大有山隧道基础加固方案经济技术分析

软弱黄土隧道基础承载能力较低,容易在施工和运营过程中出现结构变形和沉降等破坏.通过对黄土隧道基础进行加固,可以有效提高基础承栽能力,有利于隧道结构的长期稳定.但不同的加固方案在技术和经济方面有较大差异.在隧道设计和施工中,根据隧道的具体情况,通过经济及技术方面的分析和比较,选择合理的基础加固措施,对软弱黄土隧道工程的建设有着重要的意义,本文通过对大有山隧道两种基础加固方案:高压旋喷桩和灰土挤密桩的经济技术分析,确定了合理的基础加固措施.     

基坑开挖对下卧既有隧道变形影响数值分析

文章以粉土中既有隧道上部基坑开挖为例,采用ABAQUS有限元软件建立模型,在考虑了四种工况的基础上,分析基坑开挖对隧道顶部和底部位移、隧道水平位移、基坑底部位移以及桩墙位移的影响。结果表明:基坑开挖会引起隧道向上隆起,且隧道顶部隆起值大于底部隆起值,隧道底部隆起值大约为隧道顶部的60%～70%,隧道向上隆起速率与基坑开挖深度基本呈线性增长关系;随着基坑的开挖,隧道两拱腰向内部收敛,最大水平位移发生在隧道拱腰位置;随着基坑开挖深度的增加,基坑底部隆起增大,且隧道的存在对基坑底部的竖向变形影响较小,基坑中部隆起值略大于两侧;桩墙顶部水平位移最大,随着土体深度的增加,桩墙的水平位移逐渐减小。     

地铁施工对邻近桥梁桩基础内力影响分析

文章采用数值方法研究了城市盾构隧道施工对邻近桥梁单桩、两桩、四桩基础的应力与位移的影响,研究结果表明:(1)隧道施工使单桩近隧道侧轴向应力减小,远隧道侧轴向应力增大,其影响程度随桩与隧道水平距离的增大而减小;(2)隧道施工下穿两桩或四桩群桩基础后,桩身近隧道侧轴向应力增大而远隧道侧轴向应力减小;(3)隧道施工对群桩的影响远大于单桩,其中距隧道较远桩顶两侧应力差在隧道施工后显著增大,承台距隧道较近时远隧道桩上部混凝土可能承受拉应力作用;(4)桩竖向位移随桩与隧道距离增大而减小,若桩底位于隧道底面以下,则隧道施工后桩产生较小沉降值;(5)桩受隧道施工影响一般在桩顶水平位移最大处,桩与隧道较远时位移值随桩深线性减小,较近时呈非线性减小趋势,其中桩上部位移沿桩深减小较快,桩下部位移收敛到定值,桩顶位移在桩与隧道一定距离时最大。     

注浆技术在复合地层滑坡体隧道工程中的应用

蒙华铁路五原隧道滑坡堆积体内夹杂砂质新黄土、粘质新黄土、细圆砾土、粉质粘土等多种地层,斜井开挖揭示掌子面富水,初期支护变形较大。为确保隧道开挖安全,决定采用地表袖阀管注浆加固技术。文章详细阐述了袖阀管注浆施工工艺、注浆加固效果的分析评价方法以及不同地层的注浆加固机理。实际应用效果表明,袖阀管注浆兼有渗透注浆、挤密注浆和劈裂注浆的独特优势,能有效提高隧道洞身地层整体性和稳定性,确保复合地层滑坡体隧道施工安全。     

不同净距双洞隧道上下台阶法同时开挖数值模拟分析

为研究不同净距双洞隧道在上下台阶法同时开挖下的围岩变形、受力及支护受力情况,文章基于Midas/GTS软件平台对10m、14m、18m、22m净距双洞隧道进行了数值模拟分析。结果表明:(1)隧道中岩墙一侧拱腰水平位移相比左侧拱腰大,拱顶处、仰拱处水平位移较小,且随着净距变化其值基本保持不变;(2)隧道拱顶及仰拱位置处围岩竖向位移较大,拱腰处较小,随着隧道净距增大各部位竖向位移均减小;(3)随着隧道净距的增大拱顶及仰拱处的水平应力及竖向应力逐渐减小,但减小幅度较小,同时拱腰处水平应力及竖向应力变化较大,且减小幅度不断扩大;(4)随着净距的增大,锚杆轴力最大值及喷混结构最大拉应力发生了减小,减小幅度逐渐扩大。     

