考虑土体参数不确定性的供水管道地震响应分析

埋地管道周围土体性质沿管道纵向存在不确定性,直接影响到埋地管道的地震响应规律和抗震性能。为此,基于设计反应谱合成不同抗震设防烈度下的人工地震动,采用简化弹性地基梁模型,分析地震行波作用下的管道接口动力响应。考虑因安装环境差异、管道老化等因素引起的球墨铸铁管道接口强度的折减,分析土体重度、内摩擦角、黏聚力和土弹簧屈服位移4个不确定性参数对埋地球墨铸铁供水管道地震响应的影响规律,并对不同地震烈度、不同薄弱接口抗拉强度折减系数土参数不确定性规律进行总结归纳。算例分析表明:与确定性参数模型计算结果相比,4个不确定性参数对接口峰值动力响应的影响程度依次为黏聚力、内摩擦角、土体重度、土弹簧屈服位移,同时考虑4个不确定性参数的模型对结果影响最大,最大接口张开量的变异系数可高达9.54%；考虑土体参数不确定性的均值与确定性工况基本一致,最不利值为确定性工况的1.09~1.31倍；管道局部接口抗拉强度的折减对管道接口位移的响应影响显著。基于计算结果给出了不同地震动强度下接口薄弱系数与接口最大张开量的预测公式。

Seismic analysis of water pipeline considering uncertainty of soil properties

The properties of the soil around buried pipelines vary in longitudinal direction, which directly affects the seismic performance and reliability of the pipelines. On the basis of design response spectra, artificial ground motions with different seismic intensities were generated, and a simplified elastic foundation beam model was adopted to analyze the dynamic response of pipeline joints under the seismic wave passage effect. Considering the reduction in the tensile strength of ductile iron water pipeline joints caused by factors such as installation difference and pipeline aging, the effects of four uncertain parameters (soil weight, internal friction angle, cohesion, and yield displacement of soil spring) on the seismic response of buried pipelines were investigated, and the uncertainties of soil parameters under different seismic intensities and weak joint ratios were analyzed. Results show that compared with the calculation results of the model with parameter certainties, and the influences of the four uncertain parameters on the peak dynamic response of joints from large to small were cohesion, internal friction angle, soil weight, and soil spring yield displacement. The model containing four uncertain parameters had the greatest influence on the results, and the variation coefficient of peak joint opening was up to 9.54%. The mean values of the conditions with parameter uncertainties were consistent with the results of certainty condition, and the most unfavorable values of uncertainty conditions were 1.1-1.3 of the results of certainty condition. Besides, the reduction in the tensile strength of the local joint had a significant effect on the response of the pipeline joint. On the basis of the numerical results, the prediction equations between the weak joint ratio and the peak joint opening under different seismic intensities were proposed.