus of rock mass tends to be stable.Equations between deformation modulus and rock mass size are got with regression analysis.Then the macro-mechanical parameters and the REV scale are obtained.Finally,the mechanism of the size effect to rock mass deformation modulus is discussed.It shows the structural planes with different size within rock mass are the intrinsic cause for the mechanism.The REV scale of jointed rock mass is about 3 times of the length of the main structure.When the size is larger than the REV scale,the deformation modulus of rock mass would became a stable value.It is a new attempt to survey the macro parameters of rock mass by combination of multi-scale methods and statistics theory.The findings presented in this paper can provide a useful reference to the parameter determination of rock mass in geotechnique engineering and other similar projects.
2011, 19(5): 648-655.
The traditional RMR method is especially focused on constant rating parameters and the form of giving scores.So there is no doubt that it has many indeterminate and subjective factors in the process of rating and cannot get an adequate result under complicated geologic environment.In order to improve the RMR method,this paper puts forward the AHP method to use in rock mass classification.Under this method,the rock mass classification is viewed as a group decision problem.It can readjust the rating parameters based on real geologic environment and calculate parameters' proportion,establish corresponding evaluation criterion.Then it can calculate rock mass total score which is used for the rating.The fuzzy logic theory is used in AHP method to solve fuzzy problem in fact.At last,this new method has been used in the rock mass classification of Dwan tunnel.Compared to the RMR method result for this instance,the classification result of AHP method is closer to the fact.
The traditional RMR method is especially focused on constant rating parameters and the form of giving scores.So there is no doubt that it has many indeterminate and subjective factors in the process of rating and cannot get an adequate result under complicated geologic environment.In order to improve the RMR method,this paper puts forward the AHP method to use in rock mass classification.Under this method,the rock mass classification is viewed as a group decision problem.It can readjust the rating parameters based on real geologic environment and calculate parameters' proportion,establish corresponding evaluation criterion.Then it can calculate rock mass total score which is used for the rating.The fuzzy logic theory is used in AHP method to solve fuzzy problem in fact.At last,this new method has been used in the rock mass classification of Dwan tunnel.Compared to the RMR method result for this instance,the classification result of AHP method is closer to the fact.
2011, 19(5): 656-663.
The rapid development of urbanization significantly influences the urban geologic environment and especially the underground water environment.In this investigation,two long-term soil water monitoring stations were built in urban and suburban areas of Nanjing city.By using PR2,the soil profile water contents in one meter depth were monitored every day from June to September in 2009.It is found that the soil water content was significantly controlled by weather condition.Its sensitivity to weather decreased as the depth increased.A comparison of the data obtained from the two stations shows that the effect of weather to water content in the urban soil is not as significant as that in the suburban soil.The water content in the urban soil is generally lower than that in the suburban soil.An obvious urban dry island(UDI)effect is observed.During the period of June to September,the average UDI intensity is -9.1%,the highest day UDI intensity is about -20.7%,the highest month UDI intensity observed in July is about -17.0%,,and the minimal month UDI intensity observed in September is about-8.5%..In addition,it is shown that the temporal and spatial variations of soil water contents depend on the underlying surface properties.For example,the average soil profile water content under cement cover is less than those under grass and bare soil covers.It indicates that cement cover in urban area can obviously intensify the UDI effect.During the monitoring period(from June to September),it is found that,in urban area,the average profile water contents under bare soil cover,cement cover and grass cover are 26.9%, 25.6%,and 17.5%,respectively; whereas in suburban area,the three average profile water contents are 37.6%, 37.6%,(36.0%,respectively; the water content differences between the urban and suburban soils for grass,cement and bare soil covers are the highest,the intermediate and the lowest,respectively.
The rapid development of urbanization significantly influences the urban geologic environment and especially the underground water environment.In this investigation,two long-term soil water monitoring stations were built in urban and suburban areas of Nanjing city.By using PR2,the soil profile water contents in one meter depth were monitored every day from June to September in 2009.It is found that the soil water content was significantly controlled by weather condition.Its sensitivity to weather decreased as the depth increased.A comparison of the data obtained from the two stations shows that the effect of weather to water content in the urban soil is not as significant as that in the suburban soil.The water content in the urban soil is generally lower than that in the suburban soil.An obvious urban dry island(UDI)effect is observed.During the period of June to September,the average UDI intensity is -9.1%,the highest day UDI intensity is about -20.7%,the highest month UDI intensity observed in July is about -17.0%,,and the minimal month UDI intensity observed in September is about-8.5%..In addition,it is shown that the temporal and spatial variations of soil water contents depend on the underlying surface properties.For example,the average soil profile water content under cement cover is less than those under grass and bare soil covers.It indicates that cement cover in urban area can obviously intensify the UDI effect.During the monitoring period(from June to September),it is found that,in urban area,the average profile water contents under bare soil cover,cement cover and grass cover are 26.9%, 25.6%,and 17.5%,respectively; whereas in suburban area,the three average profile water contents are 37.6%, 37.6%,(36.0%,respectively; the water content differences between the urban and suburban soils for grass,cement and bare soil covers are the highest,the intermediate and the lowest,respectively.
