基于连续—非连续方法的地质体材料变形—拉裂过程模拟——以岩样紧凑拉伸试验为例   总被引：2，自引：2，他引：0  

王学滨  白雪元  祝铭泽 《地质力学学报》2018,24(3):332-340

地质体材料易发生拉裂,为了有效模拟地质体材料的变形-拉裂过程,自主研发了一种连续-非连续方法。该方法实质是拉格朗日元法与虚拟裂缝模型的耦合,既能较准确模拟应力应变场,又能较准确模拟连续介质向非连续介质转化的复杂过程。以岩样紧凑拉伸试验为例开展变形-拉裂过程研究,得到以下结果。紧凑拉伸岩样的变形-拉裂过程:在岩样的Ⅴ形缺口尖端附近出现最大主应力集中现象;节点发生分离,虚拟或真实裂缝扩展,最大主应力始终集中于虚拟裂缝的尖端位置;岩样被拉裂成两部分。最大不平衡力发生1次突增对应着1个节点的分离。在峰值之前,岩样的载荷-位移曲线表现出了硬化现象;随着岩样尺寸的增加,应力-应变曲线的峰值有所下降,这与Bazǎnt的尺度律相一致,且峰后应力-应变曲线的陡峭程度增大。目前针对紧凑拉伸试验的模拟结果是合理的,由此在一定程度上说明了提出的连续-非连续方法在连续介质向非连续介质转化模拟方面的突出能力。   相似文献   

Numerical modelling of desiccation cracking of clayey soil using a cohesive fracture method     

《Computers and Geotechnics》2017

This paper presents a numerical study on the desiccation cracking process of clayey soil. The initiation and propagation of cracks were investigated using finite element code, including the damage-elastic cohesive fracture law to describe the behaviour of cracks. The coupling between the hydraulic behaviour (moisture transfer in the soil matrix and in the cracks) and the mechanical behaviour (volume change of the soil matrix and development of cracks) were also considered. The results of a laboratory experiment performed on clay soil, taken from a literature review, were used to evaluate the numerical modelling. The results show that the code can reproduce the main trends observed in the experiment (e.g., shrinkage related to drying, crack development). In addition, the numerical simulation enables the identification of other phenomena, such as the evolution of suction and stress related to drying and the development of a single crack. These phenomena are difficult to observe experimentally.  相似文献   

双向压缩条件下闭合裂隙岩体断裂破坏机制及渗透压环境判定准则     

蒲成志  曹平  张春阳  付宗智 《岩土力学》2015,36(1):56-60

在研究双向压缩条件下压剪复合型裂纹应力分布特征及断裂破坏机制基础上,考虑渗透压对初始裂隙面上有效正应力的影响,提出高低渗透压环境的判定准则,并基于滑动裂纹模型理论及最大周向拉应力破坏准则,得到不同渗透压环境下初始裂隙尖端微裂纹起裂特征与规律。研究结果表明：压剪复合应力条件下,初始裂隙尖端发育微裂纹的最优倾角与裂隙面摩擦系数直接相关,随裂隙面摩擦系数的增大,最优初始裂隙倾角由45°起逐渐增大;低渗透压条件下,渗流场的存在使裂纹面摩擦系数发生弱化,进而使得最优初始裂隙倾角向45°靠近,而渗透压直接降低裂隙面上有效正应力且与裂隙倾角无关,其仅仅影响裂隙体材料的初裂强度;高渗透压条件下,初始裂隙面由压剪复合应力状态转化为拉剪复合应力状态,并在拉剪复合应力场作用下,尖端微裂纹起裂角随KI/KII的不断增大,由70.5°逐渐趋近于0°。  相似文献   

原油裂解过程中正构烷烃的组成变化特征及其地球化学意义          下载免费PDF全文

唐小强  黄光辉  张敏  韩金平  李碧 《地学前缘》2009,16(6):372

采用高温模拟技术,对原油样品进行模拟实验,并对其裂解过程中正构烷烃的组成和变化特征进行了地球化学研究。结果表明,原油大量裂解生成气态烃之前,原油中的高分子量正构烷烃已经开始裂解,以C1+5烃类裂解成C6～C14化合物为主。随成熟度的增加,C6～C14化合物进一步转化为C1～C5化合物,并伴随苯系物的产出,最终形成甲烷和裂解沥青。在正构烷烃的裂解过程中,苯及其同系物的丰度呈明显增加趋势,可以作为原油裂解程度的潜在判识标志。此外,利用同样的实验条件对正十六烷进行了对比模拟实验,其产物的组成和变化特征与原油中正构烷烃的基本相同。  相似文献   

重力坝坝后背管高烈度地震反应研究     

张伟  伍鹤皋 《世界地震工程》2008,24(4)

考虑管道外包混凝土在设计荷载下开裂的影响,采用振型分解反应谱法,研究了重力坝坝后背管在9度地震作用下的自振特性和承载性能规律。研究表明:管道外包混凝土开裂对结构的自振特性影响较小,而对管道钢材应力和管腰截面应力影响较大;高烈度地震作用使背管上弯段至斜直段顶部出现双向裂缝,不利于钢衬与外包混凝土联合承载,同时管坝接缝面和管腰截面呈现较大的拉剪应力状态,不利于管道和坝体的联合承载;坝段间、岸坡坝段与岩体间有可靠的相互约束作用时,横河向地震作用对整体结构的承载性能影响很小。  相似文献   

Kinetics of hydrocarbon generation for Well Yingnan 2 gas reservoir,Tarim Basin,CHina     

《中国科学D辑(英文版)》2008,(Z1)

