超深竖井原位保护古城墙暗挖法被动托换技术研究

Study on Passive Underpinning Technology of In-situ Protection of Ancient City Wall by Mining Method in Extra Deep Shaft

为解决超深竖井在部分井位平面与新发现文物平面叠交且井位选址唯一情况下的文物原位保护问题,以国内首个深层隧道竖井古城墙保护为背景,分析了国内相关领域多篇优质论文等技术成果,发现应用单一技术进行文物保护有多个成功案例,暗挖隧道下穿重要建筑物相互影响方面的研究也不少,洞桩法也已经成功运用了20多年,小导洞内做桩、做梁都有成功经验,被动桩基托换的相关研究也很多,但是整合这些技术来解决一个问题尚属首次。因此该研究创新性地采用暗挖法小导洞中浇筑纵梁与竖井中部横梁相连接形成组合托换梁的被动托换方案,将既有古城墙的自重荷载转移到竖井周围的围护结构上,实现了古城墙下部竖井的顺利开挖,解决了超深竖井开挖过程中的古城墙原位保护的问题;并通过MIDAS/GTS有限元计算软件进行了竖井施工的数值计算,对2种不同的暗挖导洞方案进行数值模拟,由此可知:小导洞内组合箱梁加井内横梁形成T型组合梁结构被动托换古城墙的施工方案可行,对类似工程很有借鉴意义,对基于坚实科学原理基础上的跨学科、跨领域的集成创新有借鉴意义。

In order to solve the problem of in-situ protection of cultural relics in the case of overlapping part of the shaft plane with the newly discovered cultural relics and the only site selection of the shaft site,this paper takes the protection of the ancient city wall of the first deep tunnel shaft in China as the research object and studies the technical achieve ments of many high-quality papers in related fields in China.There are many successful cases in the application of sin gle technology for cultural relics protection,researches on the interaction between important buildings and related re searches on passive pile foundation underpinning The hole pile method has been successfully used for more than 20 years as well as in pile making and beam making in the small pilot tunnel.However,it’s the first time to integrate these technologies to solve above problem.In this paper,the underground excavation method is used to connect the longitudi nal beam in the small pilot tunnel and the beam in the middle of the shaft.The passive underpinning scheme of compos ite underpinning beam transfers the self weight load of the existing ancient city wall to the enclosure structure around the shaft,which realizes the smooth excavation of the shaft under the ancient city wall.Then,the problem of in-situ pro tection of the ancient city wall is solved during the excavation of the ultra deep shaft.The numerical calculation of shaft construction is carried out by MIDAS/GTS finite element calculation software.Two different schemes of underground excavation pilot tunnel are simulated.The conclusion is that the construction scheme of passive underpinning ancient city wall,which with T-shaped composite beam structure is formed by composite box girder in small pilot tunnel and cross beam in shaft,is feasible.The scheme has significant reference for similar projects and interdisciplinary based on solid scientific principle Cross domain integrated innovation.