Research On Micro-expansive Cement-bsed Anti-dispersion Grouting Material For Flowing Water And Its Plugging Mechanism Of Karst Pipeline

The construction of underground engineering and the exploitation of deep resources are currently undergoing a rapid development phase in China.As a consequence,the geological conditions within these engineering projects are becoming increasingly intricate,resulting in a surge of geological disasters.Specifically,karst regions exhibit a diverse array of water-carrying structures,coupled with abundant groundwater recharge and smooth migration.This complex geological makeup substantially heightens the safety risks associated with engineering construction,making it susceptible to significant water gusher disasters if not appropriately addressed.Consequently,water inrush disasters have emerged as a pronounced issue in karst regions,posing threats not only to personnel and engineering safety but also jeopardizing the safety of groundwater and the surrounding ecological environment.Among the various types of karst structures,water gusher disasters induced by karst pipelines are characterized by large flow rates,high velocities,significant disaster potential,and formidable treatment challenges.The efficient management of such issues holds paramount practical significance for ensuring the safety of engineering construction and its sustained long-term operation and maintenance.Grouting stands out as the most commonly employed method to control water outburst disasters in karst regions,with the grouting material playing a pivotal role.The critical challenge lies in effectively enhancing the flowing water dispersion resistance of cement grouting and ensuring the long-term stability of the consolidation body,as these factors represent a bottleneck issue impacting flowing water sealing efficiency and long-term treatment effectiveness.Existing flowing water grouting materials exhibit limitations in realizing anti-dispersion performance and the long-term service performance of the consolidation body.Common issues include weak anti-dispersion performance before gelling,low underwater cementation strength,and susceptibility to volume shrinkage in the consolidation body,collectively resulting in suboptimal sealing effects for karst flowing water.Simultaneously,considering that the grouting mode is influenced by the diffusion and migration of cement grout with different properties directly in a moving water environment,and the flowing water grouting of karst pipelines is affected by various factors such as moving water conditions,pipeline characteristics,and cement grouting performance,the diffusion law and sealing mechanism of grout exhibit a high degree of complexity.Existing understanding remains insufficient,making it challenging to provide effective references for grouting parameter design.To address the aforementioned challenges,this paper conducts research on micro-expansion cement-based flowing water anti-dispersion grouting materials and the flowing water sealing mechanism of karst pipes.The study introduces a novel grouting material(EAG)suitable for the flowing water sealing of centralized karst water passages,analyzes the action mechanisms of each component,and proposes a method for controlling the working performance of the new material.Based on laboratory grouting simulation tests,numerical simulations,and field experiments,the paper expounds on the migration and diffusion patterns of the new material in the process of karst pipe grouting and elucidates the mechanism of flowing water sealing.The main work and achievements of this paper can be summarized as follows:(1)Based on the composite action principle of organic and inorganic components,with pH value,suspended turbidity content,slurry fluidity,setting time,free expansion rate,and compressive strength as control indexes,the composition and dosage of underwater anti-dispersion components,expansion components,coagulation-promoting components,and coagulation-promoting components are determined.A cement-based flowing water anti-dispersion single-liquid grouting material has been developed,which has advantages such as strong anti-dispersion property in water before and after initial setting,micro-expansion of consolidation body volume,superior long-term strength stability,and flowing control of gel time.Furthermore,the action mechanisms of these components are analyzed through X-ray diffractometer(XRD),thermal gravimetric analyzer(TG-GTA),scanning electron microscope(SEM),and other microscopic testing methods.(2)The laboratory test method is adopted to study the effects of anti-dispersion components,expansion components,and coagulation-promoting components on the rheological properties,pH value,suspended turbidity content,setting time,volume stability,and mechanical strength of the new type cement-based flowing water grouting materials.The impact of water scour and dilution on setting time,compressive strength,and volume stability is compared and analyzed through underwater molding methods.Finally,an artificial neural network is employed to establish a flowing control method for the initial flow,initial setting time,and mechanical strength of the new grouting material.(3)By utilizing a self-designed visual pipelines simulation test device for grouting and sealing in flowing water,this paper analyzes the diffusion and migration mode of the new grouting material under different water velocities and changes in inner diameter(diameter expansion and diameter reduction).Based on finite element numerical simulation,the study examines the influences of water velocity,grouting pressure,and grouting material properties on grout diffusion and migration.The sealing states of the new grouting material in flowing water pipelines are classified into three categories:complete sealing,incomplete sealing,and slurry loss due to difficulty in retaining.The phase interface between grout and flowing water is divided into the whole grout zone,grout-water mixing zone,and moving water flow zone.Based on flow deposition theory,the deposition process and blocking mechanisms of the slurry are analyzed,meanwhile,the critical conditions for pipeline flowing water sealing are clarified.(4)Based on the karst ground collapse disaster control project in Guigang City,Guangxi,the field test of the new grouting material was carried out.Based on comprehensive exploration and hydrogeological testing result,the borehole connected with the karst water passage is identified as the test hole to carry out flowing water grouting plugging test.Based on the new material performance regulation method and the specific project situation,the grouting plugging treatment method for the new grouting material is proposed,and verified the effectiveness and reliability of the new material in flowing water controlling.