New Theory & Technology Of Soft Soil Roadbed Transact Base On Pile-net Composite Foundation

Pile-net composite foundation is a type of artificial foundation in which net, piles and soil work together and perform compatibly. The pile-net composite foundation are composed of: (1) fill; (2) net and reinforced soil; (3) sand-stone mat or composite mat made with net; (4) reinforced region with nonstiff piles; (5) natural soft soil stratum or maintenance stratum.The pile-net composite foundation has the comprehensive effectiveness of pile, mat, drainage, squeezing denseness, reinforcement and prevention. It settles rapidly and has a small settlement deformation. Its residual settlement can be easily controlled, and it has a good stability, short construction period, and convenient construction. Also it does not need preloading. It can be arranged sparsely to reduce the number of piles and the cost of construction on a large scale. Pile-net composite foundation is suitable to the engineering such as railway, highway, city road, long-large dam and large area fill. So it has a wide application in the future.The main achievements in the thesis are:1. Based on the summary of practical engineering experience and the results of theoretical research, the definition of the pile-net composite foundation is given. Also its characteristics and application in the future are presented. Then its composition and cooperative working mechanism are analyzed. This method should be considered as an independent technique of foundation treatment.2. According to the static equilibrium conditions of the net element, the characteristics of embankment loading and the mechanism of residual settlement, a formula of pile-soil stress ratio is proposed. Analysis results prove that the stress ratio increases with the increase of loading, pile distance and mat stiffness and with the decrease of natural bearing capability and residual settlement. Otherwise, the stress ratio decreases.3. Based on the thin plates deformation theory and the Winkler elastic foundation model, a residual settlement formula of the pile-soil reinforcement area is proposed. Analysis results prove that the residual settlement increases with the increase of loading, pile distance and with the decrease of mat stiffness and soil stiffness (or bearing capacity). Otherwise, it decreases. The residual settlement is affected obviously by loading and soil stiffness, but it is not affected...