摘要
地面突发堆载诱发运营期内地铁隧道病害的案例屡见不鲜,广州地区地铁隧道建设中常遇洞身上部为软土、砂层,下部为硬岩的土岩复合地层。目前对于局部超载作用下,土岩复合地层中盾构隧道变形与破坏特征并不明确,现行加固标准对于该种特殊地层的适用性也亟待验证。通过1︰5的土箱模型试验,探究不同硬岩比的土岩复合地层中隧道在正上方局部超载作用下的变形规律和破坏模式。试验结果表明:地层硬岩比对局部超载下盾构隧道的位移发展及其分布影响显著,结构的临界失稳荷载等级随着硬岩比增大而提高,结构破坏椭圆度随之减小,硬岩比的增大加强了结构外部围岩的约束作用,显著地控制了隧道椭变,但约束的加强也使结构呈现脆性性状,位移发展速率出现明显突变点;硬岩限制了其范围内管片的内力发展,且土岩交界面上部邻域管片产生应力集中现象,结构首先在此区域发生破坏,且常以贯穿式裂缝形式发展,随着硬岩比增大,结构呈崩角、劈裂等脆性破坏形式;隧道拱顶附加土压力会随结构失稳进入下降阶段,且随着硬岩比增大,软土压缩对地表超载的分散效应减弱,进而导致隧道拱顶附加土压力对地表超载更加敏感;将试验数据与现行加固标准对比分析,发现现行加固标准不适用于高硬岩比土岩复合地层中盾构隧道。研究成果可为加固标准结合地层因素优化提供理论支撑。
Cases of metro tunnel damage induced by sudden surface surcharge during the operation period are commonly seen,and the construction of metro tunnels in Guangzhou often encounters soil-rock composite strata with soft soil or sand layers on the upper part of the hole and hard rock on the lower part.At present,the deformation and failure characteristics of shield tunnels in soil-rock composite strata under local surcharge were unclear.The applicability of current strengthening specification to this special stratum was still to be verified.The mechanical properties and failure modes of tunnels in soil-rock composite strata with different hard rock ratios under local surcharge were investigated by a 1:5 soil box model test.The results of the tests showed that the hard rock ratio of the strata had significant effects on the development and distribution of the displacement of the shield tunnel under local surcharge.The critical instability load level of the structure raised with the increase of hard rock ratio,while the failure ellipticity of the structure decreased.The increase of the hard rock ratio strengthened the integral stiffness of the structure,which significantly controlled the tunnel ellipticity,whereas the enhancement of stiffness also led to the brittle properties of the structure as well as the distinct inflection point of displacement development rate.The internal force development of the segment was restricted by the hard rock,and the stress concentration phenomenon occurred in the segment in the area adjacent to the upper area of the soil-rock interface.The structure was first destructed in this area,which generally manifested as the development of cracks in the form of penetration,and with the increase of hard rock ratio.The structure was in the form of brittle failure such as corner collapse and fracture.The pressure of the additional earth at the top of the tunnel arch would enter a decreasing phase in response to the instability of the structure,and with the increase of hard rock ratio,the effect of
作者
张晏铭
刘庭金
朱超
肖俊贤
ZHANG Yanming;LIU Tingjin;ZHU Chao;XIAO Junxian(School of Civil Engineering and Transportation,South China University of Technology,Guangzhou 510641,China;State Key Laboratory of Subtropical Building Science,South China University of Technology,Guangzhou 510640,China)
出处
《铁道科学与工程学报》
EI
CAS
CSCD
北大核心
2023年第11期4277-4287,共11页
Journal of Railway Science and Engineering
基金
国家自然科学基金资助项目(51878296)
广东省自然科学基金面上项目(2023A1515012084)。
关键词
局部超载
土岩复合地层
盾构隧道
硬岩比
模型试验
失稳
local surcharge
soil-rock composite stratum
shield tunnel
hard rock ratio
model test
failure
