Features of infrared thermal image and radiation

Experimental study discovered that:(i) coal rocks and sandstone in the course of loading have three types of infrared thermal image features and three types of infrared radiation temperature features; (ii) infrared detection is comparable with acoustic emission detection and electrical resistance detection. Generally, the infrared forewarning of coal rocks' failure comes later than that of acoustic and electrical resistance, but the infrared radiation temperature forewarning of coal burst comes earlier. On the basis of comprehensive study and analysis, it was suggested that stress nearby 0.79 σ_c should be taken as the stress-caution-zone for rock mass failure, ground pressure and its disasters monitoring.     

EXPERIMENT STUDY ON ACOUSTIC EMISSION,MICROSEISM AND CHARGE INDUCTION DURING FRACTURE PROCESS OF GRANITE WITH FAULT ZONE UNDER UNIAXIAL COMPRESSION

As the rock samples will produce abnormal signals of acoustic emission, microseismic and charge signals under external loading, the waveform comprehensive monitoring devices are used to synchronously monitor acoustic emission, microseismic and charge signals during the deformation and failure process of granite with fault zone under uniaxial compression. The results show that, the granite with fault zone has obvious synchronous precursory signals of acoustic emission, microseism and charge induction in the elastic deformation stage, and has high amplitude synchronous precursory signals in the instability destruction stage. The influence of fault zone on granite samples strength is remarkable, and the uniaxial compressive strength of samples with the fault zone is greatly reduced. With the angle of the fault zone decreasing, the uniaxial compressive strength of the specimens is reduced, the samples are more liable to instability and the energy of instability destruction is greater. With the fault zone angle of granite samples decreasing, the acoustic emission, microseismic and charge induction signals increase in the deformation and failure process of samples. The samples stress decreases when the acoustic emission, microseismic and charge induction precursory signals appear synchronously. The duration of acoustic emission, microseismic and charge induction precursory signals is increasing in the instability destruction stage. When the angle of the fault zone reaches 30°, the mutability of acoustic emission, microseismic and charge induction signal increases, the time to enter the dangerous stage is much earlier, and the acoustic emission events of large magnitude increase significantly, and the large angle faults of coal mine are more dangerous. The intensive and high amplitude synchronous precursory signals of acoustic emission, microseism and charge induction are produced before the instability destruction, and the signals duration is shorter. The intensive and strongest synchronous precursory signals of acoustic emission, microseism and charge induction are produced in the instability destruction, and the signals duration is longer. Acoustic emission monitoring data can better reflect the micro rupture of rock. And combined with the acoustic emission, microseismic and charge induction precursory signals, the precursory information of rock instability destruction can be obtained more accurately.     

Influence of geostatic stresses on permeability of jointed rock masses

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煤岩变形破裂电磁辐射的实验研究

对受载煤体变形破裂产生电磁辐射进行了实验研究及规律分析,并对煤岩变形破裂电磁辐射的机理进行了探讨分析．研究结果表明,煤体变形破裂时能够产生电磁辐射,电磁辐射信号与声发射信号并非严格同步,电磁辐射信号较声发射信号丰富,电磁辐射与煤岩体的变形破裂过程密切相关．煤岩电磁辐射技术在揭示煤岩变形破裂机理,预测、预报地震,矿山煤岩灾害动力现象及岩石混凝土建筑稳定性方面有着非常广泛的应用前景．     

地层压力条件下沁水盆地煤岩动静态弹性参数同步超声实验研究

静态弹性参数对储层压裂改造、应力场及裂缝预测具有重要意义,开展地层压力条件下煤岩动、静态弹性参数实验研究,获得动、静态弹性参数之间的关系,为利用动态弹性参数预测静态弹性参数提供了岩石物理依据.本次研究应用MTS岩石物理参数测试系统完成沁水盆地和顺地区的煤岩样在地层压力条件下的动静态弹性参数同步测试.结果表明:动态杨氏模量随压力的增加而增加,而动态泊松比随压力的变化较为复杂;动、静态杨氏模量之间呈线性关系,且动态杨氏模量大于静态杨氏模量;动、静态泊松比之间的相关性较差,大部分煤样的动态泊松比小于静态泊松比.获得的这些关系为动静弹性参数转换提供了基础,进而为利用地震资料进行静弹性参数预测,获得岩石力学性能参数提供了一种途径.     

