长短桩复合地基沉降试验模型与研究

Experimental Model and Study of Long-short-pile Composite Foundation Settlement

复合地基的沉降特性是一个非常复杂的问题,尤其是在长短桩复合地基方面。通过室内长短桩复合地基模型试验对复合地基在竖向荷载作用下的沉降进行分析,研究分析长短桩共同加固区、短桩与下卧层交接面的沉降变化规律,同时分析了在竖向荷载作用下的下卧层应力变化规律。试验表明:(1)长短桩复合地基的沉降与桩长的变化呈负相关。桩长越长,总沉降量越小;桩长越短,总沉降量越大。长桩作为主控桩对沉降量的控制有显著效果。(2)在长短桩共同加固区域,桩体沉降变化幅度不大;长桩单独加固区对沉降控制效果比较明显。(3)受到加固区桩土相互作用的影响,下卧层中的附加应力和桩间土附加应力的受力机理相反。长桩受迫沉降,带动桩间土协同变形,以致使中心桩下卧层应力最大。

The settlement characteristics of composite foundation is a very complex problem, especially in the long-short-pile composite foundation. The settlement of the composite foundation under the vertical load is analyzed by the model test of the long-short-pile composite foundation in the laboratory. The settlement variation law of the long and short pile joint area, the short pile and the underlying layer is studied. At the same time, under the action of the stress law is also studied. According to the test results ： ①The settlement of long short pile composite foundation is negatively related to the change of pile length. The longer the pile length, the smaller the total settlement, the shorter the length of the pile, the greater the total settlement. The long pile as the main control pile has a significant effect on the control of the settlement. ②In the long and short pile common reinforcement region, the settlement variation of the pile is not great; the control effect of the single pile reinforced area is obvious. ③Influenced on the interaction of the pile and soil in the reinforcement area, the stress mechanism of the additional stress in the underlying layer and the additional stress of the pile is opposite. Forced settlement of long piles, drives the pile of soil collaborative deformation, results in the maximum stress of the center pile under the stress.