2011, 19(5): 664-668.
Severe damage can be caused by rock burst because it occurs suddenly and strongly in deep underground engineering construction.It is very important to predict the rock burst.Due to complex influence factors and their relationship,the rock burst cannot be predicted well by using of the traditional index and evaluation-methods.However,the grey incidence system can be used to establish the relevance of various influence factors.This paper analyzes the main factors of rock burst.It selects the rock compressive strength,the rock tensile strength,the rock elastic energy index and the maximum tangential stress of cavern wall as the indexes of criterion for rock burst prediction.A grey incidence system model of rock burst prediction is established.On the bases of engineering experience,the prediction model is applied to practical engineering.The prediction results show that the method of grey incidence analysis can considers the main influence factors of rock burst.It is feasible and valid to predict the rock burst of underground engineering.Comparing with the other prediction methods,the grey incidence system has high accuracy and reliability.The prediction accuracy of rock burst can be improved by choosing more representative engineering experience.
Severe damage can be caused by rock burst because it occurs suddenly and strongly in deep underground engineering construction.It is very important to predict the rock burst.Due to complex influence factors and their relationship,the rock burst cannot be predicted well by using of the traditional index and evaluation-methods.However,the grey incidence system can be used to establish the relevance of various influence factors.This paper analyzes the main factors of rock burst.It selects the rock compressive strength,the rock tensile strength,the rock elastic energy index and the maximum tangential stress of cavern wall as the indexes of criterion for rock burst prediction.A grey incidence system model of rock burst prediction is established.On the bases of engineering experience,the prediction model is applied to practical engineering.The prediction results show that the method of grey incidence analysis can considers the main influence factors of rock burst.It is feasible and valid to predict the rock burst of underground engineering.Comparing with the other prediction methods,the grey incidence system has high accuracy and reliability.The prediction accuracy of rock burst can be improved by choosing more representative engineering experience.
2011, 19(5): 669-673.
The stability of line structure is influenced by under-excavation or over-excavation of rocks surrounding tunnels.It is of a great significance for understanding the surrounding rock stress and ensuring construction safety to research the law of under-excavation over-excavation for surrounding rocks of tunnels.This paper is based on the multi-resolution analysis of wavelet analysis and the statistical self-similarity on the surrounding rock under-excavation over-excavation for tunnels outline.It presents an approach of the fractal dimension estimation with wavelet analysis.The research results have shown that the suggested wavelet estimation method is satisfied by selection of appropriate wavelet functions and decomposition steps.The fractal dimension of overall outline,tunnel vault and tunnel wall have been calculated with wavelet analysis.The relationship between classes of surrounding rocks and the fractal dimension of tunnel outline is analyzed.The relationship between the stability of surrounding rocks and the fractal dimension of tunnel outline is also analyzed with combining with the actual situation.
The stability of line structure is influenced by under-excavation or over-excavation of rocks surrounding tunnels.It is of a great significance for understanding the surrounding rock stress and ensuring construction safety to research the law of under-excavation over-excavation for surrounding rocks of tunnels.This paper is based on the multi-resolution analysis of wavelet analysis and the statistical self-similarity on the surrounding rock under-excavation over-excavation for tunnels outline.It presents an approach of the fractal dimension estimation with wavelet analysis.The research results have shown that the suggested wavelet estimation method is satisfied by selection of appropriate wavelet functions and decomposition steps.The fractal dimension of overall outline,tunnel vault and tunnel wall have been calculated with wavelet analysis.The relationship between classes of surrounding rocks and the fractal dimension of tunnel outline is analyzed.The relationship between the stability of surrounding rocks and the fractal dimension of tunnel outline is also analyzed with combining with the actual situation.
2011, 19(5): 674-684.
The Daguangbao gigantic rockslide is located on the Gaochuan village,Anxia county.It is the hugest landslide triggered by the Wenchuan 8.0 earthquake on May 12 of 2008.This paper uses four periods of remote sensing data with high resolution before/after the earthquake and ground surveying and mapping data to analyze the basic features of the Daguangbao rockslide.The basic features include the accumulation and movement zoning,the sliding surface and exiting,and the volume.The Daguangbao gigantic rockslide is classified into sliding source,back depression,main bedrock accumulation,down-stream accumulation,up-stream accumulation and front lobe.The main bedrock accumulation remained a structure of parent layered limestone rockmass with slight separation that is 1, 100m long, 490m wide, 215m average thick and 464millions m3 in the volume.The sliding direction and boundary are outlined according to the compared result before/after topography,geomorphology,and mining adit,waste ore material and sheds.The bedrock sliding distance is about 1750m.A digital elevation model with the scale of 1 to 5000 before/after earthquake is established to calculate the area and the thickness of the rockslide accumulation.With the AutoCAD,a 3D entity model of the sliding surface is also established.The result shows the whole Daguangbao gigantic rockslide is 4300m long, 3500m wide and 550m thick in the maximum.The debris volume is about 1.15~1.2 billion m3.It is the hugest landslide not only in China,but also in the world in recent hundred years.
