摘要
低温冻融循环作用诱发寒区隧道渗漏水和冻胀破坏等冻害问题,开展寒区隧道围岩降渗加固性能研究对于寒区工程建设具有重要意义。本文以川藏铁路康定2号隧道工程为研究背景,基于微生物诱导碳酸钙理论,开展了寒区隧道围岩降渗加固性能的宏细观试验研究。结果表明:选用巴氏芽孢杆菌尿素研制了适用于寒区工程的MICP菌液,其代谢尿素水解产生的碳酸根离子(CO_(3)^(2-))与环境中钙离子(Ca^(2+))结合生成碳酸钙(CaCO_(3)),沉淀填充到寒区隧道围岩岩石裂隙,达到降渗加固的目的;采用分光光度法和电导率法测试了低温下巴氏芽孢杆菌的生长活性与脲酶活性,经MICP加固后裂隙砂岩内部形成了有效的胶结,岩体强度显著提升;SEM和XRD测试结果证实了巴氏芽孢杆菌在MICP反应中兼具诱导碳酸钙沉淀和提供晶核双重作用;60次冻融循环后的MICP修复砂岩较未修复砂岩渗透性大幅降低,而剪切强度和抗压强度大幅提高,修复砂岩经60次冻融循环后剪切强度提高40.25%,抗压强度提高15.97%。本研究成果为寒区岩石工程冻害防治提供了新方法,拓展了寒区环境下生物加固理论的应用领域。
In cold-region tunnel engineering,during long-term service,freeze-thaw cycles can lead to increased seepage,reduced bearing capacity,frost heave damage,and other issues that severely compromise the structural stability and operational safety of tunnels.There is an urgent need to explore a new reinforcement method for sur⁃rounding rock that is efficient,durable,environmentally friendly,and freeze-thaw resistant.Based on an analy⁃sis of the mechanism of microbial-induced calcium carbonate precipitation(MICP)for seepage reduction and re⁃inforcement of tunnel surrounding rock in cold regions,this study developed an MICP reaction solution suitable for cold-region rock engineering.Test research was conducted on the application of MICP for seepage reduction and reinforcement of tunnel surrounding rock in cold regions.The microbial activity,urea hydrolysis efficien⁃cy,and distribution patterns of calcium carbonate precipitation under low-temperature conditions were analyzed.The biomineralization mechanism of MICP under freeze-thaw cycles was revealed,and the improvement effects of MICP on the permeability and frost heave resistance of surrounding rock were clarified.This provided a green and long-term solution for reinforcing surrounding rock in cold-region tunnel engineering,while also contribut⁃ing to the theoretical research on bio-mediated reinforcement in cold environments.The main work and conclu⁃sions were as follows:(1)Considering the characteristics of cold-region environments,Sporosarcina pasteurii was selected.Although its metabolic activity was inhibited at low temperatures,its non-Newtonian fluid charac⁃teristics helped maintain the permeability of the cementation solution,demonstrating good cold resistance.Dur⁃ing the MICP hydrolysis reaction,Sporosarcina pasteurii not only provided urease for microbial-induced calci⁃um carbonate precipitation but also served as a nucleation site for calcium carbonate crystal formation.Addition⁃ally,it had low free energy,a simple reaction mechanism,and ease of process control,making it an ideal choice for this test.(2)The bacterial growth activity and urease activity were monitored using spectrophotome⁃try and conductivity methods,determining an optimal cultivation time of 72 hours.Quartz sand with a mesh size of 200 was selected as the MICP filling aggregate.The MICP cementation solution was prepared using a 1.0 mol·L^(-1)urea-CaCl_(2)solution as the reaction agent.The bacterial solution(with an OD₆₀₀value of 4.60)and urea-CaCl_(2)solution were mixed at a volume ratio of 1∶1.The MICP slurry was injected into pre-fractured rock sam⁃ples.After a 28-day repair period and a 7-day curing period,freeze-thaw cycle tests,capillary water absorption tests,shear strength tests,and compressive strength tests were conducted.Additionally,SEM analysis of the ce⁃mentation morphology and X-ray diffraction analysis of the biomineral phases were performed to analyze the per⁃meability and reinforcement performance of MICP on the frost-thaw fractured rock.(3)The test results showed that calcium carbonate precipitation generated by MICP effectively sealed sandstone fractures.A high-concentra⁃tion bacterial solution promoted uniform distribution of microbial cells,enhancing MICP reaction efficiency and producing a large amount of CaCO₃crystals.These crystals effectively filled pores and strengthened particle con⁃nections,significantly improving the permeability characteristics of fractured sandstone.The microorganisms simultaneously served dual functions:urease catalysis and nucleation supply.(4)After MICP treatment,the in⁃ternal structure of the sandstone was dominated by micropores and small pores.The permeability coefficient de⁃creased by 45.2%compared to untreated sandstone.The calcium carbonate precipitation by MICP effectively blocked water migration pathways,maintaining excellent seepage reduction performance even after freeze-thaw cycles.(5)MICP treatment significantly enhanced the mechanical properties of freeze-thaw sandstone.After 60 freeze-thaw cycles,the shear strength of MICP-treated samples increased by 40.25%,and the compressive strength improved by 15.97%.The enhancement in mechanical properties was primarily attributed to the calci⁃um carbonate cementation layer,which strengthened interparticle friction and interlocking.Meanwhile,MICP mitigated fracture propagation induced by frost heave stress,and the cementation layer reduced unfrozen water migration by narrowing pores,thereby decreasing the cumulative effects of freeze-thaw damage.A strong corre⁃lation was observed between the changes in the mesostructure of freeze-thaw rock and the improvement in macro⁃scopic mechanical properties due to MICP treatment.(6)MICP achieved fracture filling and structural densifica⁃tion through microbial-induced calcium carbonate precipitation.Microscopically,it optimized pore distribution and cementation morphology,while macroscopically,it significantly enhanced impermeability and mechanical strength.Even under high-frequency freeze-thaw cycles,MICP maintained excellent repair performance,pro⁃viding a novel approach for preventing and controlling frost damage in tunnel surrounding rock in cold regions that combines biological compatibility with long-term stability.
作者
刘慧
朱闽楷
金龙
梁博
刘方路
杨锦霖
郭豪
郭潇菁
王润祺
LIU Hui;ZHU Minkai;JIN Long;LIANG Bo;LIU Fanglu;YANG Jinlin;GUO Hao;GUO Xiaojing;WANG Runqi(College of Architecture and Civil Engineering,Xi’an University of Science and Technology,Xi’an 710054,China;CCCC First Highway Consultants Co.Ltd.,Xi’an 710075,China)
出处
《冰川冻土》
2025年第4期963-976,共14页
Journal of Glaciology and Geocryology
基金
国家自然科学基金项目(42277172,42177144,42077274)
陕西省重点研发计划项目(2024SF-YBXM-626)
极端环境绿色长寿道路工程全国重点实验室开放基金项目(KCJJ2025-07)资助。
关键词
冻融循环
隧道围岩
MICP
抗渗性能
力学强度
freeze-thaw cycles
tunnel surrounding rock
MICP
impermeability
mechanical strength
