软土地基上高填方刚性涵洞地基承载力分析

山区沟谷软土地基上高填方刚性涵洞的应用较为广泛，然而，现有的计算理论对该类条件下涵洞地基承载力的认识还不够充分，对地基承载力提出过高的要求，反而为结构带来了不利影响。通过数值模拟和试验手段对涵洞的地基承载力进行深入分析。探讨基础埋深、宽度及软土固结对涵洞地基承载力的影响。研究表明，当基础埋深系数 5时，涵洞地基承载力特征值随着基础埋深的增大近似线性增加，当 5时，基础埋深对地基承载力特征值影响逐渐减小；但基础宽度对软土地基上刚性涵洞地基承载力特征值的影响甚小，实际工程中可不予考虑。此外，试验结果表明，固结度和固结压力对软土的黏聚力和内摩擦角有复合影响，固结度较大时，黏聚力和内摩擦角随固结压力的增大而明显增大。固结度和固结压力对内摩擦角的影响比对黏聚力的影响要大。高填方涵洞地基极限承载力随着软土固结度的增大而提高，当固结度达到90%时，地基极限承载力通常可提高36%以上；地基极限承载力随固结压力的增加呈非线性增大，其提高的幅度逐渐减小。

Soft ground bearing capacity under high fill rigid culverts

High fill rigid culverts have been widely used in trenches of mountain area over soft ground. However, the present theories can not address the soft ground bearing capacity under the high fill rigid culvert very well; so an extremely need of ground bearing capacity may involve in some improper ground treatments, which probably induces adverse effect on culverts. In this study, a finite element numerical simulation and lab tests are carried out to investigate the soft ground bearing capacity under high fill rigid culverts. The influence factors including foundation embedded depth, foundation width and consolidation of soft soil are discussed in detail. This research reveals that the characteristic values of ground bearing capacity approximately linearly increase with the embedded depth of culvert foundation as the foundation embedded coefficient is less than 5. However, the influence of embedded depth of culvert foundation on bearing capacity gradually decrease with increasing the value of N while N is larger than 5. The influence of culvert foundation width on the characteristic value of soft ground bearing capacity is tiny, that can be ignored in the design of practical engineering. Moreover, lab tests results show that consolidation degree and consolidation pressure have inter-affect on the cohesion and/or frictional angle of soft ground soil. The cohesion and/or frictional angle increase with the consolidation pressure; the increasing rates will be faster for higher consolidation degrees. The frictional angle of soft soil is more easily affected by consolidation degree and consolidation pressure than cohesion. The ultimate bearing capacity of soft ground under high fill rigid culvert increases with increasing the consolidation degree of soft soil; the total increment is generally more than 36% while the consolidation degree reaches to 90%. Furthermore, it also nonlinearly increases with increasing the consolidation pressure; however, the increment decreases with the increasing of the consolidation pressure.