The Daguangbao gigantic rockslide is located on the Gaochuan village,Anxia county.It is the hugest landslide triggered by the Wenchuan 8.0 earthquake on May 12 of 2008.This paper uses four periods of remote sensing data with high resolution before/after the earthquake and ground surveying and mapping data to analyze the basic features of the Daguangbao rockslide.The basic features include the accumulation and movement zoning,the sliding surface and exiting,and the volume.The Daguangbao gigantic rockslide is classified into sliding source,back depression,main bedrock accumulation,down-stream accumulation,up-stream accumulation and front lobe.The main bedrock accumulation remained a structure of parent layered limestone rockmass with slight separation that is 1, 100m long, 490m wide, 215m average thick and 464millions m3 in the volume.The sliding direction and boundary are outlined according to the compared result before/after topography,geomorphology,and mining adit,waste ore material and sheds.The bedrock sliding distance is about 1750m.A digital elevation model with the scale of 1 to 5000 before/after earthquake is established to calculate the area and the thickness of the rockslide accumulation.With the AutoCAD,a 3D entity model of the sliding surface is also established.The result shows the whole Daguangbao gigantic rockslide is 4300m long, 3500m wide and 550m thick in the maximum.The debris volume is about 1.15~1.2 billion m3.It is the hugest landslide not only in China,but also in the world in recent hundred years.
2011, 19(5): 685-696.
On April 14, 2010(4.14),a Ms 7.1 earthquake happened in Yushu county,Qinghai province.It not only damaged many buildings in Yushu county and buildings in a certain scope of perimeter area,but also induced a series of geological environmental issues.These issues include triggering geological hazard,destroying geomorphology landscape,breaking formation of water-bearing stratum,changing the groundwater flow field,surface rupture,and changing the physical properties of rock-soil.A great deal of field investigations show that: firstly,the geological environmental issues should be represented as collapses,landslides,debris flow and potentially unstable slopes,earthquake surface ruptures,mountains cracks,and shaking compaction,earthquake liquefaction,and damages to cultural relics and geomorphologic landscapes; Secondly,this paper shows the features of geologic hazards distribution including the spatial features of collapses,landslides,debris flows and potential unstable slopes,in order to analyze how the earthquake geologic influences on the geologic environment.And statistics show that the influence scopes of the 4.14 earthquakes upon geologic environments has a close relationship with the length of the surface ruptures and the position of hanging wall and footwall; Thirdly,Taking structure surface of earthquake rupture as a reference,the destroying geologic environment can be divided into three parts: more serious area,serious area and general area.Such classification combines the features of geologic hazards distribution,for the purpose of making out correspondingly effective measurements and thoughts for administrating and investigating geologic hazards after earthquakes; Fourthly,there are many paleoearthquakes distributed along the earthquake fault zone.And most of them were thrown about.Thereby,through the comprehensive analyses of the effects of Yushu earthquake upon the geologic environment,relevant effective emergent measurements for inspection and examination are accordingly made in consideration of geological function induced by earthquake.As well as the administrative regions and technique ideas for earthquake stricken area are contoured and formulated.
On April 14, 2010(4.14),a Ms 7.1 earthquake happened in Yushu county,Qinghai province.It not only damaged many buildings in Yushu county and buildings in a certain scope of perimeter area,but also induced a series of geological environmental issues.These issues include triggering geological hazard,destroying geomorphology landscape,breaking formation of water-bearing stratum,changing the groundwater flow field,surface rupture,and changing the physical properties of rock-soil.A great deal of field investigations show that: firstly,the geological environmental issues should be represented as collapses,landslides,debris flow and potentially unstable slopes,earthquake surface ruptures,mountains cracks,and shaking compaction,earthquake liquefaction,and damages to cultural relics and geomorphologic landscapes; Secondly,this paper shows the features of geologic hazards distribution including the spatial features of collapses,landslides,debris flows and potential unstable slopes,in order to analyze how the earthquake geologic influences on the geologic environment.And statistics show that the influence scopes of the 4.14 earthquakes upon geologic environments has a close relationship with the length of the surface ruptures and the position of hanging wall and footwall; Thirdly,Taking structure surface of earthquake rupture as a reference,the destroying geologic environment can be divided into three parts: more serious area,serious area and general area.Such classification combines the features of geologic hazards distribution,for the purpose of making out correspondingly effective measurements and thoughts for administrating and investigating geologic hazards after earthquakes; Fourthly,there are many paleoearthquakes distributed along the earthquake fault zone.And most of them were thrown about.Thereby,through the comprehensive analyses of the effects of Yushu earthquake upon the geologic environment,relevant effective emergent measurements for inspection and examination are accordingly made in consideration of geological function induced by earthquake.As well as the administrative regions and technique ideas for earthquake stricken area are contoured and formulated.
2011, 19(5): 697-702.
