摘要
湿陷系数是评价黄土湿陷性的指标,由室内试验测定,湿陷系数与试验压力有关,一般情况下采用地基实际压力作为试验压力是最合理的,但考虑到实际压力在勘察阶段尚不确定,我国历代湿陷性黄土地区建筑规范或标准制定了试验压力的取值方案,先后有较大的调整。现行《湿陷性黄土地区建筑标准》(GB 50025—2018)对浅层马兰黄土的试验压力取值比较符合实际,而对较深Q_(2)黄土的试验压力取值还需探讨。以甘肃正宁华能电厂湿陷性黄土地基为例,对35.0 m深探井中的Q_(2)-Q4黄土按1.0 m取样做了基本物理指标和双线法高压湿陷性试验,获得了各级压力下的湿陷系数。根据试验结果,给定不同基础宽度和不同基底压力,对比了按现行标准规定的压力和实际压力下的湿陷系数随深度的变化。分析结果表明:(1)湿陷系数随压力的变化存在一个峰值,Q_(2)黄土湿陷起始压力和湿陷系数峰值对应的压力明显高于Q_(3)黄土,Q_(2)黄土的湿陷系数峰值比Q_(3)黄土的小,且随深度有减小趋势;(2)现行标准规定压力下确定的湿陷系数和湿陷沉降在Q_(3)黄土中与实际压力下的比较接近,在Q_(2)黄土中与实际压力下的随深度偏离越来越远;(3)为此提出了一个试验压力的修正方案,用修正的试验压力确定的湿陷系数和湿陷沉降与实际压力下的值较为接近。研究结果对黄土湿陷性评价具有一定的工程意义。
Collapsible coefficient is an index to evaluate loess collapsibility,which is measured by laboratory test with collected intact samples.Collapsible coefficient varies with normal pressure loaded in test.It is better to use the real normal pressure in foundation when measuring the collapsible coefficient,but for reasons of convenience,the pressures are always designated as definite values in the codes or standards of construction in collapsible loess areas. However, the designated pressure for Q_(3) (Malan) loess in the standards is reasonable and applicable, while that for Q_(2) loess is still necessary to discuss. In this paper, the collapsible loess foundation of the Huaneng Electric Plant in Zhengning, Gansu Province is used as a case, the Q_(2)-Q4 loess samples were collected in a 35.0 m deep shaft in 1 m intervals and the basic physical properties were measured in laboratory first. The collapsible coefficient is measured with the double oedometer method under low to high pressure for all the samples. Based on the test results, the collapsible coefficient with respect to depth determined with the present used GB 50025-2018 standard and the real pressure in foundation in the cases of various basement widths and basement pressures are compared. The results show that (1) the coefficient of collapsibility has a peak value. The initial collapse pressure and peak collapse pressure of Q_(3) loess are higher than those of Q_(2) loess. The peak coefficient of collapsibility of Q_(3) loess is higher than that of Q_(2) loess, which decreases with depth. (2) For Q_(3) loess, the collapsible coefficient and subsidence determined by the pressure of the present standard are close to those determined by the real pressure in foundation, while for Q_(2) loess, those determined by the pressure of the present standard in foundation deviates increasingly with depth to those determined by the real pressure. (3) Therefore, a modified test pressure for measuring collapsible coefficient of loess is proposed. It is demonstrated that t
作者
李同录
冯文清
刘志伟
高建伟
付昱凯
雷雨露
李萍
LI Tonglu;FENG Wenqing;LIU Zhiwei;GAO Jianwei;FU Yukai;LEI Yulu;LI Ping(School of Geological Engineering and Geomatics,Chang’an University,Xi’an,Shaanxi 710054,China;Observation and Research Station of Water Cycle and Geological Environment for the Chinese Loess Plateau,Ministry of Education,Zhengning,Gansu 745399,China;Northwest Electric Power Design Institute Co.Ltd.,of China Power Engineering Consulting Group,Xi’an,Shaanxi 710054,China)
出处
《水文地质工程地质》
CAS
CSCD
北大核心
2023年第6期59-68,共10页
Hydrogeology & Engineering Geology
基金
陕西省自然科学基础研究计划资助项目(2022JM-167)
国家自然科学基金项目(41877242)。
关键词
黄土
试验压力
湿陷系数
双线法
实际压力
loess
test pressure
coefficient of collapsibility
double oedometer method
actual pressure
