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2022 Vol. 30, No. 6
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Prof. Liu Guochang is one of the founders of engineering geology in China,the founder of engineering geology for regional stability,the father of education for engineering geology in China,the frontier of mineral resource exploration,the contributor for construction of the national major engineering project. He graduated from the Department of Geology,Peking University in 1936. Responsing to the anoucement of "Find Ores to Help Our Nation",he investiaged mineral resources under the war's fire for a decade more. In 1951,he was invited by Prof. Yu Deyuan to Northeast College of Geology as a teacher. He founded the Department of Hydrogeology and Engineering Geology and was appointed as the director of the department. Since that time,he started the education career of engineering geology in China. With the help of the former Soviet Union specialist B.H.Novorinov,he supervised the first class of post-graduate students in engineering geology and trained the first group of engineering geologist for the new China. All of them formed the basement of Chinese engineering geology. In 1981,he moved to Xi'an College of Geology and built the Department of Hydrogeology and Engineering Geology in the college. In 1984,with the effort of Prof. Liu Guochang,the college obtained the qualification for educating Ph. D students. He began to supervise Ph. D students in 1985. He founded the basement of hydrogeology and engineering geology discipline in the college and input the potential energy for its quick development in the later time. Prof. Liu Guochang is one of the founders of engineering geology in China,the founder of engineering geology for regional stability,the father of education for engineering geology in China,the frontier of mineral resource exploration,the contributor for construction of the national major engineering project. He graduated from the Department of Geology,Peking University in 1936. Responsing to the anoucement of "Find Ores to Help Our Nation",he investiaged mineral resources under the war's fire for a decade more. In 1951,he was invited by Prof. Yu Deyuan to Northeast College of Geology as a teacher. He founded the Department of Hydrogeology and Engineering Geology and was appointed as the director of the department. Since that time,he started the education career of engineering geology in China. With the help of the former Soviet Union specialist B.H.Novorinov,he supervised the first class of post-graduate students in engineering geology and trained the first group of engineering geologist for the new China. All of them formed the basement of Chinese engineering geology. In 1981,he moved to Xi'an College of Geology and built the Department of Hydrogeology and Engineering Geology in the college. In 1984,with the effort of Prof. Liu Guochang,the college obtained the qualification for educating Ph. D students. He began to supervise Ph. D students in 1985. He founded the basement of hydrogeology and engineering geology discipline in the college and input the potential energy for its quick development in the later time.
There are five major engineering problems faced by the deep buried tunnel projects. They include large deformation of soft rock,rock burst,active fault zone,high temperature and humidity,and high slope at the entrance and exit of the tunnel. First,the theory of deep-buried tunnel disaster prevention and control is proposed. It is called the compensation excavation method. The core material called NPR bolt/cable is developed. Then,the prevention and control measures and suggestions for deep-buried tunnels are put forward. They mainly include (1)compensation technology for high pre-tightening force of NPR anchor net and cable for soft rock tunnels,(2)energy absorption compensation technology for rockburst tunnels,(3)double gradient grouting strength compensation technology and (4)NPR anchor-net-cable-truss coupling support technology for active fault zone tunnels,(5) double partition and double control technology for high temperature and high humidity tunnels and (6)NPR anchor cable prevention-reinforcement-monitoring-early warning integrated dual compensation control technology for the high slope at the entrance and exit of the tunnel. Finally,combined with the specific practical engineering experience,the application effect of the prevention and control strategy is explained,in order to providing reference and basis for the construction of the deep buried tunnels. There are five major engineering problems faced by the deep buried tunnel projects. They include large deformation of soft rock,rock burst,active fault zone,high temperature and humidity,and high slope at the entrance and exit of the tunnel. First,the theory of deep-buried tunnel disaster prevention and control is proposed. It is called the compensation excavation method. The core material called NPR bolt/cable is developed. Then,the prevention and control measures and suggestions for deep-buried tunnels are put forward. They mainly include (1)compensation technology for high pre-tightening force of NPR anchor net and cable for soft rock tunnels,(2)energy absorption compensation technology for rockburst tunnels,(3)double gradient grouting strength compensation technology and (4)NPR anchor-net-cable-truss coupling support technology for active fault zone tunnels,(5) double partition and double control technology for high temperature and high humidity tunnels and (6)NPR anchor cable prevention-reinforcement-monitoring-early warning integrated dual compensation control technology for the high slope at the entrance and exit of the tunnel. Finally,combined with the specific practical engineering experience,the application effect of the prevention and control strategy is explained,in order to providing reference and basis for the construction of the deep buried tunnels.
China is located at the eastern edge of the Eurasian plate,and is featured with diverse geomorphological types and complex geological conditions. The smooth implementation of major national development strategies and the effective promotion of ecological civilization are facing serious geological safety risks. They are calling for solutions to geological safety problems faced by human living environment and engineering activities. This paper follows the earth system science principles and considering the interaction among geospheres,dynamics coupling,and human-earth feedback. It focuses on geosafety of national spaces,major projects,urban constructions,ecological environments,and resource developments. The major geological safety challenges faced by national strategic development are discussed. The frontiers and main research directions of geosafety are outlined. Geosafety is an important prerequisite to guaranteeing people's high-quality life,promoting social and economic development,and building livable earth. It is of great scientific significance to solving geological safety problems related to major engineering construction,geohazards prevention,ecological environmental protection,and harmonious settlement of humans. It also important to promoting scientific and technological progress and sustainable social development. China is located at the eastern edge of the Eurasian plate,and is featured with diverse geomorphological types and complex geological conditions. The smooth implementation of major national development strategies and the effective promotion of ecological civilization are facing serious geological safety risks. They are calling for solutions to geological safety problems faced by human living environment and engineering activities. This paper follows the earth system science principles and considering the interaction among geospheres,dynamics coupling,and human-earth feedback. It focuses on geosafety of national spaces,major projects,urban constructions,ecological environments,and resource developments. The major geological safety challenges faced by national strategic development are discussed. The frontiers and main research directions of geosafety are outlined. Geosafety is an important prerequisite to guaranteeing people's high-quality life,promoting social and economic development,and building livable earth. It is of great scientific significance to solving geological safety problems related to major engineering construction,geohazards prevention,ecological environmental protection,and harmonious settlement of humans. It also important to promoting scientific and technological progress and sustainable social development.
