文档介绍：We are the family! 软土地基处理新技术 ------预应力混凝土管桩
一、问题的提出
过去在一般公路通过软土地区,由于线路等级标准不高,路基
宽度窄、立交少、纵坡要求不严,且多低路堤,故对路基大部分地段
处理工程少,仅对桥头高路堤部位重视些。但从高速公路出现后,因
要求全立交、桥涵通道多,路堤高度多超过软土填土极限高度。加之
软土中含有大量亲水胶体微粒,土体多呈海棉状结构,因其孔隙比大、
含水量多、透水性小、抗剪强度低、压缩性强在路堤高填土的自重作
用下,要经过较长时间才能趋地压密稳定、因此其沉降稳定要花费长
时间。此外软土结构在大交通量、重载车辆的作用下,路基容易产生
侧向膨胀挤出滑动,基底沉降现象也严重,为了增强压密稳定力度和
较短时间达到最终沉降,消除侧向滑动位移,以免路堤向两侧膨胀挤
出,确保路基及其外侧建筑物或其他农田、虾池、鱼塘的安全,因此
必须对软基进行处理。
对软土地基处理方法的几点体会:
表层处理法
置换法
加载法
竖向排水法
表层处理法
置换法
加载法
竖向排水法
Thick layer of soft soil treatment design is difficulty in the designof foundation treatment and is the key to the ess of the whole foundation treatment project. At present domestic(国内的) mostly in coastal areas is relatively rare, monly used treatment measures are sand pile, crushed stone pile and cement mixing pile and CFG pile, vacuum preloading,  prestressed  concrete pipe pile and the EPS lightweight embankment and so  kinds of treatment’s selection mainly depends on its area, the geological hydrological conditions of treatment segment , the essful local experience ,as well as the Economy of treatment program, etc. mon treatments program in deep soft soil are as follows:
1、Cement mixing pile
2、CFG pile
3、PHC(Prestressed Concrete Piles)
4、Vacuum preloading
5、EPS embankment
pacted gravel pile
Prestressed Concrete Pile Prestressed concrete piles monly closed-ended tubular sections of 400 mm to 600 mm diameter with maximum allowable axial loads up to about 2 700 kN. Normal pile elements can be up to about 20 m long and are usually welded together using steel end plates. Prestressing concrete piles has several benefits. Tensile stresses, which can be set up in a pile during driving, can be better resisted, and the pile is less likely to be damaged during handling. Bending stresses, which can occur during driving, are also less likely to produce cracking. However, the ultimate strength in pression is decreased as the level of prestressing is increased. Therefore, prestressed piles are more vulnera