波纹塑料套管煤矸石CFG桩复合路基承载试验

Load-bearing Test on Composite Subgrade of Coal Gangue CFG Pile with Corrugated Plastic

CFG桩身外侧套上内径合适的波纹塑料套管形成统一整体,能较好改善耐久性和表面受力特性,采用理想弹塑性荷载传递函数,提出了一种竖向受荷桩顶荷载与位移比计算方法。在此基础上,依托某矿区周边CFG桩工程,按照相似理论设计完成天然路基、煤矸石CFG桩复合路基、波纹塑料套管+煤矸石CFG桩复合路基、土工格栅+波纹塑料套管+煤矸石CFG桩复合路基4组模型试验,得到复合路基在加载过程中的沉降、桩土应力比、土工格栅拉应变等变化规律,初步探讨波纹塑料套管和土工格栅对CFG桩复合路基受力特点和变形规律的影响。研究结果表明:波纹塑料套管包裹桩身,能提高复合路基承载能力,降低桩土应力比和桩土荷载分担比,其中桩土应力比峰值降低29.5%,桩土身荷载分担比峰值降低7.8%,桩端阻力比与荷载呈负相关,且荷载越高,相关程度越显著;土工格栅作用于碎石垫层,桩土应力比提升幅度为10.7%~23.5%,桩土荷载分担比提升幅度为2.9%~8.4%,路基整体沉降、桩端阻力比进一步降低;随着荷载不断增加,土工格栅拉应变提升幅度越来越快,其中桩顶土工格栅拉应变最大,四桩区域中心最小,验证了土工格栅的张拉膜效应。

The outer side of the CFG pile is sleeved with a corrugated plastic casing with a suitable inner diameter to form a unified whole,which can better improve the durability and surface stress characteristics,and a calculation method of the ratio of load to displacement on the top of the vertically loaded pile is proposed by using the ideal elastic-plastic.In addition,we rely on the CFG pile project around a mining area in this paper,through the similar theory design,4groups of model tests:the natural foundation,the coal gangue CFG pile composite foundation,the corrugated plastic casing+coal gangue CFG pile composite foundation and the geogrid+corrugated plastic casing+coal gangue CFG pile composite foundation are completed,the settlement,pile-soil stress ratio and geogrid tensile strain of composite foundation during loading are obtained,and the influence of corrugated plastic casing and geogrid on the force characteristics and deformation laws of CFG pile composite foundation is discussed preliminarily.The research results show that:The corrugated plastic casing wraps the pile body,which can improve the bearing capacity of the composite foundation,reduce the pile-soil stress ratio and the pile-soil load sharing ratio.The pile-soil stress ratio is reduced by 29.5%,the pile-soil load sharing ratio is reduced by 7.8%.The pile tip resistance ratio is negatively related to the load,and the greater the load,the more significant the correlation.The geogrid acts on the gravel cushion,the pile-soil stress ratio is increased by 10.7%to 23.5%,the pile-soil load sharing ratio is increased by 2.9%to 8.4%,and the overall settlement of the foundation and the pile tip resistance ratio are further reduced.The tensile strain of the geogrid increases with the increase of the load,and the increase rate is getting faster and faster.The tensile strain of the geogrid on the top of the pile is the largest and the minimum at the center of the four-pile area,which verifies the tensile membrane effect of the geogrid.