Research on mechanical model of unsaturated soil taking account of its thermal properties

本研究的最终目的是探讨九州岛南部地区在暴雨时经常发生的边坡失稳的机理，并将其结果应用于预测边坡失稳的规模和时间。针对上述问题，开展了非饱和桑迪三轴试验、土中吸力、温度和降雨量的现场观测以及建立力学模型的数值研究。通过对取自大隅半岛和丰浦砂的非饱和白砂在不同温度和排水条件下的三轴试验，研究了温度对土力学特性的影响。围压范围为0.5- 1.5kgf/cm ~ 2，槽温范围为10-40 ℃。研究发现，由于温度引起的表面张力和粘滞系数的变化，导致了固结和剪切过程中不同的应力-应变关系，建立了现场观测的吸力、温度和降雨量的数据采集系统，其中，数据被自动归档在数据记录器中，并且记录器中的数据被允许通过注释在软盘中每隔几个月获取一次-提出了考虑温度和压力作用下孔隙流体相变的力学模型，并对降雨和日照作用下土壤的干湿变化进行了数值模拟。将计算结果与现场土中吸力和温度观测结果进行了对比，提出了一种新的基于粘聚力的边坡稳定性分析方法，并对含水量对边坡安全系数的影响进行了数值研究。

The final aim of this research is to investigate the mechanism of slope failures, which often occur in the southern part of Kyushu Island when the heavy rains fall, and to apply the results to predict the scale and time of slope failure. The triaxial tests on unsaturated sandy soil, the field observation of suction and temperature in soil and the amount of rain fall, the numerical research to establish the mechanical model have been carried out to solve the problem above. Some consideration has also done to propose a new slope stability analysis for Shirasu ground.The triaxial test on unsaturated Shirasu sampled at Ohsumi Peninsula and Toyoura sand were carried out under drained-aired and different temperature condition to examine the thermal effect on mechanical behavior of soil. The range of confining pressure and cell temperature are 0.5-1.5 kgf/cm2 and 10-40ﾟC respectively. It is found out that the change in the surface tension and the coefficient of viscosity due to temperature caused the different stress-strain relation in the consolidation and shearing processes.The data acquired system in the field observation has been eatablished for suction, temperature and rain fall measurement, in which the data are automatically filed in the data loggers and the data in loggers are allowed to be acquired once a few months in the floppy disk by the note-type's personal computer.The mechanical model taking account of the phase change of pore fluid due to temperature and pressure was proposed and some numerical experiment was done to simulate the wetting and drying of soil due to the rain fall and sunshine. The results were compared with the data obtained by the field observation of suction in soil and temperature.The new slope stability analysis was proposed based on the consideration on the cohesion which depends on the water content and the effect of water content on the safety factor of slope was numerically investigated.