黏滑断层隧道刚柔并济抗减错技术研究

为提高强震区黏滑断层隧道的结构安全性和稳定性,以都汶高速友谊隧道F1黏滑断层段为研究背景,对黏滑断层隧道采用刚柔并济抗减错技术进行研究。研究结果表明:采用结构加强措施抵抗断层黏滑错动影响,结构位移抗减错效果不显著,结构内力的平均抗减错效果在23%~33%之间;施设减错层有利于消减断层黏滑错动对隧道结构的影响,其拱顶沉降、边墙收敛抗减错效果分别达到20%以上,结构内力平均抗减错效果在37%~47%之间,优于结构加强措施;刚柔并济抗减错措施在抵抗及消减断层黏滑错动影响方面效果显著,其拱顶沉降、边墙收敛抗减错效果均能达到30%以上,而结构内力平均抗减错效果达到80%以上。研究成果可为强震区黏滑断层隧道抗震减灾设防设计提供参考。     

黏滑断层隧道减错措施参数对减错效果的影响分析

为提高黏滑断层隧道的结构安全性和稳定性,对黏滑断层隧道设置不同缝宽减错缝、不同刚度减错层的减错效果进行研究。研究结果表明:断层黏滑错动对上盘隧道的影响远大于下盘;减错缝对上盘部分隧道结构的减错效果优于下盘,其中上盘减错效果最大为24.50%,下盘减错效果最大为9.26%;减错层对下盘部分隧道结构的减错效果略优于上盘,其中下盘减错效果最大为105.32%,上盘减错效果最大为78.07%;随着减错缝宽度的增加,隧道上盘减错效果变好,下盘缝宽10—15cm减错效果最好;随着减错层弹性模量的增加,隧道上下盘减错效果降低,当减错层弹性模量增加到一定程度（约100MPa）,减错效果趋于稳定。研究成果可为黏滑断层隧道的减错结构设计及施工提供参考。     

跨黏滑断层隧道纤维混凝土衬砌抗错断技术研究

为提高跨黏滑断层隧道的结构安全性和稳定性,以都汶高速友谊隧道F 1黏滑断层段为研究背景,通过采用纤维混凝土衬砌对跨黏滑断层隧道抗错断技术进行研究。结果表明:同体积纤维掺量条件下,混杂纤维混凝土(SBFRC)立方体抗压强度比纤维混凝土(SFRC)略低,SBFRC抗折强度比SFRC略高;断层黏滑错动对隧道上盘的影响大于下盘;纤维混凝土衬砌对下盘隧道结构的抗错效果优于上盘隧道,SFRC二衬平均抗错效果为12.22%,SBFRC二衬平均抗错效果为15.81%。研究成果可为黏滑断层隧道的结构设计及施工提供参考。     

断层错动下盾构隧道抗震措施研究

采用混凝土塑性损伤本构模拟盾构管片,建立三维有限元壳-弹簧模型,开展了在45°断层错动下盾构隧道结构响应的静力弹塑性分析。研究表明,在正断层和逆断层错动下,衬砌受压损伤最大值均分布在拱顶处,衬砌受拉损伤最大值均分布在拱腰处;正断层错动下,环间螺栓易发生受拉破坏;逆断层错动下,混凝土管片易发生拉压损伤破坏。替换断层附近土体为软土的同时提高螺栓强度等级,可有效抵御较大的断层错动位移。研究对断层错动下盾构隧道的抗震措施具有一定参考价值。     

隧道在地裂缝处的沥青混凝土复合衬砌的力学响应分析

针对隧道分缝衬砌结构为适应地裂缝错动造成位移变形而采用的流变性沥青混凝土复合衬砌置于初次衬砌和永久衬砌之间,改善隧道受力条件,以及沥青混凝土密封变形缝防止隧道渗漏的新型技术,应用有限差分数值方法,模拟隧道围岩土层结构及土材料的弹塑性、开挖支护施工过程、复合衬砌沥青混凝土的弹粘塑性、地裂缝两侧上、下盘土层相对错动位移变化,进行了地裂缝隧道永久衬砌结构分缝支护、初次衬砌和永久衬砌中间复合无缝沥青混凝土衬砌的力学响应特性分析。结果表明沥青混凝土复合衬砌能够抑制地裂缝错动位移条件下永久分缝衬砌段的水平位移和旋转位移,其流变变形调整和改善了永久分缝内衬的受力状态,减小了地裂缝附近衬砌结构的集中受拉受压作用。     