In recent years,man-made heap hills have become more and more for landscape of urban construction in Jiangsu plain area.Their sizes are growing larger and larger.The heap hills are usually made of engineering spoils,building refuses,garbage and other materials.They are built in wasteland that cannot be used for urban construction.The heap hills not only efficiently use solid waste and waste land,but also beautify very well the urban environment.They are a new fashion in urban construction.However,geological conditions of the waste land are generally complex.It is very close from the surrounding buildings.A heap hill often has a high capacity and occupies a large load area.They are far different from the general engineering projects.If the engineering measures are unreasonable,some environmental geotechnical problems shall be induced easily.For example,a heap hill project was built on soft ground in urban area of southern Jiangsu Province.The design height of this hill is 54meters.The heap hill suddenly collapsed to large-scale when it was filled up to 40meters.This project stopped once.It posed risks to the surrounding roads and buildings.In this paper,with the tests and calculations,the collapse accident of the heap hill is studied in detail.The results indicate that the safety conditions of the heap hill in the soft soil foundation are as follows.The first,the bearing capacity of foundation must meet the requirements.The second,the foundation settlement,especially the discrepancy settlement,should be controlled within a certain range.
In recent years,man-made heap hills have become more and more for landscape of urban construction in Jiangsu plain area.Their sizes are growing larger and larger.The heap hills are usually made of engineering spoils,building refuses,garbage and other materials.They are built in wasteland that cannot be used for urban construction.The heap hills not only efficiently use solid waste and waste land,but also beautify very well the urban environment.They are a new fashion in urban construction.However,geological conditions of the waste land are generally complex.It is very close from the surrounding buildings.A heap hill often has a high capacity and occupies a large load area.They are far different from the general engineering projects.If the engineering measures are unreasonable,some environmental geotechnical problems shall be induced easily.For example,a heap hill project was built on soft ground in urban area of southern Jiangsu Province.The design height of this hill is 54meters.The heap hill suddenly collapsed to large-scale when it was filled up to 40meters.This project stopped once.It posed risks to the surrounding roads and buildings.In this paper,with the tests and calculations,the collapse accident of the heap hill is studied in detail.The results indicate that the safety conditions of the heap hill in the soft soil foundation are as follows.The first,the bearing capacity of foundation must meet the requirements.The second,the foundation settlement,especially the discrepancy settlement,should be controlled within a certain range.
2011, 19(5): 703-711.
Due to concentrated distribution,strong secondary and complex structure,multiple rotational landslides in loess is one of the most complicated landslide hazard types in the loess plateau.At first,this paper gives a definition of multiple rotational landslides in loess.So,it further studies the typical basic types,the characteristics and causes of multiple rotational landslides in the loess plateau of China in terms of hazards survey,geotechnical investigation and survey.Two types of multiple rotational loess landslides are the type of Jintai and the type of Heifangtai.They have different failure mechanisms and structures.The Jintai type of the landslides includes two classes of deep-seated multiple rotational-translational landslide and deep-seated multiple rotational landslide.The Heifangtai type of the landslides has mainly two classes of middle-shallow rotational loess landslides and multiple rotational bedding loess-mudstone landslides.The Jintai landslides are mostly large-scale landslides,composed by the three strata: near-horizontal thick layer pleistocene loess,gravel layer upper pleistocene terrace and pliocene red-hard clay.The analysis indicates that triggers of multiple rotational loess landslides include neotectonic movement,lateral erosion,strata lithology and structure,irrigation and seasonally freezing and thawing.Among the triggers,groundwater is the most inducing factor.The paper lays the foundation for mechanism study of multiple rotational loess landslides.
Due to concentrated distribution,strong secondary and complex structure,multiple rotational landslides in loess is one of the most complicated landslide hazard types in the loess plateau.At first,this paper gives a definition of multiple rotational landslides in loess.So,it further studies the typical basic types,the characteristics and causes of multiple rotational landslides in the loess plateau of China in terms of hazards survey,geotechnical investigation and survey.Two types of multiple rotational loess landslides are the type of Jintai and the type of Heifangtai.They have different failure mechanisms and structures.The Jintai type of the landslides includes two classes of deep-seated multiple rotational-translational landslide and deep-seated multiple rotational landslide.The Heifangtai type of the landslides has mainly two classes of middle-shallow rotational loess landslides and multiple rotational bedding loess-mudstone landslides.The Jintai landslides are mostly large-scale landslides,composed by the three strata: near-horizontal thick layer pleistocene loess,gravel layer upper pleistocene terrace and pliocene red-hard clay.The analysis indicates that triggers of multiple rotational loess landslides include neotectonic movement,lateral erosion,strata lithology and structure,irrigation and seasonally freezing and thawing.Among the triggers,groundwater is the most inducing factor.The paper lays the foundation for mechanism study of multiple rotational loess landslides.
2011, 19(5): 712-718.
Guantan landslide is a typical anti-dipped rock slope with soft foundation,a result of combined action of Wenchuan earthquake and rainfall after the earthquake.This paper built numerical analysis models of a slope with or without soft foundation.It revealed influence induced by soft foundation to evolution of stress field and extending trend of rupturing process of the slope during earthquake dynamic response process.Calculated result shows that before the failure of the slope,the existence of soft foundation can reduce the role of earthquake dynamic effect to a certain extent,which is positive to slope stability.But once the slope failed,the existence of soft foundation may intensify extension and coalescence of rupture surface,and finally form landslide.
