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FLAC3D model construction for slide slope analysis has been one of the challenges to engineers when intending to model the topography and geology in the region of interest at the required engineering accuracy. After referring to the examples in the FLAC3D manual, this paper introduces an approach to build up slope models by utilizing an interpolation technique to simplify the data processing with a built-in function. Geological units in the slope are geometrically modeled through data interpolation and an associated logical calculation to ensure the required accuracy. Three types of built-in elements in FLAC3D have been selected to represent the geological changes such as thickness variation and termination of the geological unit. Each type of element is identified and employed automatically through FISH functions, according to the geological condition in the slope. This approach has been employed to build the FLAC3D model for the Upper Gutianzheng slide slope at Kala Hydropower Station on Yalong River, China. The modeling results are in a great agreement with limit equilibrium calculations, which intends to indicate the reliability of the model construction approach introduced in the paper. [ABSTRACT FROM AUTHOR]

Dam stability under seismic loading has long been a critical concern in water conservancy and Hydropower Engineering practice. This is particularly true when the dam is constructed in the tectonically active area. In the study of dam dynamical stability, understanding of the rock or soil behavior to dynamic loading conditions is fundamental because the response of the dam foundation to seismic loading can significantly affect the stress and deformation distribution, as well as the stability of the dam. This paper presents the entire procedure of dynamical analysis considering dam-foundation interaction during seismic loading for the case of Spillway Dam at CCS Hydropower Station in Ecuador. The analysis is implemented with FLAC in a complete non-linear manner. The models have revealed the stress and the deformation response of both dam and foundation to the seismic loading at various levels. Such results have been used to assess the dam stability through further interpretation and to help understand the mechanism of potential failures. In addition, a few important matters to dynamic analysis have been presented in the paper, including art ificial spectrum generation, estimate of dynamic properties for rock and soil; as well as boundary condition setting. [ABSTRACT FROM AUTHOR]

The quantitative understanding of the current stress state, which refers to correlation among the three principal stresses, along a fault is one of the challenging and interesting aspects in the study of fault permeability. This study is commonly conducted to help identify the possible existence of oil and gas resources for the given geological conditions during reservoir exploration and development. Taking the North Zone of DongyingBasin as an example, this paper introduces the numerical exercises with FLAC to help understand the stress distributions at different depths along the faults that are present with various dips within this domain of interest. The modeling results indicate that the stress state along a fault can be quantitatively described, and it varies with depth along the fault. The variation of stress state is essentially governed by the combination of gravity and tectonic stresses. The findings presented in this paper have provided effective indications for the further investigation of fault permeability, particularly in establishing the criterion to identify oil and gas reservoirs in faulted ground. [ABSTRACT FROM AUTHOR]

The paper firstly presents a generic approach of model construction with FLAC3D for rock slope analysis, which directly uses AutoCAD drawings to build the model by using SLIP in CAD software and FISH language in FLAC3D. Secondly the paper describes the model construction process for the left bank slope at Kala Hydropower Station, as well as the stress and strain distributions generated by the model. Finally the factor-of-safety calculation results are presented, which indicate a relatively unstable condition of the slope. During the FOS calculation, a sensitivity study has been carried out to investigate the influence of rock mass properties on the slope stability. The results indicate that FOS values are sensitive to the change of both friction and cohesion, whereas less sensitive to Young's modulus. A comparison between the FLAC3D model and the 2D EMU calculation has been conducted that indicates a reasonably good agreement with each other. However, the FLAC3D model appears to be able to more explicitly and accurately reveal and present the stability of the slope. [ABSTRACT FROM AUTHOR]

Both spalling and block failure have been observed while driving the audits in the proposed locations of the cavern in the right bank at Baihetan Hydropower Project site. Severe spalling occurred primarily in the roof, and the block failures were governed by the Shear Zone C4. In addition, field investigation showed that the stress-induced spallings are spatially associated with the existence of Shear Zone C4. The occurrences observed in the audits present a strong indication that both a stress-induced problem and structure-control failure should be anticipated and may co-exist when constructing the cavern. When conducting numerical analysis of cavern stability, attention should be paid simultaneously to both the discontinuous and the non-linear behaviors of the rock mass. This paper presents the entire procedure of numerical analysis for the cavern crown. The first step in the paper is to briefly describe the site occurrences and accordingly present their indications for numerical modeling. The model inputs are then numerically examined and calibrated against the observations, which include in-situ stress regime in general, properties for both pre- and post-peak stages in the non-linear constitutive models to be employed. The numerical modeling for crown stability analysis is finally implemented. Extra attention is paid to the potential failure modes and severities, including the stress-induced failure resulting from the stress localization in the vicinity of Shear Zone C4, as well as potential ground falls governed by C4 and additional geological structures. The modeling results provide clear and solid indications for the ground support design, particularly in the required extra support element and applicable locations, in addition to the commonly-used pattern. [ABSTRACT FROM AUTHOR]

