TSP 203在云南元磨高速公路隧道超前地质预报中的应用

TSP203系统是瑞士Amberg工程技术公司最新研制并拥有专利的隧道地震探测仪，专门为隧道超前地质预报而设计的。该系统从数据采集、处理和成果评估高度智能化。采用该系统可以预报隧道工作面前方至少100m围岩地质体的性质、位置和规模，并可算出其岩石物理力学参数，为确定合理的支护参数提供依据，确保隧道施工安全和质量。本文是TSP203系统在云南元磨高速公路隧道超前地质预报中的应用实例。     

TSP\|203在隧道超前预报中的应用

TSP\|203系统是瑞士Amberg工程技术公司最新研制并拥有专利的隧道地震探测仪，专门为隧道超前地质预报而设计的.该系统从数据采集、处理和成果评估高度智能化，采用该系统可以预报隧道工作面前方100 m左右围岩地质体的性质、位置和规模,并可推算出其岩石物理力学参数，为确定合理的支护参数提供依据，确保隧道施工安全和质量.本文对TSP\|203系统、工作原理、数据采集及资料解释方面做了系统的阐述.     

地震综合效应场函数及其在地震预报中的应用──（二）地震综合效应场函数在地震预报中的应用

应用地震综合效应场函数方法，对地震前的空区、条带及大地震的迁移现象，根据强震前地震活动的四要素，进行了计算，其预报效果令人满意。     

TSP\|203在大支坪隧道超前预报中的应用

现代工程等级在不断提高，隧道地质环境越来越复杂，隧道越来越长，隧道地质超前预报在隧道的开挖中的作用更加凸显，如何选择有效的预报措施对隧道开挖中人员、设备的安全和隧道洞室的支护具有重要的意义. TSP203是用地震原理对隧道进行探测的仪器，该系统高度从数据采集、处理实现高度智能化.本次使用此仪器对大支坪隧道横洞掌子面HDK0+064里程处进行预报，结合实际开挖，证实了预报的可行性和准确性.     

基于虚拟仪器技术的声-电效应观测系统及其在冻土模型研究中的应用

详细介绍了介质的声-电转换效应的产生机理、利用虚拟仪器技术来搭建声-电观测系统的原理、软硬件系统和实现方法.搭建的观测系统可以实现高分辨率、高采样率和多次叠加的数据采集,极大的增强了采集的微弱声-电信号的信噪比.该系统还具有混合信号同步采集功能,可以方便的通过改变接收传感器进行声-声和声-电两种信号的基本同步测量,为声-电信号的观测和分析提供重要的参考信息.文章以观测干砂摸型的声-电响应,和冻土模型的声-声和声-电响应两个具体实例验证了该观测系统的可行性和优越性.     

τ-p变换在隧道反射地震超前预报波场分离中应用的数值模拟研究

本文基于二维有限元数值方法,模拟了复杂条件下隧道内的地震全波波场,分析了隧道地震超前预报中的反射记录中的多方向和多波反射波特征,证实了分离前方有效反射波和其它方向的干扰反射波,以及有效反射波的P波、S波分离在预报准确性中的重要性.基于多个数值模型,研究了τ-p变换进行波场分离的有效性和影响因素.研究结果表明:在隧道前方反射层倾向与隧道轴线交角变化较大范围内(90°～45°),τ-p变换都可以有效的分离多方向和多波反射事件,提取主要来自掌子面前方的有效反射波剖面.来自隧道项、底的缓倾界面的具有双曲时距曲线特征的干扰波和S波的高视速度会对P波的波场分离产生较大干扰;而由于S波的低速和强能量特征,其波场分离受具有双曲时距曲线特征的干扰波的视速度影响较小,且不受P波的影响.     

