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 massive development mechanism and countermeasures for perilous rocks in the Three Gorges Reservoir area of P. R. China: The example of the Taibaiyan cliff at Wanzhou

Perilous rock is a dominant geological hazard in Three Gorges Reservoir area of P. R. China. The Taibaiyan cliff at Wanzhou is a representative case of massive perilous rocks in the area. Using this cliff as an example, the conditions triggering massive perilous rocks were studied and described. This included examining the following three conditions: alternating layers of mudstone and sandstone; steep landforms such as cliffs or scarps; and intense rainfall. The massive development mechanism for perilous rocks was discussed, including micro chained pattern gradual and interval evolution from the bottom to the summit of the cliffs individually as perilous rock, and a macro chained pattern evolving stage by stage from the cliff face backward up the mountain. In some respects, rock cells below sandstone in cliffs serves as the pulsating valve of the massive development mechanism for perilous rock. In any micro chained pattern, perilous rock situated on summits is the easiest to rupture due to the fissure pressure. For any single perilous rock, two load compositions were derived. In addition, methods for analyzing perilous rock stability were established in detail using the limit equilibrium principle. Two key techniques, a union scheme that both supports and anchors and a union scheme that nails and anchors, are proposed in light of the massive development mechanism for perilous rock.     

Violent-slide rock avalanche and excitation effect of perilous rock

The physical model of perilous rock avalanche excitation effect is deudofed based on the effect of the main factors, such as weight and fissure water pressure. It quantizes the interaction of perilous rock masses through the energy point of fracture mechanics and wave theory, and gains the departure rate formula of landslide body at momentary avalanche. The particle displacement rate calculation method of perilous rock medium under the action of excitation waves is developed based on the formation of perilous rock avalanche excitation waves and the spread mechanism in slope rock formation. The example shows that the analysis results established are coincident with actual situation. Some scientific basis is provided for the further research of perilous rock damage and evolutionary mechanisms.     

Experimental and Numerical Analysis on Rupture of Rock Bridge with Non-Coplanar Intermittent Joints Under Direct Shear

By using servo control shear loading system, specimens with non-coplanar rock-like intermittent joints were tested by the way of forward and reverse direct shear, rupture mechanism and shearing law for rock bridge with non-coplanar intermittent joints were studied under direct shear. The experimental studies showed that five apparent stages are presented in the process of rock bridge rupture under direct shear, which are linear elastic stage, initiation and extension of crack, fracture and transfixion of rock bridge, climbing and occlusion of shear plane and residual friction. Rock bridge presented profile fracture plane under forward direct shear. While under reverse direct shear, band form fracture plane is showed which penetrated along with the direction of forward shear, and the shear strength of initiation and peak shear strength under reverse direct shear are bigger than that under forward shear. Crack angle, normal stress and lap proportion among adjacent joint are the main factors that influence the initiation strength and peak shear strength. The FLAC 3D simulation for the process of non-coplanar intermittent joints rock bridge rupture and formation of shear rupture surface under forward and reverse direct shear was conducted. The results of numerical simulation agreed well with those of experiment. The simulation results revealed tension crack failure of non-coplanar intermittent joints rock bridge and shear yielding mechanism of fracture plane.     

Effect of attached particles on the mechanical propertiesof dipolar chains in magnetorheological fluids

There are some particles attached to the side of dipolar chains in magnetorheological fluids. The reorganization and rupture of these chains are simulated when a tension and shear movement are applied, respectively. And the micromechanical behavior of these chains is also analyzed. It is found that the attached particles move into the chains during the tension, which increases the strain when the chain ruptures. While in shear process, attached particles introduce localized weakness in chain, which makes the chain rupture more easily and decreases the strength of the chain.     