With the growing development of underground resources in the mining industry in China, stope stability has gradually become a research focus for extracting ores from large-scale mines in hard rock. Taking a given mine in China as an example, this paper introduces a procedure that helps optimize stope design by using a numerical approach in conjunction with an orthogonal regression method. As presented in the paper, this procedure starts with estimation of in-situ stress regimes and rock mass properties obtained through geological investigation. These data are used as inputted constants for numerical modeling with FLAC3D to analyze stope stabilities. The numerical modeling runs are set up based on the various assumptions of mining scenarios. Each scenario represents a combination of the four stope parameters including stope width, stope length, pillar width, and panel size. The setting of all these scenarios follows the orthogonal regression theory. Four indexes of maximum tensile stress, maximum compressive stress, sum of yielding area, and sum of area in tension are selected and employed as criteria to comprehensively evaluate the stope stability corresponding to each mining scenario. As a result, a statistic relation between stope parameters and stop stability has been established according to the modeling results. Such a relation is further used to calculate an optimized stope design, involving a set of stope parameters that can minimize the impact on stope stability among all assumptions. [ABSTRACT FROM AUTHOR]

Referring to the principal of the PSC Model developed by Potyondy in PFC, a constitutive model named SC Model was previously developed by the authors for FLAC3D to describe the cracking propagation behavior of brittle rock at engineering scale. This model had been validated against the monitoring data collected at the early stage (by 2009) of construction period of time at the Jinping II Deep Tunneling Project site. The model had been applied to the study of occurrence of a ground damage zone increasing over time as well as the ground support requirement and effectiveness to control such response. This paper presents the further validation of the SC model using the updated monitoring data at the time by the year of 2012. The further-verified SC Model is then used to examine the safety of the proposed ground support system including rock bolts, and particularly the concrete lining, over the operation life time. The model indicates the long-term stability can be ensured after taking into account the extra load applied to the support, resulted from crack propagation of the surrounding rock. [ABSTRACT FROM AUTHOR]

The reasonable estimate of rock mass properties is fundamental to the stability analysis and safety assessment in engineering practice. One of the challenges in property estimation is derived from scale-effect of rock mass behaviours. This paper presents a case study of the scale-effect of rock mass properties considering stochastic joints. During this study, joints samples are firstly collected on the Baiyunbo Eastern Iron Open-pit in Inner Mongolia, China, by means of a scanline method. Laboratory tests have been carried out to obtain properties of both intact rock and joints. The joint samples are then further processed using Monte-Carlo theory to generate a computerized 3D joint network. The three dimensional discrete element code, 3DEC, is finally employed to construct a number of rock mass specimens with various sizes for the attempt to conduct numerical tests at different confinements. During the numerical triaxial tests, the Coulomb-slide model is assigned to joints and the intact block is assumed to follow the strain-softening law. A number of completed stress-strain curves are obtained and each of the curves corresponds to one particular numerical test on a given size of specimen and at a given confinement. As a result, the diversity among the curves corresponding to different specimen sizes represents the influence of specimen sizes on rock mass behaviours. The numerical tests show that, for the dolomite at this particular mine site, the properties obtained from the specimen with the volume of 15 m × 15 m × 15 m are considered most representative and are thus suggested for future use in stability analysis. [ABSTRACT FROM AUTHOR]

Pile loading capacity can be affected by the reduction of effective stress due to the mobilization of excess pore pressure while driving and penetrating a pile into soil that squeezes the surrounding soil. Based on the cylindrical cavity theory and the excess pore pressure theory, this paper firstly introduces four optional approaches that can generate excess pore pressures with FLAC. Each approach is then examined through the assessment of the distribution of numerically generated excess pore pressures, as well as the comparison against the corresponding analytical calculation results. The most suitable approach can thus be identified. The studies show that, for the cylindrical cavity expansion mode in plane-strain, the elastic-plastic model considering cavity expansion and fluid-flow presents a reasonably good agreement with analytical solutions and thus seems the most applicable. The radial expansion approach appears to be the most suitable for the axisymmetric expansion mode, although the radial deformation boundary approach and the pile penetration approach may also apply. [ABSTRACT FROM AUTHOR]

