Rockburst Hazard and Its Forcast and Treatments in Underground Engineering

Rockburst is a serious damage geologic hazard. According to the rockburst phenomenon in Erlangshan tunnel and the Jinping 2nd hydropower station and a large of rockburst data,this paper proposes that rockburst is a result that many factors synthesize. These factors include teconics ,epigenetic and superficial structure, wall-rock intensity, attitude of rocks, wall-rock state of stress, wall-rock deformation and underground engineering arrangement, etc. It is given that the mechanism of rockburst is a tension fracture damage under press.     

Reason and Precaution of Seepage in NATM Tunnel

On the basis of investigation on seepage in the Jinyunshan Tunnel and the Songjiagou No.1 Tunnel,the reasons of the seepage were analyzed and the cracking in concrete that led to seepage was studied by using the probability fracture mechanics.Finally,some suggestions of tunnel waterproofing were proposed.     

Research Advance on Rockburst Theory and Its Engineering Application in Collieries

This paper summarizes and describes the progress in coal rockmass outburst theory in resent decades both at home and abroad,discusses the tendency of mechanism of rockburst,and gives a fullier review about the presently adopted prediction methods and preventive measures,simultaneously looks into the prospective development on the study of prediction and preventive measures and its practical applications.     

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.     

Experimental study on acoustic emission characteristics of coal rock at different confining pressure

This paper conducts experimental investigation on acoustic emission(AE) characteristics of coal rock at uniaxial and triaxial compression by MTS815 rock mechanics test system. The results show that the variation of AE has tendency effect at uniaxial compression and confining pressure experiments. We indicate that AE signal decreases significantly in the elastic stage, and the relatively quiet period of AE before the specimens failure is not obvious under confining pressure. The AE amplitude distribution with time and its envelope line can indirectly reflect the trend of stress. The AE events peak stress and elastic modulus decrease with the temperature increase, and the value of m which reflects the cumulative distribution of amplitude increases as the confining pressure rises. The results also show that the AE frequency distributes in three frequency domains, and the proportions of dominant frequency significantly increase while the specimens are broken.     

CT Real-time Analysis of Damage Evolution of Coal under Uniaxial Compression

In order to clarify the mechanism of rockburst, using the specified loading equipment and the CT machine, the real-time computerized tomography testing of coal under the uniaxial compression was completed. Through CT scanning, the clear CT images which included the stage from the microcrack clousre to the microcrack growth, bifurcation, development, failure and the post-failure stage were obtained. According to the CT values, the meso-damage evolution of coal under uniaxial compression was analysed, which provided the basis for the meso-damage evolution.     

APPLICATION OF INTEGRAL EQUATION TO THE STABILITY OF COMPRESSION BARS

This paper proposes integral equation to find the criticalbuckling load of compression bars in mechanics of materials,thus theresearch method of this problem has been improved.     

Solving Method for Soil Spring Stiffness of Shallow Shield Tunneling

Based on complex variable theory in plane elasticity, the equivalent spring stiffness is derived from the analytical solution by means of simplifying shallow shield tunneling to semi-infinite plane with hole, which is applied to response displacement method. The performances of the analytical solution are evaluated and compared with that of the deep shield tunneling through a series of selected various tunnel depths and soil Poisson's ratios. The relation of compression and shear spring stiffness is discussed. Meanwhile, two factors affected soil spring stiffness, tunnel depth and soil Poisson's ratio, are also analyzed. It is shown that soil spring stiffness of shallow shield tunneling is different from that of deep shield tunneling, and the ratio of compression and shear spring stiffness varies along shallow shield tunneling. It is also found that the value and distribution law of soil spring stiffness of shallow shield tunneling greatly depend on tunnel depth and soil Poisson's ratio.     

MODEL TEST RESEARCH ON A COMPOSITE LINING OF UNDERGROUND ENGINEERING IN JOINTED ROCK

Combined with thedesign precept of Cai-Yuan highway tunnel 2 in Chongqing,stress state,time ffectiveness and rupture mechanism of rock near the bounda-ries of the tunnel and the second lining in jointed rock mass arc studied with model tests.The results show that shotcretc-bolt support betters mechanical properties of the periphey rock of the tunnel,and increases the capacity of anti-deformation.The second lining also has the action of supporting structure.     

Application and Progress about Mechanics Technique Integrating with Botany

The survey and progress about the study applying mechanics to traditional botany are summarized. It gives brief analysis to the influence of plant growth and development under the mechanics factors, such as mechanical vibration, strong sound wave (or ultrasonic wave), electromagnetic field and microgravity, et al. In other word, the biological effects of plant caused by environmental stress stimulation are set out (They contain positive effects and negative effects). Furthermore, the profound biological effects and some possible mechanism of the plant tissue and cell are discussed. The paper put forward several main problems about botanical mechanics which must be researched at the beginning of 21st century, and the more significant thing about it is the operation of Ca 2+ which as a Second Messenger, will be probed into. At the end of the paper, the well development tendency and practical prospect of the newly compound subject _botanical mechanics is also presented.     

异位发酵床垫料的直剪切及压缩试验研究

为研究不同含水率的条件下异位发酵床垫料:抗剪强度、黏聚力、内摩擦系数、压缩载荷的变化规律.本研究采用土壤力学试验方法,测定垫料五种不同含水率的相关参数.结果表明:当垫料含水率为29.22％～36.13％时,抗剪强度、内摩擦角系数会随着含水率的增大而增大;当含水率为45.55％～61.11％时,抗剪强度、内摩擦角系数会随...     