Stability of various height waste dumps based on nonlinear strength criterion

Coal mining waste dumps are representative artificial accumulations of bulky rock and soil material. Certain factors make these dumps possess characteristics such as self organized criticality, nonlinear shear strength of the waste accumulation. We discusse the main waste dump characteristics and subsequently produced numerical simulations of the stability of waste dumps of various heights using the Fast Lagrangian Analysis of Continua and based on the Hoek Brown nonlinear strength criterion. The simulation calculation results show that the stability is a dynamic evolving process corresponding to increasing waste dump height. Safety factors, based on a nonlinear rule, vary with the waste dump height. Theoretical analysis and calculated outcomes reveal a progressive failure rule of waste dumps, and all indicate the methods we put forward are reasonable.     

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.     

Study on the Mechanism of Rockburst

Rockburst is often encountered in the underground engineerings of high geostress area, it is a kind of dynamic geodisaster.Depending on the examples of rockburst in the Erlang mountain highway tunnel and Jinping second powerstation tunnel, the fracture geometry shapes of rockburst are elaborated. Through the research of SEM analysis and rock mechanics tests of rockburst, three basic mechanics mechanisms of rockburst have been summarized,i.e., compression cracking, compression shear cracking,bending and breaking.     

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.     

AN EXPERIMENTAL STUDY ON CEMENT MORTAR SPBCIMENS WITN A CENTRAL SLITS UNDBR UNIAXIAL COMPRESSION

The cement mortar specimens with a central slits are tested under uniaxial com-pression.The test results show that tensile cracks initiate,as a rule near the tip and may propagatesteady for a certain length.Mean while shear fructures appear and propagate slowly to the failurestate in the zone of compressive stress concentration. So the fracture strength of rock under compres-sion might be differentiated into the initial tensile strength,the peak strength and residual strength.     

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.     

THE EFFECT OF THE BOND STRENGTH BETWEEN LAYERS ON COMPRESSIVE MECHANICAL PROPERTIES OF THE COMPOSITE ROCK

In this paper, on the basis of the compressive tests of composte rock, the different kinds of mechanical properties of composite rock under different bond states are discussed. Authers found that all mechanical properties of composite rock relate to the bond strength between layers and are dilferent when the layers'' bond strength is changed. With increasing the bond strength between layers of the composite rock, the limiting strength, elastic modulus, and breaking energy increase, and this phenomenon is to be stability gradually when they reach some volue, with increasing the layers'' bond strength, the poson ratio reduces.     

Research on Bifurcation and Chaos Characteristics of Meso-Scopic Fracture Process of Rock

On the basis of test results of meso-scopic fracture process and evolution of microcracks of rock in uniaxial compression,the number and orientation of microcracks at each stress level are obtained.A mathematical model for describing the germination and evolution of microcracks is proposed.The bifurcation and chaos behaviours of the evolution of microcracks and meso-scopic fracture process are studied for the first time with the bifurcation and chaos theory of modern nonlinear science.When the characteristic values which represent the gernimation and closure effect of microcracks take certain values,the evolution of microcracks can be described by the Logistic equation.Therefore,the evolution of microcracks of rock has the bifurcation and chaos characteristics.[WT5HZ]     

黑龙江省农业产业化企业战略联盟稳定性影响因素研究

黑龙江省农业产业化企业战略联盟仍处于起步阶段,稳定因素的影响会威胁联盟竞争力,因此研究战略联盟稳定性影响因素尤为重要。笔者在众多学者研究基础上联系黑龙江省联盟实际特点,分析提出伙伴选择匹配性、信任风险、文化契合度、外部环境4个因素是影响黑龙江省农业产业化企业战略联盟稳定性的主要因素,使用博弈方法进行深入分析并找出不稳定因素作用根源,总结提出正确选择联盟伙伴、建立详尽契约制度、加强跨文化学习交流、提升外部环境适应能力来增强黑龙江省农业产业化企业战略联盟稳定性,为提升黑龙江省农业产业化企业综合实力提供参考。     

基于随机场的岩石边坡三维稳定性分析

基于随机场理论,考虑了岩石材料属性的空间变异性对岩石边坡稳定性的影响,将边坡主滑面上的摩擦系数和粘聚力视为高斯随机变量,确定了主滑面上的摩擦系数和粘聚力的均值、方差和协方差,获得了两个随机量之间的相关系数和互相关长度。在此基础上,对岩石边坡进行了三维稳定性分析,确定了岩石边坡的稳定系数和失效概率。数值计算结果表明,摩擦系数和粘聚力的空间变异性对边坡稳定性有重要影响。     