This paper expounds the importance of in-situ observation of rock-and-soil. It reviews the evolution history of the in-situ rock-and-soil observation technology. The rock-and-soil observation technology can be divided into five categories,namely survey,remote sensing,testing,exploration and monitoring. The characteristics and shortcomings of these five categories of observation technology are discussed respectively. Based on this,the concept of multi-field sensing of rock-and-soil is further expounded. The connotation and characteristics of multi-field sensing technology are discussed emphatically. It is concluded that the time-space continuous sensing technology is a new paradigm of in-situ rock-and-soil observation in the field of geological and geotechnical engineering. Finally,the distributed fiber optic sensing technology and its application to realize multi-field sensing of rock-and-soil are briefly introduced. This paper expounds the importance of in-situ observation of rock-and-soil. It reviews the evolution history of the in-situ rock-and-soil observation technology. The rock-and-soil observation technology can be divided into five categories,namely survey,remote sensing,testing,exploration and monitoring. The characteristics and shortcomings of these five categories of observation technology are discussed respectively. Based on this,the concept of multi-field sensing of rock-and-soil is further expounded. The connotation and characteristics of multi-field sensing technology are discussed emphatically. It is concluded that the time-space continuous sensing technology is a new paradigm of in-situ rock-and-soil observation in the field of geological and geotechnical engineering. Finally,the distributed fiber optic sensing technology and its application to realize multi-field sensing of rock-and-soil are briefly introduced.
Regional mountain stability is one of the contents of regional engineering geology proposed by Prof. Liu Guochang in the 1960 s. The problem of regional mountain stability is controlled by two regional factors,namely regional and zonality elements of regional stability engineering geology. This paper takes the characteristics of tectonic denudation gravity accumulation in plate suture zone of Hengduan Mountain area as the main research object and illustrates the influence of regional factors of regional stability engineering geology and vertical zonality factors in Hengduan Mountain area on regional mountain stability. The paper further discusses the global characteristics of deep overburden on the river bed and its relationship with sea level decline and regional crust uplift during ice age. Regional mountain stability is one of the contents of regional engineering geology proposed by Prof. Liu Guochang in the 1960 s. The problem of regional mountain stability is controlled by two regional factors,namely regional and zonality elements of regional stability engineering geology. This paper takes the characteristics of tectonic denudation gravity accumulation in plate suture zone of Hengduan Mountain area as the main research object and illustrates the influence of regional factors of regional stability engineering geology and vertical zonality factors in Hengduan Mountain area on regional mountain stability. The paper further discusses the global characteristics of deep overburden on the river bed and its relationship with sea level decline and regional crust uplift during ice age.
Southeast Tibet is an important strategic region in China,because of its special geographical location,rugged topography and abundant hydraulic power resources. Several major projects were planned and constructed in southeast Tibet. Affected by internal and external dynamic geological factors such as tectonic uplift,seismic activities,marine glaciers,stereoscopic climate and engineering construction activities,long-runout landslides with high-altitude occurred in this region intensively. Such geological disasters seriously threaten the safety and operation of major projects. Due to characteristics of high abruptness,large impact force and wide scope of disaster,it is difficult to explain the initiation mechanism,reveal the landslide dynamics and predict the landslide movement. It is necessary to break through the important scientific problems. These problems include (1) the characteristics of disaster-inducing environment,(2)the landslide distribution discipline in southeast Tibet,(3)the initiation mechanism of brittle rock with high-altitude,(4)the mechanism of motion style transformation and (5)the mechanism of landslide mass fluidization. It is urgent to establish the dynamics of long-runout landslides with high-altitude,which can provide a theoretical basis for geological disaster risk prevention and guide the planning and construction of major projects. Advancing relevant research is of great practical significance to the sustainable development of southeast Tibet. Southeast Tibet is an important strategic region in China,because of its special geographical location,rugged topography and abundant hydraulic power resources. Several major projects were planned and constructed in southeast Tibet. Affected by internal and external dynamic geological factors such as tectonic uplift,seismic activities,marine glaciers,stereoscopic climate and engineering construction activities,long-runout landslides with high-altitude occurred in this region intensively. Such geological disasters seriously threaten the safety and operation of major projects. Due to characteristics of high abruptness,large impact force and wide scope of disaster,it is difficult to explain the initiation mechanism,reveal the landslide dynamics and predict the landslide movement. It is necessary to break through the important scientific problems. These problems include (1) the characteristics of disaster-inducing environment,(2)the landslide distribution discipline in southeast Tibet,(3)the initiation mechanism of brittle rock with high-altitude,(4)the mechanism of motion style transformation and (5)the mechanism of landslide mass fluidization. It is urgent to establish the dynamics of long-runout landslides with high-altitude,which can provide a theoretical basis for geological disaster risk prevention and guide the planning and construction of major projects. Advancing relevant research is of great practical significance to the sustainable development of southeast Tibet.
The mode of water migration in thick loess vadose zone has always been argued on preferential flow and piston flow. In this paper,the authors conducted in-situ observations and two model tests to demonstrate that piston flow is the unique way of water migration in vadose zone in thick loess. Based on flow behavior of unsaturated soil,it is also verified that preferential flow can only exist in saturated soils. Loess in natural condition mainly exists as unsaturated state,so piston flow is the dominant flow mode in loess. Preferential flow just occurs in shallow saturated zone locally and in the raining periods temporally. In addition,preferential paths in loess,such as vertical joints,load release cracks,animal caves and root pores are the channels for surface water discharge rather than those for groundwater recharge. The mode of water migration in thick loess vadose zone has always been argued on preferential flow and piston flow. In this paper,the authors conducted in-situ observations and two model tests to demonstrate that piston flow is the unique way of water migration in vadose zone in thick loess. Based on flow behavior of unsaturated soil,it is also verified that preferential flow can only exist in saturated soils. Loess in natural condition mainly exists as unsaturated state,so piston flow is the dominant flow mode in loess. Preferential flow just occurs in shallow saturated zone locally and in the raining periods temporally. In addition,preferential paths in loess,such as vertical joints,load release cracks,animal caves and root pores are the channels for surface water discharge rather than those for groundwater recharge.
