The Elastic-Plastic Analysis of Collinear JointsLoaded by Shearing-Compressive Stresses

In this paper the problem of collinear multi-joint in rockmass loaded by shearing-compressive stresses is simplified as that of a joint in finite rockmass. The basic equations with Mohr-Coulomb criterion are solved by the line field analysis method near the joint line in an elastic-perfectly plastic materials. Through a reasonable boundary condition on the joint surface and matching conditions at the elastic-plastic boundary, the relation between length of the plastic region on the joint line and the shearing-compressive stresses is obtained. The failure laws of the rockmass contained collinear joints are also obtained.     

Elastoplastic Analysis of Discrete Jointin Rockmass Loaded by Compress_shear

In this paper the elastoplastic stress fields near joint line in rockmass loaded by compress- shear are analyesd by the line field method in fracture mechanics with Mokr- Coulomb criterion. Through the matching conditions of the elastoplastic fields on their boundary, the relations between the length of plastic zone on the joint line and the compress- shear loads are found, and the fracture criterion of the discrete joint is also obtained     

Elasto-plastic analysis on surrounding rock of roadways based on seepage, strain softening and dilatancy

According to seepage body force, strain softening and rupture expansion of rock mass, elastic-plastic mechanics theory, distribution laws of stress and displacement of surrounding rock in seepage field are derived, and relationships between different zonation range of the surrounding rocks, pore water pressure, strain softening and rupture expansion are established. The results show that the pore water pressure and rupture expansion rock mass have a more obvious impact on the surrounding rock rupture area than the plastic zone. Both the plastic zone and the rupture area are larger when the seepage field is considered. The impact of strain softening on both the plastic zone and the rupture zone of surrounding rock is very significant, and both seepage and strain softening rupture expansion affect deformation of surrounding rock of roadways obviously. It provides certain reference values for the roadway support engineering in seepage field.     

Elastic_Brittle Fracture Analysis of Micro_Crackin Concrete Loaded by Stretching Stresses

The concrete is a typical brittle material.The fracture and propagating failure of the micro-crack in loaded concrete are very important problem in civil engineering.In this paper,from the equilibrium differential equations and failure criterion,the elastic-brittle static fracture analysis of the plane stress micro-crack in concrete loaded by stretching stresses was done near crack line.The relations between the stretching stresses and the length of brittle fracture zone on the crack line were obtained.     

Numerical Analysis of Spiral Notch-holes Loosen Blasting

ANSYS program is applied to the numerical analysis on the space flexibility and elastoplasticity of a spiral(V-notch),which suggests that: 1)The stress distribution is uneven inside the spiral V-notch as tensile stress is focused near the tip of the notch.2)Tensile stress and compressive stress areas are located alternatively inside the whole notch,the stress changes slower at a point farther from a crack tip,and much faster at a nearer point.3)Elastoplasticity study finds that there exists at the tip of the crack a plastic zone that expand and extend to the direction of the tip with increase load so that cracks initiate at the tip of the notch and extend in the direction of the tip.     

Influence of Neutral Principal Stress on the Elastic-Plastic Solution of Expansion of Cylinder Cavities

In the elastic-plastic solution of expansion of cylinder cavities based on Tresca strength criterion and Mohr-Coulomb strength criterion, the influence of neutral principal stress is not considered. In this paper the influence of neutral principal stress on elastic-plastic solution of expansion of cylinder cavities is considered. The calculation shows that the radius and displacement of plastic zone will reduce when the neutral principal stress is considered. The conclusions are of practical significance for geotechnical engineering.     

A Quantitative Description of Decreasing in Delayed Fracture Toughness of Metals Induced by Hydrogen

Based on the concept of unification between strength theory and elastoplastic fracture criterion,and using the approximate solution for elastic-plastic plane stress-strain field in the vicinity of a blunt crack tip of power-law hardening materials,which was established by Chen Chi,a correction is made for both decohesion theory and hydrogen-facilitated local plastic deformation theory.The results from the two theories are found substancially identical.     

Analysis of Damage Localization in Crack Weakened Rock Mass

Damage localization in crack weakened rock mass is closely related to the crack growth pattern. Bifurcation of the alternative evolution of cracks occurs when the cracks grow to some extent, then some cracks keep on growing while other ceased evolving. It is found that damage localization in crack weakened rock mass is caused by bifurcation of the crack growth pattern, and the initial location is also determined by the crack growth pattern. Based on the analysis on the bifurcation of crack growth pattern, the critical length of wing crack and the critical stress of damage localization in crack weakened rock mass are obtained. Subsequently, the onset location of damage localization is determined by using the eigenvalue and eigenvector of coefficient matrix, and crack interaction is also taken into account in this model. Finally, the relationship between the interval between columns and rows, the orientation of crack, confining stress and the critical stress of damage localization is defined in the example.     

