CAJ | 학술논문

土洞是覆盖型岩溶区一种隐伏的不良地质现象。土洞在水的作用下发育演化最终形成塌陷，可通过地下水位的变化来研究土洞发育和塌陷的形成。同时土洞的演化会造成覆盖土体不均匀位移和应力重分布，可通过覆盖土体位移和应力变化来进行研究土洞演化过程。采用 FLAC3D 三维有限差分程序，分析覆盖层垂向位移场表明：最大垂向位移出现在土洞顶部，使拱顶出现拉张破坏，并可根据洞顶土层位移的数值模拟结果，划分“等沉面”确定土洞扰动的土层深度。分析覆盖层剪切应力场表明：在土洞拱趾部位出现剪应力集中，会造成拱趾的剪切破坏，并可根据洞顶“剪应力低值区”，判断覆盖层中土拱效应的存在。分析覆盖层塑性区表明：较为坚硬的黏土层中，土洞以拱顶塌落和拉张破坏为主，最终可以形成坑壁较为陡直的桶状或坛状塌坑。土层较为松散时，以拱趾的剪切破坏为主，最终可以形成锥碟形塌陷坑。利用“剪应力低值区”，“等沉面”和“塑性区”可综合判断土洞的稳定性以及覆盖层所能形成的极限土洞大小。岩溶土洞演化规律及数值模拟研究对岩溶塌陷(土洞)早期监测和评价有着重要的理论及工程意义。
토동시복개형암용구일충은복적불량지질현상。토동재수적작용하발육연화최종형성탑함，가통과지하수위적변화래연구토동발육화탑함적형성。동시토동적연화회조성복개토체불균균위이화응력중분포，가통과복개토체위이화응력변화래진행연구토동연화과정。채용 FLAC3D 삼유유한차분정서，분석복개층수향위이장표명：최대수향위이출현재토동정부，사공정출현랍장파배，병가근거동정토층위이적수치모의결과，화분“등침면”학정토동우동적토층심도。분석복개층전절응력장표명：재토동공지부위출현전응력집중，회조성공지적전절파배，병가근거동정“전응력저치구”，판단복개층중토공효응적존재。분석복개층소성구표명：교위견경적점토층중，토동이공정탑락화랍장파배위주，최종가이형성갱벽교위두직적통상혹단상탑갱。토층교위송산시，이공지적전절파배위주，최종가이형성추설형탑함갱。이용“전응력저치구”，“등침면”화“소성구”가종합판단토동적은정성이급복개층소능형성적겁한토동대소。암용토동연화규률급수치모의연구대암용탑함(토동)조기감측화평개유착중요적이론급공정의의。
Soil caves in karst areasarea concealed and adverse geological phenomena.The evolution of a soil cave can cause uneven displacement and stress redistribution on the overlying soil layer,conversely changes in displacement and stress can be used to study soil cave evolution using three-dimensional finite-difference software FLAC3D.The vertical displacement field of the soil layer shows that,the maximum vertical dis-placement taking place on the arch roof of the soil cave may cause tensile failure of the arch roof.Based on the level of soil layer displacement on the arch roof,an"equal settlement plane" can be drawn to determine the depth of the soil cave.The shear stress field of the soil layer indicates that,the maximum shear stress in the arch toes can cause arch toe shear failure,and the "low shear stress area" can be used to determine the impact of the arching effect on the overlying soil layer.Through analysis of the plastic zone of the soil layer, it is concluded that,in rigid clay areas,soil caves with barrel bottle-shaped pit collapse were mainly caused by arch roof collapse and tensile failure;while in areas of loose soil,caves with taper or plate-shaped pit col-lapse resulted from shear failure of the arch toe.The low shear stress area,equal settlement plane and plas-tic zone can be adopted to evaluate the stability of soil caves and the limits on hole size in the overlying layer. Evolution and numerical simulation of karst soil caves in this study provide important theoretical and engi-neering results for monitoring and evaluation of early stage karst collapse.