This paper examines the typical types of disasters caused by groundwater seepage deformation and failure in underground mines. They include water inrush or water-sand mixture inrush from the roof,water inrush from the floor,and seepage failure of the interface between water retention bulkhead and surrounding rock,etc. The paper introduces the important role of Professor Guochang Liu in laying the foundation for the development of mine hydrogeology and engineering geology in China. It further reviews the mechanism of major engineering geological disasters caused by groundwater seepage failure of rock masses in mines and their development of prevention and control technologies. This paper also reviews the history of the proposal,improvement and application of the water inrush coefficient for the evaluation of water inrush from seam floor,and reinterprets the physics of the water inrush coefficient from the seepage mechanical mechanism of the generation of the seepage failure of the seam floor. Based on the critical hydraulic gradient of the floor rock mass structure,a water inrush discrimination method was established. The critical hydraulic gradient of the floor rock mass can be estimated by semi-empirical method. A dynamic evaluation method of water inrush risk from the seam floor based on the safety factor against seepage failure is proposed after the analysis of the evolution of evaluation methods for floor water inrush. The prevention and control principle and efficiency evaluation method of the active prevention and control measures for the flood water inrush catastrophe are analyzed. Finally,the scientific issues that require further in-depth study in the seepage stability of the seam floor are proposed. This paper examines the typical types of disasters caused by groundwater seepage deformation and failure in underground mines. They include water inrush or water-sand mixture inrush from the roof,water inrush from the floor,and seepage failure of the interface between water retention bulkhead and surrounding rock,etc. The paper introduces the important role of Professor Guochang Liu in laying the foundation for the development of mine hydrogeology and engineering geology in China. It further reviews the mechanism of major engineering geological disasters caused by groundwater seepage failure of rock masses in mines and their development of prevention and control technologies. This paper also reviews the history of the proposal,improvement and application of the water inrush coefficient for the evaluation of water inrush from seam floor,and reinterprets the physics of the water inrush coefficient from the seepage mechanical mechanism of the generation of the seepage failure of the seam floor. Based on the critical hydraulic gradient of the floor rock mass structure,a water inrush discrimination method was established. The critical hydraulic gradient of the floor rock mass can be estimated by semi-empirical method. A dynamic evaluation method of water inrush risk from the seam floor based on the safety factor against seepage failure is proposed after the analysis of the evolution of evaluation methods for floor water inrush. The prevention and control principle and efficiency evaluation method of the active prevention and control measures for the flood water inrush catastrophe are analyzed. Finally,the scientific issues that require further in-depth study in the seepage stability of the seam floor are proposed.

The evolution process of landslides with multi-sliding zones is characterized by the relative motion of multi-layer and stress discontinuities. Due to the mutual dislocation and pile-soil interaction between sliding bodies in different layers,the thrust distribution of the multi-sliding zones landslide is often complex. It is urgent to put forward the calculation method for the thrust distribution on stabilizing pile of multi-sliding zones landslide. In this paper,the horizontal limit equilibrium method is used to analyze the multi-sliding zones landslide. According to the stress analysis under the limit equilibrium state of horizontal micro segment,the landslide thrust on stabilizing pile in each layer is obtained. When analyzing the force balance in the vertical direction,it is necessary to consider the downward force transmission of sliding mass in different layers,resulting in the sudden change of landslide thrust distribution function at the sliding zone. The thrust distribution function on stabilizing pile of multi-sliding zones landslide is derived and verified by numerical simulation,which means that the function is reliable. The thrust calculation method of multi-sliding zones landslide is proposed in this paper,which provides a certain idea for the treatment of multi-sliding zones landslide.

The evolution process of landslides with multi-sliding zones is characterized by the relative motion of multi-layer and stress discontinuities. Due to the mutual dislocation and pile-soil interaction between sliding bodies in different layers,the thrust distribution of the multi-sliding zones landslide is often complex. It is urgent to put forward the calculation method for the thrust distribution on stabilizing pile of multi-sliding zones landslide. In this paper,the horizontal limit equilibrium method is used to analyze the multi-sliding zones landslide. According to the stress analysis under the limit equilibrium state of horizontal micro segment,the landslide thrust on stabilizing pile in each layer is obtained. When analyzing the force balance in the vertical direction,it is necessary to consider the downward force transmission of sliding mass in different layers,resulting in the sudden change of landslide thrust distribution function at the sliding zone. The thrust distribution function on stabilizing pile of multi-sliding zones landslide is derived and verified by numerical simulation,which means that the function is reliable. The thrust calculation method of multi-sliding zones landslide is proposed in this paper,which provides a certain idea for the treatment of multi-sliding zones landslide.

