隧道及井巷工程超前探测模拟及其偏移技术研究

隧道及井巷工程中前方地质构造超前探测是一项技术难题,目前国内在基于反射波法探测方面开展了大量的应用性研究工作,但较少进行探测方法布置及数据处理技术的研究,在实际工程探测中未取得较为理想的效果。利用多炮检反射波观测系统,通过水槽超声波试验模拟隧道及井巷掘进过程中可能遇到的不同地质条件,进行反射波超前数据采集,并实现了对数据绕射扫描偏移方法处理。探测模拟结果表明,多炮检反射波观测系统对不同地质条件产生的波阻抗差异具有明显的反应,其偏移结果与实际界面位置相吻合,但多层介质探测时对后续界面的分辨率降低。因此必须进一步完善三维多分量立体数据的采集与波动方程数据偏移方法技术的研究,增强对隧道及井巷工程前方复杂地质构造的探测能力。     

基于快速行进法地震层析成像研究

地震层析成像是通过对观测到的地震波运动学特征(射线路径、走时)和动力学特征(振幅、相位、频率)的资料进行分析,反演得到地下地质体结构、速度分布等信息的一种地球物理方法。由于快速行进法具有无条件稳定、精度高、适应能力强等优点,所以被广泛应用于地震层析成像领域。本文将二维快速行进法应用于地震层析成像的研究中,完成了均匀介质情况下的入射波和反射波走时场及射线路径模拟,结果表明基于快速行进法在二维速度随深度线性变化及横向各向异性的模型正演中取得了理想的效果。     

TST技术在隧道岩溶预报中的应用

云贵地区隧道施工中的潜在风险是岩溶突泥涌水问题。在贵南铁路隧道施工中采用TST地质超前预报技术成功地实现了对岩溶的预报。TST技术是一种地震波探测方法,通过对地震反射波的观测、波场分离、速度扫描和偏移成像等处理技术,实现了对掌子面前方地质界面和岩体波速分布的成像。岩溶发育地段在波速图像中表现为局部低波速异常,在偏移图像中表现为先蓝(波阻抗降低)后红(波阻抗升高)的界面组合。根据这一原理结合地质断面资料,成功地预报了岩溶的发育部位,结果得到了实际开挖的证实,对施工起到了指导作用。     

北京市水电物探研究所

TGP系统在隧道洞壁钻孔中布置接收与激发装置．实现隧道地震反射波和绕射波采集。现场预报测量时间短．预报距离大，以地震波偏移图、回波点位置图、极化分析图及估算介质速度图等实现对构造破碎带、岩性接触带、软弱岩层带和岩溶发育带等不良地质条件的推断和隧道围岩工程地质性质评价。     

探地雷达隧道超前预报正演模拟及应用

灰岩地区的隧道工程建设过程中容易发生突水、突泥、顶板冒落和垮塌等地质灾害,为保证隧道的安全掘进、安全施工,务必要在隧道开挖掌子面进行隧道的超前预报工作。基于时域有限差分原理,建立在灰岩地区典型的断层破碎带及充水、充气溶洞模型,模拟高频雷达波在具有波阻抗差异的断层破碎带及溶洞中传播的过程。利用正演模拟的雷达成像剖面示意及波阻抗界面的反射波极性是否反转等因素,分析了不同岩溶构造分布的雷达成像分布特征规律,为实际工程建设提供指导依据。同时以城开高速旗杆山隧道为实例,验证地质雷达正演模拟和解释准则的可靠性。     

基于高斯束偏移的倾角域绕射波分离方法研究

断层、缝洞体等非均质体在地震响应中主要表现为绕射波,但常规资料处理后的绕射波常被一次反射能量淹没,因此单独分离并研究这类绕射波在某种程度上可以提高非均质体识别的准确性。倾角域道集上的绕射波拟线性而反射波拟抛物线的形态差异为波场分离提供依据。利用高斯束偏移抽道集方法提取倾角域道集,并设计基于相似谱分析的波场分离方法实现倾角域道集中的绕射波分离。模型试算结果表明:运用相似谱分析方法进行波场分离后的倾角域道集中,反射能量得到压制,绕射能量得到较好保留。将波场分离后的绕射波场进行叠加成像,结合常规的全波场成像结果进行对比分析,可提高绕射目标构造的识别度。     

