Experimental study on water-gas pressure balance technology for the prevention and control of karst collapses

MA Xiao; ZHOU Zhihua; ZHENG Zhiwen; LI Xiujuan; JIANG Xiaozhen; WEI Pingxin; LIAO Zhongzhen; PAN Zongyuan

doi:10.11932/karst20250513

Abstract：With the expansion and increasing scale of underground engineering projects in China,geological hazards in karst areas,particularly the frequent occurrence of karst collapses,have become a major concern.To effectively prevent and control karst collapses,scholars have conducted in-depth research on the treatment methods over many years,yielding significant results.However,research on the method of balancing the water-gas pressure within karst pipeline systems remains insufficient,lacking both theoretical support and practical application to actual karst areas. To further explore this theoretical model,this study focuses on water-gas pressure balance technology for the prevention and control of karst collapses.A generalized geological model was developed,and two different specifications of indoor physical test models were designed and established.High-precision,high-frequency fiber optic pressure sensors were utilized to monitor pressure variations inside simulated karst cavities under varying conditions of vent diameter,initial water level,and flow velocity.This study specifically examined pressure fluctuations within the simulated cavities during changes in water level and the pressure pulsations occurring during water level drawdown.The aim was to identify a vent diameter capable of eliminating these pressure pulsations and balancing the internal pressure of the cavity,thereby establishing a general method for determining the vent diameter.The results of experiments show that the vent diameter required to balance water-gas pressure within the cavity can be categorized into three levels:the primary balance vent diameter that can eliminate pressure pulsations caused by water level drop;the effective balance vent diameter that can significantly reduce negative pressure within the cavity;and the optimal balance vent diameter that can effectively balance the water-gas pressure within the cavity.By analyzing the relationship between the vent diameter at each level and the cavity section diameter,the correlation between these diameters was determined,and the ratio of the vent diameter at each level to the cavity section diameter was established.It was found that the ratio of the balance vent diameter to the diameter of cavity section for eliminating water and gas pressure pulsations should exceed 0.5％.If the water vapor pressure within the cavity is to significantly reduce,this ratio should exceed 1.25％.Besides,this ratio should exceed 4.16％to fully balance the water-gas pressure inside the cavity. Finally,the determination of the vent diameter for pressure regulation,layout methods,depth design,and drilling process requirements should be considered when the application of water-gas pressure balance technology in practical prevention and control of karst collapses are discussed.This aims to refine the water-gas pressure balance technology for karst collapses and provide a theoretical basis for prevention and control measures.