Simulation Study of Water Quality for the Three Gorges Reservoir in Chongqing

In order to survey the degree of stability of dangerous rock slope and get reliable theoretical foundation about the slope restoration, earth stress measuring is performed in the engineering project through drilling on the slope surface. The survey is conducted by means of complete temperature compensation and automatic recording. In terms of experimental data, the computing ram of earth stress works out the magnitude, direction, inclination of the earth stress and their distribution. The result supplies theoretical base for the design and working of slope and dangerous rock control engineering, which has been proved to fine effects in the fields of society, security,environment, and economy in its practice.     

Study on high and steep slope stability Based on 3D laser scanning

Dangerous mountain construction projects block of high and steep slope stability is the important issue of security and disaster prevention, investigation on the surface of the dangerous mountain high and steep slope rock mass structure is the key to the analysis of the problem. The high slope of a major project of the Lancang River, the application of 3D laser scanning technique to study the long-distance survey analysis of rock mass structure analysis method to analyze the distribution of the surface space of the high and steep slope rock mass structure, statistical analysis direction of the advantages of the structure surface and the distribution of rock blocks, as the basis for the application of limit equilibrium analysis method to study the stability of rock blocks of the high and steep slope.     

Geology Problems in the Disposal of Radioactive Waste and Its Research Situation

The geological disposal of radioactive waste is a complicated system engineering that involves many disciplines,such as, radiochemistry, atom physics, geohydrology, hydrogeochemistry, tectonic geology and civil engineering. The geological work is very important in the geological disposal of radioactive waste because the main body engineering of the warehouse building is geological engineering. Based on literature survey and the author's experience ,this paper introduces the research content and the research scope and its situation of the geological disposal of low and intermediate-level waste and the high level waste,all of are significant, including geologic structure geohydrology ,hydrogeochemistry, earth physics ,mineral & rock ,engineering, and geology hazard .     

Elastic-Perfectly Plastic Solution of Tunnel Surrounding Rocks Using Mogi-Coulomb Strength Criterion

Reasonable choice of rock strength criteria is crucial for stress and displacement prediction and support design in tunnel engineering. Based on Mogi-Coulomb strength criterion and elastic-perfectly plastic model, analytical solutions of stress and displacement for surrounding rocks around a circular tunnel were derived The intermediate principal stress coefficient was used to present the intermediate principal stress effect. The results in this study were compared with the current solutions in the literatures and the influence of intermediate principal stress and shear strength parameters of surrounding rocks was discussed. The results showed extensive applicability and the Mohr-Coulomb strength criterion and Matsuoka-Nakai criterion are two special cases; when the intermediate principal stress coefficient b was equals to 0.5, the results indicated that the intermediate principal stress effect and its range for rock strength; the influence of cohesion and internal friction angle on the plastic radius and tunnel wall displacement was significant; Care should be taken to the effects of intermediate principal stress and shear strength parameter variations of surrounding rocks on tunnel design and construction.     

Determination of an Optimum Scheme forBolting Unstable Rocks on a Rock Slope

Using basic principles of stereographic projection,block theory and rock mechanics,this paper tries to find a simple and easy method for determination of an optimum scheme for bolting unstable rocks on a rock slope in design of slope engineering.finally, examination and analysis is made of the completed project for bolting the unstable,high and steep rock slope on the campus of Chongqing University.     

Deformation and Failure Model Test of Steep Dip Excavation Bedding Slope under the Action of Seismic Load

In the Wenchuan earthquake, steep dip bedding slope is a kind of slope that seismic mountain disaster very development and the slope earthquake disaster is often exacerbated by the excavation. In order to reproduce the process and analysis regularity of slope deformation and failure under the action of seismic load. The author chooses San Shuping landslide located Pingwu County as the typical examples of steep dip excavation damage bedding slope, and the indoor physical model test of slope deformation and failure under the action of seismic load are carried out. The results show that slope deformation and failure is intensified by the excavation. Collapse and sliding is the main form of failure and the results consistent with the field investigation. From the whole process of deformation and failure of view, it can be divided into the four stages. First, the initial phase of the earthquake. A wedge rock by excavation small slides along the rock layers and the slope toe stress increase sharply under the action of seismic load in this stage. Second, rock layers by excavation break-bend at slope toe. Third, the rock layers by excavation overall decline stage. Last, the rock slide blocked and dumping.     

