基于颗粒流椭球体理论的隧道极限松动区与松动土压力

砂土地层中隧道所受土压力与土拱效应及松动区的发展密切相关，而砂土地层拱效应大小又与砂土颗粒流动规律相关。基于颗粒流椭球体理论，提出了砂土中隧道松动区的计算方法，并对Terzaghi松动土压力计算公式进行了改进。研究表明：与Terzaghi土柱理论假定的直立滑动面不同，基于颗粒流的砂土隧道松动区为细长的椭圆或该椭圆的一部分，且其形状及大小随偏心率、松动系数而变化，即随砂土颗粒形状、级配、密实度等地层特性而变化；松动区竖直滑移面上的侧压系数是小于Terzaghi的建议值。最后，通过与相关文献的离心模型试验结果进行了对比分析，验证了该方法的合理性，该成果可用于砂性地层中深埋地下管道和隧道的垂直土压力的计算。

Loosening zone and earth pressure around tunnels in sandy soils based on ellipsoid theory of particle flows

The vertical loosening earth pressure on a tunnel in sandy soils is affected by the development of loosening zone and arching effect that is influenced by the sand particle flows. Based on the ellipsoid theory of particle flows, the method to determine the loosening zone of tunnels in sandy soils is presented, and the traditional Terzaghi loosening theory is improved. The research results show that, unlike the vertical sliding surface assumed by Terzaghi, the loosening zone of tunnels in sandy soils is an ellipse or part of it, which is related to the eccentricity and loosening factor associated with the shape of sand particles, granular composition, relative density and other characters of stratum. The lateral earth pressure coefficient of sliding surface in sandy soils is less than the value suggested by Terzaghi. Finally, the results of proposed method agree quite well with those reported in other literatures based on the Terzaghi theory. It can be used to analyze the vertical earth pressure in underground tunnel and pipe engineering.