Guantan landslide is a typical anti-dipped rock slope with soft foundation,a result of combined action of Wenchuan earthquake and rainfall after the earthquake.This paper built numerical analysis models of a slope with or without soft foundation.It revealed influence induced by soft foundation to evolution of stress field and extending trend of rupturing process of the slope during earthquake dynamic response process.Calculated result shows that before the failure of the slope,the existence of soft foundation can reduce the role of earthquake dynamic effect to a certain extent,which is positive to slope stability.But once the slope failed,the existence of soft foundation may intensify extension and coalescence of rupture surface,and finally form landslide.
2011, 19(5): 719-724.
Under cyclic loading,a slope can be easily deformed and damaged.The failure mode of each part of the slope is different.Based on the technology of numerical simulation,two slopes with different heights are established.And the particle motion at slope shoulders of the two slopes are analyzed under 10 Hz cyclic vertical compressive load and horizontal shear load,respectively.According to the relation between force and deformation,the potential failure mode of slope shoulder is reveal.The results show that: under cyclic vertical compressive loading and horizontal shear loading,the trail of slope shoulder' particle motion is oval shape.However,the loading pattern and slope height affect the trail of the particle motion.Under vertical compressive load,the particle at lower slope shoulder is experiencing vertical vibration seriously.So the lower slope shoulder is more easily to surfer tension cut-off.Reversely,the particle at lower slope shoulder is experiencing horizontal vibration significantly under horizontal shear load,which show the lower slope shoulder is more easily subject to shear failure.Comparing with the lower slope condition,the vertical and horizontal amplitude of vibration of the particle at the higher slope shoulder under both vertical and horizontal load are close to each other,which show the shoulder of higher slope will be tensile-shear complex failure.
Under cyclic loading,a slope can be easily deformed and damaged.The failure mode of each part of the slope is different.Based on the technology of numerical simulation,two slopes with different heights are established.And the particle motion at slope shoulders of the two slopes are analyzed under 10 Hz cyclic vertical compressive load and horizontal shear load,respectively.According to the relation between force and deformation,the potential failure mode of slope shoulder is reveal.The results show that: under cyclic vertical compressive loading and horizontal shear loading,the trail of slope shoulder' particle motion is oval shape.However,the loading pattern and slope height affect the trail of the particle motion.Under vertical compressive load,the particle at lower slope shoulder is experiencing vertical vibration seriously.So the lower slope shoulder is more easily to surfer tension cut-off.Reversely,the particle at lower slope shoulder is experiencing horizontal vibration significantly under horizontal shear load,which show the lower slope shoulder is more easily subject to shear failure.Comparing with the lower slope condition,the vertical and horizontal amplitude of vibration of the particle at the higher slope shoulder under both vertical and horizontal load are close to each other,which show the shoulder of higher slope will be tensile-shear complex failure.
2011, 19(5): 725-731.
The Sarma method is widely used to calculate the slope and embankment stability analysis.But the method assumes the horizontal direction as seismic force direction.So it does not consider the impact of the different directions of seismic force.In order to study the critical seismic coefficient and stability factor in different directions under the distribution of seismic forces,this paper,based on the traditional Sarma,assumes that non-horizontal seismic force,at any given positions of seismic force,and try to derive the formula.And the mean value is introduced to iteration when deal with the result of critical seismic coefficient.Examples are used to show the relationship among the directions of seismic force and the slope stability factor.After solving the minimum critical seismic coefficient,the represent angle of the minimum critical seismic coefficient is the angle of the smallest seismic force.On this point of the smallest seismic force,the stability analysis is gained in two classical examples.The analyses of the two examples derive the minimum value at last.Through the analysis,on the one hand,the direction of seismic forces represented by the minimum value is not necessarily pointing the outside horizontal direction.On the other hand,the corrected minimum critical seismic coefficient represents the authentic status that the smallest seismic force can be withstood by slope.Last but not the least,there is no sharp contrast between the calculated slope stability factor and the original slope stability factor.That is to say,when assuming the direction of seismic force,there will be no inaccuracy of assuming any position of the seismic force to calculate the valid slope stability factor.
The Sarma method is widely used to calculate the slope and embankment stability analysis.But the method assumes the horizontal direction as seismic force direction.So it does not consider the impact of the different directions of seismic force.In order to study the critical seismic coefficient and stability factor in different directions under the distribution of seismic forces,this paper,based on the traditional Sarma,assumes that non-horizontal seismic force,at any given positions of seismic force,and try to derive the formula.And the mean value is introduced to iteration when deal with the result of critical seismic coefficient.Examples are used to show the relationship among the directions of seismic force and the slope stability factor.After solving the minimum critical seismic coefficient,the represent angle of the minimum critical seismic coefficient is the angle of the smallest seismic force.On this point of the smallest seismic force,the stability analysis is gained in two classical examples.The analyses of the two examples derive the minimum value at last.Through the analysis,on the one hand,the direction of seismic forces represented by the minimum value is not necessarily pointing the outside horizontal direction.On the other hand,the corrected minimum critical seismic coefficient represents the authentic status that the smallest seismic force can be withstood by slope.Last but not the least,there is no sharp contrast between the calculated slope stability factor and the original slope stability factor.That is to say,when assuming the direction of seismic force,there will be no inaccuracy of assuming any position of the seismic force to calculate the valid slope stability factor.
