不排水升温条件下黏性土孔压响应

 核废料的埋置和能源桩的使用都会升高地基土的温度，改变土的力学性能(特别是强度、刚度)，造成高温结构周围地基土的额外变形、甚至失稳。以往的相关研究主要揭示排水升温(慢速升温)对土体力学性能的影响，而很少考虑实际工程中经常遇到的不排水升温(快速升温)对地基土的影响。基于理论和试验，对黏性土在不排水升温过程中的孔压响应进行了研究。在理论研究方面，基于临界状态土力学框架，推导了黏土温度与孔压的关系。同时在GDS三轴仪中增设温控仪，对2种黏土(紫金港黏土、马来西亚高岭土)不排水升温的孔压响应进行实验研究。实验结果显示，不排水升温作用下，正常固结土和超固结黏土中均产生正的超孔压。超孔压随温度的升高而增大，但随土体超固结比的增大而减小。对于正常固结土，在20 ℃～55 ℃范围，每升高10 ℃，土体有效应力约减小10%。当超固结比大于10后，不排水升温引起的超孔压几乎可以忽略。通过公式计算得到的黏土温度与孔压的关系与实验结果对比较好，验证了公式的可行性。

Effect of heating on the excess pore water pressure of clay under undrained condition

Both the nuclear waste container and energy pile buried underground will elevate the temperature and change the stiffness and strength of the surrounding soil，leading to the possible deformation and potential instability of the geo-structure. Despite the extensive investigations into the effects of heating on mechanical behaviour of clay under drained condition，little attention has been paid to the influence of heating on the clay under undrained condition，which is frequently encountered in practice. This paper aims to study the pore pressure response of clay due to undrained heating through both theoretical and experimental investigations. A simplified model base on the framework of critical state soil mechanics was formulated to predict the development of the excess pore pressure of clay due to heating. Two types of clay(Zijingang clay and kaolin clay) were investigated experimentally using a temperature-controlled GDS triaxial testing apparatus. It was shown that the positive excess pore pressure was induced in both normally consolidated and overconsolidated clays subjected to undrained heating. The excess pore pressure increased with the temperature elevation，but decreased with the over-consolidation ratio(OCR). For the normally consolidated clay heated from 20 ℃ to 55 ℃，each temperature increment of 10 ℃ led to a 10% reduction in the effective stress. When the OCR exceeded 10，the heating induced excess pore pressure was almost negligible. The calculated results using the proposed model agreed reasonably with the experimental data，confirming the validity of the proposed model .