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GoXiaojie, Yang (China University of Mining and Technology) | Fuqiang, Wang (China University of Mining and Technology) | Zhibiao, Guo (China University of Mining and Technology) | Qiaoyun, Han (China University of Mining and Technology) | Zhao, Zhang (China University of Mining and Technology) | Liuping, Han (China University of Mining and Technology)

Floor heave is one of the most difficult problems of soft rock roadway supporting in coal mines. A serious floor heave have occurred when the west wing track roadway of Tingnan coal mine was being constructed, the maximum value reached to 50 cm, which impacted the normal application of roadway severely. The article involved engineering geology, soft rock engineering mechanics and clay mineralogy etc, employed the ways of study on engineering geomechanics, laboratory testing on properties of rock mass, and combined with FDM 3D numerical simulation, and deeply researched the deformation mechanism and generating process of floor heave, it indicated clearly that the major influencing factor that led to floor heave was the horizontal extrusion stress, and the secondary ones were floor surrounding rock with high content of swelling clay minerals and soaking effect on floor rock. Thus the deformation mechanism was compound type of floor heave caused by the combined action of plastic extrusion and swelling. Aimed at the above-mentioned mechanism, a new support measures would be provided with inverted arch and floor bolt to control the floor heave. Project protice has shown good results of new supporting have been obtained with expected effects, and controlled the floor heave effectively.

When the excavation of roadway has been advanced, the balance of in-situ stress situation of rock mass was destroyed, which lead to the redistribution of stress field, and the surrounding rock would be displaced into roadway. The floor heave is a kind of dynamic phenomenon; it has always been happened in many coal mine, which lead to the decrease in roadway section, and hinder transportation, ventilation and staff operation. There are some coal mines stopping production or canceling construction caused by floor heave, which seriously affect production, and threaten life safety[1].

ISRM-ISRS-2010-062

International Symposium on In-Situ Rock Stress

SPE Disciplines: Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)

Deep borehole observation can eliminate effectively various earth’s surface interferences, providing considerable advantage over other geophysical measurements made at the ground, and improve greatly our capability to detect very small deformations and vibrations in the surrounding strata. This new technology will promote consequently our understanding of presently active geological processes and its relation to earthquakes and tectonics. Based on previous experiences of developing RZB type borehole strainmeter a new multi-component borehole instrument for deep boreholes has been developed. The new system, namely RZB-3 multi-component borehole instrument is a complete package consisting of strain, tilt, strain seismic waves and ground temperature measurement units in a stainless-steel pressure cylinder with 102mm outside diameter. Furthermore, another three channels provide the assistant observation including well temperature, well water level and atmospheric pressure. This new instruments can run at maximum sensitivity to provide strain resolution of 0.1 nanostrain with the maximum of 5×105 nanostrain and tilt resolution of 1 nanorad with the maximum of 5 microrad. Up to now these instruments have observed good tidal signals, strain-steps associated with large earthquakes, and strain changes of geophysical interests. Some details relate to design of the multi-component borehole instruments and the relevant observation data were presented, and primary analyses were discussed as well.

1 INTRODUCTION

Deep boreholes enable the high S/N ratio geophysical observations for detecting very small tectonic strain, tilt and vibration signals with negligible artificial disturbances and meteorological noises. But the cost of digging deep borehole is very expensive, therefore, the only way is to develop the multi-component borehole instrument to cut down the total cost for establishing of an compositive observation station. During last decade, the borehole strain project has progressed from a small instrumentation research effort to a larger-scale monitoring program.

ISRM-ISRS-2010-132

International Symposium on In-Situ Rock Stress

areal strain, borehole, deformation, downhole, instrument, management and information, multi-component borehole instrument, observation, orthogonal, Reservoir Characterization, reservoir description and dynamics, seismic processing and interpretation, sensor, signal, Station, strain, strainmeter, system, tilt, Upstream Oil & Gas, zhangzhou station

SPE Disciplines:

The Sep 21, 1999 Chi-Chi, Taiwan, earthquake (Mw7.6) is the largest inland earthquake that occurred in Taiwan in the 20th century, while the May 12, 2008 Wenchuan earthquake (Ms8.0) is the most affected earthquake to China in the beginning of the 21st century. In this study, we concentrated on two statistic values

ISRM-ISRS-2010-108

International Symposium on In-Situ Rock Stress

The exploitation of Carrara Marble dates back to Roman times. Throughout these twenty centuries, quarrying activity was mostly developed in the Carrara district in open pit quarries. In the last decades many quarries have been moved into underground. In some areas the mining stopes are subjected to rock burst. In order to overcome this hazard, detailed studies were carried out on Carrara Marble’s geostructural and geomechanical setting, as far as laboratory determinations of its basic physical and mechanical parameters, focused on obtaining knowledge of the right geomechanical assessment and marble rock-mass behaviour and on developing mining prospecting and stability analysis. On the basis of those studies, it is now possible to predict by means of FEM analysis, the occurrence of rock-bursts and to define the geometry and sequence of quarrying activity, such as the supports to be placed.

The exploitation of the world famous Carrara Marble (Tuscany, Italy) (Fig. 1) began with the Romans, decreased in the Middle Age and increased again during the Renaissance. The production of marble blocks gradually, but slowly, increased up to the end of XX century when both the technology and the increment of international assets brought to the necessity to evaluate the amount of marble and to organize the exploitation itself. In the last twenty years environmental concerns and mining optimization induced many quarries to move underground in order to lower the impact on environment and increase dimensional stone percentage production. Present day intense Carrara Marble exploitation, which includes the widening of the underground quarries, up to very large sized caverns, new concerns for safety and new specific laws have forced quarriers to apply to designers for up-to-date exploitation projects. This study concerns the rock-burst problems encountered in the deepest and larger of the Carrara Marble underground quarry: the Carlone quarry.

ISRM-ISRS-2010-059

International Symposium on In-Situ Rock Stress

Chen, Zheng (Institute of Crustal Dynamics, China Earthquake Administration) | Li, Tao (Institute of Crustal Dynamics, China Earthquake Administration) | Ouyang, Zuxi (Institute of Crustal Dynamics, China Earthquake Administration) | Wu, Liheng (Institute of Crustal Dynamics, China Earthquake Administration) | Li, Yujiang (Institute of Crustal Dynamics, China Earthquake Administration) | Ning, Jieyuan (Peking University)

At present, borehole strain observations are generally in the horizontal longitudinal components of the strain. These observations take stress concentration model of an infinite flat plate with hole as their theoretical basis and are used for measuring stress distribution and stress change. Measuring both horizontal and vertical normal components of the stress, we can perform three-dimensional stress distribution. This article describes the horizontal and vertical strain measurement units of a deep-seated RZB-type integrated wideband deformation observing system, especially focusing on the measuring principle of the vertical longitudinal strain and technological breakthrough. Finite element method has been used to test the robust of the equipment.

The earth’s crust has differential movement and deformation under the action of tectonic stress field. While the accumulated energy eventually leading to quick destruction of a place of the earth’s brittle crust, there is an earthquake. Employing the measured data of crust deformation, we can better understand the crust movement, which is important to establish the dynamics model of earthquakes and to reveal tectonic stress field. Since the 70s of last century, China has exerted strain observation and has already accumulated a large number of borehole strain data. Nowever, for technical limitations, the observation only limited to the horizontal strain measurements, which are difficult to carry out three-dimensional stress inversion. Japanese scholars exerted vertical strain measurements, which were used to achieve three-dimensional strain observation together with horizontal strain measurements. However, its magnetic sensor prevent them from having large dynamic range of measurement and high sensitivity. Large magnetic drift is also a severe problem. In 2009, Prof. Zuxi Ouyang and his coworkers designed and manufactured deep-seated RZB-type integrated wideband deformation observing system. The system has been accepted by the National Science and Technology.

ISRM-ISRS-2010-140

International Symposium on In-Situ Rock Stress

borehole, cement, deformation, displacement, Earthquake, Horizontal, horizontal displacement map, horizontal strain, observation, Probe, Reservoir Characterization, reservoir description and dynamics, reservoir geomechanics, sensor, strain, stress, structural geology, structure, system, Upstream Oil & Gas, vertical longitudinal strain, vertical strain, vertical strain probe, wideband deformation

SPE Disciplines:

Estimating the maximum stress in a rock mass based on hydraulic fracturing data typically depends on identification of the breakdown and/or secondary breakdown (“reopening”) pressure. Errors in this estimate can be attributed to injection system compressibility, coupled viscous fluid flowin the hydraulic fracture, and crack growth through the varying stress field surrounding a wellbore. The role of these mechanisms has not been well-quantified. Here, a coupled numerical model that includes the compressibility of the injection system and the flow of a viscous fluid in a plane-strain hydraulic fracture extending from a wellbore in the presence of a non-isotropic in situ stress field provides a basic tool for estimating the order of the error associated with analysis of the breakdown pressure under non-ideal conditions. The result is model-based guidelines on the values of relevant dimensionless parameter groups to ensure sufficient accuracy, and when these guidelines cannot be met under field conditions, the model can be further applied to obtain first order corrections that account for compressibility, viscosity, and near-wellbore effects.

Hydraulic fracturing from a vertical wellbore is a widely-used method for determining in situ stress (Haimson & Fairhurst 1970; Zoback & Haimson 1982; Haimson 1989; Sano et al., 2005). The minimum horizontal stress

ISRM-ISRS-2010-008

International Symposium on In-Situ Rock Stress

Artificial Intelligence, breakdown, case, compressibility, crack, Detournay, effect, equation, Haimson, hydraulic fracture, hydraulic fracturing, initiation, injection system, injection system compressibility, Lakirouhani, Reservoir Characterization, reservoir description and dynamics, reservoir geomechanics, solution, stress, tensile strength, Upstream Oil & Gas, well completion, Wellbore Design, wellbore integrity

Oilfield Places: North America > United States > Colorado > Piceance Basin > Greater Grand Valley Field Complex Field > Williams Fork Formation (0.99)

SPE Disciplines:

The changes of in-situ stress magnitude and directions caused by the excavation disturbance effect of pilot tunnel are usually neglected. Firstly, the surrrouding stress field of pilot tunnel was inversed finely by multiple linear regression inversion anlaysis in the local mesh model. In order to obtain the entire stress distribution of damsite region, the inversion analysis method of second stress field for the whole damsite region was presented, which combined the ground abrasion process of strata and support vector machine model. Considering the abrasion process of the strata, the second stress value of measuring points is calculated in the entire mesh model. Numerial results of real project indicate that the in-situ stress field obtained by second fine inversion method fits for the distribution law of V-shaped vally generally.

Back-analysis of in-situ stresses is of top priority to the stability analysis in the rock engineering. Most river valleys in southwest of China are mountain valleys and are the symmetrical V-shaped or the nearly symmetricalV- shaped (Fig. 1). There are extensive crustal movement, abundant active faults, extensively complicated geological environment, and the physiognomy of alpine gorges in the southwest. Its in-situ stress field is complicated due to many tectonic movements such as tectonic stress, overburden and exhumation, in addition to the crash and squeezing between Indian plate and Eurasian plate which is the primary cause to give rise to the horizonal deformation of rock mass in the depth of Chinese Mainland (Liu 2006). The measurement of in-situ stress is timeconsuming, expensive and onerous, and furthermore, it is very demanding on the skill, so it is impossible to carry out in engineering field. The measuring results are limited and discrete to some extent due to the in-situ stress and the measurement errors (Ljunggren 2003).

ISRM-ISRS-2010-104

International Symposium on In-Situ Rock Stress

Artificial Intelligence, boundary, calculation, distribution, excavation, excavation disturbance, excavation disturbance effect, field, in-situ stress, in-situ stress field, inversion, machine learning, management and information, method, model, pilot tunnel, principal stress, process, regression, Reservoir Characterization, reservoir description and dynamics, reservoir geomechanics, stress, Upstream Oil & Gas

SPE Disciplines:

Technology: Information Technology > Artificial Intelligence > Machine Learning > Statistical Learning (1.00)

A new instrument of 3-component volume borehole strainmeter is developed in China and the primarily function is for borehole strain measurement. The sensor is designed on the base of type TJ-2 volume borehole strainmeter, and it has three independent components which make it being able to observe the strain changes in three different directions. In this paper, the principle, structure, measurement circuit and measuring system of the sensor are presented, and the field observation is also introduced. The filed results show that the measurement resolution of 3-component volume borehole strainmeter is up to 10−9–10−10.

1.1 The relationship between the 3 chamber volume change and the principal strain

Dr. Shoji (Shoji, 1981) has expressed the rigorous and comprehensive theoretical explaination on the 3- component volume borehole strainmeter. The volume or pressure change of three chambers can be given after little transformation to the analytical formula.

2 THE NEW STRUCTURAL DESIGN

2.1 Three-chamber structure

When the stress and strain state of rock are delivered to the probe crust, it is converted to the volume change and finally the stress change based on the incompressibility, and the sensor records the changes. Inside the probe, the elastic cylinder is adopted and the inner circle is a solid stick. The circle is devided into 3 parts with equal volume. Three chambers are distributed in 120 degree, and each one is an independent and closed space as shown in figure 2. However, if the stainless steel plate is too thick„ the volume of the three chambers will be reduced and the sensitivity will be debased. And if the tainless steel plate is too thin, the precision and ndependency will be debased.

ISRM-ISRS-2010-129

International Symposium on In-Situ Rock Stress

Baisheng, Nie (China University of Mining and Technology) | Shengrui, Zhai (China University of Mining and Technology) | Ruming, Zhang (China University of Mining and Technology) | Chuan, Jia (China University of Mining and Technology) | Jufeng, Zhang (China University of Mining and Technology)

By analyzing the stress characteristics and simulating numerically the law of the stress distribution on the roadway face in coal mine, the mathematical model is established and calculated to determine the stress relaxation zone and the forming process and evolution rules of the stress relaxation zone were discussed. The stress distribution on the roadway face was measured with the electromagnetic emission (EME) technology. The testing results are in good agreement with the theoretical calculation results on the whole. The research results show that stress relaxation zone of the roadway face is related with the height of roof-floor and the inner frictional angle of the coal and the calculating model is accurate.

Coal and gas outburst is a kind of very complicated dynamic disaster of coal or rock containing gas in which the coal-rock containing gas in coal mines, in broken state, abruptly moves from the coal-rock stratum to mining space and a large amount of gas erupts (ZHAI et al, 2007, HE 1995). At present, the synthetic hypothesis about coal and gas outburst is widely recognized: outburst is the result from the comprehensive effects of crustal stress and the physical and mechanical properties of gas and coal. According to the statistics of the job sites where outburst occurred, most of outbursts took place on the roadway face and accounted for 66.2% of the outbursts, of which average outburst intensity was 66.9 t/times. Frequent outburst occurring during the mining of roadway constitutes a major threat to the life safety of coal mine workers. Effective prevention and control of coal and gas outburst is not only the safeguarding of safe production, but also the prerequisite to quicken roadway tunneling speed, eliminate outburst hazard for stoping face and extend space and time.

ISRM-ISRS-2010-078

International Symposium on In-Situ Rock Stress

characteristic, coal, Computation, distribution, front, gas outburst, management and information, metals & mining, outburst, Reservoir Characterization, reservoir description and dynamics, reservoir simulation, roadway, roadway face, rock, stress, stress concentration, stress relaxation, technology, testing

SPE Disciplines:

Hydraulic Fracturing, Hydraulic Tests on Pre-existing Fractures, sleeve reopening tests and the analysis of en echelon fractures developed in wells inclined to the principal stress directions, have helped determine the vertical profile of the complete stress tensor in a sedimentary formation of the eastern Paris Basin. This stress profile outlines the relaxation of shear stress in a 190m thick clayey formation that results in a strongly non linear stress variation with depth. It demonstrates that today’s stress field at this location does not depend on tectonic stresses but on active deformation processes that likely involve fluid-rock interactions.

If continuum mechanics is the paradigm applied for solving a geomechanical problem, then the concept of stress is of central importance. With this paradigm the so-called natural stress field, i.e. the stress field that exists before applying the perturbation of concern, must be evaluated and interpretation of borehole hydraulic tests has revealed very efficient for such evaluations. But overtime, the practice has progressively evolved from simple Hydraulic Fracturing tests (Hubbert and Willis, 1957, Kehle, 1964, Haimson, 1978) to integrated methods that rely on geophysical borehole imaging (Cornet 1993, Peska and Zoback, 1995) or on data obtained with different techniques (e.g. flat jacks, Cornet, 1996, or overcoringAsk, 2006). In this paper, hydraulic methods for evaluating the six components of the complete stress field are first briefly recalled. Then their application to the Meuse/Haute-Marne underground research laboratory (France) is discussed. It is shown how hydraulic tests results help constrain the six components of the stress field. Results are validated by comparison with borehole failure images. They raise the question on the origin of stresses in sedimentary formations and on spatial stress variations. Finally, consequences for integrating data collected at different depths in sedimentary formations are briefly discussed.

ISRM-ISRS-2010-010

International Symposium on In-Situ Rock Stress

borehole, breakout, component, Cornet, determination, direction, echelon fracture, field, fracture, horizontal principal, hydraulic fracturing, hydraulic test, Magnitude, principal stress, principal stress direction, Reservoir Characterization, reservoir description and dynamics, reservoir geomechanics, rock, Rock Mech, stress, test, Upstream Oil & Gas, well completion

Oilfield Places:

- North America > United States > Texas > East Texas Basin > Carthage Field > Cotton Valley Sand (0.99)
- North America > United States > Colorado > Piceance Basin > Greater Grand Valley Field Complex Field > Williams Fork Formation (0.99)
- Europe > France > Paris Basin (0.99)
- (2 more...)

SPE Disciplines:

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