拟静力法在基坑抗震中的应用探讨

DISCUSSION ON THE APPLICATION OF THE QUASI-STATIC METHOD IN FOUNDATION PIT SEISMIC RESISTANCE

  • 摘要: 基坑工程作为项目建设的重要环节,其稳定性关系城市安全。随着地下枢纽、立体交通等理念的提出,部分基坑呈现规模大、周期长、周边环境复杂等特点。此时,不能简单将其视为一种临时结构,需要考虑地震等偶发灾害的影响。为了计算地震工况下的安全性,将拟静力法引入到基坑的稳定性分析中。汇总归纳了现有规范中的拟静力法,基于各规范的特点讨论了折减系数和放大系数取值原则。通过时程分析法,从剪力、弯矩和位移等方面进行验证。结果表明:在应用拟静力法时,应该考虑基坑工程的特点。区别于边坡工程,基坑工程加速度小于或接近地表设计地震。因此,加速度放大系数可取为1。 折减系数取0.25时,拟静力法计算结果略大于时程分析法,可以达到包络设计的目的。

     

    Abstract: As an important part of project construction, the stability of the foundation pit project is related to urban safety. With the concept of an underground hub and three-dimensional transportation, some of the foundation pits present characteristics such as large-scale, long-period, and complex surrounding environments. At this time, it cannot be simply regarded as a temporary structure, and the influence of episodic disasters such as earthquakes needs to be considered. To calculate the safety under seismic conditions, the proposed static method is introduced into the stability analysis of the foundation pit. The proposed static method in the existing codes is summarized, and the principles of discount and amplification coefficients are discussed based on the characteristics of each code. The method is verified in terms of shear force, bending moment, and displacement using time course analysis. The results show that the characteristics of the foundation pit project should be considered when applying the proposed static method. Different from slope engineering, the acceleration of foundation pit engineering is less than or close to the surface design earthquake. Therefore, the acceleration amplification factor can be taken as 1. When the discount factor is taken as 0.25, the calculation result of the proposed static method is slightly larger than that of the time analysis method, which can achieve the purpose of envelope design.

     

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