沉箱码头地震液化任意拉格朗日欧拉方法大变形分析

Large deformation analysis of ALE method for seismic liquefaction of caisson wharf

摘要:

为解决传统UL方法在大变形分析中由于网格畸变出现分析中断的问题,基于水土二相混合理论和算子分离技术,开发了一种解耦合任意拉格朗日欧拉方法（ALE方法）,并将其用于松砂地基沉箱码头地震液化大变形分析。ALE方法能够在UL方法失效时完成强震作用下松砂地基沉箱码头的地震响应分析,保证网格整体质量并提供误差较小的数值解。此外,将ALE方法用于松砂地基沉箱码头地震液化减灾措施评价,为松砂地基下沉箱码头优化设计提供了一种途径。结果表明:松砂地基条件下,加密置换区土体能显著减小沉箱结构的位移和沉箱趾部前端隆起；对于置换区不加密的情况,加密回填区土体能减小沉箱结构的位移,但对置换区加密的情况,加密回填区土体对沉箱结构的位移无明显减小作用；置换区和回填区均存在临界有效加密范围,超过此范围,沉箱结构的位移响应无明显变化；碎石桩结合置换区和回填区加密措施能进一步减小沉箱结构的位移响应,并提高沉箱结构的抗液化潜能。

Abstract:

Based on the soil-water two-phase mixing theory and the operator separation technology, a decoupled Arbitrary Lagrangian Eulerian method (ALE method) was developed, aiming to overcome the analysis interruption caused by mesh distortion in large deformation analysis of traditional updated Lagrangian (UL )method. The ALE method was applied to the seismic liquefaction analysis of caisson wharf on loose sand foundation. Results show that the ALE method could complete the seismic response analysis of caisson wharf under strong earthquake when the UL method failed, and provide numerical solutions with higher accuracy while maintaining the mesh quality. In addition, the ALE method was applied to the assessment of liquefaction mitigation measures of caisson wharf, providing a method for the optimal design of caisson wharf on loose sand foundation. Results show that the displacement response of caisson structure and the uplift of the front of the caisson toe could be significantly reduced by soil densification in replacement region. Soil densification in backfill region could reduce the displacement response of caisson structure under the condition of soil non-densification in replacement region, but it had little effect on the displacement of caisson structure under soil densification in replacement region. Both the replacement region and the backfill region had critical densification ranges, and there was no obvious change in the displacement response of the caisson structure while exceeding the critical densification ranges. The combination of gravel piles with densification in replacement region and backfill region could further decrease the displacement response of the caisson structure and increase the anti-liquefaction potential of the caisson structure.