Effects of dry density and thickness of sandy soil on impact response due to rockfall

Sand cushions against impact force are widely used for rockfall prevention covers. The objective of this paper is to investigate the effects of the dry density and thickness of a sand cushion on an impact response due to a falling weight likened to a rockfall. A series of laboratory experiments for a decomposed granite soil was executed in the combination of the mass and drop height of the weight. As a result, the impact pressure applied to the soil surface increases with the dry density, but it does not depend on the thickness of the soil. The earth pressure at the bottom of the mold increases with the dry density, and it decreases with the thickness of the soil. Therefore, the transmissibility of the impact pressure decreases rapidly with the thickness of the soil.     

有限元法在三轴转台机械系统设计中的应用

本文探讨了三轴转台机械系统的设计与计算问题，以惯性三轴测试转台和三轴模拟台为例，确定了多种运转状态下的有限元法计算模型，并对其进行了静、动态特性计算，比较分析了计算结果，为合理结构的设计提供了重要数据，说明了在三轴转台机械系统设计中有限元法的重要性     

粉喷桩单桩承载力确定方法的比较

粉喷桩在高速公路软土地基处理中得到了广泛的应用,但其承载力的合理确定是工程实际中关心的一个重要问题。通过对工程中常用的几种粉喷桩单桩承载力确定方法的比较,分析了各自存在的问题和适用条件,提出了在实际工程应用中确定水泥搅拌桩单桩承载力的选用建议。     

Asymptotic Axially Symmetric Deformations for Perfectly Elastic Neo-Hookean and Mooney Materials

For axially symmetric deformations of the perfectly elastic neo-Hookean and Mooney materials, formal series solutions are determined in terms of expansions in appropriate powers of 1/R, where R is the cylindrical polar coordinate for the material coordinates. Remarkably, for both the neo-Hookean and Mooney materials, the first three terms of such expansions can be completely determined analytically in terms of elementary integrals. From the incompressibility condition and the equilibrium equations, the six unknown deformation functions, appearing in the first three terms can be reduced to five formal integrations involving in total seven arbitrary constants A, B, C, D, E, H and k ², and a further five integration constants, making a total of 12 integration constants for the deformation field. The solutions obtained for the neo-Hookean material are applied to the problem of the axial compression of a cylindrical rubber tube which has bonded metal end-plates. The solution so determined is approximate in two senses; namely as an approximate solution of the governing equations and for which the stress free and displacement boundary conditions are satisfied in an average manner only. The resulting load-deflection relation is shown graphically. The solution so determined, although approximate, attempts to solve a problem not previously tackled in the literature.      

Anisotropic parameter identification using inhomogeneous tensile test

In this contribution, an inverse identification strategy of constitutive laws for elastoplastic behaviour is presented. The proposed inverse algorithm is composed on an appropriate finite element calculation combined with an optimisation procedure. It is applied to identify material anisotropic coefficients using a set up of easy performed laboratory tests. The used experimental data are the plane tensile test and the off axes tensile tests. The identified behaviour models are mainly based on Hill's quadratic yield criterion. Two cases of this yield criterion have been considered: the transverse isotropic and the orthotropic one under an associated and non-associated flow rule assumptions for each case. The yield surface has been assumed to expand isotropically (isotropic strain hardening law) as a function of the plastic work.In order to better describe anisotropic plastic properties of the studied materials, a recently planar anisotropic yield function is used. It is a non-quadratic yield criterion which takes account of anisotropic yield stresses as well as anisotropic strain ratios. It is subsequently shown that the agreement between inverse identification results and experimental measurements were improved.We prove also that the presented strategy is a good alternative to the simplified homogeneous tests assumption, especially for the plane tensile test.     

The Experimental Approach to Effective Stress Law of Coal Mass by Effect of Methane

Effective stress law of all kinds of coal samples, including steam coal, fat coal, corking coal, thin coal and anthracite, under pore pressure of gas, is experimentally studied using a newly developed test machine. These samples are taken from Coal Mines in Wuda, Hebi, Yanzhou, Yangquan, Qingshui, and Gujiao in China. The experiment results show that, under pore pressure of gas, the tested coal samples comply with Biots effective stress law, where the Biots coefficient is not a constant, and is bilinear function of volumetric stress () and pore pressure (p), that is, We define four areas according to the numerical feature of , that is, functionless area of pore pressure, normal function area, fracturing function area, and quasi-soil function area. The effective stress law of coal mass introduced by this paper is a constitutive equation in the study of coupled solid and fluid. This has significance in the drainage and outburst of methane in coal seam.     

Interference effects of two and three super-tall buildings under wind action

Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors.     

平面八节点四边形理性元

推导平面八节点四边形理性有限元列式，采用具有直到四次多项式的平面问题的微分方程的解作为插值函数，算例结果表明平面八节点四边形理性有限元的有效性。     

常速度拉伸实验惯性效应的实验研究

本文统计了１５０根Ａ３低碳钢比例拉伸试件的断口位置，并测定了常速度拉伸（４００ｍｍ／ｍｉｎ，０．５ｍｍ／ｍｉｎ）时应变随时间和沿杆长的分布以及应力应变关系；发现７２％试件的断口靠近不动端内。同一时刻在设定速度为４００ｍｍ／ｍｉｎ时杆中最大工程应变差１８％．     

拉压性能不同材料全量型本构关系及厚壁筒的应力分析

将经典全量理论作了推广，考虑了应力状态及塑性体积变形对拉压性能不同材料的塑性行为的影响。应用该本构模型分别计算了厚壁筒在内压和外压作用下的应力分布。给出了径向应力、环向应力和轴向应力沿壁厚的分布图。将本文的计算解与拉压性能相同(不考虑体积变形、强化曲线唯一)的幂函数强化材料的厚壁筒的理论解进行了比较。结果表明，材料的拉压性能不同对厚壁筒的环向应力和轴向应力影响较大。因此，对于拉压性能不同材料，考虑到其对应力状态及塑性体积变形敏感时，是不能将其简化成拉压性能相同、体积不可压缩、强化曲线唯一的理想材料。