Hydrogeological Uncertainty-Induced Over-Seepage Control by Grouting in Basement of Existing Building in Urban Areas

Over-seepage caused by cracking of the basement floor is one very common geo-hazard for existing buildings in urban areas. It is usually caused by the under-estimated groundwater table for anti-floating. However, the exact estimation of the water table for anti-floating is very difficult due to the hydro-geological uncertainties. If the actual groundwater pressure excesses the designed value of anti-floating water table, the basement floor will bend excessively and then may cause cracking resulting in groundwater inflow into the basement. Over-seepage not only might cause massive flooding but also will trigger stability related risk of the foundation structures. Thus, it must be controlled strictly to ensure the safety of the building. Traditionally, anti-floating anchor, band drain or covering with concrete are always utilized to control the over-seepage. However, these measures might not work well when the basement floor is cracked significantly. In this paper, the grouting was utilized to control the serious over-seepage. Grouting was performed in the basement and the range to be injected was determined according to the groundwater pressure and favorable permeability to be achieved. Both voids and cracks existed in the range to be grouted can be filled or sealed properly, leading to a significant reduction in permeability of the injected formations. As a result, the injected formations can work together with the basement floor, to reduce the seepage and to resist the extra cracking of the basement floor. The result of the case reveals that the grouting method does works well and it provides a promising alternative to control the over-seepage of building basement in urban regions with water-bearing subsoil.