大断面动压煤巷全锚索围岩控制技术

针对大断面动压煤巷变形严重、易冒顶的问题,根据具体地质条件设计巷道支护方式,并模拟了锚杆锚索联合支护和全锚索支护方式下巷道围岩的应力场特征。结果表明:锚杆锚索联合支护和全锚索支护在围岩中形成了有效的压应力区并相互叠加形成一定范围的主动支护区,全锚索支护形成的有效压应力区较锚杆锚索联合支护大,明显扩大了围岩的有效承载范围,显著提高了围岩的承载能力,达到了良好的支护效果。

股骨头缺血性坏死新月征的形成机制

目的对发生股骨头缺血性坏死出现X线片上"新月征"股骨头的结构改变及与所受应力的对应关系进行研究,探讨"新月征"的形成机制。方法收集1998年3月-2003年4月全髋关节置换术前X线片显示有"新月征"的股骨头16例18髋,进行大体和冠状位断面观察。应用有效压应力原理和应力集中理论对发生在缺血性坏死股骨头上的结构改变原因进行解释和说明。结果松质骨内的骨小梁形成三维立体交互连接的网格结构,孔隙率50%～90%,髓内压20～30 mmHg。股骨头内松质骨的构造符合多孔介质的定义,是一种多孔介质。松质骨的变形机制与多孔介质材料变形机制相同。软骨下骨板与松质骨间的断面结构改变使应力易在二者交界处集中。有效压应力原理和应力集中理论可对发生在缺血坏死股骨头上的一些现象及彼此之间的关系进行明确的解释和说明。结论导致"新月征"骨折线正发生在软骨下骨板下的原因是由于在坏死灶外侧软骨下骨板局灶性被吸收发生后,软骨下骨板与未被修复坏死松质骨交界处发生应力集中,集中的应力导致骨折线正位于软骨下骨板下,施加在未被修复坏死松质骨上增加的有效压应力引起未被修复坏死松质骨的体积减小,从而导致新月形空腔在软骨下骨板下形成,新月形空腔在X线片上显示出"新月征"。

Effective stress analysis method of seismic response for high tailings dam

Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.

Diffusion and Reaction Model of Catalyst Pellets for Fischer-Tropsch Synthesis

The diffusion and reaction phenomenon in a Fe-based catalyst pellet for Fischer-Tropsch synthesis was studied. It was considered that the pores of catalyst pellets were full of liquid wax under Fischer-Tropsch synthesis conditions. The re- actants diffused from the bulk gas phase to the external surface of the pellet, and then the reactants diffused through the wax inside the pellet and reacted on the internal surface formed along the pore passages of the pellet. On the basis of reaction kinetics and double a-ASF product distribution model, a diffusion and reaction model of catalyst pellet was established. The effects of diffusion and reaction interaction in a catalyst pellet, the bulk temperature, the reaction pressure and the pellet size on the reactivity were further investigated. The relationship between the internal diffusion effectiveness factor of spherical catalyst pellet and the Thiele modulus were also discussed. The bulk temperature and pellet size have significant effects on the reactivity, while the pressure shows only a slight influence on the reactivity. The internal diffusion effectiveness factor decreases with an increasing Thiele modulus.

Stress and Displacement Distribution of Soft Clay Slope with 2D and 3D Elastoplastic Finite Element Method

Based on elastoplastic model, 2D and 3D finite element method （FEM） are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio.

Analysis on effective stress formula and consolidation of gassy muddy clay

In order to found an applicable equation of consolidation for gassy muddy clay, an effective stress formula of gas-charged nearly-saturated soils was introduced. And then, a consolidation equation was derived. Subsequently, supposing soils were under tangential loading, the expressions of pore water pressure were presented. The analytic solution of pore water pressure was attempted to be validated by the measured values in a real embankment. The parameters in the expressions of pore water pressure were gotten by the method of trial. The result shows that the consolidation model is rational and the analytic solution of pore water pressure is correct. The following conclusions can be made: 1) the influence of bubbles on the compressibility of pore fluid should be considered; 2) the effective stress would be influenced by bubbles, and the consolidation would depend on the compressibility of soil skeleton: the softer the soils are, the more distinct the influence of bubbles is; for normal clay, the influence of bubbles on the effective stress may be commonly neglected.

Evaluation of Effective Stresses and State Surfaces for Unsaturated Clayey Silt

Terzaghi had established soil mechanics as an academic scholarship due to the discovery of the principal of effective stress for saturated soils when he considered the consolidation theory of saturated clay. The reason of the existence of the effective stress is that soil particles and water are composited by incompressible solid and liquid. Although air is very compressible fluid, the principle of effective stress is also used in unsaturated soils in the resent developed numerical analyses. Schrefler＇s equation is most frequently used, but the effective stress is not verified by the experimental results. In this study, the equations for unsaturated soils proposed by Schrefler, Aitchison, Khalili and Khabbaz and Kohgo are compared with using the results of suction controlled consolidometer tests. As a result, the effective stress for unsaturated soils calculated by Schrefler＇s equation was average of them.