Numerical Analysis And Field Experiment Research Of Soft Soil Foundation Treatment With The Method Of Drain With Pre-loading

Soft soil is very widely distributed in China, soft foundation have engineering propertiesof volume settlement, low bearing capacity, long consolidation time and so on. Unequalsettlement or settlement will occur on structures built on soft foundation，affecting the thenormal use of the structures，even causing the quality and safety incidents. In recent years,with the development of the national economy, a large number of roads, airports, ports andother kinds of engineering treat soft foundation by surcharge preloading, achieving goodreinforcement effect. But large post construction settlement and lack of foundation bearingcapacity and other issues are still not saved. What is more, reinforcement design calculationscould be improved. Therefore, there is a very important practical significance to study law ofthe soft foundation settlement, gaving a reasonable construction progress, improving designmethods, so that more accurate prediction of post construction settlement can be got.Relying onpreloading ground treatment project of the Shanghai Hongqiao InternationalAirport expansion project in West Cargo Area，through on-site monitoring experiment, thetheory predicts, the numerical analysis, several aspects of the study are made:(1) Analyzing monitoring data, according to the on-site construction progress of the load,studying the drain board surcharge preloading in soft soil foundation treatment, law of soilsubsidence and soil settlement, law of pore water pressure dissipation and effect offoundation consolidation(2) The logistic model, hyperbolic model, exponential curve model is used to predict finalsettlement according to measured data. Based on deviation and fitting error, comparinganalysis predicting results, the final settlement is obtained. Layerwise summation method isused to obtain the final settlement, and experience coefficient is suggested to be improved. (3) Analyzing the problems and defects in the existing design and calculation method.Aim to the major shortcomings, to consider the soil compression characteristics as well aschanges of the average degree of consolidation along the depth, the impact of thenon-linearity of the soil, as well as the construction process, the appropriate improvedcalculating design method is taken to form preliminary control station settlement calculationmethod.(4) Using the simplified method, based on the principle of consolidation equivalent, andto consider the effects of well resistance and smear, the complex sand well the foundation istransformed into sand wall foundation, it is facilitated to the finite element calculation; Basedon ABAQUS finite element analysis software, combined with the actual engineering soilparameters, a whole process simulation is made for drainage board reinforced soft ground andthe final settlement is predicted. Comparing the calculated results with the measured data andtheoretical calculations, it shows that the numerical method to simulate the settlement ofsoft ground to meet the requirements of engineering precision, it is recommended to be usedin the actual design and construction.(5) Finite element numerical simulation for a large area loading has a large settlementdeviation. Surface subsidence was "saddle-shaped", and solutions are proposed to save thisproblem, according to load time and the size of the reinforcement area.