摘要
为了揭示强夯过程中土体应力–应变特征和加固范围发展规律,基于帽盖模型建立二维有限元动力分析模型,通过子程序二次开发实现土体模量等参数随夯击次数的变化。基于该数值模型,首先获得强夯过程中主应力–偏应力(p-q)平面内土体的应力路径和竖向与水平向的应力–应变关系,结果表明土体帽盖面随着强夯压密而逐步扩大,但不同区域土体的加固过程因其应力–应变关系的不同而又有所差异:夯锤正下方土体的加固以竖向压缩变形为主,竖向应力在加固中起主导作用,但浅层土体因侧向惯性导致侧向挤密明显滞后于竖向压密,而较深处的土体侧向惯性作用不再明显,表现为三向压密同时发生;夯锤以外的土体以侧向挤密为主,水平向应力起主要作用。随后,采用偏应力峰值点与前一击帽盖面的相对位置定量表征强夯加固效果,峰值点位于前一击帽盖面之上时,土体屈服硬化;反之,土体得不到压密。最后,对比发现以90%压实度确定的有效加固范围保守于以5%相对密度增量确定的结果,同时提出砂土有效加固范围的计算公式,对类似工程实践提供一定的参考。
In order to investigate the stress-strain characteristics of soil and the effective range of reinforcement under dynamic compaction,a two-dimensional dynamic model based on the capped yield hardening model was established and implemented through finite element method. A subroutine was programmed to simulate the parameters such as the soil modulus changing with the ramming times. With the proposed numerical model,the soil stress path in p-q plane（ p is principal stress,q is deviatoric stress） and the stress-strain relationship in both vertical and horizontal directions were firstly obtained in the simulation of successive dynamic compaction. Results indicated that the cap surface expanded with the soil densification but that the reinforcement processes varied with the soil locations due to the different characteristics of the stress-strain relationship. Soils right under the pounder were mainly compressed in the vertical direction caused by the higher vertical stresses. However,the development of horizontal deformation at the shallower depths lagged behind the vertical deformation due to the effect of lateral inertia,while the deformation at the deeper locations developed simultaneously in both horizontal and vertical directions. Soils beside the pounder were mainly compressed in the horizontal direction due to the much larger lateral stresses. Then the reinforcement effect was quantitatively characterized by the relative distance between the peak value of the deviatoric stress and its front cap surface. When the deviatoric peak stress located above the cap surface,soils experienced the yield hardening. Otherwise,soils would not be compressed. Finally,the effective improvement ranges determined by the criterion of 90% compaction degree were found to be more conservative than those by the criterion of 5% relative density increment. Empirical formulae were put forward to predict the effective ranges of improvement for the sand foundation.
作者
姚占勇
周冲
蒋红光
毕玉峰
孙梦林
周磊生
齐辉
YAO Zhanyong;ZHOU Chong;JIANG Hongguang;BI Yufeng;SUN Menglin;ZHOU Leisheng;QI Hui(School of Civil Engineering, Shandong University, Jinan, Shandong 250061, China;Shandong Provincial Communications Planning and Design Institute, Jinan, Shandong 250031, China;Qilu Transportation Development Group, Jinan, Shandong 250101, China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2018年第4期969-977,共9页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金青年基金资助项目(51608306)
山东省交通科技计划项目(2015B28
2016B20)~~
关键词
土力学
强夯
帽盖模型
p-q平面应力路径
屈服硬化
有效加固范围
soil mechanics
dynamic compaction
cap model
stress path in p-q plane
yield hardening
effectiverange of improvement