基于地质雷达的隧道综合超前预报技术

以地质雷达为超前预报的主要手段,结合TGP206地震反射波法和工程地质调查法,针对某特长隧道开展综合超前地质预报。通过时域有限差分(FDTD)法,得到了掌子面前方典型不良地质体正演模拟合成图,以此作为地质雷达实际探测图像解译的基础;采用TGP206超前地质预报系统对掌子面前方100 m范围内进行长距离预报,在接近不良地质体时,用地质雷达对掌子面前方20~30 m范围进行更精确的短距离预报;将该法应用于实际工程断层破碎带和富水带的预报中,预报结果较为准确,有效指导了隧道的安全施工,该综合超前地质预报方法可为同类工程提供借鉴。     

基于椭圆展开共反射点叠加的隧道地震波超前探测成像方法与应用

采用地震波法探明隧道前方断层、溶洞等不良地质体,是隧道施工安全的重要保障,而有效的成像方法则是关键。椭圆展开是一种新型的偏移成像方法,已在地表地震勘探中得到应用,然而尚未被引入隧道地震探测中。针对隧道环境,基于非标准椭圆方程,构建了隧道空间观测方式椭圆展开方法,同时重新设定隧道轴线方向为椭圆展开法向出射点方向,实现了对隧道掌子面前方区域地质的成像;通过共震源点地震记录的椭圆展开及相干叠加,最终实现掌子面前不良地质的识别和定位,形成了基于椭圆展开共反射点叠加的隧道地震波超前探测成像方法。在此基础上,基于交错网格有限差分方法,对岩性界面和断层进行了系统的正演成像研究,分析了不同地质模型的成像特征;最后,依托现场进行了探测试验,探测结果与开挖揭露情况基本一致,验证了成像方法的有效性和实用性。     

多种超前地质预报方法在某隧道施工的应用

正在施工的金子山隧道是宜万铁路八座Ⅰ级复杂风险隧道之一,同时也是重要控制工程.介绍了掌子面地质素描、掌子面周边探孔、地质雷达及TSP地震反射波法等多种超前地质预报的原理及特点,针对金子山隧道不同里程的地质特征,以现场调查和地质分析为主线,介绍了多种超前地质预报方法在金子山隧道中的应用,同时分析了应用成果.结果表明,围岩实际情况和预报结果基本吻合.为隧道施工防灾重点区段的确定提供了基础,并优化施工方法,为金子山隧道的安全施工提供了有力的信息支持,给施工单位提出了相应的施工建议.     

隧道超前地质预报检波器耦合介质理论及试验研究

隧道超前地质预报是隧道施工中的重要部分,其准确性影响着隧道施工安全。为提高隧道超前地质预报的准确性,对隧道超前地质探测中检波器耦合介质开展针对性研究具有重要意义。本文通过对隧道检波器耦合结构开展理论建模,探讨了耦合介质在检波器与围岩耦合过程中发挥的作用。在此基础上,选用工业黄油、石蜡、石膏、环氧树脂以及黏质土5种耦合介质进行了现场耦合试验。最后,根据理论建模结果采用数值模拟手段对不同耦合介质的耦合过程进行了分析,并就介质厚度对耦合效果的影响进行了探讨。结果表明:材料的耦合效果与其固化强度呈正相关关系,基于理论公式的数值模拟结果很好地验证了试验结论;耦合介质厚度影响耦合效果的主要因素在于厚度过大会引起地震波损耗,厚度过小会产生较大的谐振现象。研究成果可服务于工程实际应用,进一步提高隧道超前地质预报的准确性。     

A new 3D observation system designed for a seismic ahead prospecting method in tunneling

The tunnel seismic ahead prospecting method is usually used to estimate adverse geology ahead of a tunnel face. The observation system plays an important role in tunnel seismic ahead prospecting, which helps to obtain accurate imaging results. Optimizing the observation system is a key issue for seismic ahead prospecting. In this paper, observation layouts are evaluated and a new three-dimensional (3D) observation system is proposed by imaging results analysis. For linear and 3D layouts, imaging result analysis in this paper indicates that the mirror artifact caused by the linear layout (Which sets sources and geophones on a straight line) can be suppressed by the 3D layout, due to its energy concentration and convergence. Moreover, reflections using 3D layout identify real abnormal bodies better than the linear layout. Moreover, conventional observation layouts often use shot point on the tunnel face or front sidewall, which makes it difficult to filter interference waves from the back of the tunnel face. To solve this problem, typical numerical examples are conducted, and imaging results of observation layouts with shot point on front sidewall, tunnel face or back sidewall are studied. Results show shot point on the back sidewall helps to separate waves, suppress interference waves and extract effective waves (reflected P-waves by discontinuities) by apparent velocity filtering method, so shot point is designed on the back sidewall to get high-quality records. To balance record quality and application convenience, a new 3D observation system is proposed with 12 geophones and 10 shot points in a special arrangement. Compared with a linear layout, practical testing and application using the new 3D system indicate the main fractured zones are accurately identified and located, which proves the reliability and practicability of the new observation system.     