This paper analyzes the stability of a Buddha statue with approximate height of 80 meters in a three-dimension numerical model using FLAC3D. The influence of the rock tensile strength on the stability of the statue is studied. A total of five profile cases of the statue's head are compared for optimal design. The study results suggest that the deformation mechanism of the Buddha statue, as a special engineering rock mass, is due largely to the rock tensile strength having a significant impact on the stability, which is different in slope and tunnel engineering. If the rock tensile strength is not specially considered, the statue will be in tensile failure. The analyses show that when the rock statue reaches a certain height, its gravity weight will play an important role in restricting the statue's shape, especially the head, in order to keep the statue stable. The balance between the artistry and stability of the rock statue needs to be comprehensibly studied during design. [ABSTRACT FROM AUTHOR]

By means of FLAC3D, this paper presents a case study of acceptable pillar size when mining towards a steep fault at the third coal seam of the Mengzhuang Coal Mine. The numerical models indicate that high stress can be continually built up in the mining front and in the adjacent area of the fault as the mining front is approaching the fault. High stress can even be overlapped when the pillar size reduces below the critical level. Meanwhile, displacement along the fault is gradually mobilized. A critical pillar width of 30m is indicated by the model in terms of the mining-induced stress and displacement in the pillar. This suggested acceptable pillar size has been used as a great support to mining design. [ABSTRACT FROM AUTHOR]

During the overhaul period of a high pressure headrace tunnel, the pressure reduces gradually to zero on the inner surface of the lining. Meanwhile, the pressure on the external surface and the pore pressure in surrounding rock change correspondingly. As a result, high water head could be developed to the lining. It might even exceed the design limit and lead to an engineering concern, when the internal pressure reduces rapidly whereas the external varies slowly. Following the principal and procedure of fluid-flow analysis, the paper addresses the numerical modeling exercises with FLAC3D by simulating the overhauling scenario in the operation of a high pressure headrace tunnel. A sensitivity study has been carried out to look into the water head generated and applied to the lining on the shaft, i.e., the vertical segment of the tunnel examined, when the internal pressure changes with various discharging rates. A discharging rate of 3m/h has been suggested for this particular case. [ABSTRACT FROM AUTHOR]

Gas storage caverns are mostly constructed in bedded salt rock units in China, in which thin and weak layers are often present. The strength of both salt strata and the weak interlayer is one of the key matters that attract attention in engineering design of the gas storage caverns in such strata. Referring to the commonly-presented geological conditions in salt rock in China as the object for this study, this paper addresses the numerical investigations of the impact of the strengths of both salt rock and weak interlayers on the stability for gas storage cavern construction. Both stress and deformation distributions have been discussed and employed as parameters for stability assessment. The conclusion of this study is believed to be beneficial for the future design of gas storage caverns in salt rock in China. [ABSTRACT FROM AUTHOR]

This paper firstly describes the procedure of estimating the preliminary ground support parameters based on Q-System for a water-sealing petroleum storage cavern located in Shandong Province, China. In this approach the support parameters are suggested mainly based on the size of opening, as well as the discontinuities in surrounding rock. The preliminary design is then examined with 3DEC models which bring in great details into consideration, such as in-situ stress, actual distribution of discontinuities, etc. Prior to the 3DEC model simulation, regression analysis has been implemented to understand the in-situ stress distribution on an engineering scale based on the limited available measurements. Rock mass properties are estimated by using the Hoek-suggested empirical method. During this practice, GSI is converted from Q values. 3DEC models are then run in both continuum and discontinuum modes in the attempt to comparatively understand the influence of discontinuities on ground stability. An overloading scenario has been simulated to help assess the factor of safety of the ground support. The findings from numerical models include: 1) the ground support can significantly control the deformation when assuming the rock mass is a continuum. In such a case, the rockbolt has a minimum FOS value of 2.75, and the shotcrete of 1.25. Both indicate the preliminary support pattern is generally reasonable and acceptable; 2) the discontinuum model runs reveal ground support failure resulted from the movement of individual unstable rock blocks; 3) Overall, Q-System is applicable to the design of a systematic support pattern whereas it ignores the potential problem caused by some individual discontinuities. Discrete element modelling can provide an effective remedy to this empirical method in this regard. [ABSTRACT FROM AUTHOR]

