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1.
Aboozar Garavand Yuri Pavlovich Stefanov Yuri Leonidovich Rebetsky Rustam Alfredovich Bakeev Artem Veniaminovich Myasnikov 《国际地质力学数值与分析法杂志》2020,44(6):823-850
In many wellbore stability analyses, the ability to forecast both the occurrence and extent of plastic deformation and failure hinges upon a fundamental understanding of deformation mode and failure mechanism in the reservoir rock. This study focuses on analyzing plastic zones, localized deformations, and failures around a borehole drilled overbalanced or underbalanced through a highly porous rock formation. Based on several laboratory experiments, porous rocks are prone to deform under both shear-induced dilation and shear-enhanced compaction mechanisms depending on the stress state. The shapes of the deformation and failure patterns around the borehole are shown, depending on the initial stress state and the local stress paths. The inquiry of the local stress paths in the near-wellbore zone facilitates the understanding of the reasons for different types of failure mechanisms, including the mixed-mode and the plastic deformation structures. The modification of the 2D plane strain condition by imitating third stress in the numerical scheme helps us bring the stress paths closer to the real state of loading conditions. Our modeling reveals that the transition from isotropic to anisotropic stress state is accompanied by an increase in the deviatoric part of effective shear tensor that leads to the development of inelastic deformation, degradation, and subsequent rock failure. Particular interest is devoted to the modeling of strain localization especially in compaction mode around a wellbore and computing the amount of stress concentration at the tips of dog-eared breakouts. Stress concentration can result in a change in irreversible deformation mode from dilatancy to compaction, elucidating the formation of the shear-enhanced compaction phenomenon at the failure tips in the direction of the minimum horizontal stress. 相似文献
2.
自然界的土体通常具有各向异性的特点,而传统的破坏准则大多只适用于各向同性的土体。结合应力张量和反映材料各向异性状态的组构张量,定义了修正偏应力及其不变量,提出了适用于各向异性土体材料的破坏准则。给出了共轴条件下正交各向异性和横向各向异性材料在一般应力空间的破坏曲线以及不同应力区中主应力系数b与摩擦角的关系曲线,并分析了它们的特性以及与各向同性材料相应曲线的区别。通过与真三轴试验数据的比较,表明该准则能很好地描述各向异性土体材料的强度特点。 相似文献
3.
岩土工程中常用的屈服准则多以压缩剪切为其破坏机制,然而硬脆性岩体的脆性破坏包括拉伸破坏、张拉剪切破坏和压缩剪切破坏3类,且随着岩体工程向深部发展,张拉剪切破坏成为了洞壁围岩的主要破坏机制。针对此问题,开展了硬脆性大理岩的室内拉剪试验,分析了大理岩拉剪破坏特征,并结合压剪试验结果,建立了考虑张拉剪切破坏机制和应力状态影响的Mohr-Coulomb准则。研究结果表明,硬脆性大理岩破裂面在拉剪应力状态和低正应力压剪应力状态下均具有张拉剪切破坏特征,高正应力压剪应力状态下则只具有压缩剪切滑移特征;拉剪应力状态下,大理岩破裂面张拉破坏特征明显,无明显剪切痕迹,剪切力固定时,剪切位移随着轴向拉力增加而增加;凝聚力和内摩擦角受应力状态影响,凝聚力随正应力增大先减小后增大,内摩擦角则随正应力的增大而减小;凝聚力、内摩擦角随正应力的变化趋势可分为4段,拉剪段、低压应力段、中压应力段和高压应力段,每段的凝聚力、内摩擦角与正应力皆可认为是线性关系,靠近抗拉强度处,内摩擦角趋近90°,凝聚力趋于无穷大;考虑张拉剪切破坏机制和应力状态影响的Mohr-Coulomb准则曲线分为两部分,可采用二次抛物线进行拟合的拉剪段和考虑凝聚力、内摩擦角随正应力演化的压剪段,由此建立的Mohr-Coulomb准则更全面、精度也更高。 相似文献
4.
