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- analysis (2)
- Behavior (1)
- behaviour (1)
- block (1)
- borehole (1)
- borehole jack (1)
**boundary (5)**- boundary condition (1)
- calculation (2)
- coefficient (1)
- component (1)
- condition (1)
- confinement (1)
- correlation (1)
- coupling effect (1)
- criterion (1)
- dataset (1)
- deep learning (1)
- deformability (1)
- deformation (1)
- discontinuity (1)
- displacement (3)
- element (2)
- Engineering (1)
- equation (1)
- expansion (1)
- failure criterion (1)
- Figure (4)
- force (1)
- fracture (1)
- friction shell (1)
- function (1)
- geo stress (1)
- Horizontal (1)
- II hydropower station (1)
- interface (1)
- lining (1)
- loading (1)
- machine learning (1)
- measurement (2)
- method (3)
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- neural network (1)
- nonlinear (1)
- optimization problem (1)
- parameter (2)
- point (2)
- position (1)
- pressure (1)
- Probe (1)
- process (1)
- reservoir geomechanics (1)
- reservoir simulation (1)
- rock (4)
- rock mass (2)
- rotation (1)
- shotcrete (1)
- shotcrete utilization (1)
- Simulation Technique (1)
- steel pipe (1)
- strata denudation (1)
- strength (1)
- stress (3)
- stress measurement (1)
- support (1)
- surface (1)
- system (1)
- transition (1)
- triaxial (1)
- uniaxial tensile (1)
- valley (1)
- value (1)

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Although a number of numerical simulation models were developed and improved in the theory and programs for jointed rock mass, there are many drawbacks to the simulation techniques, such as discontinuity modeling and free expansion. Instead of the spring model of discontinuity, a new numerical model is developed based on the essences of deformability and mechanical characteristics of discontinuity. Discontinuity is considered as a nonrenewable and volumechangeable plastic medium. In addition, Numerical errors between the linear displacement functions and the exact solutions can accumulate when the block rotates continuously. This cause a change in block size called the free expansion phenomenon. Here, the finite rotation theory is adopted to address the drawback of free expansion. Finally, jointed rock mass is considered as a two-media model. The coupling effects between blocks and discontinuities are established. These developments of simulation techniques can reveal the essences of rock mass and improve analysis accuracy for simulation.

In order to overcome the reaction force indeterminacy, one needs to introduce the deformability of the discontinuities. For example, DEM, DDA and BSM use normal and tangential springs at the intersection point between a discontinuity face and a block’s vertex. And they consider the thickness of discontinuity as 0. The interactive forces between discontinuity and block are based on the ‘invasion’. Although this discontinuity model can address the problem of discontinuity simulation, it does not reveal the essences of discontinuity, such as discontinuity deformability, mechanical characteristics.

ISRM-SINOROCK-2009-127

ISRM International Symposium on Rock Mechanics - SINOROCK 2009

Industry:

- Information Technology > Software (0.55)
- Energy > Oil & Gas > Upstream (0.31)

SPE Disciplines:

It is important to understand rock stress state in civil, mining, petroleum, earthquake engineering and energy development, as well as in geophysics and geology. In general, however, estimating the stress spatial distribution in rock is very difficult. The differences between the estimated and the measured stresses can be first attributed to tectonic stresses, as well as other factors such as topography and inhomogeneity of the rock mass. In this research, a study combining strategy and tactics for the determination of in situ rock stress was undertaken to resolve difficulties and improve accuracy of stress estimation. Numerical and experimental tests of a new borehole jack fracturing probe by loading a steel pipe were carried out. On the other hand, an improved program was developed available for inhomogeneous modeling and its applicability was examined by comparing the numerical results with the corresponding strict solution. A non-linear numerical inverse method is presented for evaluating the in situ state of stress in a rock mass.

On the other hand, for certain geometries, the effect of topography on determination of state of stress can be analyzed by accurate analytical solutions and factors affecting the magnitudes and orientations of in situ stress can be studied.

ISRM-SINOROCK-2009-005

ISRM International Symposium on Rock Mechanics - SINOROCK 2009

SPE Disciplines: Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.68)

When dealing with tunnels in weak rock mass and with high overburden, the high displacements imposed on the lining dictate the application of ductile yielding elements with controllable stiffness and yield load. These properties are chosen with two goals in mind: the time-dependent strength of the shotcrete shell must not be exceeded; however the support pressure must be kept reasonably high and controllable. The attainable load-displacement lines of the ductile support elements are almost arbitrary. There are almost countless possible combinations of their stiffness and yield load, thus enabling the development of custom-tailored support systems and leaving considerable room for adapting to the encountered ground conditions. Tunneling in weak ground should be accompanied by increased efforts on monitoring the system behavior, best by a dense pattern of absolute displacement measurements. A simple technique for calculating the shotcrete utilization ratio has been developed. It applies a Newton- Raphson root-finding algorithm to determine the interpolation parameters while obeying the requirements of force equilibrium and fitting the measured displacements. The influence of non- symmetrical displacement behavior caused by heterogeneity and anisotropy of the rock mass, on the lining loading can be quantified and used for support system optimization.**1. INTRODUCTION**High primary stresses associated with tectonic faulting frequently create problems during construction of Alpine base tunnels. Keeping the displacements in a range which could be sustained by the support would lead to economically unfeasible lining thickness.

Ductile lining systems using in mining cannot be be transferred to traffic tunnels with their requirement of long term stability. First concepts of yielding supports for tunnels date back to the nineteen fifties (Rabcewicz 1950).