This paper aims to study the influencing factors of sand liquefaction identification and amplification effect under earthquake action. It established a one-dimensional shear beam soil column model based on the open source finite element platform OpenSees. The model used the sand constitutive developed in the boundary surface plastic model. Taking the cyclic stress ratio(CSR) and the cyclic resistance ratio(CRR)as the control indicators,the differences between two liquefaction identification methods were compared. We analyzed the influence of the seismic load type and the relative density of sand on the liquefaction identification and amplification effect. The research shows that compared with the numerical simulation results,the CSR calculated by the Seed simplified method is larger,and the possibility of judging the liquefaction of saturated sandy soil is higher. The shock-type seismic waves are more likely to cause liquefaction of saturated sandy soils than vibration-type seismic waves. The smaller the relative density of sand,the easier it is for the site to liquefy. The amplification factor increases with the decrease of the buried depth. The amplification effect caused by vibration-type seismic waves is generally greater than that of impact-type seismic waves. When the buried depth is large,the magnification factor decreases with the increase of the relative density. This paper aims to study the influencing factors of sand liquefaction identification and amplification effect under earthquake action. It established a one-dimensional shear beam soil column model based on the open source finite element platform OpenSees. The model used the sand constitutive developed in the boundary surface plastic model. Taking the cyclic stress ratio(CSR) and the cyclic resistance ratio(CRR)as the control indicators,the differences between two liquefaction identification methods were compared. We analyzed the influence of the seismic load type and the relative density of sand on the liquefaction identification and amplification effect. The research shows that compared with the numerical simulation results,the CSR calculated by the Seed simplified method is larger,and the possibility of judging the liquefaction of saturated sandy soil is higher. The shock-type seismic waves are more likely to cause liquefaction of saturated sandy soils than vibration-type seismic waves. The smaller the relative density of sand,the easier it is for the site to liquefy. The amplification factor increases with the decrease of the buried depth. The amplification effect caused by vibration-type seismic waves is generally greater than that of impact-type seismic waves. When the buried depth is large,the magnification factor decreases with the increase of the relative density.
A new approach is proposed to evaluate the destruction mode and lateral earth pressure of the finite sloping soil based on the slices method and limit equilibrium method. The strength reduction method is used to study the failure characteristic of the finite sloping soil in front of retaining wall with the different slope distances and embedded depths. The proposed method takes into account the gradient,width between retaining wall and crest of the slope(WRWCS),and shear stress of soil mass. The accuracy of the proposed method is demonstrated by comparing the experimental results,numerically calculated results,and other theoretical methods. The comparison results show that the proposed method is appropriate for predicting the distribution of passive earth pressure in the sloping condition. At last,a parametric study was undertaken to evaluate the effects of the gradient and WRWCS on passive earth pressure and shear stress by the proposed method. The results show that the characteristic of the failure surface is mainly damaged along the bottom of retaining wall and the toe of the slope under translation mode of the finite sloping soils,which is significantly different than that in the semi-infinite space condition. The passive earth pressure increases exponentially with depth,and increases with the increasing gradient and decreasing WRWCS. When WRWCS is 0,compared with the semi-infinite space condition,the passive earth pressure is reduced by 30% to 50%. The coefficient of shear stress in the infinite slope soil is 0.07~0.1 under translation mode. The proposed formulation can be simplified to Rankine's formulation of passive earth pressure when soil-wall interface is smooth and WRWCS is enough large. A new approach is proposed to evaluate the destruction mode and lateral earth pressure of the finite sloping soil based on the slices method and limit equilibrium method. The strength reduction method is used to study the failure characteristic of the finite sloping soil in front of retaining wall with the different slope distances and embedded depths. The proposed method takes into account the gradient,width between retaining wall and crest of the slope(WRWCS),and shear stress of soil mass. The accuracy of the proposed method is demonstrated by comparing the experimental results,numerically calculated results,and other theoretical methods. The comparison results show that the proposed method is appropriate for predicting the distribution of passive earth pressure in the sloping condition. At last,a parametric study was undertaken to evaluate the effects of the gradient and WRWCS on passive earth pressure and shear stress by the proposed method. The results show that the characteristic of the failure surface is mainly damaged along the bottom of retaining wall and the toe of the slope under translation mode of the finite sloping soils,which is significantly different than that in the semi-infinite space condition. The passive earth pressure increases exponentially with depth,and increases with the increasing gradient and decreasing WRWCS. When WRWCS is 0,compared with the semi-infinite space condition,the passive earth pressure is reduced by 30% to 50%. The coefficient of shear stress in the infinite slope soil is 0.07~0.1 under translation mode. The proposed formulation can be simplified to Rankine's formulation of passive earth pressure when soil-wall interface is smooth and WRWCS is enough large.
The construction of many underground projects can be in high geostress environment,and the initial geostress is the precondition and dominate factor for deformation and failure of underground surrounding rock. The term and concept of "high geostress" are closely related to the abnormal failure of surrounding rock in underground engineering and belong to the engineering concept category. The failure of surrounding rock attributed to high geostress is becoming increasingly significant with increasing burial depth of underground projects,which seriously influences the stability of engineering projects. Although various quantitative classification criteria have been proposed,they are mostly established in the form of rock strength to geostress ratio,without fully considering the absolute magnitude and coupling relationship between rock strength and geostress. In this paper,a "strength & stress" coupling criterion and its quantitative grading standard for high geostress rock failure are proposed via discussing the existing classification criteria,collecting the related engineering cases,and analyzing the failure progress of high geostress rock. This coupling criterion is expressed by 3 boundary lines considering the saturated rock uniaxial compressive strength Rc and the initial maximum principal stress σ1. The area enclosed by the boundary lines represents the high geostress zone,and that outside the boundary lines represents the low geostress zone. The coupling criterion is characterized by considering both the absolute boundary conditions of Rc and σ1,as well as their coupling interval. Through an evaluation of geostress grades in 86 typical underground projects,it is found that the judgments of this two-dimensional "strength & stress" coupling criterion are favorably consistent with the in situ rock failure phenomena. Thus,this criterion can be applied to the practical underground engineering. Moreover,the rating standards of high geostress zone of this "strength & stress" coupling criterion can better identify the failure intensity of surrounding rock,which can provide a reference for the prevention of engineering disasters. The construction of many underground projects can be in high geostress environment,and the initial geostress is the precondition and dominate factor for deformation and failure of underground surrounding rock. The term and concept of "high geostress" are closely related to the abnormal failure of surrounding rock in underground engineering and belong to the engineering concept category. The failure of surrounding rock attributed to high geostress is becoming increasingly significant with increasing burial depth of underground projects,which seriously influences the stability of engineering projects. Although various quantitative classification criteria have been proposed,they are mostly established in the form of rock strength to geostress ratio,without fully considering the absolute magnitude and coupling relationship between rock strength and geostress. In this paper,a "strength & stress" coupling criterion and its quantitative grading standard for high geostress rock failure are proposed via discussing the existing classification criteria,collecting the related engineering cases,and analyzing the failure progress of high geostress rock. This coupling criterion is expressed by 3 boundary lines considering the saturated rock uniaxial compressive strength Rc and the initial maximum principal stress σ1. The area enclosed by the boundary lines represents the high geostress zone,and that outside the boundary lines represents the low geostress zone. The coupling criterion is characterized by considering both the absolute boundary conditions of Rc and σ1,as well as their coupling interval. Through an evaluation of geostress grades in 86 typical underground projects,it is found that the judgments of this two-dimensional "strength & stress" coupling criterion are favorably consistent with the in situ rock failure phenomena. Thus,this criterion can be applied to the practical underground engineering. Moreover,the rating standards of high geostress zone of this "strength & stress" coupling criterion can better identify the failure intensity of surrounding rock,which can provide a reference for the prevention of engineering disasters.
With the development and construction of national major projects,a large number of foundation projects emerged as the times require. Some structures are particularly sensitive to the deformation of foundation soil,which requires special research to ensure the safety of related projects. However,the differences of the natural structure and consolidation state of soil can not only present an important impact on the compression characteristics and relevant mechanical indicators of soil,but also bring challenges to the analysis of deformation and settlement calculation. It would be of certain practical significance for engineering practice to clarify the combined manifestation of soil structure and consolidation state,and to discuss the dialectical relationship between them. Based on the previous studies of research group,as well as the confined compression characteristics of soil,this paper analyzes the mechanism of the abnormal 'over-consolidation' characteristics of soil,discusses the dynamic changes of the structure,and attemptes to give the concept pattern of soil structure. The following preliminary understandings are presented:(1)The essence of soil structure includes particle arrangement and structural connection. The compactness of particle arrangement reflects the spatial distribution of solid components,which is considered as the combined embodiment of multiple forces including consolidation pressure. The structural connection refers to the sum of the interaction forces between soil particles,which is characterized as the structural strength to resist deformation during confined compression. Generally speaking,all soils including undisturbed soil and remolded soil have different degrees of structure. (2)There is a dynamic coupling relationship between particle arrangement and structural connection of soil. The ′over-consolidation' property of soil,inconsistent with the stress history,results from the differential ′strengthening' derived by structural connection to soil skeleton. In addition,the compaction of soil derived by other forces except self-weight also plays an important role. (3)The concept expression of structural yield pressure σk,considering additional arrangement effect ΔPa,is proposed,i. e. σk=PcPa+q. Pc and ΔPa jointly reflect the particle arrangement characteristics,and q represents the structural strength. The related results may provide some reference for the evaluation and analysis of soil mechanical properties. With the development and construction of national major projects,a large number of foundation projects emerged as the times require. Some structures are particularly sensitive to the deformation of foundation soil,which requires special research to ensure the safety of related projects. However,the differences of the natural structure and consolidation state of soil can not only present an important impact on the compression characteristics and relevant mechanical indicators of soil,but also bring challenges to the analysis of deformation and settlement calculation. It would be of certain practical significance for engineering practice to clarify the combined manifestation of soil structure and consolidation state,and to discuss the dialectical relationship between them. Based on the previous studies of research group,as well as the confined compression characteristics of soil,this paper analyzes the mechanism of the abnormal 'over-consolidation' characteristics of soil,discusses the dynamic changes of the structure,and attemptes to give the concept pattern of soil structure. The following preliminary understandings are presented:(1)The essence of soil structure includes particle arrangement and structural connection. The compactness of particle arrangement reflects the spatial distribution of solid components,which is considered as the combined embodiment of multiple forces including consolidation pressure. The structural connection refers to the sum of the interaction forces between soil particles,which is characterized as the structural strength to resist deformation during confined compression. Generally speaking,all soils including undisturbed soil and remolded soil have different degrees of structure. (2)There is a dynamic coupling relationship between particle arrangement and structural connection of soil. The ′over-consolidation' property of soil,inconsistent with the stress history,results from the differential ′strengthening' derived by structural connection to soil skeleton. In addition,the compaction of soil derived by other forces except self-weight also plays an important role. (3)The concept expression of structural yield pressure σk,considering additional arrangement effect ΔPa,is proposed,i. e. σk=PcPa+q. Pc and ΔPa jointly reflect the particle arrangement characteristics,and q represents the structural strength. The related results may provide some reference for the evaluation and analysis of soil mechanical properties.
The intensive and continuous interactions between the high-speed surficial mass movements and the underlying rugged topography can generate seismic waves,which is referred to as "landquakes". As a unique research perspective,the research of landquake can provide unprecedented details and unparalleled quantitative data on the exploration of rock avalanche kinematics. This paper presents a systematic review of the representative achievements in the rock avalanche kinematics and the generated landqukes. In particular,it briefly reviews the diachronic process and present status of this field. Then,this paper analyzes the typical kinematic behaviors of rockfalls,rock avalanches and debris flows in terms of their seismic manifestations,and describes the general signal characteristics. Furthermore. This paper reviews the benefits of seismic methods in the toolkit for studying the key properties of rock avalanche processes,and discusses the potential for landquakes with different frequency content to drive advances in our understanding of rock avalanche dynamics. On these bases,the future directions toward seismological research on rock avalanche dynamics are analyzed and discussed. Future works that should be focused are proposed,including setting up better datasets,modeling improvements,integration between basal force fluctuations and landquakes,and deepening of interdisciplinary integration. The intensive and continuous interactions between the high-speed surficial mass movements and the underlying rugged topography can generate seismic waves,which is referred to as "landquakes". As a unique research perspective,the research of landquake can provide unprecedented details and unparalleled quantitative data on the exploration of rock avalanche kinematics. This paper presents a systematic review of the representative achievements in the rock avalanche kinematics and the generated landqukes. In particular,it briefly reviews the diachronic process and present status of this field. Then,this paper analyzes the typical kinematic behaviors of rockfalls,rock avalanches and debris flows in terms of their seismic manifestations,and describes the general signal characteristics. Furthermore. This paper reviews the benefits of seismic methods in the toolkit for studying the key properties of rock avalanche processes,and discusses the potential for landquakes with different frequency content to drive advances in our understanding of rock avalanche dynamics. On these bases,the future directions toward seismological research on rock avalanche dynamics are analyzed and discussed. Future works that should be focused are proposed,including setting up better datasets,modeling improvements,integration between basal force fluctuations and landquakes,and deepening of interdisciplinary integration.
