共查询到20条相似文献，搜索用时 578 毫秒
1.
G. Swinnen J. W. Thorbecke G. G. Drijkoningen 《Rock Mechanics and Rock Engineering》2007,40(6):577-590
Summary Seismic monitoring from the head of a tunnel-boring machine (TBM) enables improved assessment of the risks associated with
the tunnel-boring process. The monitoring system provides a live image of ground conditions along the trajectory followed
by the TBM and detects local heterogeneities such as boulders, foundations, and other obstacles that commonly pass undetected
using local geotechnical techniques. From a seismic perspective, the underground setting of tunnelling projects places limitations
on imaging capability. The principal limiting factor is the size of the area upon which transducers can be installed. This
limitation requires adjustments to traditional seismic imaging techniques in which a large area is assumed to be available
for attaching the transducers. Recently developed short imaging operators take this limitation into account and are used in
the examples described herein. The unique conditions of tunnelling yield two advantages over traditional settings in terms
of imaging: rotation of the cutter wheel and the lateral progression of the TBM. Rotation of the cutter wheel, upon which
the transducers are installed, provides the opportunity to illuminate obstacles from different angles in different recordings.
Spatial progression of the TBM enables improvement in the illumination of obstacles and the signal-to-noise ratio by combining
recordings from different lateral positions. In this paper, these specific aspects of seismic imaging during tunnelling are
discussed via models that represent different cases encountered in actual tunnelling projects. These case studies demonstrate
the way in which image quality along the trajectory of the TBM is improved over that in traditional settings. In this way,
the risks associated with the tunnelling process can be more accurately assured. 相似文献
2.
地震反演根据数据来源、信息类型、反演结果及实现方法可划分不同种类,地震反演的基本方法可分为基于波动方程的反演和以地震褶积模型为基础的反演二大类。目前国内建立在地震记录褶积模型基础的主要反演软件有STRATA、JASON、ISIS。依托国家重大产业技术开发专项“西部煤炭资源高精度三维地震勘探技术”,在阳泉二矿7个钻孔中．应用STRATA和JASON软件对其三维地震资料进行波阻抗反演,其结果不仅可提高纵向分辨率,准确界定煤层顶、底板,提高下组弱反射煤层的连续性,而且通过波阻抗切片,可获得煤层及顶板的岩性信息。另外通过对比STRATA和JASON软件,发现前者的分辨率较高,而后者在波形连续性表现较好。 相似文献
3.
Seismic Stability Analysis of a Himalayan Rock Slope 总被引：1，自引：1，他引：0
The seismic slope stability analysis of the right abutment of a railway bridge proposed at about 350 m above the ground level, crossing a river and connecting two huge hillocks in the Himalayas, India, is presented in this paper. The rock slopes are composed of highly jointed rock mass and the joint spacing and orientation are varying at different locations. Seismic slope stability analysis of the slope under consideration is carried out using both pseudo-static approach and time response approach as the site is located in seismic zone V as per the earth quake zonation maps of India. Stability of the slope is studied numerically using program FLAC. The results obtained from the pseudo-static analysis are presented in the form of Factor of Safety (FOS) and the results obtained from the time response analysis of the slope are presented in terms of horizontal and vertical displacements along the slope. The results obtained from both the analyses confirmed the global stability of the slope as the FOS in case of pseudo-static analysis is above 1.0 and the displacements observed in case of time response analysis are within the permissible limits. This paper also presents the results obtained from the parametric analysis performed in the case of time response analysis in order to understand the effect of individual parameters on the overall stability of the slope. 相似文献
4.
In general, the determination of the factor of safety and the location of the critical slip surface are two major challenges in seismic slope stability analysis. In this paper, a new approach for determining the factor of safety and the corresponding critical slip surface of a layered rock slope subjected to seismic excitations is presented, through a case study based on the combination of the shear strength reduction technique and distinct element method. According to this proposed method, the seismic factor of safety and the critical slip surface of the slope are estimated and compared with those obtained by the pseudo-static approach, combined with the limit equilibrium method. It is found that the factor of safety obtained from the proposed method is slightly greater than that computed by the pseudo-static analysis, with a difference of 4.2%, and that the critical slip surface obtained from the two methods is identical, which confirms the reasonability and feasibility of the proposed method. 相似文献
5.
