南宁软岩地基大直径灌注桩极限承载力预测

南宁市下伏泥岩粉砂岩地基具有显著的浸水崩解软化特性,使得该地基大直径灌注桩承载力难以确定。依托南宁市火车东站南广场高架平台工程软岩互层地基大直径灌注桩项目,对该工程2根群桩基桩进行了静载试验研究。针对试验中试桩未达到破坏其极限承载力难以确定问题,采用指数函数拟合法和数值反演分析法来预测其荷载沉降性状和极限承载力,并进行对比分析。结果表明:软岩互层地基桩基荷载沉降性状为缓变型,表现出端承摩擦桩的特性,可用指数函数来描述试桩受荷性状,并结合数值反演分析来预测其极限承载力,目前常用的桩基设计方法低估了该地基中基桩的承载力。

Prediction of Ultimate Bearing Capacity of Bored Pile of LargeDiameter in Soft Rock Foundation in Nanning

The bearing capacity of cast-in-place bored pile of large diameter in soft rock foundation in Nanning is difficult to determine due to softening and disintegration characteristics when soaked in water. Static load test was conducted to determine the bearing capacity of bored pile in the soft rock interbedding foundation of an elevated platform project in the railway station of Nanning Ciy. Both exponential function fitting method and numerical back analysis were used to accurately predict the load-settlement relation and ultimate bearing capacity of test pile which did not reach the ultimate state. Results show that the load-settlement curve of bored pile in soft rock interbedding foundation is an adjustment curve and the pile works as end bearing friction pile. As common design methods of pile foundation at present underestimates the bearing capacity of pile in this foundation, exponential function which is used to describe the load-settlement behaviour of test pile and numerical back analysis can be combined to estimate the ultimate bearing capacity of test pile.