The Numerical Simulation Research Of Soft Soil Ground Settlement During Long Term Under Repeated Loading

This paper based on the one-dimensional consolidation theory of Terzaghi, and derved the analytical solution of elastic consolidation theory under varying loads, and made many detailed analysis for various forms of repeated loading. Learn from the research achievement of soft soil consolidation theory under repeated loading made by the predecessors, some summaries has made. Generalized the consolidation of analytical solution formulas in order to facilitate computer programming and load type transform, and in this way the consolidation behavior of soft soil under various loads were analyzed. The part of theory of consolidation simulation based on the Modified Cambridge Model and elastic model respectively. With the use of ABAQUS finite element analysis software and its related subroutines the numerical simulation of each repeated loading has made, the two methods results analysis of finite element analysis and elasticity theory calculation are compared detailed and draw some important conclusions.Before the elastic consolidation analysis, the job unified the waves’ equation of trapezoid/rectangle/triangle must be done at first, which can be expressed by generalized trapezoidal waves. Then it can be expanded with Fourier series and using Fourier series represent the waves. Simply transform its parameters can get the arbitrary waveforms of trapezoidal/ rectangular and triangular waves. It’s a simple and practical way. In addition, using the same method, respectively, the Fourier series expansion formulas of generalized sinusoidal /half-sinusoidal/consinoidal waves can be derived. Finally, the general solutions of the analytical solutions of various loads applied on the elastic foundation which with a permeable boundary condition can be acquired. With the use of Maple mathematical software the loads routine can be programmed. Then input the soil parameters to analyze the consolidation behaviors of monolayer soft soil ground. Exporting the solving data, plotting and analyzing the results.The load parameters used in the elasto-plastic consolidation simulation are the same as elastic consolidation theory calculation. Programming the circular loading with DLOAD subroutine and outputing user defined field variables such as degree of consolidation with UVARM subroutine of ABAQUS. Exporting the calculated data, plotting and analyzing the simulation results.Through theoretical calculation and numerical simulation, the settlement/effective stress/degree of consolidation etc. can be obtained under various loads for 50 years, and the results were compared detailedly. The results show that under the same load the final settlement by numerical simulation is greater than it calculated by elastic consolidation theory. And the settlement is various from loading types to loading types. The effective stress acquired from the three methods are different as well. The effective stress of numerical simulation is increase with the number of loads as well as its volatility. Finally they are gradually become stable. And its volatility is greater than the value of theoretical calculation. Moreover, the three methods can reflect the hysteresis of effective stress. But the lag time is increasingly significant with the deepening of soil. The degree of consolidation is an important indicator of soil deformation. The logarithmic curves of consolidation degree under various loads are listed in this paper. Under the dead loading, the final degree of consolidation of the soil is basically reached 100%. While under cycle loading it will be never reach 100% even if the loading period is infinite. Different load has a different final consolidation degree, but the consolidation degree of simulation is greater than the theoretical calculation.In this paper, three methods have been used respectively for analyzing the consolidation behaviors of soft soil ground. Wherein the soil parameters used in the analysis of elastic consolidation theory are the converted average value of the soil layers’ depth. Taken it to be monolayer soil, but not according to the actual calculation of soil stratification. The analysis of numerical simulation is based on the actual stratified soil, which is closer to reality. The calculated result will difference between the methods. So it can provide a reference and guidance for practical engineering.