Optimal location and effect judgment on drainage tunnels for landslide prevention

An optimal drainage tunnel location determination method for landslide prevention was proposed to solve the existing problems in drainage tunnel construction. Current applications of drainage tunnel systems in China were reviewed and the fimctions of drainage tunnel were categorized as catchment and interception. Numerical simulations were conducted. The results show that both catchment and interception tunnels have variation of the function in the simulation of monolayer model, which shows the reduction of permeability condition in lower layer. The function of catchment can be observed in the deep slope, while the function of interception is observed near groundwater source. By using the slope safety factor and discharge water amount as the objectives of optimal drainage tunnel location, and pore-water pressure in fixed node and section flux as the judgment for construction quality of adjacent drainage tunnel, the design principle of drainage tunnel was introduced. The K103 Landslide was illustrated as an example to determine the optimal drainage tunnel location. The measured drainage tunnel efficiency was evaluated and compared with that from the numerical analyses based on groundwater data. The results validate the present numerical study.

Interaction analyses between tunnel and landslide in mountain area

This paper focuses on the analytical derivation and the numerical simulation analyses to predict the interaction influences between a landslide and a new tunnel in mountain areas. Based on the slip-line theory, the disturbance range induced by tunneling and the minimum safe distance between the tunnel vault and the sliding belt are obtained in consideration of the mechanical analyses of relaxed rocks over the tunnel opening. The influence factors for the minimum safe crossing distance are conducted,including the tunnel radius, the friction angle of surrounding rocks, the inclination angle of sliding belt,and the friction coefficient of surrounding rocks. Secondly, taking account of the compressive zone and relaxed rocks caused by tunneling, the Sarma method is employed to calculate the safety factor of landslide. Finally, the analytical solutions for interaction between the tunnel and the landslide are compared with a series of numerical simulations, considering the cases for different perpendicular distances between the tunnel vault and the sliding belt. Resultsshow that the distance between the tunnel vault and the slip zone has significant influence on the rock stress and strain. For the case of the minimum crossing distance, a plastic zone in the landslide traversed by tunneling would be formed with rather large range, which seriously threatens the stability of landslide. This work demonstrates that the minimum safe crossing distance obtained from numerical simulation is in a good agreement with that calculated by the proposed analytical solutions.

The safety distance of a tunnel under-traversing a slope body with a landslide-prone zone

At present,substantial scientific research achievements have been made in the research on landslide occurrence,movement mechanism,mitigation measures,and structural stability during tunnel excavation.However,the interaction mechanism of a tunnel under-traversing a slope body with potential landslides is still not well understood.Based on the field data provided by previous investigations in the study area,six sets of 1:100 laboratory experiment model tests were conducted to study the stability of the landslide-prone zone of the slope body with an under-traversing tunnel.The selected distances between the tunnel and the sliding surface are 1.5,3,and 5 times of the tunnel diameter,respectively.The experiment results show the interaction between the landslide-prone zone and the tunnel,elucidating the effect of potential landslides during the tunnel excavation process and the reaction of the landslide slip on the tunnel structure.Several conclusions are obtained:①During the process of tunnel excavation,the vertical displacement of the tunnel vault decreases with the increase of the buried depth.②The vertical displacement of the sliding surface increases with the increase of the buried depth of the tunnel.The horizontal displacement of sliding surface decreases with the increase of the buried depth.③After the occurrence of a rainfall-induced landslide,the vertical displacement of the tunnel vault in the 1.5-diameter-distance case is 57.29%greater than that in the 3.0-dismeter-distance case.④For a two-cave tunnel,it is suggested that the cave farther from the landslide toe should be firstly excavated since it may generate less structural deformation.

Deformation of the Zhangjiazhuang high-speed railway tunnel: an analysis of causal mechanisms using geomorphological surveys and D-InSAR monitoring

On 18 January 2016,the Zhangjiazhuang high-speed railway tunnel in Ledu,Qinghai Province,China,underwent serious deformation and structural damage.A crack formed at the top of the tunnel and the concrete on the crown peeled off.As a result,the tunnel could not be operated for three months.In order to determine the types and spatial distribution of the landslides in the region and the surface deformation characteristics associated with the tunnel deformation,we used field geological and geomorphological surveys,unmanned aerial vehicle image interpretation and differential interferometric synthetic aperture radar(D-In SAR) surface deformation monitoring.Nine ancient and old landslides were identified and analysed in the study area.Surface deformation monitoring and investigation of buildings in several villages on the slope front showed that the tunnel deformation was not related to deep-seated gravitational slope deformation.However,surface deformation monitoring revealed an active NEE–SWW fault in the area intersecting the tunnel at the location of the tunnel rupture.This constitutes a plausible mechanism for the deformation of the tunnel.Our study highlights the need for detailed engineering geomorphological investigations to better predict the occurrence of tunnel deformation events in the future.

