Taking the foundation pit project of Tanggu Station on Line B1 in Binhai New Area,Tianjin as the engineering background,where the confined aquifer water level is significantly lower than the phreatic surface,cross-layer seepage effects were identified under dewatering-excavation interactions.A numerical model simulating deep excavation processes was developed to predict deformation behaviors of retaining structures at different excavation depths,while investigating settlement evolution patterns of adjacent existing buildings.By considering cross-layer seepage characteristics of confined water,the fluid-solid coupling method was employed to analyze the impact of construction suspension at various excavation phases on soil reconsolidation and subsequent building settlements induced by confined water migration.
In order to study the advantages of shaped charge blasting over traditional smooth blasting in multi-joint tunnels,four models of double hole smooth blasting and shaped charge blasting were established to study the influence of the angle of joint and hole connection on the overcut and undercut of multi-joint tunnels,and to explore the dangerous position in the tunnel section blasting excavation.The research results show that smooth blasting shows great damage in multi-jointed shale tunnels,resulting in a significant increase in overcut and undercut.Especially when the connection direction of the hole and the joint is 45°,the amount of overcut and undercut generated by smooth blasting is the largest,reaching 1 436 cm2.Therefore,special attention should be paid to such angle conditions in the blasting scheme design.Shaped charge blasting has less damage to surrounding rock in multi-jointed shale tunnels,and can effectively reduce the amount of overcut and undercut in blasting.The average amount of overcut and undercut in the tunnel is reduced by 1 090 cm2,especially in the 45° angle model,compared with the smooth blasting,the reduction is 1 161.4 cm2,showing a significant optimization effect.To sum up,the application effect of shaped charge blasting in multi-jointed shale tunnels is obviously better than that of traditional smooth blasting,which can not only effectively reduce the damage of surrounding rock,but also significantly reduce the amount of overcut and undercut,thus improving the safety and efficiency of tunnel construction.Therefore,it is suggested to preferentially use shaped charge blasting technology in practical engineering.
With the advancement of rail transit technology,shield machines are increasingly used for pile grinding construction to undercross existing structures.Improper parameter selection may not only damage shield machine but also lead to secondary disasters such as ground collapse and existing structural damage.To enrich domestic construction experience in EPB pile grinding,we systematically summarize the construction techniques for shield machines passing underneath row piles in soft soil formations using small-angle cutter,based on practical construction cases.The paper details key information including construction challenges encountered,countermeasures implemented,and critical tunneling parameters during the construction process.This work provides robust technical support for accumulating pile grinding experience within the industry and offers practical case references for similar engineering projects.
Due to its unique geological structure and surface morphology,karst geological areas often encounter hydrogeological problems such as sudden water inflow,which pose potential threats to the stability and safety of urban tunnels.This article combines on-site monitoring and numerical simulation methods to explore the impact of karst geological sudden water inflow on urban tunnels,and proposes corresponding grouting for water blocking scheme.The research results indicate that the deformation during the entire monitoring period can be divided into three stages based on the rate of change in deformation at different locations:rapid change stage,slow development stage,and stabilization stage.When the water head of the dissolution chamber is 10 m,it can be used as the critical water head value of the dissolution chamber.When the water source pressure exceeds 0.5 MPa,a sudden water inflow occurs in the tunnel,and as the water source pressure increases,the amount of sudden water inflow continues to increase.When the thickness of the filling material is less than 10 m,a sudden water inflow occurs in the tunnel,and as the thickness of the filling material decreases,the amount of sudden water inflow continues to increase.The grouting for water blocking scheme was adopted to timely treat the leakage water during tunnel excavation and support,effectively ensuring construction quality,reducing idle waste of construction personnel and mechanical equipment,and saving costs.
The steel trestle has become an important technical means to solve the construction difficulties such as the limited working space of the deep foundation pit with cover and cut-top down method,the excavation of the foundation pit and the difficulty of transportation of construction materials because of its convenient installation and disassembly and easy recycling.In this paper,the design and construction of steel trestle for deep foundation pit in water-rich sand layer are studied.The connection form between steel pipe column top and Bailey beam is discussed,and the'slope type'connection end is developed accordingly.The connection end is welded after the steel pipe column is excavated,which ensures the installation accuracy of the steel trestle and improves the construction efficiency.In order to optimize the construction method of pile column support,the steel pipe column and the anti-pulling pile reinforcement cage are reliably connected by the pre-insertion method,and then hoisted to the design elevation on the construction work surface,which ensures the verticality of the anti-pulling pile and the steel pipe column.The Bailey beam of the steel trestle and the support between the steel pipe columns are excavated with the earthwork and installed in sections and layers,which ensures the overall safety and stability of the steel trestle.With the help of Midas finite element analysis software,the main components of the steel trestle and the stability of the steel pipe column are numerically simulated.The results show that the steel trestle is safe and reliable and can meet the construction requirements.
