富水砂性地层盾构渣土改良试验与喷涌防治技术

为解决土压平衡盾构穿越富水砂性地层螺旋输送机喷涌、排渣不畅等难题,基于渣土改良剂的地层适应性规律研发新型化学改良剂并开展相关室内试验.试验结果表明:非离子聚合型泡沫剂可兼备发泡倍数与稳定性能,适当提高泡沫剂浓度Cf能够增大发泡倍率FER和半衰期HT.当cf＞5％时,由于达到临界胶束浓度,FER和HT趋于最大值.透射电镜...

Soil conditioning tests and screw conveyor spewing prevention technology of earth balance pressure shield tunneling in water-rich sandy stratum

To resolve the problems of screw conveyor spewing and obstruction of excavated debris during EPB shield tunneling in the water-rich sandy stratum, new chemical additives were developed based on the adaptability of soil conditioning agents for different stratum, and relevant laboratory tests were carried out. The test results show that the non-ionic polymerized foam agent has both foaming and stabilizing properties. An appropriate increase of foaming agent concentration (cf) can increase the foaming expansion rate (FER) and half-life time (HT). However, when cf exceeds 5%, FER and HT tend to reach the maximum value at the critical micelle concentration. The transmission electron microscope (TEM) test results show that the new liquid spewing-preventive agent has chain structures, and the purpose of spewing prevention through the adsorption and wrapping of fine-grained soil by the long-chain structure of the polymer can be realized. The test results of conditioned soil show that the slump of conditioned sandy soil increases with the increase of foam injection ratio (FIR) and spewing-preventive agent injection ratio (PIR), and decreases with the increase of bentonite injection ratio (BIR). When FIR=40%, BIR=20% and PIR=20%, the permeability coefficient of the conditioned soil is three orders of magnitude lower than that of the unconditioned soil. A three-dimensional digital microscope system was used to analyze the microstructure of different conditioned soil. The results show that the foam morphology changes from sphere to polygon with time. The clay particles in Bentonite may reduce the porosity of the coarse-grained soil. The spewing-preventive agent congregates the soil particles of different sizes together with water molecules to reduce the permeability of the conditioned soil. Additionally, the screw conveyor spewing prevention technology in water-rich sandy stratum is put forward combined with many shield tunnel projects, so that the successful excavating-through of the tunnels can be ensured.