The Jiali fault is one of the major active faults in southeast Tibet Plateau. In recent years,many major engineering projects,such as railways,highways,and hydropower plants,have been or are being constructed in southeast Tibet. Engineering geological disasters associated with Jiali fault have brought great challenges to the construction,operation,and maintenance of those major projects. Previous studies on Jiali fault have mainly focused on its activities in Holocene. Its engineering geomechanical characteristics have not been well addressed. Major engineering projects are densely distributed in the middle segment of Jiali fault. This study,based on plenty of materials data obtained from a throughout field survey,presents an engineering geomechanical analysis on middle Jiali fault. The results show that,in middle Jiali fault,engineering geomechanical factors(include geomorphology,rock combination,rock mass structure,in-situ stress,shear zone characteristics,and Quaternary activity. They have typical sectional distribution characteristics. The engineering geomechanical model within middle Jiali fault can be categorized into two types: (1)a "ductile" engineering geomechanical model in the section near the East Himalaya Syntaxis(EHS); (2)a "brittle" engineering geomechanical model in sections far away from the EHS. The formation of the two different models is mainly affected by the strong metamorphic belt with high temperature and pressure,which is generated by the hot mantle flow under the EHS. Based on the subsection characteristics of the engineering geomechanical model,this paper further discusses some important engineering geological problems and relevant disaster characteristics in different sections of middle Jiali fault. This study is expected to provide a theoretical reference for constructions of major projects and mitigations of geological hazards in the southeast Tibet. The Jiali fault is one of the major active faults in southeast Tibet Plateau. In recent years,many major engineering projects,such as railways,highways,and hydropower plants,have been or are being constructed in southeast Tibet. Engineering geological disasters associated with Jiali fault have brought great challenges to the construction,operation,and maintenance of those major projects. Previous studies on Jiali fault have mainly focused on its activities in Holocene. Its engineering geomechanical characteristics have not been well addressed. Major engineering projects are densely distributed in the middle segment of Jiali fault. This study,based on plenty of materials data obtained from a throughout field survey,presents an engineering geomechanical analysis on middle Jiali fault. The results show that,in middle Jiali fault,engineering geomechanical factors(include geomorphology,rock combination,rock mass structure,in-situ stress,shear zone characteristics,and Quaternary activity. They have typical sectional distribution characteristics. The engineering geomechanical model within middle Jiali fault can be categorized into two types: (1)a "ductile" engineering geomechanical model in the section near the East Himalaya Syntaxis(EHS); (2)a "brittle" engineering geomechanical model in sections far away from the EHS. The formation of the two different models is mainly affected by the strong metamorphic belt with high temperature and pressure,which is generated by the hot mantle flow under the EHS. Based on the subsection characteristics of the engineering geomechanical model,this paper further discusses some important engineering geological problems and relevant disaster characteristics in different sections of middle Jiali fault. This study is expected to provide a theoretical reference for constructions of major projects and mitigations of geological hazards in the southeast Tibet.
This paper aims to study the effect of complex climatic conditions on the dynamic properties of alkali slag cured lightweight soils. Dynamic triaxial tests were conducted for alkali slag cured lightweight soils under the action of dry and wet freeze-thaw coupling. The test results show the follows. The cumulative strain curve of alkali slag cured lightweight soil exhibits three different forms,i.e.,stable,critical and destructive. The axial strain of cured soil increases with the increase of the number of dry and wet freeze-thaw coupling and the decrease of the freezing temperature,among which the effect of the first three times is greater,and basically reaches stability after five times. According to the axial strain law of cured soil,the cumulative dynamic strain prediction model is established. With the decrease of the freezing temperature,the dynamic strength of alkali slag cured lightweight soil gradually decreases. As the freezing temperature decreases,the dynamic strength of alkali slag cured lightweight soil gradually decreases,and the trend of decrease is faster and then slower,and finally stabilizes. With the increase of the number of wet and dry freeze-thaw cycles,the rate of decrease of dynamic strength is faster and then slower,and the decrease of dynamic strength is larger in the first three times,and the change is smaller after five times. Combined with the development law of dynamic strength,the relationship among the number of wet and dry freeze-thaw coupling,freezing temperature and dynamic strength is proposed,which can provide some theoretical guidance in the practical application of engineering. This paper provides some theoretical guidance in practical engineering applications. This paper aims to study the effect of complex climatic conditions on the dynamic properties of alkali slag cured lightweight soils. Dynamic triaxial tests were conducted for alkali slag cured lightweight soils under the action of dry and wet freeze-thaw coupling. The test results show the follows. The cumulative strain curve of alkali slag cured lightweight soil exhibits three different forms,i.e.,stable,critical and destructive. The axial strain of cured soil increases with the increase of the number of dry and wet freeze-thaw coupling and the decrease of the freezing temperature,among which the effect of the first three times is greater,and basically reaches stability after five times. According to the axial strain law of cured soil,the cumulative dynamic strain prediction model is established. With the decrease of the freezing temperature,the dynamic strength of alkali slag cured lightweight soil gradually decreases. As the freezing temperature decreases,the dynamic strength of alkali slag cured lightweight soil gradually decreases,and the trend of decrease is faster and then slower,and finally stabilizes. With the increase of the number of wet and dry freeze-thaw cycles,the rate of decrease of dynamic strength is faster and then slower,and the decrease of dynamic strength is larger in the first three times,and the change is smaller after five times. Combined with the development law of dynamic strength,the relationship among the number of wet and dry freeze-thaw coupling,freezing temperature and dynamic strength is proposed,which can provide some theoretical guidance in the practical application of engineering. This paper provides some theoretical guidance in practical engineering applications.
