Pressure Distribution of TAM Grouting under a Deep Excavation in Silty Soil

This paper will report a Tube-a-Manchette (TAM) grouting project carried out in the silty sand and gravel layer to seal off the bottom of a deep excavation against uplift of high groundwater pressure. The excavation was up to 33 m in depth and was retained by diaphragm wall 53 m deep. The base grouting zone covered the interface zone between sandy and gravel layers. TAM grouting method was adopted to do the grout injection. Cement-bentonite (CB) grout was injected in the first stage followed by sodium silicate grout (SL grout) in the second stage. Volume control grouting method was adopted here and the grouting pressure applied at each injection port was recorded. Based on the recorded pressure and the spatial coordinates of each injection port, a mapping of grouting pressure in the grouted zone was presented in 2D image using commercial software. The 2D grouting pressure contours at a given depth can be established based on the physical data recorded during base grouting. Meanwhile, it was also found that the deviation of drill holes alignment had no obvious effect on the 2D grouting pressure distribution, if a proper TAM grouting sequence and a lateral confinement of enclosed diaphragm wall can be provided.