基于压电效应的简易型细胞力学测试仪

针对传统的细胞力学研究方法的非无损性,不能对细胞力学参数连续、长期监测的特点,研制出一种基于石英晶体压电效应的简易型细胞力学测试仪。该测试仪以STM32 103C8 为核心,设计有石英晶体在液相环境下的起振电路、稳定振荡电路,采用了频率/电压转换电路。系统实现了对石英晶体频率变化的高精度采集,对与传感器耦合的界面层（细胞）的质量、粘弹性和表面应力多参数敏感,能对细胞黏附过程和细胞力学性能进行动态监测。通过整机在细胞培养液环境下的实验,验证了测试仪系统的可行性与稳定性。     

Mechanical Behaviors of Large Span Space Structures in the Construction Process

Traditional structural design emphasizes checking whether a loaded structure satisfies design requirements without considering the construction process. There is a great difference in structures between the states in construction processes and design, however. To solve the above problems, a method of nonlinear time varying mechanics was adopted to analyze the construction process of a structure. The structural characteristics in each construction stage were analyzed by time varying mechanics and the variations of internal force and displacements obtained. We conclude that designs will not be safe if the time varying effect in the construction process analysis is not considered. We offer advice on the design and construction of large span structures.     

Numerical Analysis of Drained undrained Triaxial Tests for Overconsolidated Clays

In the framework of critical state soil mechanics, a simplified hardening law is proposed to describe the change between subloading surface and the normal consolidation surface with plastic deformation based on subloading surface concept proposed by Hashiguchi. The characteristics of overconsolidated clays, such as stress strain relationship, strain hardening and softening and stress dilatancy are simulated, and the results are in accordance with the data from triaxial drained compression test. Numerical model is also used to predict the stress strain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests.     

Earthquake Response Properties of the Support Structure of Large Cross Section Tunnel

The response properties of displacement and stress of tunnel support structure are discussed in detail under the action of horizontal earthquake acceleration(Ya),longitudinal earthquake acceleration(Za) and horizontal-longitudinal earthquake acceleration(YZa).This discussion is based on an analysis of the surrounding rock-support structure-earthquake interaction,adoption of an ADINA nonlinear finite element and construction mechanics,and transient dynamic time domain analysis of a large cross section tunnel.Results of analysis show that:(1) Horizontal earthquake acceleration has important influence on horizontal displacement,maximum principal stress,acceleration and velocity.(2) Longitudinal earthquake acceleration has important influence on longitudinal displacement,effective stress,maximum and minimum principal stress,maximum shear stress,acceleration and velocity.(3) When Ya=0.191g and 0.440g or Za=0.141g and their combined action,the initial support of tunnel would be damaged and the local lining would have partial damage.(4) When Ya=0.440g or Za=0.326g and their combined action,the lining of tunnel would be damaged.(5) When Ya=0.880g or l Za=0.652g,the support structure of tunnel would have severe damage.     

Experimental Study on Shear Strength of High Strength Concrete Columns

On basis of the experiment on sixteen high strength concrete columns, their shear behaviors are analysed. The effects of shear-span ratio and axial compression ratio on failure behavior, cracking shear and shear strength are analysed. The authors have discussed the suitability of the design equations for shear strength in the code. This experimental study on shear strength of high strength concrete frame columns is the first one in this field at home and the results can be served as reference for the code of high strength concrete design.     

THE DIRECTING MECHANISM OF V-NOTCHF WITHJN V-NOTCHJNG BLASTING

Based on the blasting theory and "Fracture Mechanics " , the directing effect mechanism of V-netch in V-rotching blasting is studied and the positive splitting and directional explanding of crack within V-notching blasting and the priority of crack's expanding in the V-notch axle-plane etc are expounded. It's just these fracture characteristics mentioned above that ensure the fine control of the cracking plane.     

The Use of UEA Concrete in the Construction of the World Trade Centre in Chongqing

The reasons of cracking of large mass concrete construction in the early age are analysed and the technical thinking and ways of prevention of cracking are presented in this paper.UEA micro_expanding agent was used in the construction of the World Trade Centre of chongqing.The early contraction of corcrete is changed into limited expansion.the practical engineering experience is obtained in efficiently perventing the early cracking of concrete and ensuring the strength of concrete.     

Coupled Vibration of Saturated Fractional Derivative Type Viscoelastic Soil of a Circular Tunnel with Partially Sealed Shell Lining

Considering the compression of medium and fluid, coupled vibration of saturated fractional derivative type viscoelastic soil and a circular tunnel with partially sealed shell lining in the frequency domain is investigated according to theories of Biot and elastic shell. The stress and displacement constitutive behavior of the soil skeleton is described by fractional derivative model which reflects the rheological properties of the medium while regarding soil as a liquid-solid saturated porous medium. The expressions of displacement, stress and pore water pressure are obtained while the inner boundary of circular tunnel is subjected to axially symmetric radial traction and axially symmetric fluid pressure respectively by introducing a partially permeable boundary condition. With the parameter analysis, it is revealed that the order of fractional derivative model on the responses for the system subjected to the symmetric radial traction is much greater than that of the system under the axially symmetric fluid pressure. And resonance phenomenon occurs obviously. Nevertheless the system responses do not have remarkable resonance phenomenon under axially symmetric fluid pressure.     

Effect of Coarse Aggregate on Characteristics of Plastic Shrinkage Cracking of Lightweight Aggregate Concrete

The grading of lightweight aggregate (LA) and its water content has an effect on the plastic shrinkage cracking of lightweight aggregate concrete (LWAC). Test results show that the water absorption of LA and the water evaporation of the concrete increased with the increment of cubage of LA, but the area of plastic shrinkage cracking of LWAC decreased. Besides, LA with high water content is beneficial to restraining the plastic shrinkage cracking of LWAC.