可液化场地微型桩的地震响应分析是确保工程安全和优化抗震设计的前提。应用动态离心机试验和三维有效应力数值分析方法,研究了微型单桩桩台的侧向变形和加速度、不同埋深桩身弯矩、可液化场地的加速度及超孔隙水压力等响应特征。首先开展了相对密实度为57%饱和土层、输入波是频率为1 Hz和峰值加速度为1.516 m/s2正弦波的微型桩40 g动态地震响应离心机试验,进而应用基于多重剪切机构塑性模型和液化前缘状态面概念的三维有效应力分析方法,反演了试验结果,并进行了对比分析,结果表明,数值模拟与离心机试验结果吻合,液化场地特性控制着建于其中微型桩的地震响应特征,微型桩桩台的水平变形和残余变形可达78、30 mm,桩身最大弯矩和最大残余弯矩呈现向桩身底部迁移特点,同时表明,基于动态土工离心机试验和数值分析相结合的研究方法,分析可液化场地微型桩地震响应特性是有效可行的,研究结论为可液化场地微型桩的抗震设计提供了可靠的依据和参考。 相似文献
6.
Chakraborty Sayantan Bheemasetti Tejo V. Das Jasaswee T. Puppala Anand J. 《Acta Geotechnica》2020,15(11):3095-3110
Acta Geotechnica - The seismic response of a highly heterogeneous hydraulic fill dam was evaluated by studying the natural frequencies of the first and second modes of vibration and analyzing the... 相似文献
7.
地震危险性、地震危害性和地震易损性 总被引：1，自引：0，他引：1
做好城市防震减灾工作 ,关键是对未来可能遭遇地震灾害定量化预测。本文论述地震灾害定量化的三要素 :地震危险性 ,地震危害性和地震易损性 ,它们概念完全不同 ,且很容易混淆 ,但又存在因与果的关系。本文还简要介绍厦门市地震科技工作者开展的“闽南地区综合防震减灾示范工程”。 相似文献
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9.
Natural Hazards - Seismic settlement of shallow foundations constructed in seismic active areas should be considered for a reasonable estimation of the total settlement. However, the trend of the... 相似文献
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11.
《Tectonophysics》1987,140(1):115-120
The question was examined as to whether the same gravity anomaly is produced for a range of crustal velocity structures all of which produce similar seismic record sections. The results indicate that the maximum errors in the computed gravity anomalies for the various velocity structures is around 20–30 mGal for some models and is around 50 mGal for many others. A major source of error is underestimating the effect of a seismic low-velocity zone which is at one end of the correct velocity structure and which was not detected by several of the interpretations presented at a recent workshop. If no low-velocity layer is included, the error in the gravity anomaly is 30 mGal. The choice of a particular velocity-density relationship does not seem to be a serious problem in the analysis, except for the case of the low-velocity zone, as long as we use a continuous velocity-density curve. 相似文献
12.
During the continental rifting the upper mantle was unroofed, and the mantle rocks were transformed into serpentinite at the ocean-continent transition of the west Galicia margin (Spain). The serpentinite layer, several km thick, extends probably eastwards, beneath the highly thinned continental crust of the margin.
The serpentinite layer was recently imaged by seismic reflection. It is discontinuously and deeply layered. As serpentinized peridotite can have densities and seismic velocities comparable to those of the lower continental crust, we suggest that undercrusting by serpentinite can play a part in building the lower seismic crust in highly stretched continental rifted areas. 相似文献
The serpentinite layer was recently imaged by seismic reflection. It is discontinuously and deeply layered. As serpentinized peridotite can have densities and seismic velocities comparable to those of the lower continental crust, we suggest that undercrusting by serpentinite can play a part in building the lower seismic crust in highly stretched continental rifted areas. 相似文献
13.
Statistical Analysis of the Completeness of a Seismic Catalogue 总被引：1，自引：0，他引：1
Among the numerous issues that the study of seismic events presents, theincompleteness of catalogues is certainly one of the most important. It is also one that only the contribution of many and different skills canprovide with a valid solution. In this paper the search for the complete part of a catalogue is expressed in terms of identification of the changepoint in a hierarchical Bayesian model. Stochastic simulation methods, recently presented in the literature, have enabled us to overcome the computational issues that previously made this approach prohibitive. We have applied the method on data, drawn from the Italian NT4.1.1 catalogue,related to some seismogenetic zones of ZS.4 zonation within which we assumespatial incompleteness to be homogeneous. The results obtained are given inthe concluding sections of the paper. 相似文献
14.
