岩土破损力学:结构块破损机制与二元介质模型

沈珠江等在总结岩土材料的基本特性、分析理论和研究方法的基础上,提出了岩土破损力学理论框架和二元介质模型概念。基于岩土二元介质模型思想,近年来在试验、理论和数值模拟方面对结构性岩土材料进行了详细研究。通过对棒状和棱柱状结构块试件的平面试验,探讨了结构性岩土材料的破损机制,并发现了在受荷过程中结构块逐渐破损并转化为软弱带二者共同抵抗外部作用,即验证了二元介质模型对结构性岩土材料力学抽象的正确性;扩展了岩土二元介质模型对岩土材料的脆性变化进行了模拟,并与结构性土和砂岩的三轴试验结果进行了验证;基于二元介质模型概念,发展了一种模拟岩土材料破损过程的细观数值方法,同时提出了适用于结构性岩土材料的强度准则。     

模糊数学在数字测井解释岩石强度中的应用

目前岩石相对硬度分六个等级,在实际工作中,可不考虑某一岩石的抗压强度的准确性,只需求出它隶属于某一级硬度的可靠程度即可,为此提出模糊模式识别方法解决这类问题:首先确定与岩石抗压强度相关的3个数字测井参数——强度指数、杨氏模量、密度参与计算,然后分配相应权重,构建与硬度级别相对应的6个模糊子集,最后建立判别岩石硬度分级的6个隶属函数作为模糊模式识别岩石硬度等级。判别原则:将任一深度的强度指数、杨氏模量、密度3个数据加权求和,将其值作为判别对象依次代入6个模糊模式得到6个计算值,按照最大隶属原则,确定其相对的硬度级别,该值越接近1,则其隶属于那个硬度级别的程度就越大。     

A study on one‐dimensional consolidation of layered structured soils

The governing equations for one‐dimensional consolidation of layered structured soils under time‐dependent loading are established. Using simplified k‐σ′ and m_v‐σ′ models, n‐layered structured soils are transformed into (n + 1) or (n + 2)‐layered soils in which the thickness of upper and lower layers are gradually changing. The approximate solutions for the governing equations are then obtained under two types of boundary conditions, and the computer program is developed. Based on the solutions and computer program, the consolidation behavior of layered structured soils with soft interlayer is studied. It is shown that the permeability and compressibility of the soft interlayer have the greatest influences on the rate of settlement and rate of the dissipation of excess pore water pressure. Copyright © 2015 John Wiley & Sons, Ltd.     

An anisotropic strength criterion for jointed rock masses and its application in wellbore stability analyses

In this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd.     

Population balance in confined comminution using a physically based probabilistic approach for polydisperse granular materials

A novel, simplified approach is presented in order to compute variations of grading in granular assemblies during confined comminution under quasi‐static compression. The method is based on a population balance equation and requires a breakage probability, considered here as a probabilistic phenomenon that takes into account the particle strength and the loading condition of individual grains. Under basic assumptions, a simple breakage probability can be defined in order to get a valuable result for engineering applications and powder technology. The size effect in the strength of individual particles is introduced according to Weibull's theory. The particle loading and the cushioning effect in the granular packing are accounted for by considering the orientations of the contact forces obtained from 3D discrete element method simulations of highly polydisperse materials. The method proposed could have a value for engineering purposes in powder technology and geomechanics and gives a general framework for further research developments based on population balance. Copyright © 2016 John Wiley & Sons, Ltd.     

Stability analysis of membrane‐reinforced curved earth retaining walls,using a multiphase approach

The stability analysis of curved earth retaining walls, stabilized by reinforcing membranes, is investigated by means of a multiphase model developed in the framework of the yield design approach. This model is an extension of that previously developed for soils reinforced by linear inclusions. It combines the advantage of a homogenization approach in terms of improved computational efficiency, with its capability to account for a specific soil–reinforcement failure condition, in a rational and systematic way. Application of this model is performed on the illustrative example of a cylindrical‐reinforced retaining wall by means of the kinematic approach of yield design, which provides upper bound estimates for the retaining wall stability factor. Nondimensional charts are finally presented assessing the influence of relevant parameters such as the curvature of the wall, the length of the reinforcing membranes or the reinforcement pull‐out resistance. Copyright © 2009 John Wiley & Sons, Ltd.     

