基于ABAQUS生死单元技术的平衡地应力方法研究

Analysis of Balanced Geostress Based on Method of Killing Activating Elements in ABAQUS

初始地应力是岩土工程数值模拟过程中必不可少的一部分,其初始地应力平衡效果的好坏对后续的数值分析有着较为显著的影响。通用有限元软件ABAQUS虽然提供了多种地应力平衡方法,但是岩土工程材料多样、工况复杂,并不是所有的常规方法都能使地应力平衡满足要求。针对压硬性砂土地基中桶土相互作用问题,通过二次开发,对于ABAQUS软件中的Mohr-Coulomb弹塑性本构模型进行改进,从而可以考虑砂土中变形模量随平均主应力变化的压力相关性。进而基于软件中生死单元功能,提出了一种分步平衡法,通过分步创建桶土之间的接触以更好地模拟地基在桶土相互作用过程中的实际响应。结果表明,分步平衡法的地应力平衡效果明显优于常规自动平衡法,可为其他类似模拟提供参考价值。

The initial ground stress is an essential part of the numerical simulation of geotechnical engineering,and the balance effect of the initial ground stress has significant impacts on the subsequent numerical analysis.The software ABAQUS can provide a number of methods for initial ground stress balance,however,due to various geotechnical engineering materials and complex working conditions,not all conventional methods can meet the requirements of initial ground stress balance.Aiming at the bucket soil interaction in sand with hardening behavior,the Mohr-Coulomb elasoplastic constitutive model in ABAQUS is improved by redevelopment through user subroutine interface,so that the pressure dependence of modulus of sand with the variation of average principal stress can be modeled.Then based on the function of killing activating elements in the software,a two-step balance method is proposed.In the method,the contact between the bucket and soil is constructed step by step to better simulate the actual response of the foundation in the bucket-soil interaction process.The results show that the in-situ stress balance effect of the two-step balance method is obviously better than that of the conventional automatic balance method,which can provide reference value for other similar simulation.