Red mud stabilized by cement-based mixture is widely used in highway engineering,which has become a new direction for consuming industrial solid red mud waste. At present,the research on durability of road-used stabilized red mud lags behind engineering practice. In order to study it,we conducted the stabilizer proportioning,W-D circulation,F-T circulation and micro test. The results show that the standard strength of red mud stabilized by cement,lime and phosphogypsum is at least 3.6 MPa which can meet the pavement base bearing standard. The mass loss of stabilized red mud tends to be stable after both five-staged W-D circulation and F-T circulation. As the proportion of phosphogypsum decreases from 8% to 2%,the strength after five-staged W-D circulation is reduced to 1.69~3.69 MPa,with the strength loss rate(BDR/%) of 35.1% ~85.4%,and the strength after five-staged F-T circulation is reduced to 2.63~3.70 MPa,with the strength loss rate(BDR/%)reaches 54.82% ~79.79%. In the stabilized red mud system,the amount of phosphogypsum should not exceed 2% of the amount of red mud. In addition,the micro-scale MIP test reveals that W-D circulation and F-T circulation both increase the pore volume of the sample. The increase of macropores(diameter>0.1 μm) significantly affects the strength. In conclusion,we reveal that it is feasible to use stabilized red mud as road surface cement-stabilized materials,and the optimal ratio considering load-bearing performance and durability is 100︰8︰2︰2 for red mud︰cement︰lime︰phosphogypsum ratio. Based on the characteristics of cyclic strength attenuation,construction period and early maintenance are important in engineering practice,and the usage of phosphogypsum in stabilized red mud system should be strictly controlled. Red mud stabilized by cement-based mixture is widely used in highway engineering,which has become a new direction for consuming industrial solid red mud waste. At present,the research on durability of road-used stabilized red mud lags behind engineering practice. In order to study it,we conducted the stabilizer proportioning,W-D circulation,F-T circulation and micro test. The results show that the standard strength of red mud stabilized by cement,lime and phosphogypsum is at least 3.6 MPa which can meet the pavement base bearing standard. The mass loss of stabilized red mud tends to be stable after both five-staged W-D circulation and F-T circulation. As the proportion of phosphogypsum decreases from 8% to 2%,the strength after five-staged W-D circulation is reduced to 1.69~3.69 MPa,with the strength loss rate(BDR/%) of 35.1% ~85.4%,and the strength after five-staged F-T circulation is reduced to 2.63~3.70 MPa,with the strength loss rate(BDR/%)reaches 54.82% ~79.79%. In the stabilized red mud system,the amount of phosphogypsum should not exceed 2% of the amount of red mud. In addition,the micro-scale MIP test reveals that W-D circulation and F-T circulation both increase the pore volume of the sample. The increase of macropores(diameter>0.1 μm) significantly affects the strength. In conclusion,we reveal that it is feasible to use stabilized red mud as road surface cement-stabilized materials,and the optimal ratio considering load-bearing performance and durability is 100︰8︰2︰2 for red mud︰cement︰lime︰phosphogypsum ratio. Based on the characteristics of cyclic strength attenuation,construction period and early maintenance are important in engineering practice,and the usage of phosphogypsum in stabilized red mud system should be strictly controlled.
Temperature is an important influencing factor in the long-term process of rammed earth sites preserved in the open air from disease development to overall extinction. This study was based on real-time monitoring and analysis of the ambient temperature in four seasons and the diurnal variation of temperature inside sections of three typical rammed earth sites located in different climate zones in northwest China. The results show that the temperature of each monitoring point in the site section changes with the change of the ambient temperature,and the diurnal temperature of the monitoring point in the site section can be divided into two cooling stages and one warming stage. There are certain differences between the duration of the temperature change stages in summer and other seasons. More importantly,the temperature variation range and environmental response rate of the section in each temperature change stage in any season have the rule that the longitudinal change is significantly greater than the transverse change,and the temperature variation range and response rate in the second cooling stage in spring are the most significant. Temperature is an important influencing factor in the long-term process of rammed earth sites preserved in the open air from disease development to overall extinction. This study was based on real-time monitoring and analysis of the ambient temperature in four seasons and the diurnal variation of temperature inside sections of three typical rammed earth sites located in different climate zones in northwest China. The results show that the temperature of each monitoring point in the site section changes with the change of the ambient temperature,and the diurnal temperature of the monitoring point in the site section can be divided into two cooling stages and one warming stage. There are certain differences between the duration of the temperature change stages in summer and other seasons. More importantly,the temperature variation range and environmental response rate of the section in each temperature change stage in any season have the rule that the longitudinal change is significantly greater than the transverse change,and the temperature variation range and response rate in the second cooling stage in spring are the most significant.