岩土材料的强度往往表现出很强的各向异性,而已有的各向同性强度准则不能够描述这一特性。提出一个岩土材料的各向异性强度准则。为了描述材料的各向异性,引入了一个由应力张量和组构张量的联合不变量表达的各向异性参数。该参数可以描述加载方向和材料组构方向的夹角。强度准则是基于材料在子午面和偏平面上的破坏特性而建立的,这为描述广义的材料强度各向异性提供了方便。与原各向同性强度准则相比,各向异性强度准则只引入了两个新的模型参数,而且所有的模型参数都可以通过常规的室内试验结果确定。该准则的预测结果与砂土、黏土、天然黏土和岩石的试验结果比较表明,它能够很好地描述岩土材料强度的各向异性 相似文献
5.
Hua Jiang 《国际地质力学数值与分析法杂志》2015,39(13):1471-1482
This study presents two three‐parameter failure criteria for cohesive‐frictional materials based on the Mohr–Coulomb failure function. One proposed failure criterion can be linked to Mogi's empirical formula and incorporates the well‐known Von‐Mises, Drucker–Prager, and Linear Mogi criteria as special cases. Another one with smooth and convex cross sections contains a general Lode dependence in the deviatoric plane and includes the Matsuoka–Nakai and Lade–Duncan Lode dependences as special cases. The effect of the intermediate principal stress on the strength of the material can be taken into account in both criteria. The proposed criteria are numerically calibrated against polyaxial data sets of many different types of rocks and concrete. The comparison results show that the performance of the proposed criteria is excellent, and the failure criterion with a general Lode dependence performs better than the other one for concrete. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
在中国西北,建设了许多灌溉水渠,由于水渠的灌溉引起了许多滑坡破坏,并带来了人员伤亡和财产损失。以高楼村水渠灌溉引起的黄土滑坡破坏为例,提出了滑坡破环渐进过程为：水的入渗在滑体中产生一定深度的水压力,引起黄土黏聚力和摩擦角下降,使滑坡体在一定深度产生剪破坏,紧接着滑体后缘产生拉剪破坏,致使后缘黄土处于破坏后区状态,并产生不平衡剪应力。该不平衡剪应力驱动滑体向前移动,直至滑面只有一点处于临界状态,随即整个滑坡发生破坏,并伴随着滑体解体,产生泥流。这种破坏过程可以概括为：滑坡先产生剪破坏,紧接着后缘产生拉剪破坏,当破坏后区产生的驱动剪应力大于滑体的摩阻力,会推动滑坡向前移动,直至滑坡发生完全破坏。以理论和试验论证了这种破坏机制的正确性,并验证了一种新剪应力本构模型的合理性。 相似文献
7.
岩土材料剪切破坏点安全系数的研究 总被引：1，自引：0，他引：1
剪切破坏是岩土材料失效的一种主要的形式。针对这种形式强度安全考虑的点安全系数可以考察结构中各部分的安全情况,是结构安全分析的一种重要参考,尤其在由关键点控制的结构中显得尤为重要。摩尔库伦剪切破坏准则在岩土材料研究中被广泛应用,将基于该准则的点安全系数定义在三维广义Mohr空间中推广,得到了适用于不同剪切破坏失效准则的点安全系数定义,同时,在三维广义Mohr空间中推导,得到了岩土材料剪切破坏最小点安全系数的求解方法;最危险截面上偏应力和剪应力的关系,该最危险截面与最小点安全系数对应;以及在一定整体安全度下的失效条件。应用该定义及方法,可以研究判断不同岩土材料剪切破坏的安全情况,从而提高工程建设质量。 相似文献
8.
