The Study On The Mechanism Of Seepage Failure And The Application Of Geotextile In The Protecting Of Seepage Failure In Jingbian Area

Infiltration and sabotage behind the dam has become a problem to be solved of silt dam a nd risk dam in Northern Shaanxi. This test is intended to grasp the type and the development process of dam seepage failure, and to observe the change of process of infiltration and sabot age inside the soil, and to judge the effect of geotextile in the prevention of infiltration and sa botage.The main results of this experiment show that:(1)The conclusion of the dam seepage failure phenomenon simulationIn the prophase of occurring the infiltration and sabotage, the stability of entire dam is better, and the toe site of the dam is no obvious displaced. But after the water level of dam continued to maintain a certain height for some time, the back slope of dam began to crack, and with the section soil of toe displace slowly. Over the time, infiltration and sabotage continue to evolve, the part soil of back slope begins to form mud to flow,and eventually cause back slope occurred structural damage.According to the repair test after the damage, the results show, after the dam occur failure, still using the same dam soil to repair is not really to solve the problem of destruction. And the site of restoration is more prone to damage actually(2)The conclusions of infiltration and failure process of dam soilThe whole process of Infiltration and sabotage can be divided into three stages: The first is the embryonic stage. In this stage, with the height of head to increase, seepage velocity is good linear relationship with the height of head,and at this point, the overall soil samples is relatively stable,and no particle occurs movement;The second is development stage. At this stage, seepage began to appear in the sediment particles,and flow rate declined at the beginning of this stage. After the return to normal growth, sediment content also increases with the increase of flow velocity in the seepage;The third is the destruction stage. As continuously increase of the head, infiltration and sabotage further development,and sediment content is also increasing in seepage. When finally the head reaches destruction head, seepage discharge rapid increase suddenly, and infiltration and sabotage ultimately form.(3)The conclusions of variable head to explore the position of soil infiltration and sabotageFor the soil samples of 20 cm thick of this test, at the bottom of 0 cm, with increasing of head height, the fine particles of soil occur transport in the soil, and finally the soil fine particles of 10-15 cm is loss most, permeability coefficient increases. Eventually leading to changes in soil structure, and in the layer occurred the infiltration and sabotage.(4)The conclusions of the effect of geotextile on the occurring of seepage failureGeotextile can effectively improve the critical gradient and damage gradient, and also can effectively shorten the sediment transport distance of the internal earth. To a certain extent can prevent the loss of fine particles of soil, but for the drainage of the soil has played a certain role in blocking,which resulting permeability coefficient reduced, porosity decreases, the maximum flow rate of occurring damage between the three have no significant difference. In general,geotextile alone can not effectively solve the problem of drainage dam, it also can not ultimately permanent solution to the problem of Infiltration and sabotage of dam.