考虑降雨和蒸发条件的非饱和朗肯土压力计算分析

Calculation and Analysis on Rankine's Earth Pressure of Unsaturated Soil in Rainfall and Evaporation Conditions

降雨和蒸发会引起非饱和土体中水分的改变,从而导致基质吸力的变化。针对降雨和蒸发对非饱和土压力的影响,将稳定状态下非饱和土中的水流控制方程运用到朗肯土压力计算中,同时考虑中间主应力的影响,推导出降雨和蒸发条件下主动土压力公式和被动土压力公式,克服了朗肯土压力的不足。研究结果表明:降雨条件下,随着中间主应力参数b的增大和降雨强度的减小,主动土压力逐渐减小,被动土压力逐渐增大;蒸发条件下,随着中间主应力参数b和蒸发强度的逐渐增大,主动土压力逐渐减小,被动土压力逐渐增大。在进行土压力计算时,考虑降雨、蒸发和中间主应力的影响,更符合实际情况,更能发挥非饱和土体的自身性能。

Rainfall and evaporation give rise to the change of moisture in unsaturated soil,hence resulting in the change of matrix suction. In view of this,we applied the water flow control equation to the calculation of Rankine's earth pressure of unsaturated soil at steady state. Meanwhile,we overcome the shortcomings of Rankine's earth pressure by deriving the formulas of active earth pressure and passive earth pressure under rainfall and evaporation conditions in consideration of the influence of intermediate earth pressure. Results showed that under the condition of rainfall,with the increase of parameter b and the decrease of rainfall intensity,the active earth pressure decreased gradually and the passive earth pressure increased gradually; while under the condition of evaporation,with a gradual increase of parameter b and evaporation intensity,the active earth pressure decreased gradually and the passive earth pressure increased gradually. Taking the influences of rainfall,evaporation and intermediate principal stress into account in calculating the earth pressure is more consistent with the actual situation,and could also give more play to unsaturated soil's properties.