不同埋深双隧道开挖对邻近群桩承载能力的影响研究

隧道开挖将不可避免地对其邻近桩基的承载能力产生影响。文章首先对离心模型试验进行了阐述,接着基于地层损失比的位移控制有限单元法(DCM)对试验结果进行土力学物理参数反分析,最后采用数值模拟对隧道与群桩相对位置的几个典型工况进行拓展分析。研究结果表明:当群桩整体位于隧道侧上方时,双隧道开挖对群桩桩顶沉降影响最为显著,如隧道上覆土厚度(C)与隧道直径(D)之比为3.7时,其桩顶沉降值可达5.51%dp(单桩直径);当隧道底与桩底齐平时,双隧道开挖完成后群桩承载能力相对双隧道位于桩身范围和位于桩端底部时反而增强;当隧道轴线位于桩身范围内时,群桩各基桩荷载传递机理与摩擦端承桩相似;当隧道轴线位于桩端以下时,群桩各基桩荷载传递机理与端承摩擦桩相似。     

银西高铁软塑黄土隧道地表降水试验研究

银西高铁驿马一号隧道穿越黄土含水层,洞身黄土以软塑为主,施工中出现了渗涌水、隧底软化、黄土含水率增高、掌子面失稳、围岩稳定性变差等问题。为解决隧道施工中遇到的难题,首次在软塑黄土隧道中开展了地表超前降水试验研究。结果表明,地表降水能够疏干洞身范围内的地下水,减小股状涌水的风险,降低洞身地下水压力;降水后黄土含水率由34.4%降到27.2%,液性指数从0.84降到了0.6,改善了黄土的物理性质,提高了黄土的围岩稳定性;洞内监控量测结果表明,地表降水后隧道拱顶沉降累积量和变形速率明显降低,地表降水效果明显。     

基坑开挖引起邻近既有地铁隧道位移计算的研究

文章考虑基坑坑底和侧壁的开挖卸荷应力以及坑底围护结构的遮拦效应,基于Mindlin位移解公式,提出了一种半解析半经验解方法,推导得到了基坑开挖引起邻近既有隧道位移的计算公式,分析了基坑尺寸、与隧道相对位置的改变以及加固控制措施对既有地铁隧道位移的影响。研究结果表明:隧道的水平和竖向位移随着隧道埋深的加大而有所增加;随着基坑与隧道净距的减小,隧道位移则明显增大;基坑开挖长度的增加对隧道位移影响较小,而基坑开挖宽度和开挖深度会对隧道位移产生明显影响;该方法可以考虑加固控制措施的效果,随着基坑围护结构应力损失率的减小,隧道最大水平位移呈线性减小,但隧道竖向位移变化不大。     

膨胀岩铁路隧道运营期基底病害综合整治技术研究

某高铁隧道在运营期出现隧底开裂、上拱变形等病害,极大影响行车安全,文章以此为研究背景,从地层岩性、地下水及施工因素等方面对隧底结构病害原因进行了分析,提出了隧道基底注浆挤密加固、轨道板裂缝壁可法注入处理、基底纵向裂缝水泥浆高压灌注处理等综合整治方案。整治施工监测表明,隧道仰拱及道床板整个观测断面处于上拱趋势,上拱速率较小,累计上拱(180 d)基本分布在0.5～1.6 mm之间,变形基本处于稳定状态。     

大断面黄土隧道变形规律及预留变形量研究

文章统计分析了大断面黄土隧道初期支护变形量,研究了大断面黄土隧道变形规律及预留变形量合理取值范围.大断面黄土隧道变形规律表现为:隧道拱顶、拱脚下沉差异小,隧道开挖后拱部将产生一定程度的整体下沉;隧道拱顶下沉量均大于水平收敛;初期支护封闭后,隧道周边位移基本上不再发展;当隧道埋深小于40m时,隧道变形量较大且规律不明显;当隧道埋深大于40 m时,隧道变形量分布相对集中.经过对现场量测数据的统计分析可知:在Ⅳ级围岩条件下,大断面黄土隧道预留变形量可取10～15 cm;在Ⅴ级围岩条件下,大断面黄土隧道预留变形量可取25～28 cm.     

