Dynamic response characteristics of a circular lined tunnel under anisotropy frost heave of overlying soil at the tunnel portal section in cold regions

The rapid development of traffic engineering in cold regions and its consequent problems need to be considered.In this paper,the dynamic response characteristics of the tunnel portal section in cold regions with harmonic load acting on the lining were studied in the frequency domain.The lining is in close contact with the frozen soil,and there is relative movement between the frozen and unfrozen soil due to the phase change.The analytical solution of the vibration of tunnel portal section caused by the harmonic load acting on the lining was derived under the consideration of the anisotropy frost heave of overlying soil.Based on the continuity conditions and boundary conditions,the undetermined coefficients were obtained,and the analytical solutions for different medium displacements and stresses of the cold-region tunnel system were acquired.The vertical pressure coefficient was equivalently simplified as a variable that could be used to replace the thickness of the overlying soil above the tunnel.The analysis of the parameter model shows that the change of the medium parameters(lining,frozen,and unfrozen soil)affects the circumferential stresses,the radial displacements and their peak frequencies of the soil.For example,the increase of density ratio of tunnel lining to frozen soil decreases the radial stresses of the frozen and unfrozen soil;the increase of volumetric frost heaving strain of the frozen soil increases the radial displacements of the frozen surface and decreases the stability of the frozen surface;the increasing of thickness of the frozen soil significantly reduces the radial displacement of unfrozen soil at dimensionless radius η=4.5 compared with that of frozen soil at η=1.5.

Reconstructing the portal vein through a posterior pancreatic tunnel:New choice for portal vein thrombosis during liver transplantation

BACKGROUND Thrombectomy and anatomical anastomosis(TAA)has long been considered the optimal approach to portal vein thrombosis(PVT)in liver transplantation(LT).However,TAA and the current approach for non-physiological portal reconstructions are associated with a higher rate of complications and mortality in some cases.AIM To describe a new choice for reconstructing the portal vein through a posterior pancreatic tunnel(RPVPPT)to address cases of unresectable PVT.METHODS Between August 2019 and August 2021,245 adult LTs were performed.Forty-five(18.4%)patients were confirmed to have PVT before surgery,among which seven underwent PV reconstruction via the RPVPPT approach.We retrospectively analyzed the surgical procedure and postoperative complications of these seven recipients that underwent PV reconstruction due to PVT.RESULTS During the procedure,PVT was found in all the seven cases with significant adhesion to the vascular wall and could not be dissected.The portal vein proximal to the superior mesenteric vein was damaged in one case when attempting thrombolectomy,resulting in massive bleeding.LT was successfully performed in all patients with a mean duration of 585 min(range 491-756 min)and mean intraoperative blood loss of 800 mL(range 500-3000 mL).Postoperative complications consisted of chylous leakage(n=3),insufficient portal venous flow to the graft(n=1),intra-abdominal hemorrhage(n=1),pulmonary infection(n=1),and perioperative death(n=1).The remaining six patients survived at 12-17 mo follow-up.CONCLUSION The RPVPPT technique might be a safe and effective surgical procedure during LT for complex PVT.However,follow-up studies with large samples are still warranted due to the relatively small number of cases.

Geotechnical investigations and remediation design for failure of tunnel portal section： a case study in northern Turkey

Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method(FEM) in four stages. These stages are slope stability analyses for pre-and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition toslope stability evaluation, the Rock Mass Rating(RMR), Rock Mass Quality(Q) and New Austrian Tunneling Method(NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.

Nonlinear Response of Tunnel Portal under Earthquake Waves with Different Vibration Directions

Tunnel portal sections often suffer serious damage in strong earthquake events.Earthquake waves may propagate in different directions,producing various dynamic responses in the tunnel portal.Based on the Galongla tunnel,which is located in a seismic region of China,three-dimensional seismic analysis is conducted to investigate the dynamic response of a tunnel portal subjected to earthquake waves with different vibration directions.In order to simulate the mechanic behavior of slope rock effectively,an elastoplastic damage model is adopted and applied to ABAQUS software by a self-compiled user material(UMAT)subroutine.Moreover,the seismic wave input method for tunnel portal is established to realize the seismic input under vertically incident earthquake waves with different vibration directions,e.g.,S waves with a vibration direction perpendicular or parallel to the tunnel axis and P waves with a vibration direction perpendicular to the tunnel axis.The numerical results indicate that the seismic response and damage mechanisms of the tunnel portal section are related to the vibration direction of the earthquake waves.For vertically incident S waves running perpendicular to the tunnel axis,the hoop tensile strain at the spandrel and arch foot and the hoop shear strain at the vault and arch bottom are the main contributors to the plastic damage of the tunnel.The strain is initially concentrated around the tunnel foot and spandrel,before shifting to the tunnel vault and bottom farther away from the tunnel entrance.For vertically incident S waves running parallel to the tunnel axis,very large hoop shear strain and plastic damage appear at the tunnel haunches.This strain first increases and then decreases with distance from the tunnel entrance.For vertically incident P waves running perpendicular to the tunnel axis,the maximum damage factor of the slope rock and the maximum plastic strain of the tunnel are significantly lower than for S waves.Moreover,with increasing distance from the tunnel entrance,the plastic damage to the tunnel lining rapidly decreases.