At present,research on the dynamic mechanical properties of coal and rock has gradually become a hot research topic,but most of the dynamic load experiments are completed instantaneously,and some damage details cannot be studied in depth.Therefore,this study is based on the rock Holmquist-Johnson-Cook model and uses LS-DYNA software to conduct numerical simulation research on the Hopkinson compression bar experiment of coal rock samples under low-speed impact loading.At the same time,the whole experimental process is reproduced with the help of LS-PrePost postprocessor,so as to reproduce the damage process and failure details of coal rock impact failure.The results show that:(1)the stress-strain curve of coal rock impact load experiment based on HJC constitutive simulation is consistent with the measured stress-strain curve,in which the peak value of simulated stress is 7.03 MPa,and the relative error is 18.1%.(2)Under the impact loading of 3.693 m/s,both ends of coal rock are destroyed to form small fragments,and then tensile failure occurs along the axial direction of coal rock,forming axial cracks and penetrating through the coal rock specimen.Finally radial cracks are generated.Under the condition of low velocity impact,coal rock failure forms fragments of different sizes without obvious regularity,in which large and small pieces account for about half.(3)In this study,the energy consumption of coal rock under impact load is divided into three main stages.The energy consumption rate of coal rock increases slowly at first,then increases sharply,and finally tends to be flat.
The step method shows significant advantages in saving construction time and improving the level of mechanized operation,but there are some limitations in controlling the stability of the surrounding rock and preventing deformation.In order to reduce the deformation impact of the step method on the tunnel surrounding rock,this paper,based on the Chongli Tunnel project,describes the rapid excavation technology of micro-step method for cold-region tunnels;and through the method of finite element simulation,it optimizes the length and height of the steps during the construction of the step method,and determines the parameters of the steps for the construction of the single-line railway tunnel surrounded by rock using the step method.The results show that:micro-step method construction of the tunnel face of the work area processes are carried out independently and synchronously,without interfering with each other,effectively improving the construction speed;Ⅳsurrounding rock on the step height of 4 m is more appropriate,at this time,the vault settlement and surrounding convergence are smaller,while the tunnel face extrusion deformation is also within the control range;increasing the length of the step can maintain the stability of the tunnel face,but it will increase the vault settlement and surrounding convergence.Therefore,the length of the upper step is not the longer the better,and the length of the upper step for class Ⅳ surrounding rock should be controlled at 3 m.
The trenching of ultra-deep diaphragm wall has the characteristics of poor trenching quality,low trenching efficiency and high trenching cost when crossing bad engineering geology.It has a significant impact on the later excavation and stability of the foundation pit,as well as the quality of the main structure.This paper focuses on the construction of underground continuous wall under complex geological conditions in Dongdaqiao Station of Beijing Subway Line 28.The high-efficiency trenching equipment has been determined,and the technical measures for accurately controlling the verticality of the trench wall have been proposed.Management measures for the combined operation of the trenching equipment have been summarized.It solves a series of problems existing in the construction,such as not being able to form grooves quickly under complex geological conditions,low accuracy of groove wall verticality,and high construction safety risks.
When encountering water-rich geological conditions during the trenching process of ultra-deep diaphragm walls,there are defects such as low construction efficiency,high construction costs,and severe water leakage,which seriously affect the excavation and stability of the foundation pit and the quality of the main structure in the later stage.This paper focuses on the construction of ultra-deep diaphragm walls at Dongdaqiao Station on Beijing Subway Line 28 under complex geological conditions,analyzes the process characteristics of section steel joints and milling joints,proposes the principle of joint water leakage,and summarizes the theoretical basis for joint selection.It solves the problem of difficulty in selecting joint forms due to low efficiency and high cost of joint construction,unclear waterproofing effect at joint locations,and other reasons in water-rich geological conditions during construction.
