The prefabricated joint is a prominent structural feature that distinguishes prefabricated metro stations from traditional cast-in-place stations.To investigate the bending deformation and failure mechanisms of grouted mortise and tenon joints,a comprehensive study is conducted.Experiments are performed to determine the compressive deformation characteristics of the grouting material(modified epoxy resin)and its bonding properties with concrete.Based on these experimental results,a simulation method is developed to model the joint grouting surface contact,incorporating the bond strength and bond failure model.Finally,a finite element numerical model is created and analyzed to evaluate the joint under bending loads.The results reveal the following:(1)The moment-rotation curves of the joint closely align with the experimental data,and the crack distribution patterns observed during bending failure closely match test results.(2)The numerical results,including the development of principal tensile stress,the failure of the grout-concrete bonding relationship,and crack propagation patterns,further reveal the bending deformation mechanism of the grouted mortise and tenon joints.(3)A comparative analysis of three simulation methods for grouting surface contact relationships—bond failure,friction,and tie—demonstrates that using friction or tie contact models leads to an underestimation of the joint's flexural load-bearing capacity.(4)The findings highlight the importance of refined modeling of the grout-concrete bond relationship in grouted mortise and tenon joints for accurately evaluating their mechanical performance.
In view of the absence of bearing capacity analysis method for systematic bolt in the current specifications of tunnels,the total safety factor method proposes a load structure model of bolt-rock bearing arch.This method theoretically enables the quantitative design of bolts but lacks experimental verification.To address this,this paper develops a large-scale tunnel structure model experimental system from a structural experimental perspective.It conducts bearing experiments on bolt-rock bearing arch structures in unsupported tunnel and bolted tunnels with different spacings.By monitoring the stress and strain in the surrounding rock mass,tunnel displacement and bolt strain,the failure state and failure load of surrounding rock and bolt are analyzed.The deformation and force characteristics of the bolt-rock bearing arch and the distribution of bolt forces are investigated.The structural bearing capacity of the model experiment and the calculated bearing capacity of the bolt-rock bearing arch under the total safety factor method theory were compared and analyzed.The results show that the bolts can bear the load together with the surrounding rock mass,effectively increasing the confining stress of the surrounding rock mass and enhancing the compressive strength and bearing capacity.The experimental bearing capacity of the bolt-rock bearing arch is consistent with theoretical calculation results,proving the rationality of the bolt-rock bearing arch theory of the total safety factor method.This method is both safe and conservative.
A new rockburst classification, innovative works in developing a “strainburst test machine” and an “impact-induced rockburst test machine” that can reproduce rockbursts in laboratory were researched. New concepts were proposed regarding the stress paths that take into account both the static and dynamic stresses analogous to that at excavation boundaries for generating artificially-induced strainburst and impact-induced rockburst. As an important method for rockburst control, a novel energy-absorbing bolt was developed, which has a constant-resistance under both static and impact loadings and a large-elongation capacity for containing large deformations of rock masses under burst-prone conditions.
为研究上坡条件下矩形顶管开挖面稳定性,基于传统筒仓模型,引入隧道线路坡角对模型进行优化,同时考虑舱内压力在上坡条件下的作用效应,建立矩形顶管上坡掘进开挖面失稳模型.基于极限平衡理论推导隔板土舱压力表达式,讨论土体抗剪强度参数及线路坡角对开挖面稳定性的影响.参数分析表明,土舱压力随土体有效内摩擦角的增大而非线性减小,随线路坡度角的增大而线性增大.与既有理论模型及数值模拟的对比结果表明,提出的理论模型对隧道底部破坏滑移面的预测较好,土舱压力计算值优于既有模型和数值解.依托杭州某上坡掘进矩形顶管工程对失稳模型进行验证,对比结果表明,失稳模型具有较好的工程适应性.
为准确预测新建隧道上穿作用下既有盾构隧道的隆起位移,考虑土体的天然成层性,提出成层地基中新建隧道上穿作用下盾构隧道纵向位移的解析解答.首先,分析盾构隧道与周围土体的相互作用,构建盾构隧道与土体的整体耦合平衡方程.其次,基于Mindlin解求得新建隧道开挖卸荷作用下下部成层地基土的隆起位移,结合耦合平衡方程得到盾构隧道的纵向位移解.最后,与3 个上穿工程实测数据进行对比,对相关参数进行分析.结果表明:1)当既有隧道下部地基分层性不明显,前人基于弹性地基梁的预测方法与本文方法均能较好预测下部隧道的隆起位移;2)当地层具有明显分层时,所提方法预测结果与实测结果具有较好的一致性;3)增大新建隧道直径将导致既有盾构隧道隆起位移的增加和隆起范围的增大;4)减小新建隧道与下卧隧道之间的穿越净距将导致下部盾构隧道的隆起值增加;5)既有盾构隧道位于上软下硬地层之上时,其隆起范围小于上硬下软地层,但其隆起量大于上硬下软地层.
