ABSTRACT
Curtain grouting is commonly performed to cut off ground water flow and decrease the inleakage of water. Large open cut excavations in urban areas are challenging and contain significant risks of lowering the ground water level in surrounding areas, whicssh might cause significant damage to the nearby facilities. The theoretical assumptions for hydrogeological analysis are mostly based on aquifer theories and adapted for shallow excavations after simplifications. The design of curtain grouting is itself challenging for such shallow excavations considering the orientation of the joint sets and the conditions of the surface rock. The depth of the curtain grouting is generally decided based on experience. In this work, a case study is presented based on the design of curtain grouting for a large open cut excavation in Sockenplan area, at the south-east part of central Stockholm. Hydrogeological analyses were performed using several analytical solutions, in combination with conventional flow-net and numerical methods. Three dimensionalnumerical analyses were performed to estimate the inleakage of water into the excavated area for different depth of the curtain grouting and the corresponding drawdown of the ground water level in nearby areas. The results from the different hydrogeological analyses method were compared and evaluated. Finally, the inleakage of water into the excavated area was measured after the excavation and compared with the hydrogeological analyses. The study found that simplified analytical solutions underestimate the leakage in comparison with measured inleakage for this specific case. Furthermore, the depth of curtain grouting should be determined based on rock conditions and allowable water inleakage to prevent adverse effects on surrounding areas.