As one of the key hydraulic parameters of loess,soil-water characteristic curve(SWCC) is affected by soil pore structure characteristics. However,it lacks the studies about the effects of loess pore structure evolution on its soil-water characteristics. In this paper,L1,L2,and L6 specimens were taken from the loess platform at the southern bank of the Jinghe River in Jingyang County,Shaanxi Province. The evolution characteristics of loess pore structure during deposition were qualitatively analyzed through the scanning electron microscopy,and were quantitatively analyzed using the pore size distribution(PSD)curves. Meanwhile,the SWCCs of each layer of loess were measured by filter paper method,and the variation regularities along the loess profile were analyzed by comparisons of each other. The pore sizes were transformed into the potential suctions through Young-Laplace equation,and then the PSD and SWCC curves were plotted together with the same suction coordinate,finally the dependency of PSD and SWCC curves were analyzed. In details,the dominant pore sizes and their distribution densities decrease with soil depth increase. As a result,saturation sections and air entry values of SWCCs increased,and the transition sections turned to be gentler,which implied that the increasing of water retention capacities. In addition,comparing the PSD and SWCC of remolded soil specimen with that of intact ones,it could be found that the difference increased with soil depths,although both of them had the same water contents and dry densities. As one of the key hydraulic parameters of loess,soil-water characteristic curve(SWCC) is affected by soil pore structure characteristics. However,it lacks the studies about the effects of loess pore structure evolution on its soil-water characteristics. In this paper,L1,L2,and L6 specimens were taken from the loess platform at the southern bank of the Jinghe River in Jingyang County,Shaanxi Province. The evolution characteristics of loess pore structure during deposition were qualitatively analyzed through the scanning electron microscopy,and were quantitatively analyzed using the pore size distribution(PSD)curves. Meanwhile,the SWCCs of each layer of loess were measured by filter paper method,and the variation regularities along the loess profile were analyzed by comparisons of each other. The pore sizes were transformed into the potential suctions through Young-Laplace equation,and then the PSD and SWCC curves were plotted together with the same suction coordinate,finally the dependency of PSD and SWCC curves were analyzed. In details,the dominant pore sizes and their distribution densities decrease with soil depth increase. As a result,saturation sections and air entry values of SWCCs increased,and the transition sections turned to be gentler,which implied that the increasing of water retention capacities. In addition,comparing the PSD and SWCC of remolded soil specimen with that of intact ones,it could be found that the difference increased with soil depths,although both of them had the same water contents and dry densities.
Aiming at the most unfavorable environment of marl in the fluctuating zone of the reservoir area—the problem of damage and deterioration of mechanical properties under dry-wet cycle in acid environment,taking bank marl as the research object,the dry-wet cycle tests under the condition of pH=3,5,7 solution were carried out respectively,the deterioration law of uniaxial compressive strength of marl under dry-wet cycle in acid environment was analyzed,and the damage deterioration characteristics of marl to mechanical properties were found out. The influence law of different cycle times on mechanical strength parameters is explored by using particle flow software,and the mechanism of stratification deterioration is analyzed in combination with the deterioration phenomenon of rock mass in the fluctuating zone of the reservoir area. The results show that the change of uniaxial compressive strength of marl in pH=3,5,7 solution is inversely proportional to the number of dry-wet cycles,and the cumulative deterioration degree Sn varies from 34.79% to 54.31%,and shows a trend of rapid increase,slow development and tends to be stable,while the range of peak stress deterioration is 8.79% ~35.61%. The cohesion C,internal friction angle φ and elastic modulus E of marl all decrease with the increase of the number of dry-wet cycles,and the damage deterioration is carried out in the progressive mode of circle layer. After the rock mass in the fluctuating zone of the reservoir area is subjected to the dry-wet cycle of acid solution,a large number of secondary cracks will sprout in the nearby rocks. with the advance of the number of cycles and the continuous accumulation of damage,the cracks gradually run through and expand to the inner layer of the slope. The expansion range and rate are related to the number of dry-wet cycles and the pH value of the solution. The above analysis conclusions and laws can provide scientific basis and theoretical methods for the prediction and emergency prevention of disasters such as collapse and instability of landslide,softening of dangerous rock base and water storage leakage in the reservoir area. Aiming at the most unfavorable environment of marl in the fluctuating zone of the reservoir area—the problem of damage and deterioration of mechanical properties under dry-wet cycle in acid environment,taking bank marl as the research object,the dry-wet cycle tests under the condition of pH=3,5,7 solution were carried out respectively,the deterioration law of uniaxial compressive strength of marl under dry-wet cycle in acid environment was analyzed,and the damage deterioration characteristics of marl to mechanical properties were found out. The influence law of different cycle times on mechanical strength parameters is explored by using particle flow software,and the mechanism of stratification deterioration is analyzed in combination with the deterioration phenomenon of rock mass in the fluctuating zone of the reservoir area. The results show that the change of uniaxial compressive strength of marl in pH=3,5,7 solution is inversely proportional to the number of dry-wet cycles,and the cumulative deterioration degree Sn varies from 34.79% to 54.31%,and shows a trend of rapid increase,slow development and tends to be stable,while the range of peak stress deterioration is 8.79% ~35.61%. The cohesion C,internal friction angle φ and elastic modulus E of marl all decrease with the increase of the number of dry-wet cycles,and the damage deterioration is carried out in the progressive mode of circle layer. After the rock mass in the fluctuating zone of the reservoir area is subjected to the dry-wet cycle of acid solution,a large number of secondary cracks will sprout in the nearby rocks. with the advance of the number of cycles and the continuous accumulation of damage,the cracks gradually run through and expand to the inner layer of the slope. The expansion range and rate are related to the number of dry-wet cycles and the pH value of the solution. The above analysis conclusions and laws can provide scientific basis and theoretical methods for the prediction and emergency prevention of disasters such as collapse and instability of landslide,softening of dangerous rock base and water storage leakage in the reservoir area.
The NSFC proposals and grants of engineering geology field(including the engineering geological environment and disaster under the discipline of environmental geoscience,and the engineering geology subordinate to the discipline of geology) in 2022 were analyzed. The number of applications for funding projects in the field of engineering geology has increased steadily,mainly due to the continuous growing of applications for Young Scientist Funds and General Program Funds. The number of applications for other types of programs were relatively stable. The statistics of the last ten years showed that the peer-review referees well handled the peer-review scale on the NSFC proposals. The age structure of applicants for General Program tends to be younger,and that for the Youth Scientists Fund is reasonable. The field of engineering geology has been funded in several different project types,showing strong competitiveness. The NSFC proposals and grants of engineering geology field(including the engineering geological environment and disaster under the discipline of environmental geoscience,and the engineering geology subordinate to the discipline of geology) in 2022 were analyzed. The number of applications for funding projects in the field of engineering geology has increased steadily,mainly due to the continuous growing of applications for Young Scientist Funds and General Program Funds. The number of applications for other types of programs were relatively stable. The statistics of the last ten years showed that the peer-review referees well handled the peer-review scale on the NSFC proposals. The age structure of applicants for General Program tends to be younger,and that for the Youth Scientists Fund is reasonable. The field of engineering geology has been funded in several different project types,showing strong competitiveness.