置于岩石地基的独立基础力学特性研究

Study on mechanical characteristics of independent foundations on rock subgrade

置于岩石地基上的柱下独立基础长期以来都是按照国家及地方相关规范进行设计,即将基础视为弯剪构件进行受弯和受剪承载力验算。由于岩石地基与土质地基的压缩变形差异很大,使得基础设计与其实际受力特性不符,由此造成的独立基础设计缺陷在高层和超高层中尤为严重。基础自身刚度及地基的压缩变形是影响其受力特性的主要因素。通过数值模拟和试验结果分析得到以下结论:置于硬质岩石地基上的独立基础为受压构件;置于软质岩石地基上的独立基础在满足一定高度的条件下也为受压构件。在岩石地基上不能做柔性基础,必须满足最小高度的条件才能使上部荷载在独立基础内充分扩散并均匀传给地基。在没有配置钢筋的情况下独立基础以局压破坏为先。

The design of independent foundations under columns and on rock subgrade is generally carried out in accordance with the national or regional codes,which regards the foundations as flexure-shear members that requires the calculation of flexural and shear resistance.Because of the great difference of compression deformation between rock subgrade and soil subgrade,the foundation design is inconsistent with its mechanical characteristics.So it causes serious design defects,especially in tall and super tall buildings.The main factors that affect the mechanical characteristics of foundations are the stiffness and compression deformation of subgrade.According to numerical simulation and test results,the paper gets following important conclusions: An independent foundation on hard rock subgrade is a compression member,an independent foundation on soft rock subgrade is also a compression member at certain height.The flexible foundation can′t be designed on rock subgrade.Only if the independent foundation satisfies minimum height condition,upper loads will spread sufficiently in independent foundation and is transferred to subgrade uniformly.In the case of no reinforcement,local compression failure will occur firstly in the independent foundation.