【作者】 王斌；

【导师】 徐泽中；

【作者基本信息】 河海大学 ， 港口、海岸及近海工程， 2004， 硕士

【摘要】 在软土地基上进行高速公路的拼接拓宽工程，差异沉降的控制是拼接拓宽工程的核心问题。差异沉降的控制标准涉及众多因素，包括拓宽过程中及拓宽以后高速行车的平稳性、舒适性、排水的畅通以及新老路基间裂缝的开展等多种因素，其中高速行车的平稳性为主要因素。实践表明，当路堤纵横坡的改变量小于0.5％时，能有效的避免上述问题的产生，并以此作为拼接拓宽工程的差异沉降控制标准。 选择合理的地基处理方法减小新老路基间的差异沉降，是保证工程质量的又一个关键因素。减小沉降可以从两个方面入手：一是减小路堤的荷载，即采用轻质路堤填料；二是加固地基即形成复合地基，通过提高地基的承载力来达到减小沉降的目的。 轻质路堤填料，主要包括粉煤灰、聚苯乙烯硬泡沫塑料(EPS)、SLM轻质混合料等。实践表明，EPS硬泡沫塑料具有质轻、施工方便等优点，采用直立式结构能进一步减小地基压力，同时节约占地，能有效的减小新老路基间的差异沉降。它是拼接工程理想的轻质路堤填料。 传统水泥土搅拌桩法在处理深厚软基中存在处理深度浅、强度低等缺陷，为了进一步减小新老路基间的差异沉降，推荐采用强度高、处理深度大的PTC型先张法预应力管桩进行替代。为了充分发挥桩身强度大和桩间天然地基承载力的作用，应选择在桩的顶部设置桩帽和加铺碎石加筋垫层，形成桩网垫层的控沉疏桩复合地基。实践表明，其能有效的减小新老路基间的差异沉降，提高地基的承载力，处理效果明显，质量可靠。有限元分析及工程实践表明，对于加固区可采用复合模量法来进行疏桩复合地基的沉降计算，而对于原路中心处应结合原路不同的工况合理选择分析方法，使情况更加接近实际。工程实践表明，经济效益明显，与传统的深搅桩处理方法相比可节约造价20％，可在扩建、新建工程中推广应用。更多还原

【Abstract】 The control of the discrepancy settlement between the old road and the widening section is the crucial issue of the expressway widening engineering on soft soil ground. The discrepancy settlement control criterion relates to several aspects such as the placidity and comfort of driving at high speed, smooth drainage, and the crack which may occur during or after widening process. The practice indicates that if the change of the slope in length and breadth of road surface is under 0.5%, the problems above can be avoided, and this can be taken as the control criterion of discrepancy settlement of road widening engineering.The selection of reasonable foundation treatments to reduce the discrepancy settlement between the old and new roadbed is another crucial problem to ensure the engineering quality. We can reduce settlement in two ways: one is to reduce the weight of the road embankments using lightweight filling. And the other is to improve the soil ground such as forming composite ground to enhance the bear weight of the ground and reduce the settlement.The lightweight fillings include coal ash, expanded polystyrene (EPS). SLM light mixture and so on. The practice indicated that the EPS roadbed have advantages of light weight and convenient construction, erection structure will reduce more ground press and land area. This method can reduce the settlement availably and it is an ideal lightweight filling of the widening roadbed.The traditional methods of ground improvement such as cement soil piles have shortages of low strength and short treating depth. To further reduce the discrepancy settlement, we can use the PTC prestressed pipe pile which has higher strength and treating depth. To exert the strength of the piles and soil between the piles sufficiently, one pile cap is put on the top of the pile, and then gravel cushion is above, in the middle of the gravel cushion a layer of steel net is placed, and all these form the pile-net-cushion composite ground. The practice indicated that this method can reduce discrepancy settlement effectively, and enhance the bear weight of the ground. It is the effective foundation treatment of the deep soft soil ground. The finite element method analysis and the practice indicated that the reinforced foundation section can use composite modulus to computer the settlement, and the settlement of the center of the old road must be analyzed under different conditions. This method is economical than traditional cement soil method, and can save cost 20%, and can be spread to road or road widening engineering.更多还原