Experimental Analysis of Deformation Characteristic for Soil Bank Slope Under Reservoir Water Level Fluctuation

Under reservoir water level fluctuation, soil bank slope water sucking, stress concentration and slip deformation in Three Gorges Reservoir area form slope cracks system at different periods and different spatial parts. In this study, laws of cracks spatial evolution in different deformation periods for soil bank slope were analyzed during a water cycle of impoundment and decline by model test. The test results indicated that, in the initial impoundment period, cracks appeared near the water line at the bank slope leading edge with high appearance frequency, and scale increased gradually and partial bank slope collapsed and damaged. In the middle impoundment period, cracks appeared in the front and trailing edges of bank slope, the frequency of occurrence and the scale of which decreased. And in the late impoundment period, the leading edge of the cracks development disappeared, the trailing edge of the cracks continued to develop and the bank slope crept along the sliding surface as a whole. Cracks expanded slowly in the pause impoundment as the water level raised. In the water level decline stage, tensile cracks mainly occurred in the back edges of bank slope. In the early water level decline, cracks appeared in low frequency and it grew slowly. In the late water level decline, cracks appeared in high frequency and large scale, and where the bank slope produced lower seat deformation and dislocated berm. Moreover, in water level decline stage, bank slope crept along the sliding surface as a whole.     

A FRACTURE MECHANICS ANALYSIS OF FRACTURE PLANE CONTROL IN FRACTURE CONTROL BLASTING

A procedure of fracture control blasting for achieving directional breaking of rocks by blasting is presented. The criterion for initiating of radial cracks in borehole wall under dynamic load and the method for determining the permissible rang of initial gas pressure (p0) in the charge cavity are developed .and the branching of radial cracks and the effeets of the pressure (p0) and blasthole geometry (R0.a.L3) on final dimensions of directed cracks are studied .with Fracture Mechanics analysis in all three aspects of fracture process including crack initiation .crack propagation and crack arrest.     

Numerical Simulation of Microcrack Toughening in Particulate Composite

The crack tip region in an elastic composite can be divided into three different zones. The constitutive equations corresponding to these zones and the extent of the saturated damage zones are derived. The damage isotropy in the largest saturated damage zone is expressed by utilizing the Monte Carlo technique to create uniform distribution microcracks. The interaction between the main crack and microcracks can be evaluated by an alternating iteration scheme. In the assumption of a dilute concentration of microcracks, the interaction among microcracks is neglected, and the stress intensity factor produced by interaction between the main crack and each microcrack can be superposed. Two sources of loading are analyzed: one is for the main crack microcrack interaction under an applied remote load, and the other is for the main crack microcrack interaction accompanied by the relief of residual stresses on the microcrack surfaces. The results show that two sources of loading can shield the main crack tip, and microcracks behind the main crack tip can create the most shielding whereas the micro cracks ahead of the main crack tip play no role in shielding.     

Mechanical and Deformation Characteristicson Shield Tunnel Segment with Cracks

The 3D Goodman element is used to simulate segments' cracks in one section of shield tunnel in Guangzhou. Mechanical and deformation characteristics of segment structure responded to varied depth of cracks is analyzed in this paper. Meanwhile, research on coefficient of lateral earth pressure, soil coefficient and ground water level on mechanical and deformation characteristics is carried out. The research result shows that along with the increase of cracks' depth, the tensile stress, pressure stress reach the maximum value while the increment is not too much. However, when the depth equals to the thickness of segment, the reinforcements' tensile stress has increase sharply, even exceeded the allowable value. Moreover, the maximum number of tensile stress, horizontal and vertical convergent value of shield tunnel segment with cracks increase with the reduction of the coefficient of lateral earth pressure and soil coefficient, and increase with the increase of ground water level as well. Specific repair measure has been taken to segments' cracks in this section of shield tunnel based on the conclusions. In general, this section of shield tunnel is stable and safe now, and there is no longer new cracks appeared.     

A SIMPLIFIED PLASTIC ZONE METHOD FORSECON DORDER ELASTICPLASTIC ANALYSISOF STEEL FRAMES

This paper presents a simplified plastic zone method with consideration of the in-fluences of the PDelta. residual stress ,degradation of crosssectional stiffness and plastic zone lengthon the stiffness matrix for second-order elastic-plastic analysis of steel frames. The method not onlymakes up for a insufficiency which is that the degradation of crosssectional stiffness and plasticzone length in a member ean not be considered by a plastic hinge method but also overcomes a defectwhich is very costly and time-consuming because a fine mesh discretization across the crosssectionand along the member length is required by a plastic zone methed. Analysis result Shows proposedsimplified rnethod is simple and practical.     

