上拔式静力触探拉拔阻力的试验研究

Experimental study on resistance of pull-out cone penetration tests

为了研究新型上拔式静力触探拉拔阻力的变化规律,自主开发了大型模型箱试验装置,并以黏土和砂土为研究对象,在室内模拟其拉拔过程。该试验主要对不同刃口角度、刃口长度、拉拔速率、压实度、相对密度等因素对拉拔阻力的影响进行研究。研究结果表明:上拔阻力变化曲线大致分为急速上升阶段、缓慢上升阶段和稳定阶段3个阶段;拉拔阻力随着刃口角度的增加而增大;前期拉拔阻力增加速率与最大拉拔力均随着刃口长度的增加而增大;随着拉拔速率的增长,拉拔阻力在逐渐增大;随着压实度的增加,最大拉拔阻力也逐渐增加,但二者并未表现出明显的线性关系;随着相对密度的增加,拉拔试验得到的最大拉拔阻力逐渐增加。在相对密度较低时,拉拔阻力增加缓慢,相对密度较高时,拉拔阻力增加迅速。

To investigate change of resistance of pull-out cone penetration tests, pull-out tests are performed on clayey soil and sand in a new large-scale model chamber under controlled conditions. The effects of edge angle, edge length, pull-out rate, compactness and relative densities on the evolution of pull–out resistance are highlighted. The results show that the change of pull-out resistance can be divided into three stages: sharp-increases stage, slow-increase stage and stabilization. The pull-out resistance increases along with the increase of edge angle. The increasing rate of pull-out resistance at early stage of tests and the ultimate value of pull-out resistance become larger and larger as the increase of edge length. The pull-out resistance and its maximum value also increases as the increase of pull-out rate, compactness and relative densities. However, there is no obviously linear relationship between the maximum pull-out resistance and the compactness. The increase of pull-out resistance is slow at low compactness and relative densities while it is fast when the compactness and relative densities become large.