隧道反射地震超前预报波场分离方法的数值模拟研究

本文以有限元数值模拟方法为依托,依次从波场快照、地震记录、波场分离、工程实例等四个角度论证了地震波传播规律和波场分离特点.模拟了单界面介质条件下地震波在隧道围岩中传播的全波波场.研究了反射波时距曲线的线性相关系数.比较了τ-p变换和F-K变换的滤波特点.结合工程实例,讨论了这两类线性波场分离方法在提取隧道前方反射波中的可行性和准确性,研究结果表明:当隧道前方地层倾角由直立变为缓倾时,反射纵波和横波的时距关系都能很好的视为线性.地层倾角的改变主要影响反射波走时和视速度.因此,应用τ-p变换和F-K变换进行波场分离,提取隧道前方单独的反射纵波和横波是可行和有效的.但对于缓倾地层,线性变换波场分离的结果存在较大的走时和视速度误差.易误滤除反射信号,需进行偏移处理.     

反射地震零偏移距逆时偏移方法用于隧道超前预报

为了高效快速地采集到隧道开挖前方的反射地震数据并提供实时的隧道前方地质超前预报,本文提出一种基于波动方程逆时偏移原理的隧道地质超前预报方法.为了获得与该超前预报方法相适应的地震数据,本文还提出适用于隧道内有限空间环境下的PMZO（Plus Minus Zero Offset）反射地震采集方案.本研究根据理论地震记录分析了隧道中零偏移距地震记录反射波的时距关系和振幅特征,讨论了隧道中地震记录的解释方法,利用含多条断层破碎带的地质模型,模拟了基于逆时偏移算法的实时隧道地质超前预报.数值计算结果证明,PMZO数据采集方案以及逆时偏移算法可以获得隧道开挖前方地质构造的准确成像.     

隧道地质灾害超前预报的地震反射法

介绍了利用地震反射法进行隧道地质灾害超前探测的基本原理、观测方法,讨论了反射波时距曲线方程和特点以及实际应用中存在的主要问题和影响因素,指出采用地震反射法与工程地质调查法相结合可以提高超前探测的准确性和精度.     

频率域有限差分数值模拟地震波衰减和震电效应特征

地震波在地下含流体孔隙介质中传播时,会引起中观尺度的"局域流",进而产生地震波震电效应.基于Biot（1941）固结理论的准静态方程,在频率域中采用空间有限差分方法,正演模拟虚岩石物理岩样的地震波衰减和震电效应.与时间域虚岩石物理方法相比,该方法既可以直接求取任一频率下的地震波衰减和电势,便于应用于实际岩样的预测分析,也避免了讨论岩样外表面施加的力源函数表达式及时间剖分稳定性条件等问题.首先利用周期性层状介质模型验证了本文所描述方法的有效性,并进一步求取分析了周期性层状介质两种不同特征单元的渗流电流密度及电势,数值模拟结果表明由中观尺度"局域流"引起的震电效应电势振幅数量级在实验室测量范围之内,随后,分析研究了四种不同高渗介质占比值的地震衰减及震电效应特征.最后,将本文提出的震电效应数值计算方法推广至二维,并求取了二维斑块饱和模型的地震波衰减、速度频散、电势的振幅和相位角数值结果.     

Bayesian inversion of joint SH seismic and seismoelectric data to infer glacier system properties

In glacial studies, properties such as glacier thickness and the basement permeability and porosity are key to understand the hydrological and mechanical behaviour of the system. The seismoelectric method could potentially be used to determine key properties of glacial environments. Here we analytically model the generation of seismic and seismoelectric signals by means of a shear horizontal seismic wave source on top of a glacier overlying a porous basement. Considering a one-dimensional setting, we compute the seismic waves and the electrokinetically induced electric field. We then analyse the sensitivity of the seismic and electromagnetic data to relevant model parameters, namely depth of the glacier bottom, porosity, permeability, shear modulus and saturating water salinity of the glacier basement. Moreover, we study the possibility of inferring these key parameters from a set of very low noise synthetic data, adopting a Bayesian framework to pay particular attention to the uncertainty of the model parameters mentioned above. We tackle the resolution of the probabilistic inverse problem with two strategies: (1) we compute the marginal posterior distributions of each model parameter solving multidimensional integrals numerically and (2) we use a Markov chain Monte Carlo algorithm to retrieve a collection of model parameters that follows the posterior probability density function of the model parameters, given the synthetic data set. Both methodologies are able to obtain the marginal distributions of the parameters and estimate their mean and standard deviation. The Markov chain Monte Carlo algorithm performs better in terms of numerical stability and number of iterations needed to characterize the distributions. The inversion of seismic data alone is not able to constrain the values of porosity and permeability further than the prior distribution. In turn, the inversion of the electric data alone, and the joint inversion of seismic and electric data are useful to constrain these parameters as well as other glacial system properties. Furthermore, the joint inversion reduces the uncertainty of the model parameters estimates and provides more accurate results.     

