Effect of microstructure on stress–strain and pore-pressure response of sabarmati sand under the influence of mica     

P. Seethalakshmi 《Geomechanics and Geoengineering》2020,15(2):123-139

ABSTRACT

Micaceous soil is believed to be detrimental for civil engineering constructions due to the effect of high compressibility, low compacted density and low shear strength. Individual mica particle has numerous intact mica flakes foliated over each other making it flexible upon loading and rebound upon unloading due to its low hardness and resilient nature. Hence, micaceous soils with mica content more than 10% are considered undesirable for highway pavements, embankments and railway track constructions. When platy mica particles are sufficiently numerous to interact with spherical sand particles, bridging and ordering phenomena are augmented within the soil mass creating unique sand-mica particle orientation (MS microstructure) unlike sand-sand particle orientation (PS microstructure). The current experimental research was conducted to evaluate the variation in stress–strain, pore pressure and effective stress path response of Sabarmati sand under the influence of mica (sand with 30% mica and pure sand) with MS and PS microstructure respectively. Effect of particle crushing on stress–strain and pore pressure response was also studied on Sabarmati sand with MS and PS microstructure. Distinctive macroscopic response was observed in Sabarmati sand with MS microstructure under the influence of mica as well as mica particle crushing.  相似文献   

A Review of the Calculation Formula for the Four-component Borehole Strainmeter and Application to Earthquake Cases   总被引：1，自引：0，他引：1  

SU Kaizhi 《中国地震研究》2019,33(1):132-146

Based on the principle formula for the four-component strainmeters, we can directly obtain the specific plane strain, shear strain and azimuthal angle of the principal strain, and the maximum and minimum principal strains calculated afterwards are the indirect result. The problems of practicality of the sensitivity coefficients A and B of plane strain and shear strain are then discussed. Based on this idea, we analyzed the observation data of several four-component borehole strainmeters near the epicenter of the Yiliang M_S5.7 earthquake in 2012 and the Ludian M_S6.5 earthquake in 2014 in the Zhaotong area, Yunnan Province. The results show that the analysis based on the perspective of plane strain and shear strain has an obviously better effect than that based on the component readings, and can directly peel off the respective abnormality of the plane strain and shear strain. In addition, the correlation coefficient curves between measured data of two plane strains show significant anomalies which often occur several days before and during the earthquake.  相似文献   

强震作用下抗震陷黄土改良地基的微观特征分析          下载免费PDF全文

许书雅  王平  钟秀梅  王会娟  于一帆  刘红枚 《地震工程学报》2019,41(3):724-730

基于动三轴试验和SEM细观结构测试试验,结合图像分析处理软件,对强震荷载前后宝兰客运专线沿线典型震陷性黄土及其经物理、化学和复合改良方法处理后的试样进行微观尺度的结构变形演化规律研究,探讨不同改良方法对土体微结构的影响及其与震陷系数之间的内在联系。结果表明:(1)物理改良方法对于消除大孔隙和架空孔隙结构的效果最为明显,同时对颗粒级配和结构也有调整;(2)化学改性方法则从颗粒接触方式、粒间胶结程度等方面影响土体强度,且不同化学反应的参与可生成独特的玻璃微珠或絮凝状细结构,从而大大提升土体某项参数指标,进而在强震中分别起到填充、胶结或缓冲作用;(3)强震作用前后不同改良方法对各微观要素的改变与相应的残余应变现象吻合较好,说明微结构能有效反映改良黄土残余变形的强弱。  相似文献   

基于三维应变格林函数反演中小震震源机制          下载免费PDF全文

周立  林强  范涛 《地震工程学报》2019,41(6):1553-1559

随着复杂速度结构反演的发展和高性能计算能力的提升,基于高精度3D介质模型计算格林函数反演震源机制更具可行性。中小地震因具有更好的覆盖和近似点源效应,在区域结构成像中有着广泛的应用。基于波形类的反演方法如波动方程层析成像\,全波形反演都需要震源机制解,而传统的震源机制反演方法不能很好地应用于中小地震。采用有限差分法构建应变格林张量(Strain Green Tensor,SGT)数据库,将合成波形和实际波形按震相截窗并滤波到不同的频带范围,先通过最小化互相关走时差来进行震源重定位,再通过最小化波形残差反演震源机制。通过合成数据测试验证方法的正确性,随后将该方法应用于青藏高原东部边缘龙门山地区,反演一系列M_W3.4～5.7的中小地震震源机制。由于应变格林张量数据库可预先构建,该方法可以应用于(近)实时震源机制解反演。  相似文献   