为了研究彩色沥青混合料路用性能指标,对其进行了马歇尔试验、磨耗试验以及劈裂试验,确定了彩色沥青混合料的抗压性、压实性、磨耗性和水稳定性,并与热拌沥青混合料(HMA)进行了比较,实验结果表明彩色沥青混合料显示出充分的可压实性、良好的抗压性、磨耗性以及水稳定性.通过具体实际案例进行彩色沥青路面施工工艺以及施工过程中操作要点分析,结果表明彩色路面对周边的环境空间产生更积极的影响,具有较高的耐磨性能.
复杂耦合环境下隧道施工灾害防控技术问题是隧道施工中的重大技术难题.黄瓜山隧道遇到瓦斯、高压气井、采空区及层状岩层等复杂环境,灾害风险因素多,对施工安全构成严重威胁.以该隧道工程为依托,开展复杂耦合环境下隧道施工灾害防控技术研究,获5 项专利.实践表明:研发的用于瓦斯异常涌出的监测装置、用于隧道临近高压气井裂隙扩展的监测装置、用于层状岩层隧道断面岩层位移监测装置,实现了隧道内瓦斯涌出异常、临近高压气井段围岩裂隙扩展情况、层状岩层隧道断面变形的实时监测、预警;采用非对称不耦合精细爆破技术,减小爆破扰动对高压气井的影响;提出了基于遥感技术的隧道多点位移同步监测的方法,使得监测流程简单,无需人工记录;优化部分层状围岩的锚杆设计,采用三代新型聚能管光面爆破,并优化爆破参数,改善层状岩层超欠挖情况,降低了成本.
为研究落石冲击柔性钢棚洞的力学特性,并优化柔性钢棚洞的结构参数,依托成昆铁路复线老鼻山隧道工程溶洞处理方案中的柔性钢棚洞防护结构,建立有限元数值模拟模型,对落石冲击柔性钢棚洞的力学特性及落石不同冲击角度对柔性钢棚洞的影响进行研究,得到不同条件下落石的位移、速度变化及棚洞的应力变化情况;同时研究不同跨度条件下落石冲击对柔性钢棚洞的影响,并对柔性钢棚洞钢架跨度进行优化.结果表明:落石以不同角度冲击棚洞时,应力集中均出现在H型钢钢拱架拱顶与横向撑杆相接处,施作时应加强该处结构,在以垂直角度冲击棚洞时,对其稳定性影响最大,本工程条件下可保证棚洞安全稳定;钢架跨度越大,棚洞结构越不稳定,但应考虑施工是否方便,综合选用钢架跨度为3m.
针对目前隧道掘进机施工环境复杂恶劣,关键部件监测方式不足,关键部件故障状态诊断不及时的现状,研究了隧道掘进机关键部件监测诊断系统流程;基于监测诊断流程,对关键部件运行状态、设备参数、健康状态参数等进行分析,设计了隧道掘进机关键部件监测诊断系统,分别对关键部件的温度、压力、流量、振动、应变、油液磨损、油液污染度等参数进行实时监测;根据监测参数对关键部件运行状态进行异常状态识别,识别到异常状态后进行故障诊断,并实施故障决策,最后完成记录归档.以切实可行的方式,对关键部件的运行状态进行监测诊断,保证隧道掘进机的高效安全运行.
跨海区段的钢-混结合梁斜拉桥主跨一般设置在通航区域,该区域船只密集、船舶吨位大,且施工条件复杂,控制因素多,因此,斜拉桥梁部的架设方案是桥梁施工的重点及难点.以新建福州至厦门铁路安海湾特大桥主桥(40+135+300+135+40)m双塔双索面结合梁斜拉桥钢-混结合梁的架设方案为例,分析在跨海区域,特别是海湾及浅滩区域进行结合梁架设需考虑的诸多因素,并对浮吊船整节梁段提升架设、分节段顶推施工两种施工方案进行技术经济比选,拟定最适宜方案,可为类似工程提供借鉴.
通过总结和分析无锡地铁S1 线汽～江区间土压平衡式盾构机在中风化石英砂岩地层中掘进的滚刀刀具磨损情况,结合滚刀刀具磨损特性,将滚刀磨损情况划分成不同的种类,并深入分析滚刀磨损的原因及影响因素,针对性地研究出减少滚刀磨损的措施,以此保障盾构机在岩石地层顺利推进,使硬岩地层盾构机掘进施工能够在加快掘进速度的同时减少换刀的成本,对今后中风化石英砂岩地层施工具有一定的指导意义,在类似地层施工的盾构机选型、刀具配置等方面提供借鉴.
