Abstract：The measured data of the groundwater level，rainfall and the drainage tunnel discharge about the landslide are studied. Compared with the data of the groundwater level monitored by artificial and automatic measures before and after the implementation of underground drainage works，it is shown that the slope groundwater level has declined after excavating the underground drainage tunnel in crushed-rock slope. By analyzing the correlation of the groundwater level and rainfall，it is shown that the rising of the groundwater level is generally lagged behind the rainfall process；and if there has any accumulation rainfall previously，the groundwater level may be raised immediately with the latter strong rainfall，and the landslide will be induced. By analyzing the relationship between the drainage tunnel discharge and rainfall，it presents that the change of the drainage tunnel discharge is basically synchronous with the rainfall. And only when the rainfall is larger than a certain threshold value，the tunnel drainage discharge will increase correspondingly. By studying the changes process both of the drainage tunnel discharge and the groundwater level，it is shown that the increase of the drainage tunnel discharge is earlier than the rising of the groundwater level. Therefore，the maximum height of the groundwater level can be effectively reduced for the drainage role of the drainage tunnel during a rainfall process. The correlation of the groundwater level，rainfall and the drainage tunnel discharge is discussed based on the monitored data；and it is shown that the underground drainage tunnel measures in crushed-rock slope are reasonable and effective. If any similar crushed-rock slope needs to be controlled，the underground drainage tunnel would be a good choice.
