Model for increment of static earth pressure of unsaturated silty clay under wetting conditions
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摘要: 在基坑工程和重力式挡墙工程中，非饱和土体在浸湿条件下会产生显著的侧向土压力增量，严重时还会造成支挡结构的破坏。为定量评估浸湿作用对非饱和土侧向土压力的影响，通过室内试验实测浸湿饱和作用下，不同初始饱和度的试样，在不同上覆荷载条件下的侧向土压力增量；并建立相应的静止土压力增量计算模型。研究结果表明：①试样湿化饱和后，其静止土压力系数K0值大小一致，与初始饱和度和上覆荷载无关；②湿化前的初始饱和度越低，湿化饱和后的静止土压力增量越大；③湿化饱和后的静止土压力增量，随湿化时的上覆荷载增加而变大；④基于试验数据和机理分析，得到了湿化条件下考虑上覆荷载与初始饱和度的双线性土压力增量计算模型；将该计算模型应用于某支挡工程，发现湿化后的土压力可达初始土压力1.8倍以上，在设计时必须予以重视。Abstract: In excavation and retaining wall engineering, wetting of unsaturated soil can result in significant increment of lateral soil pressure and even structural damage. To assess this effect, the tests with different initial saturation degrees and varying overburden loads are conducted, and the relevant model is established. The results show that: (1) After wetting saturation, the static soil pressure coefficient K0 remains constant and is not affected by the initial saturation degree or overburden load. (2) The samples with lower initial saturation degrees exhibit greater increment in static soil pressure after wetting saturation. (3) The increment of the static soil pressure after wetting saturation increases with higher overburden loads. (4) Based on the experimental data and mechanical analysis, a bilinear model considering the overburden load and initial saturation degree under wetting conditions is established. The model shows that the wetting soil pressure can exceed the initial soil pressure by over 1.8 times and emphasizes the need to consider wetting in design.
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Keywords:
- unsaturated soil /
- wetting condition /
- static earth pressure /
- retaining structure /
- expansion force
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图 1 准备不同初始含水率的试样
Figure 1. Preparation of samples with different initial moisture contents
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图 3 静止土压力随竖向压力变化关系(Sr=0.2)
Figure 3. Variation of static earth pressure with vertical pressure (Sr=0.2)
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图 4 静止土压力增量与初始饱和度关系
Figure 4. Variation of increment of static earth pressure increment with initial saturation
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图 5 静止土压力增量与上覆荷载关系
Figure 5. Variation of increment of static earth pressure with load
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图 6 不同累计深度处静止土压力与其相关计算值关系
Figure 6. Static earth pressures and their correlation with depth
表 1 土的基本物理性质
Table 1 Basic physical properties of soil
最大干
密度/
(g·cm-3)最优含水率/% 液限
wL/%塑限wP/% 塑性指数IP 土粒相对密度GS 1.80 16.5 30.7 15.2 15.5 2.73 
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表 2 浸水条件下非饱和粉质黏土试验方案
Table 2 Test schemes under water immersion conditions
上覆荷载/kPa 加载过程 初始饱和度 100/200/
300/400100(200/300/400)kPa→湿化→逐级加载至1600kPa 0.2/0.3/0.4/
0.5/0.6
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表 3 湿化静止土压力增量计算值统计
Table 3 Statistics of calculated increment static earth pressure
初始饱和度Sr 0.2 0.3 0.4 0.5 0.6 100 kPa下增量值 35.14 25.10 17.41 12.5 3.53 200 kPa下增量值 68.95 48.38 33.32 22.97 6.31 300 kPa下增量值 95.01 68.95 47.86 29.99 8.98 400 kPa下增量值 118.02 90.00 60.99 35.97 10.11
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