砂土地基的黏性特性及其有限元模拟     

彭芳乐  史文政  谭轲 《岩土力学》2015,36(Z2):648-654

采用非线性弹塑黏性有限元法模拟了砂土地基变速率加载室内试验,再现了砂土地基荷载-沉降曲线对加载速率突变、砂土蠕变以及应力松弛等加载情况下的响应和瞬时黏性中砂土黏性随加载进行的衰减现象。在有限元分析中,以非线性三要素模型为理论框架构建了可以综合考虑砂土黏性特性的弹塑黏性本构模型,用动态松弛法进行有限元求解,最后通过有限元与室内试验的对比分析研究了砂土地基所具有的黏性特性,同时验证了非线性三要素弹塑黏性模型用于模拟砂土黏性特征的合理性和正确性。  相似文献   

日本MW 9.0级大地震前后华北和东北地区现今构造应力作用调整过程与研究意义探讨     

谭成轩  胡秋韵  张鹏  丰成君  秦向辉 《地学前缘》2015,22(1):345-359

为了探讨日本M_W 9.0级大地震前后华北和东北地区现今构造应力作用调整过程与研究意义,对华北和东北地区进行原位现今地应力绝对测量与实时监测、GPS测量,结果表明：日本大地震在山东半岛、华北北部地区和东北地区所诱发同震位移引起的张性效应调整周期分别约为6个月(即调整结束时间大约在2011年9月)、15个月(即调整结束时间大约在2012年6月)和26个月(即调整结束时间大约在2013年5月),张性效应调整周期与同震位移大小成正比。在这种调整过程中,往往表现出区域现今构造应力作用方式和构造应力场转换,并可能伴随重大地质事件(如地震等)的发生。2012年5月28日和29日、6月18日、8月26日及2013年1月11日在唐山及其周围地区分别发生的4.8级、3.2级、4.0级、3.3级和3.0级地震与华北北部地区构造应力作用方式和构造应力场转换有关,而2013年10月31日以来在吉林省松原市发生的地震群应与东北地区构造应力作用方式和构造应力场转换有关,而非一个大地震前的小震群。  相似文献   

江苏及邻近地区地震视应力特征研究   总被引：1，自引：0，他引：1  

孙业君  刘红桂  江昊琳  詹小艳  居海华  杨云 《地震研究》2015,38(1)

采用江苏省数字地震台网记录的地震波形资料,利用震源位移谱低频水平与拐角频率计算了2000~2010年江苏及邻近地区561个ML≥1.5中小地震视应力值。结果显示,江苏及邻近地区的地震视应力平均值为0.91 MPa,与中国大陆的平均水平相当。视应力与震级无明显的线性关系,在震级相对较大时表现出一定的高震级对应高视应力的特点。视应力高值地区主要集中在江苏中部至南黄海海域,次高值集中分布在郯庐断裂带中南段的苏鲁交界地区、安徽段固镇至定远附近地区和肥东、巢湖一带,反映了以上地区较高的地震活动水平及地壳应力状态。不同区域ML2震级档视应力的差异性基本反映了区域地质环境、构造活动等特征的差异。  相似文献   

喜马拉雅东构造结附近强震对滇西南地区断层的影响研究     

孟令媛  史海霞  周龙泉 《地震研究》2015,38(1)

以在喜马拉雅东构造结发生的2000年6月7日缅甸MS6.9地震、2011年3月24日缅甸MS7.2地震和2012年11月11日缅甸MS7.0地震作为主要破裂源,计算3次地震震后周围应力的空间变化,给出其对滇西南地区断层造成的静态库仑应力变化的时间影响范围。结果表明:3次地震对滇西南地区活动断层库仑破裂应力变化主要为负值,即受到应力卸载的影响,其中包括大盈江断裂、龙陵—瑞丽断裂、南汀河西支断裂、南汀河东支断裂、孟连—澜沧断裂、打洛—景洪断裂和怒江断裂,量值范围在-0.06~-0.002 bar(1 bar=0.1 MPa),卸载影响最大的断裂为打洛—景洪断裂,为-0.06 bar,木嘎断裂和龙陵—澜沧断裂受到加载的影响,断层的库仑破裂应力分别为+0.002 bar和+0.004 bar。  相似文献   

芦山地震前后龙门山断裂带西南段地应力状态对比分析   总被引：2，自引：0，他引：2  

邱君  吴满路  范桃园  张重远  李冉  陈利忠 《地质学报》2017,91(5):969-978

2013年4月20日芦山Ms7.0级地震后,为研究龙门山断裂带西南段震后的地应力状态,应用水压致裂法和压磁应力解除法在该区开展了2个钻孔的原地应力测量工作。测量结果显示硗碛测点在128～188m深度范围内最小水平主应力的量值为10.47～18.47 MPa,最大水平主应力的量值为19.60～25.83 MPa,方向为N63°～85°W;天全测点在114～142m深度范围内最小水平主应力的量值为5.20～7.73 MPa,最大水平主应力的量值为8.21～9.31 MPa,方向为N59°W。两个测点水平主应力与垂直应力的关系均为σ_Hσ_hσ_v,其中硗碛测点最大、最小水平主应力与垂直应力比值的平均值分别为5.27和3.01,天全测点最大、最小水平主应力与垂直应力比值的平均值分别为2.60和1.76,表明有利于逆断层活动。通过比较该地区芦山地震前后实测地应力状态,发现芦山地震后,龙门山断裂带西南段的北段(即邛崃大邑西-宝兴北-汶川南一带)和南段(即天全-荥经-泸定-康定一带)应力积累量增加。相同深度范围内,北段硗碛测点震后的应力大小要比地震前有明显的提高,这也与硗碛测点地应力监测结果一致。实测应力方向与震前基本一致,都为NW-NWW。基于实测地应力资料,根据库伦破裂准则和Byerlee定律分析,位于北段的硗碛测点震前部分压裂段的最大水平主应力处于使断层滑动临界值的上下限之间,而地震后最大水平主应力则均已超过断层滑动临界值的上限。位于南段的飞仙关测点震前最大水平主应力均未达到断层滑动临界值的下限,而地震后天全测点的最大水平主应力则均处于使断层滑动临界值的上下限之间。采用最大剪应力(σ_1-σ_3)/2与平均应力(σ_1+σ_3)/2的比值μ_m(断层摩擦)参数评估研究区地应力的积累水平和地震危险性。震前硗碛测点μ_m的量值为0.16～0.72,平均为0.50,震后为0.71～0.81,平均为0.77。震前飞仙关测点μ_m的量值为0.31～0.35,平均值为0.32,震后天全测点μ_m的量值为0.53～0.57,平均值为0.55,两个研究区的μ_m的量值均变大。分析认为芦山地震后龙门山断裂带西南段的北段和南段的应力积累量增加,都有发生断层滑动的可能性,尤其是北段。  相似文献   