Seismic Behavior of a Slope Protected by a Soil Nailing Retaining Wall during an Earthquake

The dynamic elastic plastic finite element method was used to study the seismic performance of a slope protected by a soil nailing retaining wall. On the basis of working in parallel and interaction between loess and a flexible retaining wall, a 3 D nonlinear finite element method (ADINA) also was established. Rational earthquake excitation and damping were discussed for geological engineering. Horizontal and vertical excitations were considered simultaneously in the analyses. A model capable of simulating the nonlinear static and dynamic elastic plastic behavior of soil was used to model the soil, and a bilinear elastic plastic model having hardening behavior was used to model the soil nailing. A friction element was employed to describe the soil structure interaction behavior. Our research focused on the seismic performance of the horizontal and vertical slope deformation, soil nailing axial force, and earth pressure subjected to horizontal and vertical excitations. The results show that the seismic performance of slope protected by soil nailing is good; soil nailing axial force increases after an earthquake; permanent slope displacement occurs during an earthquake; and the peak earth pressure distribution during an earthquake is similar to the earth pressure before the earthquake. These conclusions can provide references for seismic analyses and design in soil nailing engineering.     

Laboratory similar model test investigation of prestressed anchor rope strengthened slope fractured rock mass

Now in the highway construction of the mountain area, fractured rock mass slope always strengthened by the anchor rope. In order to investigate the strengthen effect of the slope fractured rock mass strengthened by the prestressed anchor rope, laboratory similar model test was designed and preceded. By the self-made facilities, a new method of modeling prestressed anchor rope was used in the test. Nylon ropes and the aluminum flakes were used to model the anchor rope and discrete rock mass joints. Gypsum based mix material was used to model rock. According to the real slope engineering site circumstances, six sorts of different disposed prestressed nylon rope strengthened model specimens and the specimens without prestressed nylon rope were made by the similar theory. With the test results, the strength and deformation properties of different model specimens were investigated. Comparison to different anchor effects of the different model specimens was made. The final analysis shows that in order to make full use of the anchor rope's strengthen ability, anchor rope should be disposed perpendicularly to the fracture structure rock mass's main joint direction and should be placed in the upper or top area of the fractured rock mass slope.     

Development and Failure Principle of Differential Weathering Overhanging Rock

Differential weathering overhanging rock by hard rock and soft rock interlayer is common for geological failure.To study the influence of ground stress in rock slope and cave deepness to differential weathering overhanging rock,a mechanical model was proposed.And hollow cylinder stress meter was used to test and analyze on site ground stress at Hongyadong in Chongqing.Moreover, the development range of overhanging rock was determined.And a case studywas used to analyze the relationship among tension ground stress, cave deepness and growth of controlling crack.A method for forecasting overhanging rock failure pattern was proposed.     

Numerical Analysis on Stability of Rock in Sijiaotian Tunnel

The Sijiaotian Tunnel in Yunnan Dabao Highway lies in the narrow defile landscape,and the engineering geology condition is complex,with plenty of cienega.According to the actual situation of the Sijiaotian Tunnel Project in Yunnan Dabao Highway,the stability of the surrounding rock mass is studied by using a 3-D non-linear FEM.The Drucker-Prager criterion is chosen as the failure criterion of the rock.The relatively dangerous zone and the monitoring points in the tunnel are determined.The numerical results show that the Sijiaotian Tunnel is relatively stable.The conclusion has some significance for guiding the construction of similar projects.     

INVESTIGATION OF INITIAL STRESS FIELD IN COMPOSITE STRATIFIED ROCK MASS

According to the weight stress field, the seismic stress field, the temperature stress field in the composite stratified rock mass, the initial stress field in rock mass is discussed theoretically in this paper. The obtained results are useful to make a recognition of the initial stress field in the composite stratified rock mass caused by influencing each other with different physical and mechanical properties between the rock beams.     

Reflected Wave Isotraveling Time Circle and Its Application in Inverting Jointed Rock Masses

Joints are crucial factors in rock masses engineering,so using stress waves to invert joint attitude is a valuable practice.The stress wave emitted from a vibration source is reflected by joints and returns to the ground.A formula to calculate the reflected wave travel time was deduced using analytic geometry theory.In the formula,a direct relationship was established between a joint's real dip angle,real dip direction and the travel time at test spots on the ground.The reflected wave's isotravel time circle described by the formula has a clear conception and a definite meaning.Using the program on the MATLAB platform,this formula can be applied to invert the joint attitude by searching the center of the circle based on the measured travel time at the testing spots around the wave source.     

Simulation Analysis of Spatial Distribution of Roadway′s Surrounding Rock Stress

To get the spatial distribution characteristic of roadway's surrounding rock stress, circular section roadway was taken as a case study. The solution of stress was got by using complex function method, and roadway's surrounding rock stress field was analysed after the solution of mapping space was transformed into the solution of roadway space. As a result, the visual diagram of stress field distribution of roadway's surrounding rock was obtained, which could describe intuitively stress distribution of roadway's surrounding rock at any position. Considering the influence of different radius and side pressure coefficients on surrounding rock stress field, the following conclusions have been obtainded: the peak value and direction of circular roadway's surrounding rock stress has nothing to do with the radius; when side pressure coefficient is less than 1/3,the roof can produce tensile stress; when side pressure coefficient is more than 3, the surrounding rock in two sides can produce tensile stress. And the change rule of hoop stress, radial stress, shear stress and the maximum and minimum of stress have also been generated.     

