NONLINEAR UNIFIED STRENGTH MODEL OF GEOMATERIALS

将材料的破坏归结为剪切破坏,每种材料对应于特定的剪切滑动面,抗剪强度为滑动面上正应力的函数,基于不同材料的强度特性将一系列的剪切滑动面统一起来,建立了岩土材料的非线性统一强度模型.非线性统一强度模型的滑动面为β应力空间内的等倾面,在β应力空间内的强度面为圆锥面;在普通应力空间内的强度面为一系列连续光滑、外凸的锥面,在偏平面上强度曲线涵盖了从下限Matsuoka-Nakai曲线到上限Drucker-Prager圆之间的所有区域,子午面上强度线为直线.非线性统一强度模型只有3个材料参数,参数都具有明确的物理意义,通过与国内外学者已取得的岩土类材料真三轴强度试验结果的比较,表明模型可适用于多种类型的材料,并合理描述其非线性强度特性.     

Prediction of the effective elastic moduli of materials with irregularly-shaped pores based on the pore projected areas

Statistical modeling is used to correlate geometric parameters of pores with their contributions to the overall Young’s moduli of linearly elastic solids. The statistical model is based on individual pore contribution parameters evaluated by finite element simulations for a small pore subset selected using the design of experiments approach, so there is no need to solve the elasticity problem for all pores in the material. A polynomial relating pore geometric parameters to the contribution parameters is then fitted to the results of the simulations. We found a good correlation between normalized projected areas of the pores on three coordinate planes and their contributions to the corresponding effective Young’s moduli. The model is applied and validated for two large sets of pore geometries obtained by X-ray microcomputed tomography of a carbon/carbon and a 3D woven carbon/epoxy composite specimens.     

Green’s functions for multi-phase isotropic laminated plates

This work develops a series of Green’s functions for multi-phase Kirchhoff isotropic laminated plates. First, we derive the Green’s functions for a composite laminated plate composed of two bonded dissimilar isotropic laminated semi-infinite plates. Second, the obtained results for bimaterials are judiciously applied to obtain the Green’s function solution for a circular elastic inclusion embedded in an infinite isotropic laminated plate. Third, Green’s functions for a composite space composed of an arbitrary number of wedges of different isotropic laminated plates are derived. Finally, we derive Green’s functions for a laminated plate with an elliptical and a parabolic boundary, respectively.     

Rayleigh waves in an isotropic elastic half-space coated by a thin isotropic elastic layer with smooth contact

In the present paper, we are interested in the propagation of Rayleigh waves in an isotropic elastic half-space coated with a thin isotropic elastic layer. The contact between the layer and the half space is assumed to be smooth. The main purpose of the paper is to establish an approximate secular equation of the wave. By using the effective boundary condition method, an approximate, yet highly accurate secular equation of fourth-order in terms of the dimensionless thickness of the layer is derived. From the secular equation obtained, an approximate formula of third-order for the velocity of Rayleigh waves is established. The approximate secular equation and the formula for the velocity obtained in this paper are potentially useful in many practical applications.     

Trapped modes due to narrow cracks in thin simply-supported elastic plates

We consider an elastic plate of infinite length and constant width supported simply along its two parallel edges and having a finite length crack along its centreline. In particular, we look for and find trapped modes (localised oscillations) in the presence of the crack. An explicit wide-spacing approximation based on the Wiener–Hopf technique applied to incident wave scattering by semi-infinite cracks is complemented by an exact formulation of the problem in the form of integro-differential equations. An application of a Galerkin method for the numerical calculation of results from the latter method leads to a novel explicit ‘small-spacing’ approximation. In combination with the wide-spacing results this is shown to provide accurate results for all lengths of crack.     

表层嵌贴CFRP板条-混凝土界面粘结应力模型的试验与理论研究

为研究寒冷地区饱和砂岩的冻融损伤机理,采用DMA450伺服压机,在静载100N、动载80N、波动频率5～200Hz、温度-40～40℃的条件下,进行了饱和砂岩在不同频率正弦波单轴载荷作用下杨氏模量随温度变化的实验研究,获得滞(粘)弹性的弛豫衰减,以及有衰减引起的砂岩样品微结构变化情况。结果表明：饱和砂岩的杨氏模量和弹性波速度随温度升高而降低,随频率提高而增大; -40～20℃温度范围是冻融损伤最严重的区域。同时,在三种低频条件下(1.6Hz、2.8Hz和5.0Hz)用共振法在0℃获得相变衰减峰,反映了饱和砂岩的冻胀融缩效应,其产生的应力导致了饱和砂岩的损伤。从机理来看,前者是微观缺陷的演变,长期积累会导致破坏;后者是一种物理风化作用造成的宏观损伤。本文结果可为研究寒冷地区饱和岩石冻融损伤的机理及规律提供一定的参考。     

Novel procedure for complete in-plane composite characterization using a single T-shaped specimen

This paper deals with the direct identification of the in-plane elastic properties of orthotropic composite plates from heterogeneous strain fields. The shape of the tested specimen is that of a T subjected to a complex stress state. As a result, the entire set of unknown parameters is directly involved in the strain and displacement responses of the sample. No exact analytical solution is available for such a geometry, and a specific strategy is used to identify the different stiffness components from the whole-field displacements measured over the tested specimen with a suitable optical method. The paper focuses mainly on the experimental aspects of the procedure, and an example of mechanical characterization of a fabric-reinforced composite plate is given.     

样条子域法在桥头搭板内力分析中的应用

对具有一边简支支承的部分悬空，部分支承在温克勒弹怀地基上的板作为整体式桥头搭板的力学计算模型，采用样条子域法建立了桥头搭板内力计算的基本公式，并编制了计算程序。     

构造裂隙对巷道稳定性影响的评价方法

地下岩石工程中，构造裂隙分布状况与发育程度对巷道的稳定性影响很大。结合潞安矿区3个矿井的构造理解隙实测结果，提出裂隙因素巷道稳定性的评价方法，为裂隙岩体巷道稳定性的定量化评价奠定了基础。     

软岩隧道建造过程三维有限元仿真分析

根据地下隧道施工不同的开挖程序和锚固施工方法，运用三维有限元数值分析方法模拟地下隧道施工建造过程，以期寻找有利于围岩稳定的开挖和支护方式。依据岩体破坏特性和弹塑性力学应变能原理，给出了隧道开挖的优化指标和方法，并以此得到较优的施工方案。