土压平衡盾构非满舱气压辅助施工螺旋输送机闭气能力分析

Analysis on Air-tightness Capacity of Screw Conveyor Under Non-full Chamber Compressed-air Assisted Construction of Earth Pressure Balance Shield

摘要:

针对压缩空气沿着螺旋输送机出口方向逃逸导致难以在压力舱内建立起稳定气压的问题，基于Geostudio Air/w软件建立压缩空气在压力舱?螺旋输送机中的气?水?固耦合计算模型，分析不同空气压力、渣土性质及盾构压力舱空舱高度下压缩空气对螺旋输送机出口处渗气率的影响。结果表明，渣土渗水系数和舱内压缩空气压力是影响压力舱内压缩空气逃逸的2个主要原因，渣土改良可以降低渣土渗水系数，从而提高空气压力。当渣土渗水系数从6×10^-6 m·s^-1逐渐降低至6×10^-8 m·s^-1时，压力舱保压能力从130 kPa线性增长至240 kPa；当渣土渗水系数进一步降低且小于4×10^-8 m·s^-1时，压力舱保压能力可以达到300 kPa。螺旋输送机的内部构造可有效降低压缩空气的逃逸，未考虑螺旋输送机结构内部特征时的渗气率是考虑时渗气率的7倍以上。

Abstract:

This study focuses on the issue of compressed air pressure escaping along the outlet direction of the screw conveyor， which makes it difficult to establish a stable air pressure within the pressure chamber. A gas-water-solid coupling calculation model for compressed air in the pressure chamber-screw conveyor system is developed based on Geostudio Air/w. The effect of compressed air under different air pressures， conditioned soil properties， and empty chamber heights of the shield pressure chamber on the air leakage rate at the screw conveyor outlet is analyzed. The results indicate that the conditioned soil water permeability coefficient and compressed air pressure in the chamber are the two main factors affecting the escape of compressed air in the pressure chamber. Soil conditioning can reduce the water permeability coefficient of conditioned soil， thereby increasing the auxiliary air pressure. When the water permeability coefficient is gradually reduced from 6×10?? m·s?1 to 6×10?? m·s?1， the pressure retention capacity increases linearly from 130 kPa to 240 kPa. When the water permeability coefficient is further reduced to less than 4×10?? m·s?1， the pressure retention capacity of the pressure chamber can reach 300 kPa. The internal structure of the screw conveyor can effectively reduce the escape of compressed air. The air leakage rate without considering the internal structural characteristics of the screw conveyor is seven times more than that when the structural characteristics are taken into account.