逆断层错动对隧道工程影响的数值模拟

由于断层错动导致的围岩永久变形会对隧道结构产生危害,为研究隧道在逆断层错动下的变形与受力特征,本文以成兰铁路穿越北川—映秀断裂的跃龙门隧道工程为研究对象,利用Abaqus软件建立穿越逆断层隧道结构的数值模型,选择参数和设定边界条件,模拟分析在逆断层错动作用下隧道衬砌结构的受力与变形情况。结果表明:逆断层错动引起隧道衬砌结构发生了“S”状弯曲变形,衬砌结构的纵向应力随断层位错量的增加而增加,整体表现为衬砌顶部与底部所受拉压应力分布相反;衬砌顶部拉压应力值均大于底部,且衬砌顶部和底部的压应力值均大于拉应力。      

青海门源M6.9地震典型隧道破坏特征分析与启示

地震引起的断层强烈错断是造成隧道等地下结构严重破坏的重要原因。以2022年青海门源6.9级地震中左旋走滑逆断层错动造成的隧道震害为调查基础,对左旋走滑逆断层错动下的震害特征及震害成因进行研究分析,主要得到如下结论：(1)左旋走滑逆断层造成大梁隧道线位严重错动,水平最大偏移约1.78 m,竖向最大抬升约0.68 m;(2)震害主要集中在断层影响范围内,其中隧道受破坏严重段约350 m,占隧道全长的5.33%,受破坏较严重段分别位于严重段大里程侧402 m和小里程侧646 m范围内,占隧道全长的15.96%,其余段落震害总体轻微;(3)施工缝、仰拱填充层等部位对强震较为敏感,震害表现突出。此次研究通过对震害特征分析得到的有益启示可为同类工程抗震设计提供参考与指导。     

地震作用下盾构隧道变形性能试验研究

地震作用下,盾构隧道的抗震变形性能限值是个重要指标。采用盾构区间隧道为原型,设计1/20的相似模型,考虑管片接头以及土体-结构相互作用,采用隧道结构加载试验系统,对盾构管片结构在不同的拼装方式和埋深下的变形行为进行了研究,测得了管片环的内力和位移。通过对6组试验结果进行分析对比,得出结论:埋深和拼装方式对盾构隧道结构变形有影响,对通缝结构的影响大于错缝结构;弹塑性分界点直径变形率限值,对通缝结构为0.56‰~1.00‰,对错缝结构为0.42‰~1.09‰;临界失稳点直径变形率限值,对通缝结构为16.87‰~21.44‰,对错缝结构为15.22‰~19.52‰。     

近距离垂直交叠地铁盾构隧道的动力响应分析

以郑州地区某地铁隧道段为工程背景,采用三维精细化管片和正交各向异性圆环衬砌模型模拟隧道结构,将地铁列车运行荷载简化为人工激励函数,构建地铁列车运行对相邻近距离垂直交叠隧道动力响应的数值模型,对不同列车位置、隧道结构、列车速度、隧道净距等工况下近距离垂直交叠相邻隧道的竖向振动响应、影响范围和动应力进行分析。研究结果表明:上隧道运行列车对下部近距离隧道的拱顶的振动影响较大,其他区域影响较小;下隧道运行列车对上部近距离隧道的振动影响整体较小;采用错缝拼装有利于降低近距离垂直交叠隧道在交叠段的振动影响;上隧道列车在启动加速阶段和达到最高速度行驶两个阶段对下隧道拱顶的加速度影响较大;随着隧道净距的减小,上隧道列车引起近距离交叠垂直隧道的下隧道的拱顶竖向加速度显著增加,交叠区域的整体振动最强烈,当远离交叠段1倍洞径后,净距对加速度值的影响可忽略不计。     