A new ellipsoidal gravimetric, satellite altimetry and astronomic boundary value problem, a case study: The geoid of Iran

A new gravimetric, satellite altimetry, astronomical ellipsoidal boundary value problem for geoid computations has been developed and successfully tested. This boundary value problem has been constructed for gravity observables of the type (i) gravity potential, (ii) gravity intensity (i.e. modulus of gravity acceleration), (iii) astronomical longitude, (iv) astronomical latitude and (v) satellite altimetry observations. The ellipsoidal coordinates of the observation points have been considered as known quantities in the set-up of the problem in the light of availability of GPS coordinates. The developed boundary value problem is ellipsoidal by nature and as such takes advantage of high precision GPS observations in the set-up. The algorithmic steps of the solution of the boundary value problem are as follows:

- Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and of the ellipsoidal centrifugal field for the removal of the effect of global gravity and the isostasy field from the gravity intensity and the astronomical observations at the surface of the Earth.

- Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the gravity intensity and the astronomical observations at the surface of the Earth the effect of the residual masses at the radius of up to 55 km from the computational point.

- Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and ellipsoidal centrifugal field for the removal from the geoidal undulations derived from satellite altimetry the effect of the global gravity and isostasy on the geoidal undulations.

- Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the geoidal undulations derived from satellite altimetry the effect of the water masses outside the reference ellipsoid within a radius of 55 km around the computational point.

- Least squares solution of the observation equations of the incremental quantities derived from aforementioned steps in order to obtain the incremental gravity potential at the surface of the reference ellipsoid.

- The removed effects at the application points are restored on the surface of reference ellipsoid.

- Application of the ellipsoidal Bruns’ formula for converting the potential values on the surface of the reference ellipsoid into the geoidal heights with respect to the reference ellipsoid.

- Computation of the geoid of Iran has successfully tested this new methodology.

Acoustic emissions associated with the formation of fracture sets in sandstone under polyaxial stress conditions‡

A polyaxial (true‐triaxial) stress‐loading system, developed originally for determining all nine components of P‐ and S‐wave velocities and attenuation and fluid permeability for 50.8 mm‐side cubic rock specimens tested to failure, has been modified to permit the measurement of acoustic emission events associated with the failure process. Results are reported for Crosland Hill sandstone tested to failure under loading conditions leading to the formation of sets of aligned microcracks, achieved by maintaining the minor principal stress at a low value while increasing the two other principal stresses until failure of the rock. An ultrasonic survey associated with the test has been employed to map the transversely‐isotropic velocity structure created by through‐going parallel fractures resulting from the sets of aligned microcracks. This velocity structure has then been employed to locate acoustic emission events recorded during the test by four acoustic emission sensors located in each of the six specimen loading platens. A selection of acoustic emission events associated with one of the fractures has been processed for moment tensor analysis information, in order to determine the source type and orientation of microcracking as the fracture grows. The mechanisms indicate tensile behaviour during initial fracture propagation. Shear failure, however, appears to dominate as the fracture finally approaches the opposite face of the cubic specimen. The work presented here has, in part, led to the development of new rock testing systems and geophysical monitoring and processing technologies that will enable laboratory study of rock behaviour under conditions better resembling those experienced in situ.     