白城市水稻种植区土壤的地球化学特征与水稻产量的相关性研究

吉林省白城市水稻种植区土壤的地球化学特征研究表明，土壤中的SiO2,TiO2,Al2O3,FeO,MnO和P2O5等主要元素的含量与水稻产量具有正相关性，而CaO和MgO等主要元素的含量与水稻产量呈负相关性。土壤中的稀土元素含量和水稻产量呈正相关性。     

大别山超高压榴辉岩流变强度——来自高温高压实验的证据

利用Griggs型 5GPa高压仪器 ,在柯石英稳定域围压条件下 ( >3GPa)完成大别山超高压榴辉岩流变学实验 ,建立了榴辉岩流变状态本构方程 (流动律 ) : ε=Aexp( -Q/RT)σn ,应力指数 (n)为 3 .4 ,活化能 (Q)为 4 80kJ/mol,结构常数 (A)为 10 3.3.实验结果表明 :( 1)作为两相矿物组成的榴辉岩 ,其流变学强度在很大程度上取决于强相矿物 (石榴石 )和弱相矿物 (绿辉石 )含量比例 ;( 2 )天然榴辉岩塑性变形机制是以位错蠕变为主 ;( 3 )根据实验成果比较榴辉岩和上地幔方辉橄榄岩流变学强度相当 ,两者耦合在大陆深俯冲 10 0km左右深度发生拆沉作用可能性很小 ,与上地幔上隆 (upwelling)作用有关的造山期后伸展作用对超高压岩石折返更具有重要意义 .     

Runoff‐induced sediment yield over dune slopes in the Negev Desert. 1: Quantity and variability

Although extensive data exist on runoff erosion and rates for non‐sandy hillslopes, data for arid dune slopes are scarce, owing to the widespread perception that the high infiltrability of sand will reduce runoff. However, runoff is generated on sandy dunes in the Hallamish dune field, western Negev Desert, Israel (P ≈ 95 mm) due to the presence of a thin (usually 1–3 mm) microbiotic crust. The runoff in turn produces erosion. Sediment yield was measured on ten plots (140–1640 m²) on the north‐ and south‐facing slopes of longitudinal dunes. Two plots facing north and two facing south were subdivided into three subplots. The subplots represented the crest of the active dune devoid of crust, the extensively crusted footslope of the dune, and the midslope section characterized by a patchy crust. The remaining plots extended the full length of the dune slope. No runoff and consequently no water‐eroded sediments were obtained from the crest subplots devoid of crust. However, runoff and sediment were obtained from the mid‐ and footslope crusted subplots. Sediment yield from the footslope subplots was much higher than from the midslopes, despite the higher sediment concentration that characterized the midslope subplots. The mean annual sediment yield at the Hallamish dune field was 432 g per metre width and was associated with high average annual concentrations of 32 g l^?1. The data indicate that owing to the presence of a thin microbiotic crust, runoff and water erosion may occur even within arid sandy dune fields. Copyright © 2001 John Wiley & Sons, Ltd.     

Isoductile strengths and strength reduction factors of elasto‐plastic SDOF systems subjected to simple waveforms

The inelastic response of elasto‐plastic SDOF oscillators subjected to 24 simple waveforms was studied. The waveforms contain linear, quadratic, sinusoidal, and triangular acceleration components that repeat for not more than several cycles. Similarities and differences in oscillator response characteristics are presented, organized by a characteristic period. The strengths and corresponding strength reduction factors required for constant ductility responses are discussed. Response data are compared with expectations based on the concepts of equal energy, equal displacement, and preservation of force. Limitations on the applicability of the equal energy concept are identified. Copyright © 2001 John Wiley & Sons, Ltd.