浅覆土砂层土压平衡盾构始发掘进对环境的影响分析

盾构始发和到达安全掘进控制技术是困扰盾构隧道施工的主要难题之一。盾构进出洞施工中,面临掌子面失稳、土体坍塌、涌水涌砂、地表沉陷、盾构"抬头及磕头"等诸多施工风险。本文从基坑及隧道的破坏模式,塑性区分布范围出发,通过有限差分法针对易受扰动的浅埋砂层地层盾构始发段进行了研究,为加固区范围大小的选择提供了依据。研究表明,在不采取加固措施时,基坑开挖后隧道始发段的竖向位移、拱底的隆起和最大纵向挤出变形量均过大,显示基坑将发生坍塌等破坏。当盾构始发段主要加固措施为旋喷桩,加固后的土体的物理参数得到了显著的提升。本文在此基础上得出了旋喷桩的合理加固区域。     

Analysis of Ground Response and Structure Stress Induced by PBA Method北大核心CSCD

The application of prefabricated tunnel technology has been become a new research field both in China and abroad. Based on the running tunnel between Yufuhe station and Wangfuzhuang station of Jinan rail transit line R1, a new prefabricated tunnel construction technology, the PBA method is presented. This paper makes a detailed discussion on section form, supporting scheme and construction process of the PBA method. In this study, 3D a new 3D numerical model for PBA method is presented by finite difference numerical simulation software Flac and the construction processes are modeled. The rule of ground surface settlement, ground deformation and structural stress caused by PBA method is studied in detail. Results show that the structure of PBA method can effectively control the deformation magnitude and scope. Stress concentration appears at the prefabricated connection parts and the reinforcement needs to check. The total assembled structure forms the load-bearing system after the completion of the lateral wall. The built-in depth of the precast pile and pile bottom grouting quality should to be ensured to control the displacement of the precast piles. The results of this study will be a useful reference for similar projects in the future. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

复杂地应力红层泥岩隧道持续底鼓原因分析北大核心CSCD

为揭示复杂地应力红层泥岩隧道持续底鼓特征及底鼓原因,以某隧道为研究对象,通过长期变形监测、地下水位监测、隧底围岩位移监测等方法对底鼓变形特征进行了统计分析,并结合钻孔取芯岩样分析、地应力测试、围岩膨胀力测试、岩石蠕变试验、数值模拟分析等手段对可能导致隧道底鼓的因素逐一进行了分析。结果表明:受控于近水平层状泥岩以及复杂地应力,隧道部分段落呈现出底鼓时间“不收敛”、底鼓段落“不连续”、底鼓程度“不均衡”的三大特征;隧道岩层产状近水平,岩性为粉砂质泥岩,属于软质岩,未达到膨胀岩判定标准,具有中—低蠕变特性,隧址区地应力场以水平构造应力为主,水平应力在9.5~13.73 MPa之间;隧道开挖后,局部应力集中导致围岩发生蠕变,当蠕变产生的形变压力过大时,仰拱局部进入塑性状态,隧道即产生底鼓。     

城际铁路隧道与邻近建筑物的相互影响研究

城际铁路隧道不可避免地要下穿建筑物密集的市区,其开挖施工会引起地表沉降,危及建筑物的安全,因此评估城际铁路隧道和邻近建筑物的相互影响就成为迫切需要解决的问题。文章以实际工程为例,将隧道、地基和上部结构作为一个整体,系统地研究了建筑物和下穿隧道的相互影响,针对不同的施工工法和不同的地质情况进行了敏感性分析,并对各类工程措施的效果进行了评估。研究结果表明,基础桩端嵌入地层性质对建筑物沉降、结构内力以及后续的加固处理措施影响很大;相对于隧道不同部位的桩基受隧道施工的影响各不相同,隧道正上方和侧上方45°附近桩基受开挖影响较大;同样地层情况下,盾构法开挖后建筑物的沉降和内力值要比矿山法低;桩基托换对整体沉降的控制要好于加固地层措施,然而桩基托换措施却增大了建筑物局部变形和内力值;建筑荷载作用位置附近隧道段内力会有所增大。因此需要预计各类可能的情况,并根据具体情况综合采取相应的措施。     

Study of Controlling Measures for Existing Railway Deformation Caused by Metro Shield Tunnel Under-passing Construction北大核心CSCD

Based on the background of the first phase project of the R3 line of Jinan Rail Transit, and in view of the metro shield tunnel passing under the existing railway bridge and subgrade, this paper uses Abaqus to establish a numerical model to simulate the deformation of the existing bridge and subgrade of the Jiaoji railway line under the two conditions of non-active reinforcement and reinforcement. The results show that under the condition of no reinforcement, the maximum settlement of the top bridge on the pier is -5.88 mm, and the maximum settlement difference is 5.16 mm, which exceed the deformation control requirements of the 5 mm regarding the bridge pier of the railway with ballast track. The maximum lateral displacement and longitudinal displacement of the pier are 0.28 mm and -3.01 mm, respectively. After the reinforcement measures of the bored piles are adopted, the maximum settlement of the top bridge on the pier is -1.71 mm, and the maximum settlement difference is 1.16 mm, which fully meet the bridge pier deformation control standard. The maximum lateral displacement and longitudinal maximum displacement are -0.245 mm and -2.83 mm, respectively, which meet the requirements of the control standard. The vertical settlement of the railway subgrade is relatively small. The maximum settlement values under the two working conditions are -12.31 mm and -11.97 mm, respectively, which meet the subgrade settlement control requirement of 20 mm. It is proved that the reinforcement effect of the bored pile is good, and the reinforcement scheme is safe and feasible. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

