Prediction and Design of Grouting Parameters for Long and Large-Diameter Postgrouted Drilled Shafts

The two main parameters of grouting volume and grouting pressure are the keys to ensuring the quality of postgrouting. However, there is no equation for predicting the main grouting parameters of long and large-diameter postgrouting drilled shafts. In this paper, field data of 708 shafts in 128 projects were systematically investigated utilizing mathematical statistics, and equations for predicting the grouting volume and grouting termination pressure of long and large-diameter drilled shafts suitable for various soil layers were proposed. The range of coefficients of the grouting volume classified by soil types was defined. When establishing the equation for predicting the grouting termination pressure for a long drilled shaft, the influences of the cement grout weight in the grout pipe and the height difference between the pressure sensor and the grout valve on the grouting pressure were considered. Taking the grouting pressure and grouting volume as the control conditions of postgrouting operation, the criteria conditions for terminating postgrouting were proposed.The proposed equations for predicting the grouting volume and grouting termination pressure were verified based on a project case study. The factors affecting the grouting termination pressure were analyzed in detail. These research results were of great significance to the design of postgrouting drilled shafts.