Abstract: Throughout the study and analysis of the measurement principle of a differential pressure density test device and combined with the investigation and study of the working condition of this device in the bedrock grouting site, the error source of the differential pressure density test results and the structural defects of the device in the grouting process were evaluated. The following conclusions are obtained: the conventional differential pressure density test device is directly connected to the main grouting pipe in the test process, which is affected by the fluctuation of the grouting pressure as well as the flow rate of the grout in the grouting pipe, resulting in a large measurement error and the waste of the cement grout. According to the above disadvantages analysis, the density test device can be improved by removal the test device from grouting pipe through the diverter valve and then parallel connecting to the main grouting pipe. By doing this can largely avoid the unstable environment induced by the main grouting pipe and effectively reduce the grouting density testing error.

Key words: Grouting Engineering, Differential pressure Density Test Device, Disadvantages Aspects, Improved Method