浩吉铁路至大海则煤矿铁路是浩吉铁路集疏运体系的重要组成部分,主要为榆横矿区北区、纳林河矿区井田集疏运服务.本次研究结合大海则井田集运方案,结合矿区规划、工业广场位置及中煤大海则铁路专用线的既有设备情况,共研究了扩建既有大海则矿站方案、沿井田边界新建装车站方案和深入井田新建装车站方案三个方案,并对接轨站改扩建方案进行了比选,最终确定了经济合理的改扩建方案.本次研究对于浩吉铁路至大海则煤矿铁路引入大海则井田集运方案和大海则矿站改扩建方案实施具有一定的指导和借鉴意义.
模壳材料是新型楼承板——装配式IRF楼承板的重要组成部分,是基于超高性能混凝土优化后的水泥基复合材料.为了解决实际生产中模壳材料性能不稳定问题,基于模壳材料基准配合比,采用2 种间断级配的石英砂替代原骨料进行优化.首先,利用石英砂级配模拟和空隙率试验方法分析不同比例石英砂混合后的级配情况;然后,试验研究了混合后石英砂级配对模壳材料流动度、抗折强度、收缩率的影响规律,并分析了作用原理,根据模壳材料的性能,择优选择确定了2 组石英砂混合比例作为优化后的配合比.最后,试验验证了优化后 2 组配合比的模壳材料性能满足设计要求,统计连续生产中优化后模壳材料的性能数据,证明了采用2 种间断级配的石英砂进行模壳材料性能优化的可行性,实际生产中可实现模壳材料性能稳定性和产品一次成品率的双提升.
为避免单桩基础建成后在海流影响下局部形成冲刷坑,进而影响桩基础的稳定性,结合山东能源渤中海上风电B场址工程,开展海上风电桩周软弱土层防冲刷加固技术研究,获 5 项专利.实践表明:研发的海上风电桩周砂被施工方法,适用于砂质、淤泥质等土层;研发的一种海上风电桩周防冲刷固化结构施工方法,通过动力组件驱动搅拌叶转动进行搅拌,使固化剂和淤泥搅拌混合均匀,提高混合效果;研发的一种海上风电桩周网兜抛石装置及施工方法,能够高效地完成钢管桩桩周网兜抛石施工任务;研发的一种海上风电桩周混凝土板铰链沉排及其施工方法,能够高效地完成钢管桩周边铺设混凝土板铰链沉排施工任务;并用双波束扫测软弱土层桩周加固前后的施工效果,加固后防冲刷保护效果明显,经济和社会效益显著,这些防冲刷加固技术与经验,可供类似工程参考.
针对轨排铺设过程中钢轨与轨枕之间扣配件丢失产生的故障,振动加速度数据特征表征不明显的问题,为了提高铺轨过程中轨排故障识别精度,提出了一种基于数据扩充的深度置信网络的地铁轨排故障识别方法.首先,将采集到的轨排振动加速度数据利用改进的相似度准则进行样本扩充,再通过小波降噪处理得到新的样本作为数据集,并按比例划分为训练集和测试集;然后,将训练样本集输入到DBN模型中进行训练,利用训练好的DBN模型对测试样本集进行故障识别,从而确定故障位置和故障类型;最后,将本方法应用于轨排振动加速度数据进行故障识别,同时与基于原始数据的故障识别方法相比较,结果表明:所提出的方法对轨排故障类型、故障位置的识别准确率有了明显提升.
随着社会不断发展,城市内有限的黄河桥位成为稀缺资源,这就需要设计者运用科学方法对高铁黄河桥位进行细致研究.本文以济滨高铁跨越黄河比选方案为例,运用SWOT分析法对不同跨越黄河桥位方案进行分析,找出影响线路方案的内部和外部因素,根据具体情况分别给予科学合理赋值,构建SWOT矩阵,得出不同方案在矩阵图坐标象限的位置,再通过进一步分析,得出较为科学的推荐方案.为使方案更为合理,对推荐方案制定相应的行动计划,最大限度促使向利于方案优势方面发展,如公铁合建桥梁推荐桥位方案在设计中可以采取进一步优化设计,降低结构高度以满足机场净空要求,结合公路设计综合比选方案,尽量降低工程投资,减少与其他方案投资差额,促使劣势向优势方面转换,减少不利因素,扩大优势,最终使工程项目可实施性更强,更加科学合理.