基于层面法向局部坐标系中的横观各向同性弹性本构模型,根据层面产状方位角,推导出整体坐标系中弹性应力的转换方法。针对层状岩体的各向异性特征,将岩体的破坏模式细分为5种,分别对每一种破坏模式建立各自的判别函数和屈服准则,根据塑性流动正交法则推导出相应的应力修正迭代计算方法。通过单轴、三轴压缩数值试验,对层状岩体的强度和变形性质进行研究,分析层面倾角和围压对层状岩体力学行为的影响。将所建模型与FLAC3D自带的横观各向同性弹性模型以及遍布节理模型进行对比,验证模型的正确性及精度。同时,将模型应用于三向等压理想圆形隧洞的开挖计算中,分析层状岩体破坏方式受层面方位角影响的变化规律,分析结果表明层面对围岩破坏模式和塑性区扩展方向起到了控制作用。 相似文献
9.
岩石变形破坏的熵突变过程与破坏判据 总被引：2，自引：0，他引：2
在岩石的变形破坏过程中,当进入不稳定的破裂发展阶段之后,系统不断调整结构抵抗外力的扰动,裂纹向局域集中的有序方向发展,应变能不断耗散,并以应变能的耗散为媒介,使系统与外扰动所追加的负熵流产生能量流通,也使系统熵值和系统的维数逐次降低,这一阶段岩石系统远离平衡态,岩石的破坏是系统熵的突变过程。基于这一认识,并在验证应变能分布与结构块度分布模式的一致性的基础上,推导出包含了结构因素和能量分布的熵表达式;对熵表达式进行平衡分析获得局部突变的分岔集,得到了岩石局部破坏的熵折迭突变破坏准则;同时,探讨了熵表达式所表征的结构有序度的尖点突变性,解出岩石系统的分岔集,这个分岔集就是岩石系统熵突变的整体破坏准则。 相似文献
10.
边坡的渐进破坏特征一直以来是边坡计算仿真中的一个难点。实际边坡的破坏很少是一个整体达到极限状态,突然滑动的过程,往往是逐步发展由局部破坏到最终整体失稳,即临界状态小扰动导致的链式多米洛骨牌式失稳。利用颗粒流软件,设计了0.1 m粒径高10 m土坡的数值模型,粒间黏聚力为36 kPa,摩擦系数为0.36。初始模型在重力作用下不会发生破坏,通过单独折减粒间黏聚力到18 kPa使得边坡破坏,监测竖向颗粒组group的变化获取每20 000个时间步的边坡破坏形态,实现200 000个时间步内边坡的渐进破坏过程。边坡总是从局部开始破坏,坡体物质的运移造成次一级破坏,形成最终的近似弧形的滑动面,说明滑体不是整体下滑,不是刚体,不是整体达到极限状态;坡体内应力的变化也不是单调的,有涨有落,均区别于当前极限平衡法中有限条块的刚体假设;滑动面上同时达到极限状态假设,问题本身是静不定的,通过给出条间力的传递方式使之静定可解;整体分析不能考虑破坏的局部化和渐进特征。这说明边坡计算方法的未来在于能反映动力问题和材料破坏特征的离散元方法。 相似文献
11.
通过对乌努格吐山铜钼矿露天采场边坡自然背景条件、岩体结构类型、岩石力学参数、工程地质岩组特征、结构面特征、边坡工程地质分区、边坡稳定性评价、边坡破坏类型及规模等论述,阐明了露天采场边坡工程地质特征.边坡稳定性计算结果表明,A区A-A'剖面、C区E-E'剖面稳定性计算结果不能满足安全系数的要求,其他区边坡总体稳定性较好.露天采场现处于生产建设阶段,边坡正处于剥离形成过程中,边坡几何形态保存较完整,仅局部出现小型崩塌、垮塌、粒状解体、楔形破坏、地裂缝和大气降水冲刷等.尚未出现较大规模破坏,现状边坡总体稳定,基本可代表未来边坡的破坏类型和稳定状态. 相似文献
12.