An approach to combined rock physics and seismic modelling of fluid substitution effects

The aim of seismic reservoir monitoring is to map the spatial and temporal distributions and contact interfaces of various hydrocarbon fluids and water within a reservoir rock. During the production of hydrocarbons, the fluids produced are generally displaced by an injection fluid. We discuss possible seismic effects which may occur when the pore volume contains two or more fluids. In particular, we investigate the effect of immiscible pore fluids, i.e. when the pore fluids occupy different parts of the pore volume. The modelling of seismic velocities is performed using a differential effective‐medium theory in which the various pore fluids are allowed to occupy the pore space in different ways. The P‐wave velocity is seen to depend strongly on the bulk modulus of the pore fluids in the most compliant (low aspect ratio) pores. Various scenarios of the microscopic fluid distribution across a gas–oil contact (GOC) zone have been designed, and the corresponding seismic properties modelled. Such GOC transition zones generally give diffuse reflection regions instead of the typical distinct GOC interface. Hence, such transition zones generally should be modelled by finite‐difference or finite‐element techniques. We have combined rock physics modelling and seismic modelling to simulate the seismic responses of some gas–oil zones, applying various fluid‐distribution models. The seismic responses may vary both in the reflection time, amplitude and phase characteristics. Our results indicate that when performing a reservoir monitoring experiment, erroneous conclusions about a GOC movement may be drawn if the microscopic fluid‐distribution effects are neglected.     

An investigation into the seismic behaviour of dams using dynamic centrifuge modelling

Dynamic response of dams is significantly influenced by foundation stiffness and dam-foundation interaction. This in turn, significantly effects the generation of hydrodynamic pressures on upstream face of a concrete dam due to inertia of reservoir water. This paper aims at investigating the dynamic response of dams on soil foundation using dynamic centrifuge modelling technique. From a series of centrifuge tests performed on model dams with varying stiffness and foundation conditions, significant co-relation was observed between the dynamic response of dams and the hydrodynamic pressures developed on their upstream faces. The vertical bearing pressures exerted by the concrete dam during shaking were measured using miniature earth pressure cells. These reveal the dynamic changes of earth pressures and changes in rocking behaviour of the concrete dam as the earthquake loading progresses. Pore water pressures were measured below the dam and in the free-field below the reservoir. Analysis of this data provides insights into the cyclic shear stresses and strains generated below concrete dams during earthquakes. In addition, the sliding and rocking movement of the dam and its settlement into the soil below are discussed.     

联合速度建模及其在反射波法隧道超前预报中的应用

We propose a combined migration velocity analysis and imaging method based on Kirchhoff integral migration and reverse time migration, using the residual curvature analysis and layer stripping strategy to build the velocity model. This method improves the image resolution of Kirchhoff integral migration and reduces the computations of the reverse time migration. It combines the advantages of efficiency and accuracy of the two migration methods. Its application in tunnel seismic prediction shows good results. Numerical experiments show that the imaging results of reverse time migration are better than the imaging results of Kirchhoff integral migration in many aspects of tunnel prediction. Field data show that this method has efficient computations and can establish a reasonable velocity model and a high quality imaging section. Combination with geological information can make an accurate prediction of the front of the tunnel geological structure.     

T-matrix approach to seismic forward modelling in the acoustic approximation

Forward seismic modelling in the acoustic approximation, for variable velocity but constant density, is dealt with. The wave equation and the boundary conditions are represented by a volume integral equation of the Lippmann-Schwinger (LS) or Fredholm type. A T-matrix (or transition operator) approach from quantum mechanical potential scattering theory is used to derive a family of linear and nonlinear approximations (cluster expansions), as well as an exact numerical solution of the LS equation. For models of 4D anomalies involving small or moderate contrasts, the Born approximation gives identical numerical results as the first-order t-matrix approximation, but the predictions of an exact T-matrix solution can be quite different (depending on spatial extention of the perturbations). For models of fluid-saturated cavities involving large or huge contrasts, the first-order t-matrix approximation is much more accurate than the Born approximation, although it does not lead to significantly more time-consuming computations. If the spatial extention of the perturbations is not too large, it is practical to use the exact T-matrix solution which allows for arbitrary contrasts and includes all the effects of multiple scattering.     

