黄土塬滑坡地貌演化与水文过程响应机理

The response mechanism of geomorphological evolution and hydrological process in Loess Platform

中国黄土高原地区农业灌溉面积较大,使得地下水位显著上升。在甘肃省黑方台地区,因灌溉引起的黄土滑坡灾害达几十起,通过野外调查和数值模拟对黑方台滑坡灾害与地下水的响应规律进行研究。黑台地区滑坡具有明显的地貌演化特征,在此基础上,建立黑台水文地质数值模型。模拟结果表明,黄土泥流型滑坡的发生会影响地下水系统的边界条件,通过不断扩大的渗透面增加黑台地下水系统的排泄量,同时,因为塬面面积的变小进而减小地下水系统总的补给量。在给定的补给量的条件下,黑台地下水位首先随着滑坡的持续发生达到峰值,然后降低到接近2004年的水位,达到近似稳定状态,此时滑坡的累计体积达到了4600万m3。考虑到2004年的地下水位仍然高到足够引发泥流型滑坡灾害,此时黑台的塬面面积将会减少至7.8km2以下。如果不采取有效的措施,滑坡还会继续发生,研究区的滑坡灾害风险将会持续很长时间。

Due to the large area of agricultural irrigation in the Loess Plateau,the groundwater table in the plateau has been greatly increased and a large number of landslides have been induced.In the Heifangtai region of Gansu Province,dozens of loess landslides caused by irrigation has occurred.This paper studies the response law of landslide hazard and groundwater in Heifangtai region through field investigation and numerical simulation.The landslide in Heifangtai region has obvious geomorphological evolution characteristics.On this basis,the numerical model of Heitai platform hydrogeology is established.The simulation results show that the occurrence of loess landslide will affect the boundary conditions of the groundwater system,and increase the drainage of the Heitai groundwater system through the expanding seepage face.At the same time,because the irrigated area becomes smaller,the total recharge of the groundwater system is reduced.For a fixed recharge amount,the groundwater phreatic level first peaked with the continuation of the landslide,and then decreased to a level close to the 2004 level,and the cumulative volume of the landslide reached 4600×10^4 m^3.Considering that the groundwater level in 2004 is still high enough to cause landslides,the area of the Heitai will be reduced by less than 7.8 km^2.If effective measures are not taken,the landslide will continue to occur and the risk of landslide disasters in the study area will continue for a long time.