基于案例推理的隧道洞门智能设计方法研究

为将以往隧道案例的经验应用到新建隧道设计中,以解决传统设计方法工作量大且效率低下的问题,提出基于案例推理的隧道洞门智能设计方法。结合隧道洞门工程特点,选取影响洞门设计的主要因素,将影响因素划分为12个属性单元来表征工程案例,运用三角模糊数的层次赋权计算方法对各属性单元权重进行赋值,借助相似度理论建立隧道洞门设计方案相似决策模型。基于GIS技术开发了隧道洞门工程案例库,实现对既有工程的存储管理,同时利用SQL查询语言及Python计算脚本实现案例的属性特征值计算与最相似匹配,进一步修正后可实现隧道洞门修建方案的设计决策。以某山区隧道为例对智能设计方法进行验证,结果表明:根据属性单元特征值计算结果,在案例库中比选得出与拟建隧道相似度最高的既有工程为凤凰山隧道,且相似度为0.707。因此,设定阈值为0.7时能加快案例库的检索速率与匹配准确率,该方法吸取了既有工程案例的经验,能应用于隧道洞门施工方案的决策设计,可供今后隧道洞门方案的智能化设计参考。

亮度和速度协同下公路隧道口路段驾驶舒适度研究

为探究山区双车道公路隧道口路段驾驶心理负荷的变化特性,本文采用实车试验的研究手段,招募27名驾驶人作为被试,选择重庆市境内的9座隧道作为试验场景,采集驾驶人、车辆和驾驶环境的行车数据,使用驾驶人的心率增长率表征驾驶心理负荷。通过数据分析,对驾驶人在隧道口路段的驾驶心理负荷与亮度和速度的相关性进行研究。结果表明,山区双车道公路隧道入口段的驾驶心理负荷大于出口段;在环境亮度小于500 cd·m^(-2)时,驾驶心理负荷对亮度的变化更为敏感,进而提出亮度变化率的计算公式,当亮度变化率在60%时,黑洞和白洞效应对驾驶人的心理影响趋于相同;在隧道口路段,速度对驾驶心理负荷具有放大效应;根据驾驶心理负荷值,划分隧道口路段的驾驶舒适度区间,提出基于驾驶舒适度需求的亮度变化率和速度的安全阈值,并给出计及亮度变化率和隧道口净空高度的亮度曲线。

高桥隧比条件下桥隧相连的隧道洞口联络道设计探讨——以重庆巫溪至陕西镇坪高速公路为例

为确定高桥隧比条件下高速公路桥隧相连的特长隧道洞口联络道的转换长度和结构形式,采用数值模拟方法,选用18.1 m的长头铰接列车为典型车辆,针对10 m~30 m五种左右幅间距及0°~45°四种行驶转换角度,模拟车辆行驶轨迹并计算联络道通行的最小长度。结果表明:1)在满足转换车道基本长度的前提下,模拟隧道洞口联络道推荐长度采用30 m或40 m;2)基于模拟结果推荐的联络道长度,为超高桥隧比的巫镇高速隧道洞口联络道设计提供了重要的基础依据;3)在运营期间,该高速的洞口联络道实现了养护维修或异常工况下的交通转换,有效提升了道路防灾减灾和运营养护能力,为类似工程的设计提供了有益参考。

框架梁与锚索桩板墙加固隧道洞口边坡的动力响应特性

针对山岭隧道洞口在降雨、地震等因素作用下易产生变形破坏的问题,以某处采用框架梁与锚索桩板墙支护的隧道洞口边坡工程为原型,开展几何比尺为1∶50的振动台模型试验,分析降雨后地震作用下边坡的动力响应特性及失稳变形规律。结果表明:降雨后坡面无局部破坏,地震作用下边坡的破坏过程可归纳为坡顶张拉破坏—坡脚剪切溃裂—坡体整体失稳滑动,边坡表现为张拉—剪切型破坏;边坡峰值加速度放大系数呈层状分布,“高程效应”与“趋表效应”显著,均随输入正弦波频率、幅值的增加而增大;边坡土体峰值应变分布与坡体滑动破坏面较吻合;桩体锚索轴力与输入正弦波频率、幅值呈正相关,强震作用下锚索轴力增幅显著;桩后峰值土压力近似呈三角形分布,桩体嵌固段内桩土压力最大;桩体弯矩呈“b”型分布,嵌固段内桩体峰值弯矩最大,抗震设计中应注意验算其抗弯强度;桩后土压力与桩体加速度FFT谱幅值主要集中于低频段,结构动力响应主要受地震波低频段部分影响。

