Investigating the sealing efficiency of grouting in joints: insights from effects of the rheological properties of grout and joint characteristics

In tunnel construction, grouting is frequently used to decrease the permeability and increase the rock mass strength. One of the most challenging steps in grouting is choosing the best grout type to achieve the highest penetration and sealing efficiency in the joints. The main purpose of this study is to investigate the sealing efficiency of different grout types in the joints of a high-risk section of the Kerman water conveyance tunnel (KWCT). For this purpose, the penetrations of three types of grouts including Ordinary Portland Cement (OPC), Ultra-Fine Cement (UFC), and silica sol were determined using analytical equations. Thereafter, the sealing efficiency of each type of grout in joints with different apertures was calculated. Also, the penetration radius of each type of grout was simulated and calculated using UDEC code. Based on the results of the analytical equations, by performing the grouting for 20 min using silica sol-based grout, the joints of the high-risk section of the KWCT with apertures of 0.5-2.5 mm and 2.5-10 mm can be sealed at 'Fair' and 'Excellent' levels, respectively. Furthermore, based on the results of numerical simulations, the UFC and silica sol-based grouts can seal the joints in 'Good' and 'Excellent' levels, respectively.