2011, 19(5): 732-748.
A new complete loess profile has been found in Baoji region of the Loess Plateau in recent years.Based on this profile,this paper presents a study of the features of loess engineering geology.The loess is about 200m thick and formed from Holocene epoch to Lower Pleistocene epoch.The study is based on a detailed field investigation of typical loess section at Jiacun Terrace in Chenchang of Baoji region.Borehole drilling in the typical loess layer was conducted.Approximately undisturbed cores were obtained for the entire borehole depth.Subsequently,a systematic laboratory tests were carried out for the physical and mechanical parameters and material formation of the cores.The data was for the analysis of landslide mechanism and prevention.The test results show that 1)there is an inverse correlation between density and porosity ratio,2)there is a positive correlation between liquid limit and plastic limit along with the borehole depth, 3)there is an inverse correlation between modulus of compression and compressibility factor,and 4)there is an inverse correlation between internal cohension and internal friction angle with large variation range along the borehole depth.The analyses on the grain size analysis,carbonate content and major clay minerals of the typical loess show that a)there is a positive correlation between the 0.075mm to 0.010mm grain contents and the carbonate content,b)the grain and carbonate contents have an inverse correlation with the internal cohesion and a positive correlation with the internal friction angle,and c)there is a positive correlation of the less than 0.002mm colloid particle contents with the mixed-layer mineral of illite and montmorillonite,illite,kaolinite and other major clay minerals,and d)the less than 0.002mm colloid particle contents also have a positive correlation with the internal cohesion and an inverse correlation with the internal friction angle.The systematic test results presented in this paper will have an important significance to increase the scientific degree and reliability of loess landslide risk assessment.
A new complete loess profile has been found in Baoji region of the Loess Plateau in recent years.Based on this profile,this paper presents a study of the features of loess engineering geology.The loess is about 200m thick and formed from Holocene epoch to Lower Pleistocene epoch.The study is based on a detailed field investigation of typical loess section at Jiacun Terrace in Chenchang of Baoji region.Borehole drilling in the typical loess layer was conducted.Approximately undisturbed cores were obtained for the entire borehole depth.Subsequently,a systematic laboratory tests were carried out for the physical and mechanical parameters and material formation of the cores.The data was for the analysis of landslide mechanism and prevention.The test results show that 1)there is an inverse correlation between density and porosity ratio,2)there is a positive correlation between liquid limit and plastic limit along with the borehole depth, 3)there is an inverse correlation between modulus of compression and compressibility factor,and 4)there is an inverse correlation between internal cohension and internal friction angle with large variation range along the borehole depth.The analyses on the grain size analysis,carbonate content and major clay minerals of the typical loess show that a)there is a positive correlation between the 0.075mm to 0.010mm grain contents and the carbonate content,b)the grain and carbonate contents have an inverse correlation with the internal cohesion and a positive correlation with the internal friction angle,and c)there is a positive correlation of the less than 0.002mm colloid particle contents with the mixed-layer mineral of illite and montmorillonite,illite,kaolinite and other major clay minerals,and d)the less than 0.002mm colloid particle contents also have a positive correlation with the internal cohesion and an inverse correlation with the internal friction angle.The systematic test results presented in this paper will have an important significance to increase the scientific degree and reliability of loess landslide risk assessment.
2011, 19(5): 749-755.
The construction and operation of many water conservancy and hydroelectric projects in the Minjiang River region have brought some significant changes to the hydrodynamic field.Such changes include stream velocity,river discharge,sediment discharge and silt carrying capacity.They have also changed the distribution and intensity of stress field in those coastal belts.Therefore the types,the intensity and the evolution of geological processes have been greatly changed,and many environment geological hazards have also been caused.They hazards are considerably growing in terms of wider distribution and longer duration.This paper makes some preliminary studies on three relations.One relation is between the construction and operation of Minjiang River water conservancy project and the instability hazards of littoral slopes.The second is the earthquakes induced by Shuikou Reservoir.The third is the downstream channel stability behind the dam and its harmfulness.The results show that the instability of the reservoir banks is obvious correlation with the water conservancy project operation and the hazards frequency significantly increases as the operation continued.By enhancing the fluvial erosion behind the dam,the reservoir impounding becomes the important factor which affects the lower river channel and the littoral environment geological hazards.In addition,the impounding and hydration of Shuikou Reservoir are also the important factors inducing an earthquake.Its aftershocks will last for a long period.The point of view that the more intensive and destructive reservoir earthquake may occur in the next few years is put forward.Almost simultaneously the research on the special monitoring and forecasting for geological disasters should be carried out and the regional information monitoring and forecasting system about geological disasters of the water conservancy project should also be established.
