考虑强震激励的某核岛厂房非岩性地基不同处理方案的对比研究

Comparative Study of Different Non-rock Foundation Treatment Schemes for a Nuclear Plant Subjected to Earthquake Excitation

摘要:

如何选取非岩性地基的处理方案对于不满足抗震适应性要求的核岛厂房地基而言具有重要的工程实用价值。结合国内某内陆核电不符合抗震适应性要求的实际厂址条件，给出地基处理方案评价的数值计算模型及分析过程。首先针对该核电工程实际项目，提出嵌岩桩、CFG桩及水泥土搅拌桩三种地基预处理方案，并以规范法验证处理后地基的承载力要求；进而通过建立非岩性地基条件下的桩-土-结构动力相互作用计算模型来综合考虑各方案对核岛厂房的地震响应影响，其中通过引入黏性人工边界和能量传递边界模拟无限地基辐射阻尼效应，采用等效线性法描述近场地基非线性特征，并基于上述有限元模型以全耦合方式考虑群桩效应的影响；最后从满足厂址地基适应性和经济效益两方面进行综合评价，给出针对本工程的最佳设计方案。该分析方法及研究成果可为类似条件下的核岛厂房非岩性地基处理方案的比选问题提供借鉴与参考。

Abstract:

A comparison study of treatment schemes for non-rock foundation has important practical engineering value for a nuclear plant that does not meet seismic suitability requirements. According to the actual site conditions of such an inland nuclear power plant, a numerical calculation model is proposed, and the evaluation for foundation treatment scheme is carried out in this work. First, three schemes (the rock-socketed pile, CFG pile, and cement-soil mixing pile) are applied to the foundation processing based on the actual engineering situation, and the bearing capacity of foundation is verified by the normative method. In order to meet the requirements of bearing capacity, the calculation model of pile-soil-structure dynamic interaction of non-rock foundation is established, which can be used in the seismic response analysis of the nuclear plant. Meanwhile, viscous artificial boundary and the energy transfer boundary are applied to simulate the infinite foundation radiation damping effect. Meanwhile, the viscous artificial boundary, which is recommended by ASCE4-98, is used to simulate wave transmission in the artificial boundary by decorating a series of dampers in the boundary in such a way that they can absorb the reflection undulation energy of the external boundary. In the meantime, the equivalent linear method is used to describe the nonlinear characteristics of the near field ground. The equivalent linearization technique is then solved using the frequency-domain linear wave method. The calculation was done by substituting shear modulus and damping ratio in different strain amplitudes for the equivalent shear modulus and damping ratio, thus transforming nonlinear issues to linear one. In addition, the influence of the pile group effect is determined by using the full coupling method based on the finite element model. Finally, the optimum design scheme is obtained from the comprehensive evaluation of the site foundation adaptability and economic benefits. The research results can provide reference for the selection of various non-rock ground treatment schemes under similar conditions.