环境负温与升温温差作用下冻土强度特性的试验研究

Experimental Study on Strength Characteristics of Frozen Soil under Combined Environmental Temperature and Temperature Rise

随着西部经济快速发展,冻土区工程日趋活跃,冻土灾害问题愈显突出。为了减少灾害,提高工程耐久性,必须进行冻土区地基承载力的力学特性与温度变化的关系研究。采用青海省果洛州海拔4 200 m处冻土,在室内模拟不同环境负温与升温温差的冻土常规三轴压缩试验,得到冻土在不同环境负温、不同升温温差下的应力-应变曲线以及强度-温度关系曲线。试验结果表明,低温冻土到高温冻土的破坏特征是由脆性破坏过渡到塑性破坏,其应力应变关系由广义双曲线模型变为邓肯-张模型;环境负温与升温温差的不同,使得冻土强度折减不同;设计冻土区地基承载力时,需根据当地温度和升温温差等变化特点修正冻土区地基承载力特征值。

With the rapid economic development in the western region,the permafrost region is becoming more and more active,and the problem of frozen soil is becoming more and more serious.In order to improve the durability of the project and reduce the disaster,the relationship between the mechanical properties and the temperature change of the foundation bearing capacity of frozen soil area must be studied.The frozen soil is from 4 200 m above sea level of Guoluo region Qinghai province which can do an experiment with conventional three axial compression tests of frozen soil under different negative temperature and temperature difference.The stress-strain curves and the strength-temperature curves of frozen soil under different negative temperature and temperature difference were obtained.The experimental results show that the shear strain characteristics of low temperature frozen soil to high temperature in frozen soil change from strain softening to strain hardening and the relationship between stress and strain of frozen soil is changed from the generalized hyperbolic model to the Duncan Chang model.The difference of negative temperature and temperature difference makes the strength of frozen soil decrease.The results show that the bearing capacity of frozen soil foundation can be modified according to the local temperature and temperature gradient.