破碎岩体隧道洞口开挖诱导滑坡与古滑坡耦合分析

以大栗树高速公路隧道洞口施工为工程背景,研究了在考虑古滑坡因素下洞口工作面边坡失稳及其加固技术。利用钻孔测斜数据(BCD)和Midas GTS折减强度有限元分析模型,分别推测了最危险滑动面,得知两者滑动面位置相似。并采用不平衡推力传递法,基于BCD推断滑动面计算安全系数。以BCD和有限元法的滑动面为基础,将滑动面近似假设为对数螺旋线,考虑地形因素,建立考虑多台阶边坡上限分析模型,研究了不同加固措施对边坡稳定的影响。结果表明,3种方法计算出的边坡安全系数结果相近。

充填型岩溶隧道仰坡滑塌机制及稳定性控制技术——以宜宾巡场至玉和公路下坝隧道出口段为例

为解决充填型岩溶隧道进洞过程中引起的仰坡滑塌问题,利用现场调查和MultiFracS多物理场断裂分析软件,对隧道进洞过程中仰坡体内裂缝发展过程和围岩变形情况进行分析,提出洞口仰坡加固措施并进行效果评价,得出如下结论:1)连续降雨是引起仰坡滑塌的直接原因,随着含水率的增加,碎石土充填物抗剪强度降低,溶腔区位移变化显著且出现微裂隙;当含水率增加至20%时,溶腔区裂缝进一步发展,局部出现开裂,地表滑动位移不断增加。2)隧道进洞施工扰动加速了地表覆盖层与下伏基岩间贯通裂缝的形成,仰坡体呈现整体滑动趋势。基于现场调查和数值分析,采用“缓坡+钢锚管/锚索框架梁”的仰坡防护形式,用注浆钢锚管替代锚杆和部分锚索,能够避免溶腔内碎石土在雨水下渗中产生变形破坏。经现场实测数据验证,加固后的仰坡在隧道二次进洞过程中处于稳定状态,隧道洞内变形和地表沉降均得到了有效控制。

不同滑带角度滑坡作用下隧道衬砌与抗滑桩结构非线性受力特征研究

随着隧道滑坡体系支护研究的深入,隧道滑坡与抗滑桩支护之间的受力研究尤为重要。为研究在0°、10°、20°、30°、40°、50°共6种滑带角度影响下隧道衬砌结构与抗滑桩的受力特征,以大准铁路南坪隧道为原型,采取室内缩尺试验以及数值模拟的方法,对三者间受力变形规律进行研究。得到以下结论:随着滑带角度的增大,桩身与隧道衬砌结构变形逐渐减小,作用在隧道以及桩身的土压力、弯矩值逐渐减小;同时,滑带角度为0°、10°、20°、30°时滑坡水平推力对隧道衬砌结构受力影响较大,40°、50°时滑坡水平推力影响显著衰减,拱脚竖向荷载占比逐渐增大。当滑带角度小于30°时,应当主要考虑滑坡水平推力对隧道结构的影响,大于30°时主要考虑由滑坡体所产生的竖向荷载对隧道衬砌结构的影响,此时应当对隧道仰拱及靠近坡体处拱脚位置重点加固。所得试验、模拟结果为隧道与抗滑桩体支护施工提供一定参考。

滑坡易发环境下公路隧道洞口施工安全系统韧性评价

为合理评价公路隧道在滑坡易发区进洞阶段施工安全系统的韧性,首先,构建基于D-S证据理论的贝叶斯网络韧性评价模型:1)依据PSR模型从压力、状态、响应3方面建立公路隧道洞口施工安全系统的16个韧性评价指标;2)通过各指标间的二元关系绘制贝叶斯网络;3)使用D-S证据理论计算BN节点条件概率并利用Netica软件对韧性水平进行分析计算。然后,以甘肃省卓合高速公路白崖山隧道洞口施工为例,运用该模型进行实例分析。计算结果表明:在滑坡灾害影响下,白崖山隧道洞口施工安全系统韧性水平为良好,评价结果与现场施工监测数据相符,有效验证了该指标体系的合理性和韧性评价模型的适用性。

隧道开挖诱发滑坡与衬砌开裂处治与分析

山区隧道的勘察设计通常都会规避穿越大型滑坡,但山区隧道洞口段不可避免穿越斜坡。隧道工程建设中经常出现因隧道开挖诱发古滑坡体和斜边坡变形滑动,从而导致隧道坍塌和衬砌开裂。以寒山口隧道为例,探讨了隧道施工诱发边坡滑动和衬砌开裂的机理,评价了加固措施的有效性,并根据衬砌裂缝的分布特征和宽度随时间变化规律,再结合衬砌整体的变形特征,总结得到了2种衬砌开裂机理。其中,第1种类型为衬砌内张拉裂缝,对应着隧道深埋侧拱脚裂缝形成机理,裂缝处于张开状态,宽度较大,且其宽度随时间的变化较为明显;第2种类型为衬砌内压缩裂缝,对应着隧道浅埋侧拱肩裂缝的形成机理,裂缝一般处于闭合状态,宽度较小,且宽度随时间的变化较小。

