Study On Infiltration Process Of Water In Undisturbed Loess

China is loess covering the largest state in area, the Loess Plateau area of 44 million km2, loess not only cover a wide area and large thickness, loose structure, geological conditions is extremely unfavorable, the fragile geological environment and improper human engineering activities(improper excavation of slope and irrigation), concentrated rainfall patterns, resulting in the region become the landslide geological disasters occurred most frequent area. Rainfall and irrigation infiltration is one of the main factors to induce the loess landslide. Therefore, it has important theory and engineering practice to carry out the infiltration process of rainfall and irrigation water in undisturbed loess. This paper use indoor large undisturbed soil column experiment simulation of different rainfall and irrigation conditions in the height of 1 meter of the undisturbed soil column side wall buried moisture meter, water meter and a data acquisition system connected, observation moisture permeability in four depth loess water volume rate changes with time of intact loess moisture migration rules, based on using Hydrus-1D numerical simulation method to simulate the process of water movement and is of important scientific significance for in-depth understanding of rainfall and irrigation type loess landslide mechanism.The study found that in the rain along the undisturbed loess infiltration process, soil column infiltration early because of the relatively low moisture content and matric potential is related to the water rate and its gradient is larger, and therefore of the soil column infiltration capacity is relatively strong, the volume of water rate increased rapidly. Increase with time, the rain gradually into the loess soil column, moist peak constantly goes forward, loess soil column lower moisture content increased gradually, and matric potential gradient between the upper loess decreases, resulting in soil accept moisture ability gradually weakened. Therefore, the Loess Slope lost its stability, and soil suction decrease and even loss of closely related. Again irrigate into infiltration process, due to the initial moisture content is high, the matric suction is relatively small, under the pressure of the upper part of the head, suction and gravity, beginning to wetting front transport rate of growth very quickly, when the water motion to the soil at the bottom of the column, matric potential gradient and the loss and the maintain saturated infiltration. Soil column infiltration test results with the HYDRUS-1D numerical simulation results also exist certain errors, may is the use of small soil sample determination of the moisture characteristic curve parameter and unsaturated water coefficient with the actual soil column soil parameters also exist certain deviation, so in the simulation of intact loess moisture infiltration process to choose appropriate soil water characteristic curve of the classical model, consider the matrix suction and water content was between the existence of hysteretic curve, and must take into account the moisture absorption and removal effect on soil water characteristic curve.