一种均匀黏性土黏聚力计算方法

黏聚力是黏性土的重要力学性能参数，土的密度、孔隙比是影响黏聚力的重要因素，但密度、孔隙比变化时土的黏聚力难以估算。作者依据固体颗粒分子吸引力理论，研究了均匀黏性土黏聚力随孔隙比及干密度的变化规律。以颗粒均匀的黏性土为研究对象，将土体简化为由土颗粒与粒间孔隙2个部分、依靠土颗粒间吸引力连接而成的整体，将黏聚力简化为单位面积上土颗粒间吸引力的合力；基于此，提出均匀黏性土孔隙结构模型，推导了土颗粒净距与土体孔隙比的函数关系，分析了土颗粒净距随孔隙比的变化规律。根据Lifshitz固体颗粒分子吸引力理论，建立了均匀黏性土黏聚力与干密度、孔隙比之间的函数关系，据此提出一种考虑密度、孔隙比变化的均匀黏性土黏聚力计算方法。通过均匀细粒土的直剪试验测得了不同含水量下的黏聚力，将理论计算结果与直剪试验结果相对比，验证了所提黏聚力计算方法的合理性。结果表明：均匀黏性土颗粒净距与孔隙比正相关，但随孔隙比增大，其对土颗粒净距的影响逐渐减小；黏聚力与干密度正相关，与孔隙比负相关，且随干密度的增大，其对黏聚力的影响更加显著。

A Method for Calculating the Cohesive Force of Uniform Cohesion Soil

Cohesive force is an important mechanical parameter of cohesive soil, and the density and void ratio of soil are important factors affecting its cohesion, but the cohesion force of cohesive soil is difficult to estimate, while its density and void ratio have changed. With the theory of molecular attractive forces between solids, the functional relationship between soil cohesion and its dry density or void ration was analyzed. To establish the conceptual model of pore structure in cohesion soil, the uniform cohesive soil was simplified into a combination of soil particles and pores, in which the soil particles are connected into a whole by molecular attractive forces, and the soil cohesion was simplified into the resultant force of molecular attractive forces per unit area. On the base of the conceptual model, the relationship between soil particle spacing and soil void ratio was built, and the influence of void ratio on soil particle spacing was analyzed. According to the theory of molecular attractive forces between solids established by Lifshitz, the functional relationship between soil cohesion and its dry density or void ration was established, and a mathematic method for calculating the cohesive force of uniform soil was derived. The calculation results of the cohesive force were compared with that of the direct shear test, and the rationality of the proposed method was verified. The results showed that, the soil particle spacing is positively correlated to void ratio, as the void ratio increasing, its influence on soil particle spacing gradually decreases. The cohesion force of uniform soil is positively correlated to dry density, and negatively correlated to void ratio. At the same time, the effect of dry density on cohesive force is more significant with its increase.