An application of 4D seismic monitoring technique to modern coal mining

To study the impact of modern coal mining on the overlying formation, a full‐life‐cycle four‐dimensional seismic monitoring study has been carried out. Four seismic data campaigns have been performed using flexi‐bin geometry with square bins, with total duration of 171 days. The four seismic datasets have been processed with the same processing workflow and parameters; major problems such as statics correction, signal‐to‐noise ratio, resolution, and consistency processing are addressed taking into account the geological features of the research area. This guarantees that remaining four‐dimensional differences between the time‐lapse datasets show mostly geological factors due to the coal mining and effects such as surface subsidence. Our four‐dimensional seismic monitoring of modern coal mining shows that mined and unmined areas have significant zoning characteristics; coal mining has a direct impact on the overlying formation. The mining leads to obvious event subsidence, which reflects that overlying formations undergo subsidence during the mining process. The overlying formation appears as two zones called caving zone and fractured zone. We determine the fault dip of the overlying formation at one end of the working face to be 56°or so by calculation and conversion. We also see that, during the coal mining process, over time, the overlying formation has a self‐recovery capability, which gradually strengthens from the roof siltstone upward to the Aeolian sandstone near the surface. The stability of 20‐m coal pillars between working faces displays a strengthening trend and remains safe during the mining process due to both coal seam supporting and formation compaction effects.     

Forward induced seismic hazard assessment: application to a synthetic seismicity catalogue from hydraulic stimulation modelling

The M _w 3.2-induced seismic event in 2006 due to fluid injection at the Basel geothermal site in Switzerland was the starting point for an ongoing discussion in Europe on the potential risk of hydraulic stimulation in general. In particular, further development of mitigation strategies of induced seismic events of economic concern became a hot topic in geosciences and geoengineering. Here, we present a workflow to assess the hazard of induced seismicity in terms of occurrence rate of induced seismic events. The workflow is called Forward Induced Seismic Hazard Assessment (FISHA) as it combines the results of forward hydromechanical-numerical models with methods of time-dependent probabilistic seismic hazard assessment. To exemplify FISHA, we use simulations of four different fluid injection types with various injection parameters, i.e. injection rate, duration and style of injection. The hydromechanical-numerical model applied in this study represents a geothermal reservoir with preexisting fractures where a routine of viscous fluid flow in porous media is implemented from which flow and pressure driven failures of rock matrix and preexisting fractures are simulated, and corresponding seismic moment magnitudes are computed. The resulting synthetic catalogues of induced seismicity, including event location, occurrence time and magnitude, are used to calibrate the magnitude completeness M _c and the parameters a and b of the frequency-magnitude relation. These are used to estimate the time-dependent occurrence rate of induced seismic events for each fluid injection scenario. In contrast to other mitigation strategies that rely on real-time data or already obtained catalogues, we can perform various synthetic experiments with the same initial conditions. Thus, the advantage of FISHA is that it can quantify hazard from numerical experiments and recommend a priori a stimulation type that lowers the occurrence rate of induced seismic events. The FISHA workflow is rather general and not limited to the hydromechanical-numerical model used in this study and can therefore be applied to other fluid injection models.     

协同办公系统在地震行业中的应用

协同办公系统为地震行业提供了一个基于"十五"信息网络应用的高效率沟通平台.该系统可实现强大的远程会议功能;提供高效实用的数据协作平台;具有良好的音视频效果;提供易操作的应用界面.协同办公系统改变了地震系统传统的工作模式,解决了异地办公、远程沟通的地域障碍问题,不仅大大提升了工作效率,而且节约了日常开销,也使得全国地震行业网络各节点间的联系更加紧密、快捷.