Pre-stack elastic reverse time migration in tunnels based on cylindrical coordinates

Seismic forward-prospecting in tunnels is an important step to ensure excavation safety. Nowadays, most advanced imaging techniques in seismic exploration involve calculating the solution of elastic wave equation in a certain coordinate system. However, considering the cylindrical geometry of common tunnel body, Cartesian coordinate system seemingly has limited applicability in tunnel seismic forward-prospecting. To accurately simulate the seismic signal received in tunnels, previous imaging method using decoupled non-conversion elastic wave equation is extended from Cartesian coordinates to cylindrical coordinates. The proposed method preserves the general finite-difference time-domain (FDTD) scheme in Cartesian coordinates, except for a novel wavefield calculation strategy addressing the singularity issue inherited at the cylindrical axis. Moreover, the procedure of cylindrical elastic reverse time migration (CERTM) in tunnels is introduced based on the decoupled non-conversion elastic wavefield. Its imaging effect is further validated via numerical experiments on typical tunnel models. As indicated in the synthetic examples, both the PP- and SS-images could clearly show the geological structure in front of the tunnel face without obvious crosstalk artifacts. Migration imaging using PP-waves can present satisfactory results with higher resolution information supplemented by the SS-images. The potential of applying the proposed method in real-world cases is demonstrated in a water diversion tunnel. In the end, we share our insights regarding the singularity treatment and further improvement of the proposed method.     

基于薄壁圆柱壳理论的盾构隧道抗震拟静力分析法

为简化盾构隧道抗震分析,在获得深埋盾构隧道周边自由场剪应变和剪应力的基础上,基于弹性薄壁圆柱壳理论,给出了求解深埋盾构隧道水平地震剪切波作用下的附加内力计算公式,并与同等条件等效刚度数值分析方法结果进行了对比。研究表明：滑移和不滑移条件下的拟静力计算结果与相应的数值分析结果具有良好的一致性,说明基于弹性薄壁圆柱壳理论获得的盾构隧道拟静力公式具有良好的合理性。研究还表明：水平地震剪切波作用下,可滑移条件下的附加弯矩和附加剪力分别大于不滑移条件下的附加弯矩和附加剪力,可滑移条件下的附加轴力小于不滑移条件下的附加轴力;附加弯矩和附加轴力呈现反对称分布特性,其最大值通常分布在45°和225°雷达对称轴或135°和315°雷达对称轴上,附加剪力最大值一般分布在0°和180°雷达对称轴上。研究结论对盾构隧道工程抗震设计具有一定的参考价值。     

区域场地近地表速度结构建模研究

近地表速度结构是全面考虑城市区域场地地震效应,精细模拟地震动场及建筑群震害的基础.针对复杂交错沉积的区域场地,建立了先基于工程地质先验信息限定交错土体边界,利用序贯指示模拟求解各类交错土体空间概率分布,再依据剪切波速与工程地质结构的空间相关关系,借助序贯高斯模拟构建波速结构模型的方法;在搜集分析钻孔波速资料基础上,构建...     

SH波作用下山岭隧道洞口段结构动力响应研究

 基于弹性波动理论,将山岭隧道洞口段简化为单面边坡模型,考虑波在洞口边坡的反射效应,推导垂直入射SH波作用下隧道轴线上的位移场分布,并将隧道简化为三维薄壁壳结构,以得到在该位移场作用下隧道结构的动力响应。针对上述分析结果开展山岭隧道洞口段振动台模型试验,以验证理论模型的合理性,并综合分析得到如下结论：将隧道结构动力响应看作横截面与纵向响应的叠加,隧道结构横截面发生剪切变形,两侧拱肩与拱脚为抗震的薄弱环节,变形效应沿轴向缓慢增加,此响应为平行隧道结构横截面传播的SH波作用所致;隧道结构纵向发生水平剪切变形,变形效应沿隧道轴向逐渐减弱,洞口处产生较大刚性位移,在施工缝存在的情况下,隧道结构在洞口附近易沿施工缝产生错台现象,此响应为沿轴向传播的SH波所致。此规律表明,隧道结构的纵向抗震设计同样值得关注。     

瞬变电磁技术在隧道超前地质预报中的应用

介绍了瞬变电磁技术在隧道超前地质预报中的探测原理及方法,结合华蓥山隧道中的应用实例,指出了瞬变电磁法超前地质预报的优势及存在不足,说明了瞬变电磁法应综合应用地震波反射法、电磁波反射法等,才能全方位掌握掌子面前方地质情况,以实现指导施工。     