玉米裂纹及其检测

我国粮食部门经过较长时间才认识到玉米裂纹的重要性。玉米裂纹是指人眼能观察到的玉米表面和胚乳内部裂缝宽度为0.1 mm左右的缝隙。玉米籽粒内部生来就有许多微裂纹,构成胚乳内众多的微毛细管。借助电子显微镜可以观察到纳米级的微毛细管。目前检测玉米裂纹的仪器需进一步改进。     

Experimental analysis of the deformation of sandstone under cyclic pore water pressure and wavelet transformation

To explore the characteristics of deformation of sandstone under cyclic pore water pressure, the experiments with different axial stresses (60%, 70% and 80% of peak intensity) of sandstone subjected to cyclic pore water loading are investigated by using MTS815 rock mechanics testing system, and irregular small deformation in deformation curve of sandstone are also processed by wavelet transformation of Matlab. The results show that with the increase of constant axial stress, fatigue deformation under cyclic pore water pressure will accelerate the failure of the sandstone. With the increase of the number of cyclic pore water pressure, the deformation evolution of the plastic-loop is illustrated as sparse-dense-sparse. The deformation curves of sandstone under cyclic pore water pressure affected by many factors are decomposed, reconfigurable processed and evaluated by using wavelet transformation, which indicates that the basic curve with optimal decomposition scale fits well with the experimental curves and reveals the deformation evolution of sandstone.     

承压水基坑突涌的水力劈裂

突涌是基坑工程施工过程中常遇的主要灾害之一。现有的承压水基坑突涌稳定分析方法均不能反应突涌破坏机理。从水力劈裂的机理入手,建议承压水基坑突涌问题应考虑应力-渗流场耦合作用。在Biot固结理论基础上,建立了基坑突涌分析水力劈裂耦合模型,考虑了土体物理力学性质的动态演化。试图通过分析工作面推进过程中基底土体应力场和渗流场的变化,来判断突涌发生的可能性。研究结果表明：突涌始于基底隔水层所发生的张拉破坏,基底周边是发生突涌的危险位置;渗透弱面(初始张拉裂缝)的水压楔劈效应所导致的水力劈裂为基坑突涌提供了通道;高水压力的存在是突涌发生的前提条件,高水力梯度的产生是基坑突涌的根源。     

Slip Line Field of Plane Strain Problem Obeying the GeneralizedHoek Brown Failure Criterion

According to the characteristics of plane strain problem of elastic and plastic mechanics, the bi parametric expressions were derived for stress components satisfying the generalized Hoek Brown failure criterion. Being substituted into the static equilibrium partial differential equations, a group of first order hyperbolic pseudo linear differential equation partial differential equations was obtained. Utilizing the determinant method and proper variable transformation, the characteristic direction and the differential relation equation for the stress partial differential equations were acquired. The characteristic direction indicted that in plastic zone obliquely intersecting conjugate shear slip surfaces formed two families of non orthogonal slip lines, in which conjugate angle varied with the limit stress state and the material physical properties of Hoek Brown rock mass. Since the principal direction of the maximum principal stress was circumferential in perfectly elasto plastic surrounding rock of the plastic zone around a circular opening suffering the symmetric initial stress field, the angle between the tangential direction of slip line with the principal direction of the maximum principal stress was the function of the minimum principal stress(i.e. the radial stress). Combined with the analytical solution, the polar coordinate differential equation was derived and furthermore, the polar coordinate curve equation for the slip line was obtained.     

Multi-field coupling effect on coalbed methane seepage characteristics and numerical simulation

This paper studies the seepage of coal samples under the influence of each single factor, the axial stress, confining pressure, gas pressure, and temperature by experiments. It uses Ansys12.0 to numerically simulate the law of coalbed methane seepage, coal deformation, pore pressure, the distribution of flow field under the influence of each single field and multi-field coupled. The numerical simulation show that the result of numerical simulation of gas seepage law in the coal under each single fields is basically the same as the experimental result. The curve of gas seepage and average effective stress under the condition of multi-field coupled is negative exponential relationship. Stress influenced the deformation of the specimen is greater than the seepage field. The axial stress on the deformation of the specimen is greater than confining presses The influence on the flow field by confining pressure is greater than axial stress, the influence of axial stress on the pore pressure is greater than confining pressure, pore-pressure under the action of multi-field is bigger than pro-pressure under each single field. To study the seepage law of coalbed methane, it should consider the influence of gas-solid-heat at the same time.     

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。     

Influence of Characteristic of Zeolite on Loading Nano-TiO2 for Photocatalytic Degradation of Oxytetracyline in Aqueous Solution

The composite photocatalysts were made by using solid dispersion method with nano-TiO2 loaded on hydrophobic or hydrophilic zeolite and zeolite with different pore diameters. The removal and mineralization efficiency of oxytetracycline (OTC) in aqueous solution were investigated under the irradiation of 32 W UV lamps by composite photocatalysts loaded with different ratios of nano-TiO2. The results showed that UV/10%TZ2 (hydrophilic zeolite) achieved a better removal efficiency of OTC than UV/40%TZ1 (hydrophobic zeolite) while UV/15%T5A (hydrophilic zeolite with a pore diameter of 0.5 nm) achieved a better removal efficiency of OTC than UV/10%T13X (hydrophilic zeolite with a pore diameter of 1 nm). That is to certify that the hydrophilic zeolite and zeolite with small pore diameters loaded with nano-TiO2 could achieve better removal effects for OTC in aqueous solution. The OTC that adsorbed on the inside surface of 13X cannot be degraded due to the out range of hydroxyl radicals attack.