Ứng dụng giải pháp khoan trộn vữa áp lực cao để ngăn dòng thấm dưới chân tường vây khi thi công hố đào trong đất cát

Abstract

In geologic regions with the sandy layer thickness is very large and ground water level is high, control work of ground water is always very difficult to not influence on adjacent buildings in excavating process for deep pits. The Jet grouting technology was concentrated in this study to treating the soil below the bottom of the pit to reduce the permeability of soil to prevent seepage flowing into the pit. With the Hardening-Soil model (HS) in Plaxis program, back-analysis results show that horizontal displacement of diaphragm wall was appropriated with the monitoring results when modulus of the ground was taken from 2300 NSPT to 2600NSPT. The influence of the Jetgrouting slab layer (JGS) below the bottom of the pit was alnalyzed. The JGS layer shall be analyzed with three variables parameters: the permeability k, thickness T, Z position of JGS layer from bottom of pit. Analysis results show that the parameters k, T, Z has the great influence on the stability of JGS layer beneath the bottom of the excavation, the minimum factor of safety against uplift water pressure [FSuplift] on JGS layer is not constant, that depend on the permeability coefficient k of JGS layer, with the suitable value of k, T, Z, the JGS layer underneath the bottom of the pit is completely feasible to prevent seepage flow into the pit and total seepage discharge flow into the pit can decrease about 100 times whereas JGS layer is still stable.