松散地层浅埋水工隧洞现场监测试验研究

在北京市南水北调配套工程南干渠工程试验段工程实践中,对松散土层浅埋水工隧洞施工中地层沉降进行了现场监控量测.文章基于监测结果,分析了该隧洞地层的变形特点,指出了松散土层中浅埋暗挖隧洞地层的变形规律,以及开挖影响的时空范围.研究分析的方法和结论可为类似条件下隧洞工程的设计、施工、监测和进一步的理论研究提供参考和借鉴.     

Analysis of the Stability of the Shield Tunnel Excavation Face Considering Fluid-Solid Coupling Effect北大核心CSCD

In order to study the impacts of the transient seepage on the stability of tunnel excavation face during the installation of lining segments, the fluid-solid coupling effect based numerical model of the tunnel excavation face was developed by the finite element software PLAXIS. With adoption of the variablecontrolling approach, the influences of the depth/diameter ratio (the ratio of the buried depth to diameter of the tunnel) and the support pressure ratio (the ratio of the face support pressure to water and soil pressures ahead of the excavation face) on the face stability and ground settlement were investigated, respectively. At same time, the failure modes of the excavation face under the fluid-solid coupling analysis were also discussed. The results show that:1) the transient seepage leads to the development of the soil arching at the front of the excavation face, in which the smaller deformation at the excavation face is achieved, and so less support pressure for the face stability is allowed. While for the plastic analysis without taking into account the effect of transient seepage, a higher support pressure is required to maintain the stability of the excavation face; 2) in the fluid-solid coupling analysis, the depth/diameter ratio has less impacts on the stability of the excavation surface, but has larger impacts on the ground settlement. The larger the depth/diameter ratio, the larger the ground surface settlement and the settlement profile; 3) however, with the combination of the decrease of the support pressure and the impact of transient seepage on the settlement of ground surface, the soil arching effect in front of the excavation face is gradually reduced. The deformation zone at the ground surface is then connected with the deformed part ahead of the tunnel face to form a wedge-shaped soil sliding zone. It is also observed that the wedge-shaped body tends to have a larger funnel-shaped failure mode than that in the plastic analysis without considering the transient seepage. The results show that the transient seepage has a great impact on the stability of tunnel excavation face in the soil condition with high permeability ratio. The fluid-solid coupling analysis should be adopted to evaluate the deformation of excavation face and ground settlement. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

基坑开挖引起下方运营隧道位移的预测与控制技术研究

针对基坑开挖过程中对下方运营地铁隧道的保护问题,通过基于工程实测的隧道回弹隆起值的监控,对隧道回弹隆起的规律进行了分析研究。在考虑基坑开挖时空效应的基础上,分别对基坑放置时间、开挖方式、分块开挖宽度对隧道回弹变形的影响进行了分析和归纳,得出了隧道位移受基坑放置时间、开挖方式、分块开挖土体宽度的影响的规律。     

高速铁路黄土隧道初期支护受力特性研究

支护结构的合理设计是大断面黄土隧道设计的关键环节。文章结合在建铁路黄土隧道,采用数值模拟,分析了大断面黄土隧道在不同初期支护时机情况下,支护结构、围岩受力状态和力学行为变化情况;基于控制围岩变形为核心,对大断面黄土隧道施工中初期支护施作时机的选择给出了合理的建议;根据现场监测结果,总结出了黄土隧道初期支护受力规律。黄土具有明显的流变特性,支护结构受力很大一部分承受围岩流变产生的附加荷载;另外,支护结构受力在空间上分布并不均匀对称,这些在设计中都应加以考虑。     

冻土地区既有隧道上地铁车站深基坑工程实践

结合哈尔滨市地铁1号线龙江街站深基坑工程的特点,详细介绍了在冻土和既有人防隧道段中实施深基坑的设计思路和实践经验,并分析了冻胀力对围护桩的影响。对在冻土地区进行基坑围护设计和施工,以及对基坑内既有构筑物处理方面的设计实践进行了总结。