摘要
静止土压力系数(K_(0))是岩土工程中计算侧向土压力的关键参数,原状和重塑黄土的K_(0)系数在固结过程中的发展规律明显区别于黏土或砂土。为研究围压和初始孔隙比对原状和重塑黄土的K_(0)系数的影响,采用加装高精度局部径向位移计(LVDT)的应力路径三轴仪开展了K_(0)固结试验研究,结果表明:(1)重塑黄土的K_(0)系数受初始孔隙比(e_(0))的影响较为明显,当试样的初始孔隙比减小(从0.775变为0.503),其K_(0)系数的最大降幅为55%;然而原状黄土的K_(0)系数受有效围压(σ_(3)′)的影响较为明显,比如在σ_(3)′<350kPa时,K_(0)系数为0.77~0.85,在σ_(3)′>350kPa时,K_(0)系数为0.46~0.51;(2)在固结过程中,原状黄土试样和重塑黄土试样的K_(0)系数均发生陡降,具体表现为重塑黄土密样(e_(0)<0.6)的陡降发生在固结的起始阶段,重塑黄土松样(e_(0)≈0.77)的陡降发生在有效围压接近100kPa,而原状黄土试样的陡降发生在有效围压为350kPa附近;(3)在相同的有效围压和密度条件下,原状黄土的K_(0)系数大于重塑黄土。采用核磁共振技术(NMR)获取了重塑和原状黄土的孔隙分布,并辅以试样的超孔隙水压力、排水体积等数据进行了讨论,发现结构性是造成黄土K_(0)系数差异的主要原因。
The coefficient of lateral earth pressure(K_(0))is a key parameter for calculating lateral earth pressure in geotechnical engineering.The development trend of K_(0) value of intact and remolded loess during consolidation is obviously different from that of clay or sand.In order to study the influence of confining pressure and initial void ratio on K_(0) value of intact and remolded loess,K_(0) consolidation tests were carried out by using the stress path triaxial apparatus,that is also equipped with a high precise internal radial LVDT.The results reveal that:(1)the K_(0) value of remolded loess samples is strongly affected by the initial void ratio(e_(0)),when the initial void ratio decreases from 0.775 to 0.503,the maximum reduction of K_(0) value is about 55%.For the intact loess samples it is strongly affected by the effective confining pressure(σ_(3)′),the K_(0) value is 0.77~0.85 whenσ_(3)′<350kPa and 0.46~0.51 whenσ_(3)′>350kPa;(2)in the consolidation stage,a sudden drop of K_(0) value is found in intact and remolded loess samples.In brief,in dense sample of remolded loess(e_(0)<0.6)the drop takes place at the initial stage of consolidation.In loose sample of remolded loess(e_(0)≈0.77)the drop is near the effective confining pressure of 100kPa.For intact loess samples the drop is observed at the effective confining pressure of 350kPa;(3)under otherwise similar conditions in terms of stress level and density,the K_(0) value of intact loess is higher than that of remolded loess.By using the nuclear magnetic resonance(NMR)technique,the pore size distributions of remolded and intact loess are obtained.In conjunction with the experimental results in excess pore water pressure and changes of sample volume,etc.The observed discrepancies in the K_(0) value is mainly attributed to the characteristics of soil fabric.
作者
王瑜川
黄光靖
刘鑫
黄良
兰恒星
WANG Yuchuan;HUANG Guangjing;LIU Xin;HUANG Liang;LAN Hengxing(School of Geological Engineering and Geomatics,Chang an University,Xi'an 710064,China;State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing 100101,China)
出处
《工程地质学报》
CSCD
北大核心
2022年第5期1381-1388,共8页
Journal of Engineering Geology
基金
国家自然科学基金(资助号:42041006,41927806,41807226)
陕西省自然科学基础研究计划(资助号:2022JQ-251)
长安大学中央高校基本科研业务费专项资金(资助号:300102260201).