Experimental Study Of Frozen Soil Model With A Simulative Frost-thawing Interface

Frozen soil distributes broad in China. After Qingzang Railway being constructed, engineering problem resulting from permafrost must be taken into account during construction period or transport operation one. The influence which frozen soil brings to roadbeds and engineering structures come mainly from activity layer. In despite of vertical connected permafrost or vertical detachment of frozen soil, activity layer exist a frost-thawing interface that develops downwards. As frost-thawing interface being typical solid-liquid phase transition one, the position can be ascertained using acoustoelectric transferring method. This experiment is conducted to build a correct frozen soil model that simulates frost-thawing interface and look for using acoustoelectric transferring method to confirm the position of frost-thawing interface in activity layer and the thick of activity layer. This will also establish the foundation of laboratory research of acoustoelectric effect.This thesis carrys on research work surrounding design and making frozen soil model with a simulative frost-thawing interface. It includes mainly four parts: the analysis soil sample, the model design and making, the design of observation platform and the observation of acoustoelectric effect on the model.Because of model experiment belonging to analogue method, the thesis give an outline of similarity simulation. With reference to the three principle of model formation, ground temperature status and influencing factor of frozen soil in Qingzang Altiplano are analyzed, and geotechnical test and chemical analysis of frozen soil sample from permafrost zone are done. Because the soil sample comprises soil and rock, the geotechnical test and chemical analysis be carried through in parts. For soil sample, the determined seven parameter are density water content specific gravity particle analysis liquid limit plastic limit and single axis compressive strength. For rock sample, water absorption rate saturation water absorption rate and acoustic wave velocity are determined.The emphasis of the thesis is making a study of design and making rightly two models: one with fixing frost-thawing interface and the other with changing one. To verify the correctness of models, temperature monitoring and sound electricity transferring method are done. The yardstick is that they are uniform. For design, the structure of model size of model body and temperature control are main considerers. For making, most considerers be laid some skill problems such the surface of model body cleaning and the laying of electrode etc.The observation platform is very important in model experiment. For temperature measuring, a observation system is made that can collect in synchronism the temperature information of eight resistance thermometer sensor and real-time recording automatically them. The observation system of ultrasonic measurement is basically same with acoustoelectric measurement. Only they use different receiving sensors. This system can carry out data acquisition of high resolution high sampling rate and multiple stackings.As a result, acoustoelectric transferring method can match case with temperature monitoring, and this is a witness to that sound electricity transferring method has actual value on confirming frost-thawing interface of frozen soil.