A phenomenological constitutive model for rocks with shear failure mode     

G. L. Zhou  L. G. Tham  P. K. K. Lee  Y. Tsui 《国际地质力学数值与分析法杂志》2001,25(4):391-414

In this paper, a phenomenological constitutive model is proposed to simulate the stress–strain behaviours of intact rocks with shear failure mode. The model captures a wide range of behaviours of rock material such as elastic, plastic, strain softening, ‘Class II’, strain localization, elastic modulus degradation, etc. The sensitivity of the stress–strain relation on the parameters is also investigated. Typical results obtained by testing a number of granite and marble specimens are used to validate the proposed model. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Rheological Properties and Incipient Motion of Cohesive Sediment in the Haine Estuary of China     

白玉川  NG Chiu-on  沈涣庭  王尚毅 《中国海洋工程》2002,(4)

The Haihe cohesive sediment, which is typical in China, is studied systematically for its basic physical and incipient motion properties. Following the requirements of dredging works in the Haihe Estuary, cohesive sediment samples were taken from three locations. Laboratory experiments were conducted to delermine the rheological properties of these samples and to examine the incipient motion of the cohesive sediment. it is found that the cohesive sediment has an obvious yield stress τb, which increases with the mud density in a manner of an exponential function, and so does the viscosity parameter η. The cohesive sediment behaves like a Bingham fluid when its density is below 1. 38 - 1 .40 g/cm3 , and when denser than these values, it may become a power-law fluid. The incipient motion experiment also revealed that the incipient velocity of the cohesive sediment increases with the density in an exponential manner. Therefore, the incipient motion is primarily related to the density, which is different f  相似文献   

剪切带运动学：重点评述三斜模式和区分韧性滑动擦痕与拉伸线理的重要性     

林寿发  姜大志Paul F. Williams Shoufa LIN Dazhi JIANG Paul F WILLIAMS 《地质通报》2007,26(9):1139-1153

详细评述了剪切带运动学和内部几何学研究的新进展。剪切带内的递进变形一般为三斜对称,单斜剪切带(包括简单剪切带)是特例情形。理论模拟表明,如同许多天然剪切带中所见到的,在三斜剪切带中,拉伸线理的方位可从近水平到平行于倾向连续变化。过去一般将拉伸线理的方向当作剪切运动方向的做法是以简单剪切模式为基础的,不适合于一般剪切带。在三斜剪切带中,拉伸线理和剪切方向之间不存在简单关系。然而,C面上的韧性滑动擦痕平行于剪切方向发育,是剪切方向的可靠标志。因此,在剪切带运动学解释中区分韧性滑动擦痕与拉伸线理非常重要。  相似文献   

A Study on the Peak Strength of Brittle Rocks     

Z. H. Chen  L. G. Tham  M. R. Yeung  Y. Tsui  P. K. K. Lee 《Rock Mechanics and Rock Engineering》2002,35(4):255-270

Summary A study on the peak strength of brittle rock materials having random strength distributions was carried out using the re-normalization group theory approach. A major advantage of the approach is that it is scale invariant, and therefore, one can relate the micro-fractures with macro-fractures of rocks at the critical state. The stress transfer from the broken sub-sections to the unbroken sub-sections is defined by a conditional probability. The critical probability P ^* and the relation between the peak strength and the mean strength of the elements have been obtained theoretically. On the other hand, the whole process of rock brittle fracture has also been simulated numerically from micro-fracture to macro-fracture by using the Rock Failure Process Analysis (RFPA) code. The peak strengths obtained by the numerical model agree fairly well with those obtained by the re-normalisation group theory. Due to the stress transfer from the broken subsections to the unbroken subsections, the peak strength is considerably less than the mean strength of the elements. Received October 24, 2000; accepted February 26, 2002 Published online September 2, 2002  相似文献   

不同刚度约束对能量桩应力和位移的影响研究     

王成龙  刘汉龙  孔纲强  吴宏伟  李建斌 《岩土力学》2018,39(11):4261-4268

能量桩是一种在传递上部建筑荷载的同时获取地热能源的新技术,其实际工作过程中,热荷载会引起桩体的膨胀或收缩,而桩顶建筑和桩底持力层则会对桩体变形产生约束,进一步影响桩体的应力和位移,但是目前对该问题的研究却十分有限。基于模型试验和数值模拟方法,对桩顶和桩底不同约束条件下两种埋管形式（单U和W型）的桩体位移和热应力进行了分析,并进一步探讨了位移零点随桩顶和桩底约束条件的变化规律。研究结果表明,随着桩顶上部荷载约束刚度的增大,桩体位移零点上移,桩体热应力随着深度增大而减小;随着桩端土体约束刚度的增大,桩体位移零点下移,桩体热应力随着深度增大而增大;相较于无外荷载,工作荷载作用下位移零点上移。  相似文献   