Seismic response of box-type tunnels in soft soil: Experimental and numerical investigation

A series of dynamic centrifuge tests were carried out at the geotechnical centrifuge facility of IFSTTAR in Nantes, to investigate the response of box-type tunnels embedded in dry sand under sinusoidal and seismic excitation, as affected by soil-tunnel relative flexibility and soil-structure interface rugosity. The system under investigation was analyzed by means of full dynamic time history analyses, implementing rigorous finite element models. The numerical models were calibrated on the basis of back analysis of tests, while the numerical predictions were compared with experimental data, in terms of soil and tunnel horizontal acceleration, soil shear strains and tunnel deformations. The validated numerical models were then employed to further investigate several aspects of the system seismic response. Results indicate a rocking deformation mode coupled with the well-known racking distortion of box-type tunnels under seismic shaking. The effect of the soil-tunnel interface characteristics and soil yielding on the racking deformation of the tunnel, the dynamic earth pressures and shear stresses around the tunnel, as well as on dynamic lining forces is also reported. Soil yielding leads to post-shaking, residual, dynamic earth pressures, shear stresses and lining forces, especially in the case of flexible tunnels, while interface characteristics affect the distributions of these response parameters around the perimeter of the tunnel section. The ability of simplified seismic design methods for tunnels to predict the response is finally discussed, by comparing their predictions with the recorded data and the numerical results.     

溪洛渡电站地下洞室群爆破地震效应的研究

 采用现场爆破振动测试研究复杂地下导流洞群爆破地震波传播规律,并利用萨道夫斯基经验公式对测试数据进行回归分析,测试结果表明水平向爆破质点峰值振动速度可以作为地下洞室的安全判据;应用FLAC3D数值软件模拟爆破振动对相邻洞室的影响,得到爆破振动作用下相邻洞室振动速度、应力和位移的分布规律,并从静载作用和动载作用两方面分析评价相邻洞室的安全稳定性。计算结果表明：现场测试结果与计算结果吻合较好;采用振动速度作为安全判据是可行的;爆破振动作用下相邻洞室迎爆侧是容易出现破坏的区域,且随着冲击荷载增大,迎爆侧直墙最容易出现拉伸破坏。最后针对具体工程,根据相邻洞室洞壁最大拉应力与最大振动速度的统计关系,并结合岩石动态抗拉强度准则提出爆破振动作用下相邻洞室发生破坏的临界振动速度。     

山岭隧道受震损害类型与原因之案例研究

 以1999年台湾集集地震造成完工通车仅1 a的三义壹号铁路隧道损害为例,应用隧道受震数值分析成果及相关研究,探讨隧道受震损害的原因。研究成果显示,受震损害区段皆落于埋深接近0.25倍岩体波长的范围内,即隧道埋深与岩体特性的组合强化震波受地表自由面反射与隧道散射的效应,导致衬砌受震引起应力大幅增加而造成破坏。而衬砌损害可归纳为4种类型：纵向裂缝、环向裂缝或环向施工缝错动、环状剥落以及斜向裂缝与剥落。分析隧道施工地质记录及震后检测结果显示,衬砌纵向裂缝主要受地盘深处上传的S波垂直方向或45?入射导致衬砌轴力与弯矩受震增加而影响。环向裂缝或环向施工缝错动则受到水平方向P波造成的张力破坏以及乐夫波造成衬砌应力增加的影响。环状剥落系隧道承受较显著的水平方向应力下,S波45?入射导致衬砌应力增量以及避车洞开口结构配置的影响。而斜向裂缝则受S波通过软硬地盘互层的应变差异以及隧道衬砌结构刚度特性所致。研究成果表明隧道受震损害原因与影响因素,可为山岭隧道耐震分析与设计提供参考。     

Seismic imaging ahead of a tunnel face with three-component geophones

The present paper proposes an accurate imaging technique for looking ahead of a tunnel face using three-component geophones with tunnel blasting and TBM vibrations as seismic sources. Its procedure is as follows: (1) using three-component receivers set on the tunnel walls, record the seismic signal from the reflectors ahead of the tunnel face; (2) detect the direction of incidence of the reflected wave and (3) by weighting according to the direction of incidence of the reflected wave, image the reflector planes using the equi-travel time plane.The proposed technique is applied to datasets collected at an actual drilling operation site, and the results agreed with the geological observation of the walls after the drilling of the tunnel.