考虑桩端持力层效应的能源桩受力变形特性研究

Investigations on thermomechanical behavior of energy piles considering bearing stratum effects at pile end

能源桩作为一种具备建筑承载和地热开发双重功能的新型建筑节能技术,近年来得到了越来越广泛的研究和关注。温度荷载的施加对桩体的设计和安全服役带来了新的挑战,但现有理论计算方法仍未能全面揭示热力耦合作用下不同承载性状能源桩的受力变形特性。基于弹性分析理论框架,进一步考虑了桩端持力层的影响,建立了能源桩热力分析模型,并结合典型现场试验结果进行了模型验证,着重分析了地层结构特征和桩基几何参数对能源桩荷载传递及位移行为的影响。研究结果表明:热致轴向荷载将随着持力层刚度的增加而增加,相较于摩擦型桩,温度变化将导致支承于硬持力层的能源桩产生更大的温度应力;桩端持力层、桩周土体及桩顶刚度情况是影响热致应力大小和分布以及热致位移的关键因素。基于理论模型获得的归一化计算结果旨在实现对能源桩热致应力及位移的估算,为不同承载性状能源的设计计算提供参考依据。

As a new type of energy-saving technology,the energy piles have received increasing attention due to their dual functions of load bearing and heat transferring.The application of thermal loads poses new challenges for the design and serviceability performance of the energy piles.However,in the existing theoretical studies,the stress-deformation characteristics of the energy piles subjected to the combined thermomechanical loading under different bearing conditions have not been fully revealed.In this study,an analytical model for the energy piles under different bearing conditions is established based on the framework of the elastic analysis theory,taking into account the effects of the end-bearing layer.The model is validated against the field test data.This study focuses on analyzing the effects of geotechnical conditions and geometrical parameters of the piles on the load transfer and displacement behavior of the energy piles.The results show that the thermally induced axial loads increase with the stiffness of the bearing layer.Compared to the floating-bearing piles,temperature variations will cause greater thermal stress in the piles bearing on stiff soil strata.The stiffnesses of the end-bearing layer,surrounding soil and pile head are the critical factors affecting the magnitude and distribution of the thermally induced stress and displacement.The normalized calculated results obtained from the analytical model can be used to estimate the thermally induced stress and displacement of the energy piles in practice and provide a reference for the design and calculation of the energy piles under different bearing conditions.