Multi-stratigraphic centrifugal model test method for determination of self-weight collapsible deformation of loess
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摘要: 黄土的自重湿陷变形对上部建筑物具有较大的危害,现有的黄土室内湿陷试验方法和现场浸水试验方法,难以同时满足工程建设对试验结果在经济性、期限和准确性方面的要求。在之前提出的黄土湿陷变形的典型层离心模型试验方法的基础上,以咸阳渭城区布里村自重湿陷性黄土地基为对象,开展了包含地基多个地层的单线法和双线法自重湿陷变形离心模型试验,提出了黄土自重湿陷变形的多地层离心模型试验方法,并与室内湿陷试验和现场浸水试验结果进行了对比；同时分析了Q2和Q3黄土自重湿陷的分层变形特征。研究结果表明：多地层离心模型试验结果得到的地区修正系数
值与现场浸水试验测得的 值相差0.04,其相对误差为2.5%。证明多地层离心模型试验方法可以得到与现场浸水试验相近的结果,且具有费用少、试验周期短的优势,在一定情况下可以取代现场浸水试验进行黄土自重湿陷变形的测定。 Abstract: The self-weight collapsible deformation of loess is harmful to the upper buildings. The existing indoor collapsibility and on-site water immersion test method for loess are difficult to satisfy the requirements of the project construction in terms of the economy, duration and accuracy of the test results. Based on the typical-stratigraphic centrifugal model test method, with the self-weight collapsible loess foundation of Buli Village, Weicheng District, Xianyang City as the object, a multi-stratigraphic centrifugal model test method for determination of loess self-weight collapsible deformation is proposed, and the results of the indoor collapsibility tests and on-site water immersion tests are compared. The stratified deformation characteristics of Q2 and Q3 loess self-weight collapsibility are also analyzed. The results show that the value of the regional correction coefficientobtained from the multi-stratigraphic centrifugal model test is different from that obtained from the on-site water immersion tests with a difference of 0.04, and the relative error is 2.5%. It is proved that the multi-stratigraphic centrifugal model test method can be used to obtain similar results with the on-site water immersion test, and has the advantages of low cost and short test cycle. Thus, under some circumstances, it can replace the on-site immersion tests to determine the self-weight collapsible deformation of loess. -
Keywords:
- collapsibility /
- loess /
- self-weight collapsible deformation /
- centrifuge modelling /
- correction
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图 5 天然含水率模型压缩变形情况
Figure 5. Compressive deformations of natural moisture content model
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图 6 天然含水率模型标志点压缩变形
Figure 6. Compressive deformations of markers for natural moisture content model
表 1 土样的基本物理性质指标
Table 1 Basic physical properties of loess
土样埋深/m 天然含水率/% 干密度/(g·cm-3) 天然孔隙比 饱和度/% 相对密度Gs 土的分类 1~15 14.5~16.1 1.20~1.44 0.88~1.26 33.11~47.32 2.71 CL 
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表 2 黄土湿陷性试验结果
Table 2 Indoor test results
深度/m 层厚/m 土层类型 含水率/% 干密度/(g·cm-3) 自重湿陷系数 饱和密度/(g·cm-3) 饱和自重压力/kPa 自重湿陷量/mm 1 1 Q3新黄土 14.5 1.30 0.023 1.74 17.423 20.7 2 1 Q3新黄土 14.7 1.23 0.037 1.69 34.365 33.3 3 1 Q3新黄土 15.5 1.25 0.021 1.71 51.444 18.9 4 1 Q3新黄土 15.7 1.26 0.047 1.71 68.592 42.3 5 1 Q3新黄土 15.4 1.38 0.043 1.80 86.563 38.7 6 1 Q3新黄土 15.6 1.20 0.040 1.67 103.300 36.0 7 1 Q3新黄土 15.4 1.27 0.046 1.72 120.516 41.4 8 1 Q3新黄土 16.0 1.28 0.040 1.73 34.502 36.0 9 1 Q3新黄土 16.1 1.36 0.009 1.78 121.134 0.0 10 1 Q3新黄土 15.4 1.30 0.007 1.74 138.556 0.0 11 1 Q3古土壤 15.2 1.44 0.033 1.84 156.940 29.7 12 1 Q3古土壤 15.4 1.44 0.033 1.84 175.323 29.7 13 1 Q3古土壤 15.6 1.41 0.021 1.82 193.501 18.9 14 1 Q2老黄土 15.6 1.41 0.007 1.81 211.645 0.0 15 1 Q2老黄土 15.8 1.42 0.005 1.82 229.808 0.0 Σ 自重湿陷量（mm） 345.6
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表 3 离心模型试验中物理量的相似律
Table 3 Scaling law of physical quantity in centrifuge model test
符号 名称 量纲 相似比 g 重力加速度 LT-2 N v 速度 LT-1 1 s 位移 L 1/N L 几何尺寸 L 1/N w 含水率 1 1 Sr 饱和度 1 1 σ 应力 ML-1T-2 1 ε 应变 1 1 k 渗透系数 LT-1 N 注： 表中L为长度量纲,T为时间量纲,M为质量量纲,N为模型率。
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表 4 试验基本内容
Table 4 Test design
模型试样 尺寸（长×宽×高）/(cm×cm×cm) 初始离心加速度/g 终级离心加速度/g 离心加速度步长/g 试验过程 备注 天然含水率模型 20×20×30 0 80 5 离心加速度分级加至50g— 浸水至饱和—分级加至80g 每级离心加速度待变形稳定后再加下一级；当离心加速度至50g时,运行较长时间。连续拍摄照片观察变形,稳定标准为连续多张照片位移无变化。 饱和模型 20×20×30 0 80 5 模型饱和,密封静置48 h—离心加速度分级加至80g 注： 模型率为50,在离心加速度为50g时浸水,离心加速度为50g,对应场地土层厚度为15 m,但为了保证数据的完整性,离心加速度最大到80g,离心加速度为80g时,对应场地土层厚度为24 m。
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表 5 模型基本情况
Table 5 Basic conditions of models
模型土样 层数 模型土层类型 模型层高/cm 代表场地深度/m 尺寸（长×宽×高）/(cm×cm×cm) 初始含水率/% 干密度/(g·cm-3) 天然含水率模型 第一层 Q3新黄土 20.80 0.00~10.40 20×20×30 15.4 1.27 第二层 Q3古土壤 5.00 10.40~12.90 15.4 1.44 第三层 Q2老黄土 4.20 12.90~15.00 15.6 1.41 饱和模型 第一层 Q3新黄土 20.80 0.00~10.40 20×20×30 15.4 1.27 第二层 Q3古土壤 5.00 10.40~12.90 15.4 1.44 第三层 Q2老黄土 4.20 12.90~15.00 15.6 1.41
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表 6 各地层变形情况
Table 6 Deformations of soil layers
类别 土层 地层类型 50g离心加速度时 压缩量/mm 沉降量/mm 湿陷量/mm 模型 第一层 Q3黄土 0.94 6.49 5.55 第二层 Q3古土壤 0.19 3.32 3.13 第三层 Q2黄土 0.69 2.79 2.10 Σ 1.82 12.60 10.78 原型场地 第一层 Q3黄土 47.00 324.50 277.50 第二层 Q3古土壤 9.50 166.00 156.50 第三层 Q2黄土 34.50 139.50 105.00 Σ 91.00 630.00 539.00
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