穿越活断层铰链式衬砌隧道减震措施动力响应研究

鉴于穿越地震活动带逆断层的铁路山岭隧道易受逆断层滑动的影响,且目前铁路隧道穿越多条活动性断层可供借鉴经验较少的现状。文章采用数值分析方法,对活动逆断层错动下的铰链式衬砌隧道在地震荷载作用下围岩加固方式、超挖设计结构的动力响应进行对比分析。结果表明逆断层错动时,对浅部地层变形的影响范围大于深部,但最大附加变形出现在深部断层面附近,且错距越大其最大附加变形值越大,断层活动对隧道结构安全影响较为显著。注浆加固并不改变衬砌在地震中的震动频谱特性,宜采用施作单层衬砌预留修复空间的设计方案。对于是否超挖设计的两种工况下,衬砌位移变化规律一致,衬砌的震动频谱特性一致。经过监控量测发现支护压应力在埋设2个月左右后趋于稳定。所得结论可为今后类似工程结构设计与施工提供参考。     

走滑断层和逆断层位错作用下地铁隧道损伤特征对比分析

隧道作为重要的轨道交通工程,近年来在地震中受到了不同程度的破坏,特别是跨断层的隧道,其抗震性能越来越受到人们的关注。为了能够更好地评价隧道的整体损伤情况及把握其损伤特征,以北京地铁7号线为研究对象,利用有限元软件ABAQUS建立模型,采用拟静力法,以隧道直径变化率作为损伤指标分析了隧道在走滑断层以及逆断层位错作用下的损伤特征,对比了两种断层位错作用下损伤状态与地震强度之间的关系、损伤范围和位置以及损伤程度。结果表明:跨断层隧道在断层错动作用下损伤只发生在断层带附近;当震级处于6.0～8.0级时,隧道衬砌损伤程度随震级的增大而增大;在覆土厚度相同的条件下,同震级时逆断层位错作用下隧道损伤程度要比走滑断层作用下大得多;走滑断层位错作用下隧道结构损伤主要发生在拱腰处,逆断层位错作用下主要发生在拱肩－拱脚以及拱顶－拱底处。     

Experimental study on nucleation process of stick-slip instability on homogeneous and non-homogeneous faults

The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of stick-slip on the homogeneous fault is of weak slip-weakening behavior under constant loading point velocity. The existence of a short "weak segment" on the fault makes slip-weakening phenomenon in nucleation process more obvious, while the existence of a long "weak segment" on the fault makes the nucleation process changed. The nucleation is characterized by accelerating slip in a local region and rapid increase of shear stress along the fault in this case, which is more coincident with the rate and state friction law. During the period when fault is locked, increasing of shear stress causes lateral elastic dilation near the fault, and the rebound of the dilation at the time of instability causes an instantaneous increase of normal stress in the fault plane, which is an important factor making fault be rapidly locked and its strength recovered.     

Granular Controls on Periodicity of Stick-Slip Events: Kinematics and Force-Chains in an Experimental Fault

It is a long-standing question whether granular fault material such as gouge plays a major role in controlling fault dynamics such as seismicity and slip-periodicity. In both natural and experimental faults, granular materials resist shear and accommodate strain via interparticle friction, fracture toughness, fluid pressure, dilation, and interparticle rearrangements. Here, we isolate the effects of particle rearrangements on granular deformation through laboratory experiments. Within a sheared photoelastic granular aggregate at constant volume, we simultaneously visualize both particle-scale kinematics and interparticle forces, the latter taking the form of force-chains. We observe stick-slip deformation and associated force drops during an overall strengthening of the shear zone. This strengthening regime provides insight into granular rheology and conditions of stick-slip periodicity, and may be qualitatively analogous to slip that accompanies longer term interseismic strengthening of natural faults. Of particular note is the observation that increasing the packing density increases the stiffness of the granular aggregate and decreases the damping (increases time-scales) during slip events. At relatively loose packing density, the slip displacements during the events follow an approximately power-law distribution, as opposed to an exponential distribution at higher packing density. The system exhibits switching between quasi-periodic and aperiodic slip behavior at all packing densities. Higher packing densities favor quasi-periodic behavior, with a longer time interval between aperiodic events than between quasi-periodic events. This difference in the time-scale of aperiodic stick-slip deformation is reflected in both the kinematics of interparticle slip and the force-chain dynamics: all major force-chain reorganizations are associated with aperiodic events. Our experiments conceptually link observations of natural fault dynamics with current models for granular stick-slip dynamics. We find that the stick-slip dynamics are consistent with a driven harmonic oscillator model with damping provided by an effective viscosity, and that shear-transformation-zone, jamming, and crackling noise theories provide insight into the effective stiffness and patterns of shear localization during deformation.     

