ISSN 1000-3665 CN 11-2202/P
    李同录,冯文清,刘志伟,等. Q2黄土湿陷系数试验压力取值的讨论[J]. 水文地质工程地质,2023,50(6): 59-68. DOI: 10.16030/j.cnki.issn.1000-3665.202211006
    引用本文: 李同录,冯文清,刘志伟,等. Q2黄土湿陷系数试验压力取值的讨论[J]. 水文地质工程地质,2023,50(6): 59-68. DOI: 10.16030/j.cnki.issn.1000-3665.202211006
    LI Tonglu, FENG Wenqing, LIU Zhiwei, et al. A discussion of the test pressure of collapsible coefficient for Q2 loess[J]. Hydrogeology & Engineering Geology, 2023, 50(6): 59-68. DOI: 10.16030/j.cnki.issn.1000-3665.202211006
    Citation: LI Tonglu, FENG Wenqing, LIU Zhiwei, et al. A discussion of the test pressure of collapsible coefficient for Q2 loess[J]. Hydrogeology & Engineering Geology, 2023, 50(6): 59-68. DOI: 10.16030/j.cnki.issn.1000-3665.202211006

    Q2黄土湿陷系数试验压力取值的讨论

    A discussion of the test pressure of collapsible coefficient for Q2 loess

    • 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Q2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Q2-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,Q2黄土湿陷起始压力和湿陷系数峰值对应的压力明显高于Q3黄土,Q2黄土的湿陷系数峰值比Q3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Q3黄土中与实际压力下的比较接近,在Q2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。

       

      Abstract: 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 Q3 (Malan) loess in the standards is reasonable and applicable, while that for Q2 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 Q2-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 Q3 loess are higher than those of Q2 loess. The peak coefficient of collapsibility of Q3 loess is higher than that of Q2 loess, which decreases with depth. (2) For Q3 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 Q2 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 the collapsible coefficients determined by the modified test pressure agree well with those by the real soil pressure.

       

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