2018年9月8日云南墨江5.9级地震预测回顾与资料论证     

杨建文  赵家本  张鹏映  何应文  王军  茶文剑 《中国地震》2019,35(3):509-520

通过分析墨江5.9级地震前预测意见和预测资料，认为云南地区M≥5.5地震平静异常突出，M≥5.0地震连续间隔时间达200天以上，通海2次5.0级地震震级偏小是震前地震活动异常的显著特征；通海地震的指示意义、前兆异常M≥5.7地震中期和M≥5.0地震短临综合预测指标是判断地震短期可能性的主要依据；1900年以来，通海50km范围内M≥5.0地震后云南地区发生M≥5.0地震优势对应关系和GNSS表征的区域面应变变化特征为地点判定提供了线索。墨江5.9级地震的预测经验及资料的论证丰富了对地震孕育复杂性的认识，为震例积累了新的资料。  相似文献   

京西北地区地应变观测与小震震源机制解一致性研究     

茅远哲  曹筠  高晨  冯向东  王晓山 《中国地震》2019,35(4):709-717

以京西北地区作为研究区域，采用应变参数方法解算定点地应变观测数据，将所得应变参数时间序列作为研究对象，利用该结果与研究区内同期小震震源机制解进行一致性分析，研究得出呈拉张性质的定点观测最大主应变方位与震源机制解最大拉张变形方向（T轴）水平投影具有良好的对应性，整体以NNW—NE向为主，且自西向东排布的测点最大主应变方位与震源机制解最大拉张变形方向均表现为逐渐东向偏移的趋势，与华北平原块体北部发生顺时针旋转活动的特征相吻合，结果进一步检验了地应变观测反映区域应变场信息的能力。  相似文献   

Modelling the time‐dependent behaviour of granular material with hypoplasticity          下载免费PDF全文

Shun Wang  Wei Wu  Zhen‐Yu Yin  Chong Peng  Xuzhen He 《国际地质力学数值与分析法杂志》2018,42(12):1331-1345

This paper presents a constitutive model for time‐dependent behaviour of granular material. The model consists of 2 parts representing the inviscid and viscous behaviour of granular materials. The inviscid part is a rate‐independent hypoplastic constitutive model. The viscous part is represented by a rheological model, which contains a high‐order term denoting the strain acceleration. The proposed model is validated by simulating some element tests on granular soils. Our model is able to model not only the non‐isotach behaviour but also the 3 creep stages, namely, primary, secondary, and tertiary creep, in a unified way.  相似文献   

铁路路基粗粒土填料临界动应力试验研究     

王康宇  庄妍  耿雪玉 《岩土力学》2020,41(6):1865-1873

粗粒土填料被广泛应用于铁路基床填料中，直接承受轨道结构传递的列车动循环荷载的长期作用，研究其在列车动荷载作用下的动力行为特征及塑性变形特性可为路基状态评估、沉降控制提供思路。采用GDS动三轴试验系统对铁路基床表层的粗粒土填料动力响应开展研究，通过引入塑性应变率和安定理论，将不同频率、围压、循环动应力比等条件下路基填料的轴向塑性应变的发展规律划分为塑性安定、塑性蠕变和增量塑性破坏3种类型，并确定了塑性安定和塑性蠕变状态的临界动应力水平。研究表明：粗粒土填料的临界循环应力比随着围压的增大而增大，随着荷载频率的增加而减小。通过对试验结果的拟合分析，提出了以围压为变量的临界动应力经验公式，为合理评估列车荷载作用下路基任意深度的动力稳定提供了理论依据。  相似文献   

PBO钻孔应变同震响应分析     

陈燚飞  吕品姬 《大地测量与地球动力学》2019,39(7):765-770

以2017-09-08墨西哥8.1 级地震为例，分析14个PBO综合钻孔应变仪和地震仪同址记录的地震波信号，结果表明，应变仪记录的地震波符合射线传播规律。对不同震中距的站点进行基于S变换的应变仪与地震仪的同震响应特征分析，二者同震响应一致性较好，应变仪频段主要在0.25 Hz以下。取震后1 h应变数据进行分析发现，同震阶段应变主方向指向震中。  相似文献   

Mechanical behavior of porous solid considering mesoscopic elastic buckling     

Hao-Yue Zhang  Xiao-Xong Hu  Gao-Feng Zhao 《国际地质力学数值与分析法杂志》2020,44(7):962-982

In this work, the elastic buckling of porous solids was investigated using a lattice spring model (LSM). The capability of the LSM to solve elastic buckling problems was comprehensively verified by comparing well-established numerical and analytical solutions. Following this, the buckling of a porous solid was studied, in which two porous structures were considered, ie, the random porous model and the Voronoi porous model. The results reveal that both the porosity and the shape of the pores influence the elastic buckling bearing capacity of the porous solid. Finally, the mechanical responses of a porous solid with an extra high porosity (0.85) were numerically investigated. Our numerical results demonstrated that the nonlinear elastic response of the porous solid might come from its mesoscale elastic buckling. This work shows the ability and promise of using the LSM as a fundamental numerical tool for the deep investigation of the buckling mechanical behavior of porous solids.  相似文献