滑坡-隧道正交体系变形特性试验研究

【目的】对于滑坡-隧道正交体系,滑坡的变形失稳是引发隧道病害的重要原因。为了研究滑坡-隧道正交体系在滑坡失稳过程中的宏观变形特性,【方法】以阳坡里隧道为研究对象,使用自主研发的牵引式滑坡分级滑动模拟试验装置设计开展了12组室内模型试验,研究了在滑坡-隧道正交体系中滑坡失稳情况下隧道埋深、隧道在滑体内的布置位置以及滑动段位置对“洞周位移指数”的影响。【结果】结果显示:滑坡发生失稳时的坡面宏观变形存在一定规律,通常表现为坡面的后缘裂缝以及次级裂缝,且坡面位移沿次级裂缝存在明显分级情况;在其他变量相同的情况下,隧道在滑坡体内部埋深越大、隧道布置位置越靠近滑坡体前缘、滑动段越靠近滑坡中段时,滑坡滑动对隧道周围0.5~1.0倍隧道直径范围内土体的位移影响越大;滑动段位置对洞周位移指数影响最大,当滑动段分别位于滑坡前段、中段和后段时,洞周位移指数分别为小于0.8、大于1.8和介于1.0~1.5之间。【结论】研究成果可为滑坡隧道的变形演化机理、滑坡诱发隧道病害的预测预报以及防治技术等研究提供参考。

某隧道-多滑面滑坡斜交体系稳定性及综合处治技术研究

以某高速公路隧道为研究对象,借助物探、钻探、监测等手段研究了该隧道-多滑面滑坡斜交体系稳定性及综合处治技术。研究结果表明:该滑坡存在3个滑面,第2滑面稳定性最低,为主滑面,暴雨工况下该滑面处于失稳状态;对于正在变形的隧道-多滑面滑坡斜交体系,提出了分区、分期治理,在监测的基础上先采取应急工程,且应急工程与永久工程、洞内与洞外处治相结合的综合防治思路。监测数据表明,该隧道-多滑面滑坡斜交体系通过坡脚反压、钢管群桩、抗滑桩、提高衬砌支护强度及洞内反压、护拱等综合措施处治后,坡体及结构均处于安全状态。

阿克特蒲1#隧道超前支护技术的应用研究

隧道工程在开挖阶段时常发生滑坡现象,严重影响工程的顺利开展,也威胁到施工人员的安全,为解决隧道工程建设这一难题,避免安全事故的发生,在建设施工中采用超前支护技术进行有效控制。该文以阿克特蒲1#隧道为案例,分析超前支护技术的优势,在隧道开挖期间积极应用超前支护技术,比如超前大管棚、超前小导管、超前药卷锚杆和超前帷幕注浆等技术,有利于稳定大坡面,给开挖工作提供保障,有效避免滑坡带来的危害,确保隧道工程的安全、稳定。

公路隧道进口滑坡分析与治理方案比选

以桐梓至新浦高速公路舒家岩隧道进口滑坡为工程背景,先进行滑坡成因分析,再进行稳定性分析和治理方案比选。为了获得较准确的计算参数,参考《公路滑坡防治设计规范》,先根据监测数据和钻探判断第一滑面上部坡体处于蠕滑阶段,稳定系数Fs取0.98;而第二滑面无明显滑动迹象,稳定系数Fs取1.05;结合土工试验,采用极限平衡法反算滑坡力学参数值,并通过传递系数法计算第一滑面处坡体的剩余下滑力(1449.10 kN/m),边坡急需采取抗滑措施。为了提高滑坡治理后隧道进洞施工的安全性,根据滑坡发展情况,对抗滑桩支挡与回填反压方案进行了方案比选,结果表明,抗滑桩方案工程费用较小,有利于运行期间山体的稳定性,对环境影响较小;回填反压方案工程费用大,易诱发次生滑坡的发生,故选择抗滑桩方案,并取得良好的治理效果。

有压引水隧洞塌方原因分析及处理措施——以博瓦水电站引水隧洞为例

结合博瓦水电站引水隧洞涌水段塌方情况,分析塌方原因、处理难点,并提出塌方处理原则和措施,并对结构进行复核。通过采用积水引排、反压回填、分台阶开挖、“超前支护”“刚性支护”和“柔性支护”相结合等措施,阐述了该塌方处理的主要技术和关键思路。安全有效地完成塌方处理后,监测数据及运行效果良好,证明了该措施的合理性和有效性。

