Application of Comprehensive Exploration Method in the Investigation of Sand Gravel Layer

As the bearing layer of foundation, sand gravel layer has the advantages of low compressibility and high bearing capacity. However, the stability of sand gravel layer is poor, which has the characteristics of no cohesion, strong permeability, high hardness and great difference in gradation, so it is difficult to survey and construct the subway. Based on the first phase project of Beijing Metro Line 19, the comprehensive exploration method of drilling, artificial exploration well, geophysical exploration, in-situ test, indoor test, on-site pumping test and underground water flow velocity measurement and other exploration methods were conducted, which were used to find out the characteristics of sand gravel layer, such as density, particle gradation, sand gravel layer strength and the occurrence of groundwater. This study could provide the basis for the design and construction of tunnel, and also provides a reference for the investigation of sand gravel layer.