门式抗浮框架作用下上方开挖既有盾构隧道响应解析解

上方开挖卸载导致既有盾构隧道结构产生上浮,易引发结构渗漏水、开裂等病害。竖井开挖联合门式框架技术是限制上方开挖引起既有隧道上浮的一种有效控制措施,但是目前仍缺少相应的理论方法用于指导门式抗浮框架的设计。为此,提出了既有隧道结构响应的解析解,可以实现竖井和基坑开挖阶段既有隧道结构纵向和横截面变形计算,并给出了相关的计算流程。通过与工程实例和三维数值模拟结果进行对比,验证了解析解的可靠性。通过典型算例计算和参数敏感性分析讨论了门式抗浮框架的作用机理以及既有隧道埋深和竖井开挖尺寸等因素的影响规律。结果表明:门式抗浮框架在基坑开挖阶段可以有效控制上方开挖引起的既有隧道变形,控制效果与既有隧道上方剩余覆土厚度密切相关,剩余覆土越小控制效果越明显;门式抗浮框架的作用效果主要取决于抗浮板与土体之间的作用力,抗拔桩与土体的作用力对既有隧道变形影响较小。

微型排桩支护结构在隧道明洞段的应用

为探索微型排桩在高陡边坡明洞段支护结构中的适应性,基于二维杆系荷载-结构模型,提出三排桩支护结构设计计算方法;结合工程案例拟定多种钢管排桩+锚索支护方案,对排桩支护结构的内力及变形特征、不同方案的适应性、钢管桩直径的影响等进行深入研究。结果表明:1)排桩支护中,前排桩、中排桩、后排桩具有几乎相同的内力和变形特征,但前排桩的变形和内力值略大于其他2排桩,前排桩坑底位置是整个支护结构中最不利部位;2)采用增设锚索、预留压脚岩体等方式降低相邻支撑间的竖向间距,可以有效降低支护结构位移和内力,从而使支护结构变形满足相关规范要求;3)随着桩径的增大,钢管桩刚度增大,支护结构水平位移呈指数形式降低;4)增加三排桩直径和仅增加前排桩直径均可以有效降低支护结构变形。支护结构设计中,可以根据开挖高度、施工机械、地形地貌等,选择合适的支撑方式和钢管桩直径,从而实现支护结构快速、机械化施工。

强震区浅埋偏压隧道洞口段减震层减震效果分析

依托某铁路隧道洞口段,利用FLAC3D软件研究隧道施设不同厚度减震层的减震效果。结果表明:(1)与不设减震层相比,施设5 cm减震层后,二衬结构最大、最小主应力分别减小了26.05%、21.57%,竖向、纵向位移分别减小了74.68%、36.13%,竖向位移差减小了0.32 mm,最小安全系数平均提高了50.46%;(2)施设10 cm减震层后,二衬结构最大主应力增大了134.45%,最小主应力减小了26.70%,竖向、纵向位移分别减小了70.80%、26.89%,竖向位移差增大了1.85 mm,最小安全系数平均提高了11.10%;(3)施设15 cm减震层后,二衬结构最大、最小主应力分别减小了45.38%、25.16%,竖向、纵向位移分别减小了70.89%、13.45%,竖向位移差增大了1.89 mm,最小安全系数平均提高了12.56%;(4)衬砌与围岩之间施设5 cm减震效果优于施设10 cm、15 cm减震层的减震效果。研究成果可为隧道洞口浅埋偏压段减震技术的发展提供参考。

高烈度地震区倾斜隧道洞口段抗减震技术研究

为提升高烈度地震区倾斜隧道洞口段的抗震性能,依托某隧道工程,利用有限差分数值软件FLAC3D研究了注浆加固和减震层的抗减震效果。结果表明:(1)隧道纵向应力极值和位移最大值出现在洞口中间过渡段,监测面内应力极值和位移最大值均出现在衬砌结构拱脚;(2)与无抗减震措施相比,注浆加固与施作减震层均能减少隧道二次衬砌位移差,施作减震层后隧道竖向位移差减少最多,减震效果达到74.83%;(3)工况1(无措施)最小主应力峰值最大,为-28.64 MPa,施作减震层后为-20.05 MPa,减震效果达到29.99%;(4)随着隧道纵向长度的增加,最小安全系数先减小后增大,最小值出现在中间过渡段监测面S3处;工况1安全系数为1.95,工况2为2.24,但仍低于安全阀值,工况3为2.56,符合安全要求。综合位移、应力和安全系数,采用减震层的抗减震效果优于注浆加固。研究成果可为倾斜隧道洞口段抗减震设防设计提供参考。