The construction and operation of many water conservancy and hydroelectric projects in the Minjiang River region have brought some significant changes to the hydrodynamic field.Such changes include stream velocity,river discharge,sediment discharge and silt carrying capacity.They have also changed the distribution and intensity of stress field in those coastal belts.Therefore the types,the intensity and the evolution of geological processes have been greatly changed,and many environment geological hazards have also been caused.They hazards are considerably growing in terms of wider distribution and longer duration.This paper makes some preliminary studies on three relations.One relation is between the construction and operation of Minjiang River water conservancy project and the instability hazards of littoral slopes.The second is the earthquakes induced by Shuikou Reservoir.The third is the downstream channel stability behind the dam and its harmfulness.The results show that the instability of the reservoir banks is obvious correlation with the water conservancy project operation and the hazards frequency significantly increases as the operation continued.By enhancing the fluvial erosion behind the dam,the reservoir impounding becomes the important factor which affects the lower river channel and the littoral environment geological hazards.In addition,the impounding and hydration of Shuikou Reservoir are also the important factors inducing an earthquake.Its aftershocks will last for a long period.The point of view that the more intensive and destructive reservoir earthquake may occur in the next few years is put forward.Almost simultaneously the research on the special monitoring and forecasting for geological disasters should be carried out and the regional information monitoring and forecasting system about geological disasters of the water conservancy project should also be established.
2011, 19(5): 756-763.
Landslides and avalanches in mountains are the important geological events in slope evolution.Their emergencies and development are closely related to the relative river geomorphic process.Although studies on the factors affecting landslide are considerable now,they are mostly limited to the landslide itself.This paper is based on studying of the river geomorphic process.It further discusses on the response relationship between slope stability and river change.The results can help us to understand the slope evolution more in-depth and to serve better to the evaluation and prediction of slope stability.By the method of analysis of natural history and analogy,and age dating,the paper discusses the shifting and evolution of the valley in the middle and lower reaches of Qingjiang River.It is inferred that the river geomorphic process began in Late Middle Pleistocene.The inferring is according to age dating of the river terraces and comparison with adjacent area's terrace age and archaeological data,and based on surveying and analyzing systematically the river terraces and linear continuous distribution of the ancient valley(both bottom and single bottom valley in valley).Through age comparison with landslides and terraces,four peaks of landslide emergencies are discovered according to the ages of some important landslides.They coincide with the ages of the four river terraces.At the same time,it can be discovered that the slope stability does exist significant difference and regularity.This discovery is based on the comparison of landslides distribution and the four types of the river evolution.
Landslides and avalanches in mountains are the important geological events in slope evolution.Their emergencies and development are closely related to the relative river geomorphic process.Although studies on the factors affecting landslide are considerable now,they are mostly limited to the landslide itself.This paper is based on studying of the river geomorphic process.It further discusses on the response relationship between slope stability and river change.The results can help us to understand the slope evolution more in-depth and to serve better to the evaluation and prediction of slope stability.By the method of analysis of natural history and analogy,and age dating,the paper discusses the shifting and evolution of the valley in the middle and lower reaches of Qingjiang River.It is inferred that the river geomorphic process began in Late Middle Pleistocene.The inferring is according to age dating of the river terraces and comparison with adjacent area's terrace age and archaeological data,and based on surveying and analyzing systematically the river terraces and linear continuous distribution of the ancient valley(both bottom and single bottom valley in valley).Through age comparison with landslides and terraces,four peaks of landslide emergencies are discovered according to the ages of some important landslides.They coincide with the ages of the four river terraces.At the same time,it can be discovered that the slope stability does exist significant difference and regularity.This discovery is based on the comparison of landslides distribution and the four types of the river evolution.
2011, 19(5): 764-770.
There are multiple factors affecting the optimal selection of the high speed railway route.The factors are interactive.To obtain the optimized route scheme,the set pair analysis method is used.From the perspective of geologic factors,the analysis and evaluation on geological factors affecting the rail lines are made.For choosing the best route line,the analytic hierarchy process(AHP)is used to determine the rate of the various influencing factors.The set pair analysis(SPA)is used in variable fuzzy sets calculation.In this paper,the principles and steps of the AHP and SPA are described and analyzed.Then,this paper takes the six schemes in Daba Mountains of the high-speed railway program,a segment of the Xi'an to Chengdu railway,for the research objects.The investigation includes the study data collection of the engineering geological conditions,field investigation,the indoor data analysis.The paper determines six evaluation factors which have the impact on the selection of the proposed lines.Through a nine-scale method,the matrix of the evaluation factors on the rail program is obtained.From AHP calculation,the rates of evaluation factors are obtained.The SPA is used for the pros and cons evaluation of each line and to select the best alignment of optimal design.It is concluded that among the suggested six lines,the DK1 is the best one.
