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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。
The burial of nuclear waste and the use of energy piles will increase the temperature of the foundation soil and change the mechanical properties (especially strength and stiffness) of the soil, causing additional deformation and even instability of the foundation soil around the high temperature structure. Previous studies mainly revealed the effect of drainage temperature increase (slow temperature rise) on the mechanical properties of soil, and seldom considered the effect of undrained temperature rising (rapid warming) on the foundation soil frequently encountered in practical projects. Based on the theory and experiment, the pore pressure response of clayey soil during undrained temperature rise was studied. In theoretical research, the relationship between clay temperature and pore pressure is deduced based on the critical mechanics framework. At the same time, an additional temperature controller was added to the GDS triaxial apparatus to experimentally study the pore pressure response of two kinds of clays (Zijingang clay and Malaysia kaolin). The experimental results show that under undrained heating, positive excess pore pressure is produced in both normal consolidated and overconsolidated clays. The excess pore pressure increases with the increase of temperature, but decreases with the increase of overconsolidation ratio of soil. For normal consolidated soil, the soil effective stress is reduced by about 10% for every 10 ℃ increase in the range of 20 ℃ ~ 55 ℃. When the overconsolidation ratio is greater than 10, the excess pore pressure caused by undrained heating is almost negligible. The relationship between clay temperature and pore pressure calculated by the formula is comparatively good with the experimental results, which verifies the feasibility of the formula.