基于WebGL的斜切式洞门数字建模与工程应用

针对隧道斜切式洞门BIM模型创建与应用效率低、可视化依赖已有建模平台的问题,提出基于WebGL的数字化建模方法。分析总结隧道斜切式洞门基本结构组成与特征,基于点-线-面-体的实体生成理论,利用数学公式完成对隧道斜切式洞门BIM模型的参数化建立;依托WebGL技术实现隧道斜切式洞门BIM模型的在线浏览。同时,研究隧道斜切式洞门BIM模型的辅助施工方法,拓展隧道斜切式洞门BIM模型的工程应用场景。结果表明,该方法可辅助设计人员高效完成对隧道斜切式洞门的正向设计,提高隧道斜切式洞门BIM模型的创建效率与实用性。

基于BIM技术的隧道洞口二三维同步设计方法研究

为解决设计人员完成隧道洞口二维设计文件后还需耗费额外时间进行BIM翻模的问题,提高隧道洞口设计质量,实现精细化设计目标。基于Bentley OpenRailDesigner CE软件对地形与线路中线支持的特性,结合隧道洞口设计流程与习惯,提出基于中心数据库的隧道洞口二、三维同步设计方法;利用数字地形高程生成网格化地形模型,基于三维线路中线定位动态剖切地形模型生成横、纵断面,参数化驱动洞门设计模板图元,选取与地形适应的洞门类型并确定洞口位置;通过二三维互动的参数化交互方式设计边仰坡开挖及支护参数、明洞回填高度与坡度、端墙式洞门结构参数、洞口截水沟及超前大管棚设计参数;最后,通过这些设计参数同步生成三维BIM模型与二维设计图纸,并统计相关工程数量。利用C#、C++API接口研发了“隧道洞口二三维同步设计系统”。通过在西十、西康高铁项目中应用表明,该方法与系统符合设计习惯,能够实现隧道洞口工程的二维与三维设计与成果输出,在后续项目中具有推广应用价值。

基于三维场景隧道洞口方案设计系统研发与应用

针对铁路隧道洞口工程变化多、工程数量计算复杂以及传统二维设计方式不直观等问题,研发了一种基于三维场景开发的洞口方案设计系统。该系统以隧道设计数据为核心,搭建隧道参数化构件库,交互式设计隧道边仰坡、洞门结构、防护结构等,快速实现隧道洞口方案设计,还可以统计工程量。通过人工智能手段还可以快速识别隧道洞口偏压。经过工程应用验证,该系统技术方案可行,能明显提高隧道洞口方案设计的工作效率和质量。

严寒地区公路隧道洞口保温防冻关键应用技术研究

随着越来越多的寒冷地区隧道的建设,隧道修建过程中的冻害问题愈发频繁。隧道洞口作为隧道的初始与咽喉部位,常年受雨雪或气温变化的影响,多有冻害产生,隧道的冻害主要为衬砌洞内的挂冰、渗水,衬砌开裂等。以本溪市玉兰岭公路隧道为工程依托,开展严寒地区隧道洞口不同保温材料对隧道温度场的变化规律分析,针对目前寒区隧道广泛采用的保温隔热材料进行各方面的分析对比,提出更优化的保温方法。对洞口段的防冻保温至关重要,这是确保隧道防冻保温的关键所在。只有在洞口段做好防冻保温,才能把整个隧道的防冻保温做好。

淤泥质软土地层急曲线盾构隧道施工关键技术研究及应用

中心城区地下管网建设受复杂道路交通组织、既有密集地下管网、邻近建(构)筑物避让及保护等制约,不可避免地形成急曲线隧道线型。针对淤泥质软土地层急曲线盾构隧道施工所面临的地层反力不足、管片易错位或上浮、地面沉降较大、盾构姿态不稳定等问题,结合上海桃浦初期雨水调蓄工程,开展了淤泥质软土地层急转弯曲线盾构隧道施工关键技术研究,分析了软土地层急曲线隧道施工难点,提出并实施了急曲线段“偏心门式”MJS土体加固法结合同步注浆模式下的附袋注浆管片稳定控制方法的关键技术。监测结果显示,工程实施效果良好,且周边环境仅为微扰动,可为今后类似工程提供参考。

轨道工程穿越矿山宕口地质灾害防控技术——以南京某城际轨道工程为例

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