Well Yingnan 2,an important exploratory well in the east of Tarim Basin,yields high commercial oil and gas flow in Jurassic.Natural gas components and carbon isotopic composition indicate that it belongs to sapropel type gas.Because this region presents many suits of hydrocarbon source rocks,there are some controversies that natural gases were generated from kerogen gas or crude oil cracking gas at present.By using the kinetics of hydrocarbon generation and carbon isotope,natural gas of Well Yingnan 2 is composed mainly of crude oil cracking gas,about 72%,it is generated from secondary kerogen gas of Cambrian-Lower Ordovician source rock and crude oil cracking gas of Mid-Upper Ordovician oil reservoir.The main oil and gas filling time is 65 Ma later in the Jurassic gas reservoir of Well Yingnan 2,so the gas reservoir belongs to late accumulation and continuous filling type.  相似文献   

Rainfall runoff and erosion in Napa Valley vineyards: effects of slope,cover and surface roughness     

M. C Battany  M. E Grismer 《水文研究》2000,14(7):1289-1304

The effects of slope, cover and surface roughness on rainfall runoff, infiltration and erosion were determined at two sites on a hillside vineyard in Napa County, California, using a portable rainfall simulator. Rainfall simulation experiments were carried out at two sites, with five replications of three slope treatments (5%, 10% and 15%) in a randomized block design at each site (0%bsol;64 m² plots). Prior to initiation of the rainfall simulations, detailed assessments, not considered in previous vineyard studies, of soil slope, cover and surface roughness were conducted. Significant correlations (at the 95% confidence level) between the physical characteristics of slope, cover and surface roughness, with total infiltration, runoff, sediment discharge and average sediment concentration were obtained. The extent of soil cracking, a physical characteristic not directly measured, also affected analysis of the rainfall–runoff–erosion process. Average cumulative runoff and cumulative sediment discharge from site A was 87% and 242% greater, respectively, than at site B. This difference was linked to the greater cover, extent of soil cracking and bulk density at site B than at site A. The extent of soil cover was the dominant factor limiting soil loss when soil cracking was not present. Field slopes within the range of 4–16%, although a statistically significant factor affecting soil losses, had only a minor impact on the amount of soil loss. The Horton infiltration equation fit field data better than the modified Philip's equation. Owing to the variability in the ‘treatment’ parameters affecting the rainfall–runoff–erosion process, use of ANOVA methods were found to be inappropriate; multiple‐factor regression analysis was more useful for identifying significant parameters. Overall, we obtained similar values for soil erosion parameters as those obtained from vineyard erosion studies in Europe. In addition, it appears that results from the small plot studies may be adequately scaled up one to two orders of magnitude in terms of land areas considered. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

A Modified Cyclic Cracking Model for RC Structural Walls Behaviour Under Dynamic Excitation     

Tsai-Fu?ChuangEmail author  Andrew?H.?C.?Chan  Les?A.?Clark 《Bulletin of Earthquake Engineering》2005,3(3):299-331

In this paper, a simple cyclic cracking model incorporating crack dilatancy effect is proposed to model the behaviour of reinforced concrete structures under earthquake-like dynamic loading. This model has been implemented into a FE programme [LUSAS (2004) Luscas User Manual (version 12.3), FEA Ltd., London, England] to simulate reversed and cyclic loading. A shaking table test performed in Switzerland at the Swiss Federal Institute of Technology at Zurich (ETHZ) has been chosen for comparison. The test performed on the shaking table simulated a wall of a 3-storey building. The natural frequency and the crack pattern have been calculated and show reasonable agreement with the experimental results  相似文献   

黏土失水开裂演化过程的影响试验     

谢建宝  姚亚辉  龚绪龙 《江苏地质》2016,40(2):346-351

裂隙性为黏土的主要特性之一。探讨黏土的开裂规律,对于分析地裂缝成因机理,开展预测研究具有重要的理论意义和工程价值。通过室内试验,研究了黏土干燥收缩过程中含水率的变化规律。分别制备不同厚度、宽度、含砂量的试样,获得不同条件下黏土失水过程含水率的变化规律。在试验所设定的条件下,土体开裂时的含水率很接近,平均约为33.48%;当样品宽度不变时,土层越厚,含水率变化速率越小;当样品厚度相同时,宽度不同,含水率变化速率几乎相同;当厚度、宽度都相同时,含水率变化速率随含砂量的增大而减小。对于同一样品,土体厚度越大,样品裂隙率越小;土体厚度相同时,样品的裂隙率随着样品宽度的增大先减小后增大,且样品的开裂周期与样品的裂隙率同步变化。  相似文献   

特低渗透砂岩储层微裂缝特征及微裂缝参数的定量研究——以鄂尔多斯盆地沿25区块、庄40区块为例   总被引：1，自引：0，他引：1  

王瑞飞  陈明强  孙卫 《矿物学报》2008,28(2):215-220

对鄂尔多斯盆地沿25区块、庄40区块长6油藏进行精细描述,指出微裂缝对提高储层的渗流能力,提高特低渗油藏开发水平具有十分重要的意义.阐述了特低渗透储层的岩块、显裂缝系统及其各自特征,指出显裂缝大致由三组裂缝组成.研究认为:岩块系统包括基质和微裂缝两部分,微裂缝一般长度小于200 μm,规模小;两区块特低渗储层微裂缝呈条带状展布,且呈平行或雁式排列,具有明显的方向性,条带性随着岩性的变化而变化;可将微裂缝划分为有效缝和无效缝,有效缝对渗流起作用,无效缝充填方解石,对渗流不起作用.微裂缝和基质的储、渗性能差别很大,沿25区块微裂缝的储集能力是基质的0.0377倍,渗流能力是基质的42倍;庄40区块微裂缝的储集能力是基质的0.0337倍,渗流能力是基质的78倍.  相似文献