Analysing the Rockmass Permeation of a Low-medium Radioactive Waste Disposal Field

The fractures distribution and fracture rock mass permeation research is the premise condition that to study groundwater movement and pollutant migration in fracture rock mass in bed rock area, which includes the dominance orientation of fracture that groundwater fluxes in it, the brisk zone distribution of fracture water and the permeability calculation of rock mass. This paper mainly analyzes the fracture distribution and the dominance orientation of fracture and the permeability of a low-medium radioactive waste disposal field based on its rich geologic record. The following results are found through Statistical analysis and comparison calculation.The active zone of fractural water in bed rock is an active channel of active nucleus migration. Tthe headrace fracture of disposition have a dominant orientation. The penetrating coefficient tensor in bed rock fracture is also calculated.     

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.     

Rock classification method for tunnel boring machine

In order to study the geological factors which impact penetrating rate of tunnel boring machine (TBM), this paper uses three-dimensional discrete element model 3DEC to build simulated models on rock fragment by TBM cutter. It analyzes the influence of different geological conditions on TBM penetrating rate and classified the surrounding rock in west route of south-to-north transfer project according to the drill ability of TBM in surrounding rock. The results show that the penetrating rate of TBM is closely related to the mechanical properties of rock and joint conditions in rock mass. In certain extent, TBM penetrating rate will be increased with the decrease of rock strength or closely distributed joints. TBM penetrating rate will be decreased with the increase of rock strength or rarely distributed joint. Another result is that the surrounding rock by TBM penetrating can be divided into three classes based on the drill ability of TBM in surrounding rock, which can guide the TBM penetrating.     

The Criterion Tor Shear Strength of Discontionuties with Different Rock Properties in Rock Mass

In this paper,with shear device, shear test of discontinuties with different rockproporties in rock mass under various surface roughness and different normal stress is investigated,the com mon shear strangth criterion of discontin uties is set up as follows.     

Wirkungen meliorativer Gaben von Gesteinsmehlen und Gesteinssanden auf das Wachstum verschiedener landwirtschaftlicher Kulturpflanzen sowie auf physikalische Kennwerte eines Sandbodens und eines Tonbodens

Effect of amelioration doses of rock powder and rock sand on growth of agricultural plants and on physical characteristics of sandy and clay soil
The effect of rock powder to increase the water holding capacity and adsorption degree of sandy soil and the influence of rock sand to augment the aeration and improve the workability of clay soil were tested in pot experiments.
Additions of different rock powders (Basalt, Grauwacke, Kuselit, Muschelkalk and Porphyr) from 5 to 20 weight percent to sandy soil increased the field capacity; the increase in values ranged from 12 to 23% as compared to control. An 11% increase in coarse pore volume (< pF 1.8) of clay soil was noticed when 10 weight percent rock sand was mixed in it. The shear strength of clay soil was hardly decreased. In short time tests five different plants reacted mostly positive to rock powders in sandy soil, the degree of reaction being different depending on rock type and amount used whereas in clay soil the reaction was slightly negative. Ten percent weight additions were better than 20 percent.
Up to 67% increase in spring barley grain yield was registered in sandy soil with addition of 10 weight percent of different rock powders both at about 40 and 80% field capacity water levels. High N-application i.e., 1600 mg N/7 kg soil caused a depression in yield at control whereas it increased the dry matter yield in treated pots. In clay soil at 80% field capacity an increase in grain yield was registered only in Grauwacke and Basalt treatments, which was off set at high N-level. Porphyr and Kuselit treatments produced yield depressions.
Addition of 10 weight percent of rock powders in sandy soil in the first year of experiment reduced the amount of leachate and nitrate leached between 8 to 29% in fallow treatments, but in planted treatments these were dependant on plant type and rock type even showing an increase in one case.