隧道洞口处巨型黄土老滑坡稳定性综合评价

为有效评价隧道洞口段滑坡的稳定状态,以隧道洞口处胡家村滑坡为工程背景,先结合其地质条件,通过数值模拟开展洞口段滑坡稳定性的初步评价,再以洞口段地表变形监测成果为基础,通过变形预测实现滑坡稳定性的预测评价,以保证滑坡稳定性评价结果的全面性。结果表明:隧道洞口处滑坡未见整体滑移迹象,整体稳定较好,但不排除在暴雨工况、地震工况或剧烈工程活动影响下发生局部滑坡的可能。在滑坡洞口段局部稳定性评价结果中,经数值模拟结果的初步判断,洞口段滑坡在不利工况条件下存在较大的局部失稳风险,尤其是在地震工况条件下失稳风险较大;经变形预测,验证了FA-LSTM-CNN模型的预测能力,且得出洞口段滑坡的后续变形趋势等级为Ⅱ级,即后续变形的收敛趋势一般,稳定性会暂时维持现状,但不排除进一步减弱的可能,因此,需尽快开展洞口段滑坡的防治工作。

洞口膨胀土滑坡桩基+横梁复合抗滑技术研究

山岭隧道洞口膨胀土滑坡在人工扰动和强降雨条件下极易出现失稳滑动趋势,是影响隧道施工安全的重要因素之一。雅万高铁4号隧道围岩成分复杂,膨胀特性明显,在隧道进口施工过程中受连续降雨影响造成洞口仰坡变形和拉裂,隧道拱顶大幅沉降和偏压变形。为保证隧道进洞安全,提出“桩基+横梁”洞口滑坡体加固措施,通过数值模拟与现场实测,验证了该加固技术可降低隧道拱顶沉降约85%,确定了桩基长度对加固效果的影响和桩长范围,有效降低了对隧道洞口仰坡的扰动。

水利枢纽工程溶塌角砾岩隧洞涌水塌方施工技术

对溶塌性角砾岩特性地貌岩溶发育特点进行综合分析后发现,使用普通的处理方法很难实现对塌方体的高效处理,因此,出台了自进式管棚处理办法,使塌方体得以高效处理。论文针对水利枢纽工程溶塌性角砾岩隧洞涌水塌方的初期支护和施工工序等情况开展了全面而透彻的分析,实现了人们从涌水塌方段的安全通过。

大断面浅埋高速铁路隧道施工关键技术研究

为了提升高速铁路隧道施工技术,总结了大断面浅埋隧道的判定方法,并以某铁路隧道为研究对象,利用MIDAS软件建立计算模型,对比了台阶法、留核心土法、CD法、双侧壁法的加固效果,并从隧道进洞、超前支护、塌方处治等方面探讨了大断面浅埋隧道的施工要点。同时,以双侧壁导坑法为例,计算了不同开挖高度和开挖面距离下隧道围岩的变形。

隧道穿越滑坡体失稳机理及处治技术

针对隧道穿越大偏压、潜在滑坡体而造成隧道局部出现裂缝、变形等工程问题,文中以韶新高速公路寒山口大断面隧道为工程背景,通过现场调查和监控量测,研究隧道洞口及滑坡的变形情况,分析隧道洞口滑坡的诱发因素及形成机理,并提出有效的处治措施及监控技术。研究结果表明,隧道在穿越潜在滑坡体时发生较大的挤压变形(最大变形量为44.4cm,最大变形速率为30mm/d);洞口滑坡是由偏压地形、不利的工程地质、施工扰动、降雨等因素综合导致;通过采取裂缝封堵、洞身加强、坡脚加固的临时紧急措施和预应力锚索框架梁、洞内注浆、超小导管支护等综合处治措施,隧道及滑坡的变形得到有效控制。研究结果可为类似工程提供参考和借鉴。

公路隧道洞口滑坡的机制分析及监控预报

由于受工程地质条件、水文地质条件及人为因素等影响,公路隧道洞口施工过程中易发生洞口滑坡。以浙江省杭千高速公路横路头隧道洞口为例,首先从地质因素、水的作用及人为因素三方面分析了滑坡产生的机制,然后结合对边坡的监控量测,分析滑坡产生的过程并针对监测数据进行了动态反馈,同时检验施工单位根据反馈情况采取措施后的效果,最后通过Plaxis有限元计算软件模拟了整个滑坡发生的过程,得到较好效果。由此可见,通过有效的监控动态反馈,能对出现的隧道洞口边坡病害加以控制并对滑坡进行预测,从而大大降低隧道洞口施工中的风险,保证隧道洞口施工安全。