The influence of the plastic potential on plane strain failure 总被引：1，自引：0，他引：1
The influence of the shape of the plastic potential in the deviatoric plane on plane strain collapse is investigated. The most commonly employed elastic‐perfect plastic models are considered, which adopt well‐known failure criteria for defining the yield and plastic potential surfaces, namely the von Mises, the Drucker–Prager, the Tresca, the Mohr–Coulomb and the Matsuoka–Nakai criteria. Finally, the conclusions are also extended to strain hardening/softening models. For simple constitutive models based on perfect plasticity, it is shown that the value of the Lode's angle at plastic collapse in plane strain conditions strongly depends on the specific failure surface adopted for reproducing the plastic potential surface. If the value of the Lode's angle at yield coincides with the failure value prescribed by the plastic potential, the stress–strain curves exhibit the typical perfect plastic behaviour with yield coinciding with failure, otherwise the stress changes after yield and the stress‐strain curves resemble those of strain hardening/softening models. The infinite strength which is in some situations exhibited by the Drucker–Prager model in plane strain condition is investigated and explained, and it is shown that this can also affect strain hardening/softening models. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
13.
不同应力路径下土体的变形特性与破坏特性 总被引：13，自引：0，他引：13
在固结不排水加荷与卸荷两种情况下,基于土体常规的三轴压缩试验结果和真三轴平面应变试验结果,指出不同的应力路径下土体具有不同的变形特性和破坏特性,并且这些特性差异的根本原因在于不同的应力路径,有着其球应力p和广义剪应力q与球应力p的比值q/p的不同变化趋势。最后,依据Matsuoka-Nakai破坏准则和其相应的转化型式,进一步探讨了其破坏参数k2值的确定方法。试验检测的结果表明,Matsuoka-Nakai破坏准则能给出土体较为准确的破坏强度预测结果。 相似文献
14.
The study of rock pillar failure mechanisms is an issue that is faced routinely in mining and civil industries. In mining operation, the establishment of several mining levels is often necessary to ensure adequate production. This result in the formation of pillars that must be recovered under often high stress conditions at later stages of excavation. It is, therefore, beneficial to develop guidelines that can be used in the design of rock pillars. The aim of this paper is to delve into the mechanisms involved in pillar failure as well as to investigate the non-linear behavior of rock pillars. An extensive numerical analysis was carried out to study the pillar deformation and failure process under natural loading conditions. Effects of pillar geometry and pillar strength parameters on pillar behavior were investigated for hard rock material typical of Canadian mining conditions. Numerical data were compared against field data recorded in Canadian mines. A fairly good match was achieved between numerical and field data and the conducted analysis can be used as a qualitative guideline in the design of rock pillars in underground structures. 相似文献
15.
针对天津滨海地区围海造陆工程所形成的上软、下硬双层软黏土地基,利用室内载荷试验和数值模拟开展了双层软黏土地基的承载特性及破坏模式研究。研究表明：由于下层沉积土的补强效应,双层软黏土地基的P-S曲线会出现明显的凹凸转折点,其出现的位置与宽厚比密切相关,宽厚比越小,转折点出现的时间越靠后,下层沉积土的补强效果越不明显。数值结果表明：双层软黏土地基破坏模式随着上覆土厚度的变化相差不大,均为整体剪切破坏。随着载荷板宽度的增加,双层软黏土地基以冲剪破坏模式过渡为局部剪切破坏,当载荷板宽度大于3.0 m时,表现为整体剪切破坏。 相似文献
16.
17.
深部巷道围岩变形破坏机制分析 总被引：1，自引：0，他引：1
采用弹脆性本构模型以及滑移破坏理论,对深部围岩应力分布以及变形破坏机制进行分析。计算结果表明,开挖卸荷将引起剪应力的增长,滑移剪切变形的发展将围岩划分成具有一定尺度的块体（或条带）,它们之间的相互摩擦决定着残余强度的大小;在各向不均匀压缩的作用下,深部围岩能够产生区域拉伸破碎,使围岩开挖断面监测到的位移大大超出按连续介质理论计算得到的数值。采用考虑扩容的计算模型可以得到围岩产生区域拉伸破碎的条件,计算得到的该条件与岩体力学性质以及破碎尺度密切相关。 相似文献
18.