Stability Analysis of a Rock Column in Seismic Conditions 总被引：1，自引：0，他引：1
15.
人工 合 成 地 震 记 录 是 利 用 已 知 测 井 资 料 ,通 过 数 学 方 法 模 拟 实 际 地 震 记 录 的 一 项 技 术 ,其 主 要 用 途 是 :鉴别 反 射 波,识 别多 次 波 ,建 立 地震 模 型 。该 技 术 在 铁法 矿 区 地 震勘 探 中 的 应用 ,优化 了 地 震 勘探 设 计 、提 高 了 采 集 及解 释 精 度、准 确标 定 地 质 层位 。 相似文献
16.
H. Elahi H. G. Poulos H. Hajimollaali A. Elahi 《Geotechnical and Geological Engineering》2018,36(2):855-874
This paper presents a simple approximate pseudostatic method for estimating the maximum internal forces and horizontal displacements of a pile group located in a soil slope. The method is extension of an existing similar method developed by the authors for the case of a horizontal ground surface. The method employed for horizontal ground case involves two main steps: first, the free-field soil movements caused by the earthquake are computed; Then, the response of the pile group is analyzed based on the maximum free-field soil movements as static movements, as well as a static loading at the pile head, which depends on the computed spectral acceleration of the structure being supported. This newly developed methodology takes into account the effects of group interaction and soil yielding. Simple modifications are applied to take into account the effect of slope on seismic deformations of the pile group, making use of the Newmark sliding block method. The applicability of the approach and the developed program is verified by comparisons made with both experimental shaking table tests and the results of a more refined analysis of a pile-supported wharf. It is demonstrated that the proposed method yields reasonable estimates of the pile maximum moment and horizontal displacement for many practical cases, despite its relative simplicity. The simplifying assumptions and the limitations as well as reliability of the methodology are discussed, and some practical conclusions on the performance of the proposed approach are suggested. 相似文献
17.
The assessment of seismic hazard parameters is important in the seismically active regions. A straightforward approach is considered for the statistical estimation of the maximum values of earthquake hazard parameters. The Bayesian estimator is suggested and emphasis is given to the evaluation of the maximum possible Mmax (regional) magnitude in a future time interval T. This approach allows the uncertainty of earthquake magnitude to be accounted for. Seismic hazard parameters like the -value which is the slope of the magnitude-frequency law (where, b = loge) and the intensity (rate) of seismic activity and their uncertainties are also estimated. The quantiles of functions of distributions of true and apparent magnitude on a given time interval [0, T] are evaluated, as well. Two main assumptions are adopted for the method:(1) earthquake occurrence is Poissonian and(2) the magnitude-frequency law is of Gutenberg-Richter type with a cutoff maximum value of magnitude. It is needless to say the seismic catalog used must have a large number of events. This requirement leads to the estimation of the parameters referred to some of the most seismically active regions of the world, e.g., Chile, Peru-Equador-South Colombia,Central America and Mexico, which belong to the east part of the circum-Pacific belt. 相似文献
18.
Maochen Ge H. Reginald HardyJr Hongliang Wang Jin Wang 《Geotechnical and Geological Engineering》2011,29(1):137-142
A Simple Mechanical Impact System (SMIS) was developed recently as a non-explosive seismic source. The SMIS consists of an
impact head, a steel rod with extensions, and an anchoring system. The system is small and simple, and can be conveniently
installed in a shallow borehole oriented in any direction. The SMIS was developed to address two problems commonly associated
with non-explosive seismic sources: insufficient seismic strength and lack of repeatability. Field tests have shown that it
is possible to produce clear and repeatable signals with this system even when the SMIS is installed in a coal seam. 相似文献
19.
利用地震道积分技术识别三维地震解释的陷阱 总被引：1，自引：1，他引：1
在铁法某井田内，利用三维地震勘探得到的地震时间剖面上并无断层显示，但巷道揭示有一个落差9m的断层，后采用三维地震道积分，在其时间剖面识别出一个与实际规模相符的断层。为此对该区所有三维地震资料进行地震道积分，解释出一条新的断层。后经巷道验证，该断层位置、性质与解释结果完全一致，可见地震道积分技术可以准确避开三维地震时间剖面上的断层陷阱。 相似文献
20.