Research On The Dam Seepage In The Basalt Area Based On The Comprehensive Detection Methods

In recent years, the dam leakage has occurred frequently due to the poor construction quality and the selction of dam sites. The leakage issue would cause the water level failed to reach the normal designed retaining level, which means the reservoir cannot be functioning as design and the benefits of the water conservancy project would reduce. A serious leakage problem would lead to an abandoned reservoir. The outbreak of a dam failure would bring on the loss of life and property of the dowmstream residents. Therefore, leakage detection is necessary for the safty of people’s life and property.During the prevention and reinforcement process, finding out the reason of water leakage and ascertaining the leakage passage are a prerequisite to the reasonable anti-seepage measures. The geological condition in the multi-period basalt zone is complex. Both the primary joint and the stress-release crack developed more in the zone. The contact area is mostly filled with the mud and gravel. In these conditions, grouting technique is difficult to operate. The leakage issue is widespread in the zone. Previous results obtained by a single detecting approach usually have multiple solutions, and cannot accurately analyze the cause of leakage and detect leakage passage. By using a variety of methods for comprehensive detection and through the interplay, the result can be accurate relatively.This paper selected a reservoir in the north of Neimenggu province as the study area. Based on several times of geological survey and grouting measures, a comprehensive tracer test is performed to detect the reservoir leakage. In this way, the main recharge source of the leakage location under the dam is judged. The strength grade of leakage is also divided. The method offered a reference for the leakage detection in the multi-period basalt zone.By this research, the following conclusions are obtained:1)The results of the geological drilling, groundwater level oberservation, temperature test of the borehole, tracer test and flow rate test are in good agreement. The cause of leakage and leakage passage determination is consistent.2)The geological condition and hydrogeologic condition in the zone are complicated, which cause difficulty in grouting. Several groutings cannot contribute to the leakage issue.3)The left dam abutment has a bypass leakage problem. In some region there exists stronger seepage. The key position of leakage in the range of 30 m, vertical to the slope, between the diaphragm wall and the shallow rock contact zone of the left dam abutment. And that is the main recharge source of the free flow under the dam.4)The sand-gravel aquifer of the Tertiary in study area has a strong leakage; most of the seepage flow pass through this aquifer and discharge to the downstream. Only a small amount of leakage water is recharged to the Quaternary phreatic groundwater.