Jean‐Yves Delenne Moulay Saïd El Youssoufi Fabien Cherblanc Jean‐Claude Bnet 《国际地质力学数值与分析法杂志》2004,28(15):1577-1594
We investigate the stress–strain behaviour and failure of a cohesive granular material both by experiments and numerical simulations. The material is an assembly of aluminium rods glued together by means of an epoxy resin. The behaviour of cohesive bonds (force–displacement relationship, failure conditions) is characterized by performing simple loading tests (tension/compression, shear…) on a couple of rods. Then, this local behaviour is introduced in a numerical code based on a discrete element method in order to perform numerical compression tests on large samples. The validation of this approach was the main goal of the present investigation that is essentially achieved by a direct comparison between the numerical results and similar experimental tests. As a basic application, we derive the macroscopic cohesion and friction characteristics of random cohesive materials by systematic numerical simulations in a biaxial geometry. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
19.
Earthquake losses due to ground failure 总被引：2，自引：0，他引：2
Juliet F. Bird 《Engineering Geology》2004,75(2):147-179
Ground shaking is widely considered to be the primary cause of damage to structures, loss of life and injuries due to earthquakes. Nonetheless, there are numerous examples of earthquakes where the losses due to earthquake-induced ground failure have been significant. Whereas ground shaking causes structural and non-structural damage, with associated loss of function and income, ground failure is less likely to cause spectacular structural collapses, but is frequently the cause of major disruptions, particularly to lifelines, which can lead to prolonged loss of function and income, even for undamaged areas.Those involved in earthquake loss modelling are currently presented with three choices with respect to the incorporation of ground failure: they can choose to ignore it, assuming that any estimation of losses caused by shaking would effectively subsume the impact of these secondary hazards; they can include ground failure in a simple manner, using published approaches based upon qualitative data and a large degree of judgement; or, they can opt for a detailed site- or region-specific assessment of damage due to ground failure, with the associated time and expense.This paper presents a summary of the principal features of earthquake losses incurred in damaging earthquakes over the last 15 years. Survey data are impartially analysed, considering both ground failure and ground shaking as sources of damage, and their relative contribution to overall damage in each section of the regional infrastructure is presented. There are many other variables influencing these contributions, including the size of the earthquake, the economic status of the affected region, local geology and terrain and the building stock, which have been considered.The findings of the study are discussed from the point of view of loss modelling and which components of a model should merit the most time and resource allocation. The general assumption that ground shaking is the principal cause of damage and loss is strongly supported by the study. However, there are a number of scenarios identified where the failure to appropriately include the effects of ground failure would lead to unrealistic loss projections. Such scenarios include the assessment of building losses in small zones rather than on a regional basis, and the incorporation of lifeline damage or disruption and indirect losses into a model. 相似文献
20.
真三轴条件下Q2黄土的破坏模式与强度特性研究 总被引：3，自引：0，他引：3
基于西安理工大学自主研发的新型真三轴试验仪,对不同含水率Q2黄土在不同b值、不同固结围压条件下进行了真三轴试验研究,分析了真三轴试样破坏方式、中主应力对抗剪强度参数的影响以及π平面上的强度破坏面。结果表明,Q2黄土真三轴试样破坏方式主要有侧胀破坏、锥形破坏、梯形破坏、六边形破坏;不同b值应力路经条件下黏聚力与三轴压缩条件下黏聚力的比值在0.9～1.9之间,内摩擦角比值在0.7～1.5之间。土的结构性和土体破坏方式对π平面上的强度破坏面的形状影响较大,固结围压对π平面上的强度破坏面的大小影响较大;原状Q2黄土在π平面上的强度破坏面形状主要呈现梨形和轴对称六边形;随着结构性由强到弱,π平面上的强度破坏面形状由梨形向轴对称六边形变化。 相似文献