膨胀土地基中隧道施工对群桩影响研究     

马少坤  WONG K S  吕虎  吴宏伟  赵乃峰 《岩土力学》2013,34(11):3055-3060

在膨胀土地基中进行隧道对群桩影响的三维离心模型试验研究,目标地层损失比为2%,着重研究引起的地基沉降槽、桩的附加沉降、附加弯矩、轴力的变化规律。试验得出：隧道开挖沉降槽空间效应明显;隧道开挖从-0.75D至1.25D时,桩附加沉降呈线性增长,隧道开挖至1.25D以后,桩依然沉降明显。前桩与后桩沉降值不同,桩帽会出现倾斜;前桩上部出现负附加弯矩而下部出现正附加弯矩,而后桩仅在下部出现正附加弯矩;前桩附加弯矩最大值出现在隧道轴线附近,且比后桩附加弯矩大得多;前桩附加轴力随着隧道的开挖而增加,且每步最大值在隧道轴线附近。后桩的轴力也随隧道的开挖而增加,但每步最大值出现在桩顶附近。  相似文献   

Improving hydrodynamic modeling of an estuary in a mixed tidal regime by grid refining and aligning     

G. M. Jahid Hasan  Dirk Sebastiaan van Maren  Hin Fatt Cheong 《Ocean Dynamics》2012,62(3):395-409

Water levels and flows in the Singapore coastal waters are driven by the complex interactions of the Indian and Pacific Ocean tides, seasonal monsoon-driven contributions and also forced by local winds. The Singapore Regional Model was developed to simulate hydrodynamics in the Strait of Singapore which produces representative sea level variation in this region. However, resolution and alignment of the grid system of the model with respect to depth contours in some of its subregions, i.e., the Johor Estuary area require further improvement. For this, the grid system of the model was modified and compared the simulated results with field measurements. The computed flow velocities agreed better with field observations when the grid resolution was increased. However, improving the alignment of the grid with the channel boundary (with a much lower increase in grid resolution) provided a substantially larger improvement of the model performance. The grid modification greatly influenced the computed salinity in the estuary, while water levels are slightly affected. Further analysis of model results showed a pronounced ebb tidal asymmetry generated by the O1–K1–M2 tidal constituents in the estuary.  相似文献   

Investigating landslide‐related cracks along the edge of two loess platforms in northwest China     

L. Xu  F. C. Dai  L. G. Tham  Y. F. Zhou  C. X. Wu 《地球表面变化过程与地形》2012,37(10):1023-1033

Cracks are widely developed along the edge of loess platforms in northwest China. Field surveys reveal that these cracks can be grouped into shallow and deeply penetrating ones. The former occur at a small distance from the platform edge, normally penetrate into the top unsaturated loess with the penetration depth being controlled by the joints in loess. The latter penetrate deeper into the saturated loess farther away from the platform edge. These cracks control the inflow and drainage of irrigation water. The shallow penetrating crack can fail as a slide or fall with a volume of up to hundreds of cubic meters. The deeply penetrating crack can fail as a flow‐like landslide with a volume of thousands of cubic meters or more. A full‐scale field test simulating irrigation on the platform surface was conducted. The two types of crack can be interconnected so that the water applied in the test finally flowed into the deep crack and was discharged from the platform. Analysis of soil stress states and the results of field test show that the deeply‐penetrating cracks could have both positive as well as negative effects on slope stability. On the one hand, water can flow more freely in the cracks, and the loess could be saturated and trigger a landslide. On the other hand, the water can drain more easily along the crack and slope stability could be enhanced as the groundwater level is suppressed. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

地下水开采引起的次压缩对隧道长期沉降的影响     

刘国彬  李青  吴宏伟 《岩土力学》2012,33(12):3729-3735

软土地区盾构隧道建成后往往伴随有明显的长期沉降,较大的隧道沉降会严重影响地铁系统的运营及安全。然而,目前对于软土地区隧道长期沉降机制的认识尚不明确。以上海地区地铁盾构隧道1999－2007年间的隧道沉降为例,通过室内试验及现场监测对引起隧道长期沉降的因素,特别对地下水开采引起的软土及砂土层次压缩进行了研究。结果表明,第4含水砂层具有明显的次压缩特性,抽取地下水引起的第4含水层的压缩,特别是其次压缩变形,是引起隧道长期沉降的主要原因之一。因此,严格控制该承压含水层地下水开采是目前缓解上海地铁隧道长期沉降的主要措施。  相似文献   

黑方台黄土泥流滑坡及发生机制研究   总被引：2，自引：0，他引：2  

武彩霞  许领  戴福初  闵弘  谭国焕  邝国麟  周跃峰 《岩土力学》2011,32(6):1767-1773

黑方台因农业灌溉触发了大量泥流滑坡。为了充分反映黑方台黄土泥流滑坡发育特征,首先基于IKONOS影像对黑方台泥流滑坡进行了遥感解译,随后又开展了详细野外调查工作。结果表明,黄土泥流滑坡呈流态化运移特征,滑距可达300 m以上,是黑方台危害最为严重的一类滑坡。钻探和塬边露头测量显示,研究区黄土底部黏土高程西高东低。地下水数值模拟结果显示,研究区地下水总体上由台塬西部流向地势较低的东部台缘,使得该处地下水抬升幅度要高于西部,从而造成泥流滑坡集中分布于东部台缘。为充分反映该条件下黄土泥流滑坡的破坏机制,开展了室内饱和原状黄土应力路径试验,分析研究了黄土泥流滑坡液化机制  相似文献