正应力扰动对断层滑动失稳影响的实验研究

利用双轴伺服控制加载装置,采用三块花岗闪长岩标本组成的含有两个滑动面的直剪结构,开展了摩擦滑动实验.实验中通过在垂直滑动面的载荷上叠加正弦波状和方波状的扰动,研究了正应力扰动对断层黏滑失稳的影响.研究表明,在恒定的正应力和位移速率下,标本表现为规则的黏滑,叠加正应力扰动后,随扰动振幅的增加黏滑发生时间与扰动的相关性增大,黏滑应力降和时间间隔的分布趋于离散.黏滑应力降和时间间隔的平均值随平均正应力的增加呈线性增长,扰动叠加后黏滑应力降的离散度随平均正应力的增加而增大;黏滑应力降和时间间隔主要受应力变化幅度的影响,而与应力变化的速率关系不大.剪应力和正应力扰动都会对断层黏滑失稳产生影响,而正应力扰动的影响更明显.这两种扰动对断层黏滑失稳影响的机制存在差异,剪应力扰动只是改变断层滑动的推动力,而正应力扰动则改变了断层面上凹凸体的接触状态.     

Behaviour of deep immersed tunnel under combined normal fault rupture deformation and subsequent seismic shaking

Immersed tunnels are particularly sensitive to tensile and compressive deformations such as those imposed by a normal seismogenic fault rupturing underneath, and those generated by the dynamic response due to seismic waves. The paper investigates the response of a future 70 m deep immersed tunnel to the consecutive action of a major normal fault rupturing in an earthquake occurring in the basement rock underneath the tunnel, and a subsequent strong excitation from a different large-magnitude seismic event that may occur years later. Non-linear finite elements model the quasi-static fault rupture propagation through the thick soil deposit overlying the bedrock and the ensuing interaction of the rupture with the immersed tunnel. It is shown that despite imposed bedrock offset of 2 m, net tension or excessive compression between tunnel segments could be avoided with a suitable design of the joint gaskets. Then, the already deformed (“injured”) structure is subjected to strong asynchronous seismic shaking. The thick-walled tunnel is modelled as a 3-D massive flexural beam connected to the soil through properly-calibrated nonlinear interaction springs and dashpots, the supports of which are subjected to the free-field acceleration time histories. The latter, obtained with 1-D wave propagation analysis, are then modified to account for wave passage effects. The joints between tunnel segments are modeled with special non-linear hyper-elastic elements, properly accounting for their 7-bar longitudinal hydrostatic pre-stressing. Sliding is captured with special gap elements. The effect of segment length and joint properties is explored parametrically. A fascinating conclusion emerges in all analysed cases for the joints between segments that were differentially deformed after the quasi-static fault rupture: upon subsequent very strong seismic shaking, overstressed joints de-compress and understressed joints re-compress—a “healing” process that leads to a more uniform deformation profile along the tunnel. This is particularly beneficial for the precariously de-compressed joint gaskets. Hence, the safety of the immersed tunnel improves with “subsequent” strong seismic shaking!     

Experimental study on nucleation process of stick-slip instability on homogeneous and non-homogeneous faults

The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of stick-slip on the homogeneous fault is of weak slip-weakening behavior under constant loading point velocity. The existence of a short “weak segment” on the fault makes slip-weakening phenomenon in nucleation process more obvious, while the existence of a long “weak segment” on the fault makes the nucleation process changed. The nucleation is characterized by accelerating slip in a local region and rapid increase of shear stress along the fault in this case, which is more coincident with the rate and state friction law. During the period when fault is locked, increasing of shear stress causes lateral elastic dilation near the fault, and the rebound of the dilation at the time of instability causes an instantaneous increase of normal stress in the fault plane, which is an important factor making fault be rapidly locked and its strength recovered.