Yangjiawa Iron and Zinc Mine is located in Henan Province, China, in which sub-level caving method was employed at the early mining stage. Caving mining has caused ground surface movement with the boundary extending towards and close to a highway and a river near the mine site. In order to control subsidence and to ensure a safety mining environment, it has been decided to change the mining method from caving to backfill for the region above the 300 Level. This paper introduces the studies with FLAC3D of the potential instability issues resulting from such transition. The numerical model indicates that stress condition and rock mass quality in the mining transition area have been significantly impacted by the caving mining at an early stage. In order to maintain a safe mining condition using backfill method, the pillar size needs to remain in the range between 1 and 1.25 times of stope span, according to the numerical model. [ABSTRACT FROM AUTHOR]

This is a case study on dynamic compaction. The finite difference software FLAC3D is used for non-linear dynamic analyses on vibration wave propagation and attenuation during dynamic compaction. A three-dimensional grid is created using FISH, based on the geographic data from Surfer, so that the topography can be realistically modeled. The dynamic compaction load is simplified to a triangular distribution. An empirical function is used to relate the increase in soil compressive modulus with blow counts. The numerical model is validated by the agreement of the numerical results with the field data. This study can be a useful reference to the assessment of the impact of future dynamic compaction on the surrounding environment. [ABSTRACT FROM AUTHOR]

As the development of foundation pit engineering is becoming more and more challenging, the numerical analysis method has become an important means of the analysis of foundation pit construction. One of the key points for 3D numerical modeling practice is the proper selection of existing constitutive models for soil as well as the reasonable estimate of properties for parameters associated with the model. After reviewing previous research, a particular case of foundation pit has been selected for the study of further investigation of the two most commonly-used constitutive models, i.e., the Mohr-Coulomb model and the Modified Cambridge model. The advantage of one model over another is judged in terms of the agreement of the model-referred deformation with the actual one collected in the field on both the foundation and the sidewalls of the pit. Through this study it has been found that the Mohr-Coulomb model seems to be applicable to preliminary analysis due to the assumption of equal modules for both loading and unloading. In this case, an unrealistic relief response may be expected on the pit foundation when removing the materials. The stiffness in the Modified Cambridge model depends on the stress level as well as stress path and thus appears to be theoretically more rational. This model can be used for investigations in greater details. The conclusions should be able to serve as a solid reference for the numerical modeling of foundation pit construction. [ABSTRACT FROM AUTHOR]

The particle flow theory and PFC program are utilized to simulate the direct shear test of rock joints under cycle loading. Firstly, a number of implementation matters, such as eliminating floating particles as well as setting up the constant normal stress servo-mechanism and loading velocity, need to be addressed to obtain convincing results when PFC is applied to the implementation of numerical tests. Then, the mechanical evolution law and failure mechanism during the shear test process is discussed at both macro and micro-scale perspectives. The modeling results show that the joint exhibits the following mechanical characteristics during the direct shear process under cycle loading: (1) The hysteresis effect has been obviously presented on the shear stress-shear displacement curves. The peak shear strength decreases as the peak normal displacement increases. (2) The vector direction of the normal contact on the joint mainly deflects towards the direction of maximum load. The number of normal contacts on a joint surface decreases when the upper block returns to the original position. (3) The cracks are mainly generated near the joint and increase rapidly when the load reaches the peak shear strength. Finally, such numerical findings seem to benefit the study of joint strength through physical tests in the future. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing technique has been widely used to extract and release gas in coal mining practice. By means of the particle flow code PFC2D, a number of numerical models have been established to investigate the factors that may influence crack propagation during hydro-fracturing. The findings are presented as: crack patterns are governed by in-situ stress regimes; the number of cracks is positively correlated with the injection pressure; crack length increases with coal permeability and also with Young's modulus as well as Poisson's ratio. On the other hand, crack propagation is slightly impacted by shear strength when the coal appears less fractured with high tensile strength. In conclusion, the orientation and size of cracks are mainly governed by the factors including in-situ stress regime, tensile strength, permeability, as well as Young's modulus, Poisson's ratio, and shear strength of the coal, in addition to injection pressure. [ABSTRACT FROM AUTHOR]