The technical requirements posed on a ductile support system are quite clear:

- The load-displacement characteristics should be “steerable” within a broad range, allowing the avoidance of overstressing the shotcrete shell, while enabling easy modifications in order to cope with the ground heterogeneity and usually long-lasting displacement increments.
- The support resistance has to be reasonably high, allowing a certain amount of control over the displacement magnitude.

(Figure in full paper)

ISRM-SINOROCK-2009-162

ISRM International Symposium on Rock Mechanics - SINOROCK 2009

behaviour, boundary, calculation, displacement, element, Figure, function, lining, loading, measurement, method, optimization problem, parameter, point, position, shotcrete, shotcrete utilization, stress, support, system

SPE Disciplines:

Hashemi , M. (Civil Engineering Department, University of Isfahan) | Ghazvinian, A.H. (Tarbiat Modares university) | Taghichian , A. (Tarbiat Modares university)

Empirical rock failure criteria generally relates lateral stresses to axial strengths by a particular equation in which uniaxial tensile and/or compressive strengths are to be estimated from the failure criterion by applying the obtained parameters from triaxial datasets into the criterion equation. In order to satisfy the exact amounts of uniaxial tensile and compressive strengths in a failure criterion, a rational function is proposed as a failure criterion for isotropic, dry and intact rocks to be used in both tensile and compressive regions. The proposed criterion is validated by using 59 series of accurate triaxial test datasets which are belong to 20 different rock types selected from the literature. It has been shown that the proposed criterion is capable of predicting the triaxial behavior of rocks in both tensile and compressive regions. There are two coefficients for the proposed criterion (‘c’ and ‘d’) which have been estimated for used rock datasets by applying brittle-ductile transition as an initial boundary condition. The most proper brittle into ductile boundary, the confinement in which ∂ τ/ ∂ σ

It is well recognized that the behavior of most rocks changes from brittle to ductile at some elevated confining pressure, defined by Byerlee [6] as the BDT pressure.

ISRM-SINOROCK-2009-021

ISRM International Symposium on Rock Mechanics - SINOROCK 2009

Behavior, boundary, boundary condition, coefficient, confinement, correlation, criterion, dataset, failure criterion, parameter, pressure, rock, strength, transition, triaxial, uniaxial tensile, value

SPE Disciplines:

- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.48)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (0.34)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (0.34)

Jiang, Q. (Institute of Rock and Soli Mechanics) | Feng, X.T. (Institute of Rock and Soli Mechanics) | Xiang, T.B. (Institute of Rock and Soli Mechanics) | Wan, X.B. (East China Investigation and Design Institute)

JinpingIIhydropowerstationisanimportantcascadestationof Ya-Long RiverinSichuan province.TheregionofhydropowerstationistypicalV-shapedrivervalleymorphology. Tectonicmovement,includingIndo-Chineseepochmovement,Yanshanmovementand Himalayan movement, madetheregionpreserveprodigioushorizontaltectonicstress. But,the corrosion of Ya-Longriverleadstofiguration ofthe “V” shaped valley andrelease oftectonic stress.

To understand the effect of inter dynamical geological process and outer dynamical geological process to current geo stress of Jinping, a new nonlinear back analysis method of initial geo stress ispresented,whichintegratesthestratadenudationsimulation,numericalelasto-plastic calculation and neural networkinversion. The methodtakesthe geo structure order processinto accountbyelasto-plasticcalculationandsimulatesthestratadenudationprocessbysurface excavation. The method includes several steps. Firstly, a numerical model including immemorial plantationsurfaceisbuildupinalargearea.Secondly,thegivendisplacementboundary conditions are applied on the model in order of tectonic movement time and the balance is gained byelasto-plasticcalculation.Thirdly,surfaceexcavationiscarriedouttosimulatethestratum corrosion, the “V” shaped valley and the current geo stress field of Jinping II hydropower station region is obtained by several excavation calculation. In the method, the “the given displacement boundaryconditions”isrecognizedthroughnonlinear mappingfrom measuredgeo-stress with artificial neural net.

As we all know, the current geo stress in stratum is the result of complicatedinter dynamical geological process andouterdynamicalgeologicalprocess(McKinnon, 2001; Hudson, 2003). On one hand,theinter dynamical geologicalprocess,includingtheIndosinianorogeny, Himalaya movement, and so on,leadsto preservation of great horizontal tectonic stress in rock. On the other hand, the outer dynamical geological process, including stratum abrasionandrivererosion,leadstothereleaseand adjustment of tectonic stress (Obara, 2000; Mello, 2002). Therefore,areasonablestudyofgeostressshould consider the history of tectonic evolvement.

JinpingII hydropowerstationis animportant cascade stationofYa-LongRiverinSichuanprovince.The hydropowerstationregionistypicalV-shapedriver valley morphology with high grand mountainsand deep gorges(Figure1).Thein-situstressmeasurement indicatesthatthe geo stressfieldisaffectednot only by immemorial tectogenesis but also by exogenic geological processes (Zhong, 2002).

(Figure in full paper)

To understand the effect of inter dynamical geological processandouter dynamicalgeologicalprocesstoform the curr

ISRM-SINOROCK-2009-080

ISRM International Symposium on Rock Mechanics - SINOROCK 2009

Industry:

- Energy > Renewable > Hydroelectric (0.75)
- Energy > Power Industry > Utilities (0.75)

SPE Disciplines: