考虑土对水吸附性的渗流破坏理论与应用

 工程实践和模型试验结果都表明，上覆土层往往能够承受比自重压力更大的水头压力，目前还没有相关理论能够解释这一现象。考虑土颗粒对孔隙水的吸附性及结合水的连通情况，提出广义浮力、浮重度及广义水力梯度概念，给出具体的计算方法；明确计算中所用的参数 ， 和 的物理意义，建议了估算 的方法，设想了测定 和 的方法，提出 与起始水力梯度 的理论关系式。这些方法考虑土层性质的差异，针对砂土和疏松土，广义浮力、广义浮重度及广义水力梯度变为传统的阿基米德浮力、浮重度及水力梯度。进一步得到不同土层中渗流力的计算方法，最终，得到土体在地下水作用下破坏条件的统一表达式，该公式可以解释土体在地下水作用下的几种不同破坏模式。依据该理论，基坑抗渗流稳定性和抗承压水稳定性的计算方法都应被修正，目前采用的计算方法都只是适应于砂土和疏松土的计算方法。采用该方法对不同组合的土层在地下水作用下的稳定性进行分析，得到的一些结论与传统说法并不相同。如：基坑围护结构插入深度分析时，如果不存在承压水作用，黏性土中的基坑很难发生渗流破坏，粉土地层中基坑的抗渗流破坏能力比砂土中的大；基坑抗承压水突涌分析时，如果上覆土层有一定渗透性，传统的压重平衡计算结果偏于不安全，含有一定量粉土的承压水层的上覆土层抵抗承压水能力会有所提高。最后，以上述成果为基础对水土压力统一计算理论做了修正。

SEEPAGE FAILURE THEORY AND ITS APPLICATION CONSIDERING WATER-SOIL ADSORPTIVITY

Engineering practices and model test results all indicate that overburden soil stratum is often able to withstand greater head pressure than the pressure of its own weight. Currently，no relevant theory can explain this phenomenon. The concepts such as generalized buoyancy，generalized buoyant unit weight and generalized hydraulic gradient are proposed by considering adsorptivity of soil particles to pore water as well as considering connectivity of bound water；and then specific calculation method is given，explaining the physical meaning of the parameters such as  ，  and   used in the calculation and recommending the estimating method of  . The tests envisaged on measuring  and   are also given，then the relationship between  and initial hydraulic gradient   is established. Aforesaid calculation method takes the different natures of soil into account. For sand and loose soil，generalized buoyancy，generalized buoyant unit weight and generalized hydraulic gradient are changed into Archimedes buoyancy，traditional buoyant unit weight and hydraulic gradient. Further，calculation method of seepage force in different soils has been given. In the end，the unified expression of failure conditions of soil under the action of groundwater is got，which can interpret several different failure modes of soil under the action of groundwater. According to this theory，the calculating method of anti-seepage stability and the stability of resistance to the confined water of foundation pits should be amended and the current calculation method can only be applied to sand and loose soil. Some conclusions derived by using this calculation method to analyze the stability of soil in groundwater under different strata combinations are different from traditional arguments. For example，when analyzing the embedment depth of enclosure structures，if there is no impact of confined water，the seepage failure of the foundation pit is difficult to occur in the clay stratum and the ability of foundation pits to resist seepage failure in the silt stratum is better than that in sand layer. When analyzing the anti-upbursting of confined water in foundation pit，the traditional ballast-balance calculation is unsafe to the overburden soil stratum with permeability，while for the overburden soil stratum of confined water stratum containing a certain amount of silt，its ability to resist the confined water pressure is relatively increased. Finally，based on the result of the paper，the unified calculation theory on soil-water pressure is amended.