Analysis on stress wave effect during the process ofrock breaking by pulsed jet

A mathematical model of rock breaking under pulsed jet is established by introducing the Johnson-Holmquist-Concrete constitutive relation and the smoothed particle hydrodynamics method. Based on this model, the formation, propagation and attenuation of stress wave during rock breaking by pulsed jet are simulated. The relations between pressure and time at different points on rock surface and the curve of peak stress wave versus distance to action spot are obtained. Destruction behaviors of rock under pulsed jet and effects on stress wave effect from jet velocity and lithology are studied according to the above calculation results, analysis results show that stress wave effect of pulsed jet acts locally and the peak stress wave shrinks sharply as the acting distance increases. The rock breaking mechanism of stress wave is tensile failure during the high speed process of load-unload. Power and effect range of stress wave is in high direct proportion with jet velocity. There is a threshold velocity before the macroscopic failure. Rocks of different lithologies have different destruction types under pulsed stress wave of pulsed jet. Destruction type of low strength rock like sandstone is crack propagation under the tensile stress during the high speed process of load-unload, while the destruction type of high strength brittle rocks like granite and limestone is vertical failure of stress concentration.     

基于摩尔库仑准则的膨胀土弹塑性本构模型及其数值实现

膨胀土的应力应变关系与含水量的变化有关，通过室内试验对膨胀土的变形、强度以及膨胀参数与含水量之间的关系进行研究，以湿度应力场理论为基础，提出了一个具有工程实用价值的基于摩尔库仑准则的膨胀土弹塑性本构模型。依据FLAC3D数值模拟软件所提供的二次开发程序，给出了该膨胀土弹塑性本构模型二次开发程序过程的基本原理以及模型的程序框图。结合渗流软件计算的湿度场分布，进行膨胀土基坑边坡实例验算，验证了该本构模型的正确性。     

Analysis on key problems of initiative decompression pre-reinforced structure

In slope engineering, the shear resistance of rock and soil can never be exerted themselves by general pre-reinforced structure, through the coupling mechanism between reinforced structure and slope, an initiative decompression pre-reinforced structure consists of soft stuffing and pre-reinforced structure is presented. The setting and thickness of soft stuffing are both key questions during the design of initiative decompression pre-reinforced structure. On one hand, the setting of soft stuffing assure that parts of initiative decompression pre-reinforced structure cannot interact each other under reinforcing; on the other hand, the thickness of soft stuffing can assure that the shear resistance of rock and soil can be exerted by themselves, the sliding thrust which is endured by pre-reinforced structure alone is changed to be endured by soil and pre-reinforced structure together. Then the sliding thrust endured by pre-reinforced structure minimizes, accordingly the effect of initiative decompression is achieved. In the end, the calculation procedure of thickness is illustrated by a practical project and the result is rational.     

A Cosserat Theory-based Numerical Simulation of an Underground Cavern in Layered Rock Mass

Conventional equivalent continuum theory poorly interprets the bending deformations and damage phenomena encountered in rock engineering because the theory ignores the influence of gradient stress.The influence of the bending effect on deformation characteristics of the media has been considered in Cosserat continuum theory which introduces the concepts of coupled stress and bending curvature.The basic principle of Cosserat medium theory and its expanded constitutive model were introduced firstly.Next,a numerical simulation of an underground cavern was carried out using FLAC software.After this,the results of the Cosserat model and explicit joint model were compared.The simulation results not only displayed the bending deformation of layered rock mass well,but also demonstrated the validity and superiority of the Cosserat expanded model.     

Study on Shear Stress Distribution and In-situ Test of Pressure-Dispersive Anchor

Combining the Mindlin elastic displacement solution with the elementary theory of finite element, in this paper, the shear stress distribution of pressure-dispersive anchor is calculated. Its work performances were compared with those of tensile anchor. According to the in-situ pull-out test of pressure-dispersive anchors in weak rock stratums, it is proven that the bearing capacity of pressure-dispersive anchor increases rather evidently than that of tensile anchor under the same condition and the effect of spacing between load-supporting bodies on the bearing capacity of pressure-dispersive anchor is analyzed. The analysis results of this paper can offer some references to the engineering application of this new type of anchor in the future.     

A Fracture Mechanics Solution for Control Fissures in Perilous Rock under Seepage Stress

Crack propagation of control fissures in perilous rock under loads is a key process in the failure of perilous rock. Based on the loading mechanism, the control fissures are classified into compression shear and tension shear types. By introducing a model of seepage stress, the calculating principle of the stress intensity factor and the propagation orientation of control fissure under seepage stress are put forward using fracture mechanics methods. Using Shoulishan perilous rock in the Wanzhou district of Chongqing, P. R. China, as an example, the calculated results show that there is an obvious increase of the stress intensity factor. The influence of hydrostatic pressure and hydrodynamic pressure also are analyzed.     

Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.