Effects of scour-hole dimensions and soil stress history on the behavior of laterally loaded piles in soft clay under scour conditions     

《Computers and Geotechnics》2017

Bridge pile foundations in the midst of water current are often subjected to scour, which induces the loss of soil support around the piles and thus results in a significant decrease of foundation capacities or even the failure of bridges. In the current practice, when the scour-affected behavior of the pile foundations is analyzed, either the whole scour-hole geometry or the possible changes in the stress history of the remaining soils is often ignored. In reality, however, scouring creates scour holes with certain dimensions around the pile foundations and the remaining soils that are not scoured away undergo an unloading process at the same time, which will increase the over-consolidation ratios of the remaining soils and accordingly changes of their mechanical properties. This paper examines the behavior of laterally loaded piles in soft clay under scour conditions by using the p-y method. The conventional p-y curves have been modified appropriately to reasonably reflect the effects of three-dimensional scour-hole geometry as well as the stress history of the soils, with the aid of integration of Mindlin’s fundamental solutions. A field test is used to serve as a reference case and to investigate the effects of stress history, scour depth, scour width, and scour-hole slope angle on the responses of laterally loaded piles in soft clay. The results indicate that neglecting the stress history effect can be unconservative for scour-affected pile foundations in soft clay, whereas neglect of the scour-hole dimensions and geometry would lead to over-conservative predictions/design of the laterally loaded piles under scour condition.  相似文献   

Influence of the intermediate principal stress and principal stress direction on the mechanical behavior of cohesionless soils using the discrete element method     

《Computers and Geotechnics》2017

In this paper, the Discrete Element Method (DEM) is employed to numerically explore the response of hollow cylinder specimens of granular soils under complex stress paths. Two series of numerical tests are conducted to clarify the effects of the principal stress direction α and the intermediate principal stress through the b-value on the mechanical response of granular materials. The effects of α and b-value on the non-coaxiality of the principal stress and the principal plastic strain increment directions are investigated. It is observed that b-value and α significantly affect the non-coaxial behavior of granular materials. Finally, the results are discussed and compared with those obtained from physical laboratory tests.  相似文献   

Cone penetration test in sand: A numerical-analytical approach     

《Computers and Geotechnics》2017

Separation of the effects of initial horizontal stress and relative density on cone tip resistance in sandy soils has been a complicated issue for many years. In order to overcome this problem, a numerical modeling of CPT which has been verified by calibration chamber tests, has been used in this paper to achieve a reliable analytical solution. The analytical solution has resulted in two relationships for sleeve friction and cone tip resistance in terms of the initial conditions of sandy soil. Based on the presented solution, the initial horizontal stress and relative density can be determined according to CPT measurements.  相似文献   

Buckling failures of reserved thin pillars under the combined action of in-plane and lateral hydrostatic compressive forces     

《Computers and Geotechnics》2017

The reasons that pillars with small width-to-height ratios fail remain unclear. This study established a mechanical model for the buckling failure of a thin pillar subjected to compressive forces to investigate the stability of reserved thin pillars (RTPs) on both sides of mining units during barrier pillar recovery. The critical buckling stress of the thin pillar was obtained using the energy variational method, and its relationship to the aspect ratio (length-to-width ratio) was investigated. The buckling instability of RTPs can be determined by comparing the RTP stress obtained from numerical simulations with the buckling stress derived from the mechanical model.  相似文献   

Numerical investigation of the opening effect on the mechanical behaviours in rocks under uniaxial loading using hybrid continuum-discrete element method     

《Computers and Geotechnics》2017

Openings including their size, shape and distribution in rock play a significant role in the performance of rock related structures. The well-established knowledge in this area can contribute to the engineering practices, for example, underground space design, planning and optimisation in Civil and Mining Engineering and wellbore stability in Drilling Engineering, among others. Thus, understanding the failure mechanism of rock with openings is theoretically and practically meaningful. Laboratory testing on rock or rock-like materials with openings have been studied extensively in the literature, which, however, primarily focuses on the cracks/fractures. In this paper, a comprehensive numerical study on the effect of non-banded openings, i.e., circular, rectangular, and triangular opening, on the rock mechanical behaviour is performed using a hybrid continuum-discrete element method. It is revealed that the proposed simulation method can reproduce reasonably the crack initiation and propagation, and predict well the change of the mechanical behaviour due to the openings. In addition, the influence of the opening shape and opening ratio (=area of opening/specimen area) on the mechanical behaviour is also investigated.  相似文献