The Black Forest Observatory, Schiltach

The purpose of the geoscientific Observatory at Schiltach in the Black Forest in SW-Germany is to measure and monitor motions and deformations of the earth in a frequency band as broad as possible. The spectrum of geodynamic signal contains

• - the short period waves (up to 40 Hz) of near earthquakes,

• - the longer period body and surface waves from teleseismic events,

• - the free oscillations of the earth excited by giant earthquakes,

• - the earth tide deformations caused by the gravitational forces of the moon and the sun having periods of 12 h and longer,

• - deformations of the earth in a wide period range from other sources (e.g. atmosphere).

Besides providing high quality data with some continuity using ‘standard’ sensors, the observatory must be considered as an experimental station and research facility where new instruments and techniques can be tested.     

Influence of subsurface injection on time‐lapse seismic: laboratory studies at seismic and ultrasonic frequencies

Seismic monitoring of reservoir and overburden performance during subsurface CO₂ storage plays a key role in ensuring efficiency and safety. Proper interpretation of monitoring data requires knowledge about the rock physical phenomena occurring in the subsurface formations. This work focuses on rock stiffness and elastic velocity changes of a shale overburden formation caused by both reservoir inflation induced stress changes and leakage of CO₂ into the overburden. In laboratory experiments, Pierre shale I core plugs were loaded along the stress path representative for the in situ stress changes experienced by caprock during reservoir inflation. Tests were carried out in a triaxial compaction cell combining three measurement techniques and permitting for determination of (i) ultrasonic velocities, (ii) quasistatic rock deformations, and (iii) dynamic elastic stiffness at seismic frequencies within a single test, which allowed to quantify effects of seismic dispersion. In addition, fluid substitution effects connected with possible CO₂ leakage into the caprock formation were modelled by the modified anisotropic Gassmann model. Results of this work indicate that (i) stress sensitivity of Pierre shale I is frequency dependent; (ii) reservoir inflation leads to the increase of the overburden Young's modulus and Poisson's ratio; (iii) in situ stress changes mostly affect the P‐wave velocities; (iv) small leakage of the CO₂ into the overburden may lead to the velocity changes, which are comparable with one associated with geomechanical influence; (v) non‐elastic effects increase stress sensitivity of an acoustic waves; (iv) and both geomechanical and fluid substitution effects would create significant time shifts, which should be detectable by time‐lapse seismic.     

煤样变形破坏声电效应的演化规律及机理研究

通过实验研究不同煤样变形破坏全过程的声发射和电磁辐射效应的演化规律,分析了煤样变形破坏过程中电磁辐射和声发射信号的相关性和煤样变形破坏的微观机理,提出了煤样变形破坏过程中电磁辐射和声发射信号分别是在煤样内的裂纹面滑移和裂纹扩展时产生的观点,较好地解释了煤样变形破坏过程中声电效应的变化规律和特征,为进一步提高电磁辐射及声发射、电磁辐射综合预测煤岩动力灾害的可靠性和准确性提供了理论基础.     

The effectiveness of nitrate vulnerable zones for limiting surface water nitrate concentrations

This study considers the surface water concentrations of nitrate in areas designated as nitrate vulnerable zones (NVZs) for between 12 and 15 years. The study proposes a range of tests of the effectiveness of nitrate management within the NVZs and in particular the results from within NVZs were compared to a range of controls. The tests show that:

(i) Sixty-nine percent of NVZs showed no significant improvement in surface water concentrations even after 15 years.

(ii) In comparison to a control catchment 29% of NVZs showed a significant improvement but 31% showed a significant worsening.

(iii) The average improvement relative to a control due to NVZ designation was 0.02 ± 0.08 mg N/l/yr.

(iv) Differences between NVZs could not be significantly related to the size of the NVZ, uptake of the scheme, extent of uptake, land use change or geology of the local aquifer.

(v) Land use data suggest that NVZ designation buffered the designated areas against wider changes in arable farming in England and helped maintain a higher proportion of arable within the areas than would be expected.

The lack of objective success for NVZ designation suggests that nitrate pollution control strategies based on input management need to be rethought.     

Acoustic emission and sorptive deformation induced in coals of various rank by the sorption-desorption of gas

Simultaneous measurements of acoustic emission (AE) and expansion/contraction of coal samples subjected to gas sorption-desorption processes were conducted on high-and medium-rank coal. The aim of this study was to examine the influence of the coal rank and type of sorbate on measured AE and strain characteristics. The experimental equipment employed in this study consisted of a pressure vessel and associated pressurisation and monitoring units. The arrangement of pressure-vacuum valves permitted the coal sample to be pressurised and depressurised. Carbon-dioxide and methane were used as sorbats.     

态矢量方法的实验研究

在地震等灾变的发生之前，会出现一定的前兆现象。中通过实验方法对这些前兆现象之一的态矢量的异常变化进行了研究。实验使用声发射技术(Acoustic Emission)，对三轴应力条件下岩石试件内部微裂纹的产生和扩展进行了记录。实验结果表明在岩石试件最终破坏之前，表征态矢量的相关参量都发生了异常明显的变化，这表明态矢量的异常变化可以被用作为岩石等脆性材料灾变的前兆，使用态矢量方法可以对脆性材料的破坏乃至地震作出预测。     

International standard (ISO) on seismic actions for designing geotechnical works–An overview

The seismic performance of geotechnical works is significantly affected by ground displacement. In particular, soil–structure interaction and effects of liquefaction play major roles and pose difficult problems for engineers. An International Standard, ISO23469, is being developed for addressing these issues in a systematic manner within a consistent framework. The objective of this paper is to give an overview of this International Standard.In this International Standard, the seismic actions are determined through two stages. The first stage determines basic seismic action variables, including the earthquake ground motion at the site, the potential for earthquake-associated phenomena such as liquefaction and induced lateral ground displacement. These basic variables are used, in the second stage, for specifying the seismic actions for designing geotechnical works. In the second stage, the soil–structure interaction plays a major role. Types of analyses are classified based on a combination of static/dynamic analyses and the procedure for soil–structure interaction classified as follows:

– simplified: soil–structure interaction of a global system is modeled as an action on a substructure;

– detailed: soil–structure interaction of a global system is modeled as a coupled system.

Influence of source region properties on scaling relations forM<0 events

Excavation induced seismic events with moment magnitudesM<0 are examined in an attempt to determine the role geology, excavation geometry, and stress have on scaling relations. Correlations are established based on accurate measurements of excavation geometry and methodology, stress regime, rock mass structure, local tectonics, and seismic locations. Scaling relations incorporated seismic moments and source radii obtained by spectral analysis, accounting for source, propagation, and site effects, and using Madariaga's dynamic circular fault model. Observations suggest that the interaction of stresses with pre-existing fractures, fracture complexity and depth of events are the main factors influencing source characteristics and scaling behaviour. Self-similar relationships were found for events at similar depths or for weakly structured rock masses with reduced clamping stresses, whereas a non-similar behaviour was found for events with increasing depth or for heavily fractured zones under stress confinement. Additionally, the scaling behaviour for combined data sets tended to mask the non-similar trends. Overall, depth and fracture complexity, initially thought as second order effects, appear to significantly influence source characteristics of seismic events withM<0 and consequently favour a non-similar earthquake generation process.     

岩石试件刚度及压力机刚度对岩石主破裂前声发射相对平静的影响

本文通过对岩石试件的真三轴压缩实验，分析了岩石试件卸载刚度ＫＦ与压力机系统刚度比值对岩石破裂型式及破裂前声发射相对平静的影响，结果表明：当ＫＦ／ＫＳ＞１时，岩石试件产生突发断裂；当ＫＦ／ＫＳ＜１时，岩石试件产生缓裂，并且ＫＦ／ＫＳ的值越小，相对平静时间赵长；ＫＦ／ＫＳ的值越大，相对平静时间越短，而当ＫＦ／ＫＳ＞３时，声发射相对平静时间为零。