THE MIXED MODE FRACTURE CRITERION OF BRITTLE ROCK UNDER COMPRESSION-SHEAR STRESS STATE

In this paper the test results of mixed mode fracture of three kinds of brittle rock under two kinds of stress paths are reported. The fracture mechanism and failure patterns of brittle lock under different stress paths are discussed. Theory analysis and test results show that the Compression- Shear fracture criterion of brittle rock can be expressed:     

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.     

STUDY ON MIXED MODE FRACTURE AND STRENGTH PROPERTIES IN ROCK UNDER COMPRESSION

Mixed mode fracture in rock subjected to compressive loading has many differ-ent features in fracture hehaviour from those subjected to tensile loading,especially when the aper-ture is partly or fully closed.The traditional theory of elastic fracttire mechanics can not be used tosolove compressive-shear fracture problem. Based on fracture characteristics of rock under compres-sion,the formulas to calculate stress intensity factor are updated so that the new strength criterion isevolved to evaluate the crack initiation streilgth.The stress distribution and the relative displacementof crack surface in central slit is confirmed by FEM analysis.     

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.     

A CATASTROPHE ANALYSIS OF THREE -POINT BEND ROUND BEAM SPECIMENS OF ROCK

The snap-back instability (also known as catastrophe behavior) .which may happen during the process of fracture testing with three-point bend round beam of rock .concrete and ceramic materials is analysed,an instability criterion for this kind of specimen is propoesd.it is different from that of the three-point bend rectangular beam.     

STRENGTH PROPERTIES OF ROCK MASS WITH BIDIRECTIONAL INTERMITTENT CROSS JOINTS

In this paper,the strength properties of rock mass withrows of intermittent bidirectional cross joints by simulating models arediscussed.Work has been done on finding the failure mechanism of therock mass as well as the influence of joint direction and lateral pressureon tne strength of the rock mass.At the end of the paper,model testresults ahd FEM analyses are presented and strength criteria for thiskind of rock mass are proposed.     

银盐法测定稻谷中无机砷含量的不确定度评定

按GB/T5009.11-2003《食品中总砷及无机砷的测定》无机砷测定中第二法银盐法要求对稻谷中无机砷的含量进行检测,并评定了检测结果的不确定度。评定发现最终不确定度来源主要来自于标准曲线引入的不确定度和重复性实验引入的不确定度。     

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.     

A NEW IDEA FOR PROTECTING ROCK AROUND UNDERGROUND EXCAVATION-STUDIES OF SOFTENING SURROUNDING ROCK METHOD

This paper advances a new idea for protecting rock around underground excavation, based on the analyese of movements of surrounding rock,then studies the sloting in surrounding rock-a kind of softening technique for surrounding rock by means of BEM and modle tests. It is proved that this method is useful and effective.     

AN INVESTIGATION ON THE MULTI-ARCH STRUCTURE OF A STRATA AROUND A STOPE

This paper analysis the mechanical process with the photoelast-ic model test ane the finite element method, and presents the basic cause of existing different pressure and different transfiguration in the strata around a stope.     

THE STUDY ON CHARACTERISTICS OF ELASTIC WAVE PROPAGATION IN ROCKS UNDER COMPLICATED STRESS STATES

This paper is aimed at investigating the acoustic properties of rock mass under the three-dimentional different stress states, and is presented to discuss emphatically the characteristics of the acoustic wave propagation and the stress-velocity relation in both rocks (sandstone and limestone) under uniaxial and true triaxial compression. The results indicate three regions in which the acoustic velocities and the strains change with the stresses are approximately similar under different stress states; and the acoustic velocity-stress relations for elastic rocks may be represented by different interdependence coefficients under uniaxial compression. At a time, The acoustic measurement method of rock mass stresses and the horizontal tectonic stress are discussed.     

A SIMPLE METHOD OF SEPARATING FRINGES IN HOLOPHOTOELASTICITY

A simple method of separating fringes has been discussed. Only setting a piece of depolarizable tracing paper in the common object beam path of holo-photoelasticity and using the differential-load double exposure method,the separate and non-modulated isopachics are obtained.     

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.