There are multiple factors affecting the optimal selection of the high speed railway route.The factors are interactive.To obtain the optimized route scheme,the set pair analysis method is used.From the perspective of geologic factors,the analysis and evaluation on geological factors affecting the rail lines are made.For choosing the best route line,the analytic hierarchy process(AHP)is used to determine the rate of the various influencing factors.The set pair analysis(SPA)is used in variable fuzzy sets calculation.In this paper,the principles and steps of the AHP and SPA are described and analyzed.Then,this paper takes the six schemes in Daba Mountains of the high-speed railway program,a segment of the Xi'an to Chengdu railway,for the research objects.The investigation includes the study data collection of the engineering geological conditions,field investigation,the indoor data analysis.The paper determines six evaluation factors which have the impact on the selection of the proposed lines.Through a nine-scale method,the matrix of the evaluation factors on the rail program is obtained.From AHP calculation,the rates of evaluation factors are obtained.The SPA is used for the pros and cons evaluation of each line and to select the best alignment of optimal design.It is concluded that among the suggested six lines,the DK1 is the best one.
2011, 19(5): 771-777.
Unregulated landfill sites largely use natural conditions to fill out the untreated garbage and take over lots of land resources.They not only affect the city environmental sanitation,but also pose significant risks to resident domestic water.Because there are many unregulated landfill sites in Beijing,the needed funds for treating all of them are huge.Therefore,preliminary survey and assessment on the unregulated landfill sites are urgently needed to provide the scientific basis for government decision precedence order and choice of technical treatments.Survey and assessment on unregulated landfill sites have a remarkable difference with traditional geotechnical investigation,especially in the areas of required investigation,prospecting technique,exploration of arrangements,and inspection and testing projects.China has not yet enacted domestic standards and guidelines about the preliminary survey and assessment on unregulated landfill sites.The risk assessment method and the indicator system are established first in this papers.They combine the ground water pollution risks and dangers of garbage itself by hierarchy process method.Also the concepts of anti-contamination effective thickness and anti-contamination index are first put forward.Finally,this paper takes a project in Beijing as an example.It discusses the actual application of the risk assessment method,and summarizes systematically the procedures and techniques for survey and assessments. The practical results show that the proposed preliminary survey and method assessment have important reference value to similar unregulated landfill survey.
Unregulated landfill sites largely use natural conditions to fill out the untreated garbage and take over lots of land resources.They not only affect the city environmental sanitation,but also pose significant risks to resident domestic water.Because there are many unregulated landfill sites in Beijing,the needed funds for treating all of them are huge.Therefore,preliminary survey and assessment on the unregulated landfill sites are urgently needed to provide the scientific basis for government decision precedence order and choice of technical treatments.Survey and assessment on unregulated landfill sites have a remarkable difference with traditional geotechnical investigation,especially in the areas of required investigation,prospecting technique,exploration of arrangements,and inspection and testing projects.China has not yet enacted domestic standards and guidelines about the preliminary survey and assessment on unregulated landfill sites.The risk assessment method and the indicator system are established first in this papers.They combine the ground water pollution risks and dangers of garbage itself by hierarchy process method.Also the concepts of anti-contamination effective thickness and anti-contamination index are first put forward.Finally,this paper takes a project in Beijing as an example.It discusses the actual application of the risk assessment method,and summarizes systematically the procedures and techniques for survey and assessments. The practical results show that the proposed preliminary survey and method assessment have important reference value to similar unregulated landfill survey.
2011, 19(5): 778-783.
This study carried out slaking tests of two different weathering of basalt residual soil,and analyzed the slaking curve of the undisturbed soil,dried one hour and weathered 48 hours.As a result,it was found that the slaking velocity of the dark red sample was the fastest.Because of the different water contents,the slaking time for the undisturbed sample,the dried one hour sample and the weathered 48 hours sample lasted the longest,the second and the shortest of all,respectively.Slaking destroyed forms were different under different conditions and were influenced by content change.The fractures induced by wetting/drying cycle was the one of the most important facts in slaking of basalt residual soil.The results are useful for the design of protecting and strengthening measures for the basalt residual soil.
This study carried out slaking tests of two different weathering of basalt residual soil,and analyzed the slaking curve of the undisturbed soil,dried one hour and weathered 48 hours.As a result,it was found that the slaking velocity of the dark red sample was the fastest.Because of the different water contents,the slaking time for the undisturbed sample,the dried one hour sample and the weathered 48 hours sample lasted the longest,the second and the shortest of all,respectively.Slaking destroyed forms were different under different conditions and were influenced by content change.The fractures induced by wetting/drying cycle was the one of the most important facts in slaking of basalt residual soil.The results are useful for the design of protecting and strengthening measures for the basalt residual soil.
2011, 19(5): 784-791.
The NSFC proposals and grants of engineering geology in 2011 were analyzed.The amount of proposals increases fast.The competitiveness of the proposals has been improved.The distribution of researchers in fundamental studies is not balanced,and concentration ratio of research capability increases,among institutions.The age pattern of the PIs tends to be optimizing.There are reasonable differences of funded ratio between different age group.
The NSFC proposals and grants of engineering geology in 2011 were analyzed.The amount of proposals increases fast.The competitiveness of the proposals has been improved.The distribution of researchers in fundamental studies is not balanced,and concentration ratio of research capability increases,among institutions.The age pattern of the PIs tends to be optimizing.There are reasonable differences of funded ratio between different age group.
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