Upscaling of fractured rock mass properties – An example comparing Discrete Fracture Network (DFN) modeling and empirical relations based on engineering rock mass classifications

2021 ◽  
pp. 106382
Author(s):  
D. Gottron ◽  
A. Henk
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Fracture Network ◽  
Discrete Fracture Network ◽  
Rock Mass Properties ◽  
Fractured Rock Mass ◽  
Empirical Relations ◽  
Mass Properties ◽  
Discrete Fracture

scholarly journals Study on Water Inflow Variation Law of No.1 Shaft Auxiliary Shaft in HighLiGongshan Based on Dual Medium Model

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 930
Author(s):  
Jiabin Li ◽  
Yonghong Wang ◽  
Zhongsheng Tan ◽  
Wen Du ◽  
Zhenyu Liu
Keyword(s):  
Rock Mass ◽  
Continuous Medium ◽  
Fractured Rock ◽  
Analytical Formula ◽  
Fracture Network ◽  
Discrete Fracture Network ◽  
Water Inflow ◽  
Fracture Group ◽  
Medium Model ◽  
Discrete Fracture

When the fracture is not developed and the connectivity is poor, the original single medium simulation cannot meet the accuracy requirements. Now, the seepage simulation of fractured rock mass has gradually developed from equivalent continuous medium to dual medium and multiple medium. However, it is still difficult to establish the connection between a discrete fracture network model and a continuous medium model, which makes it difficult to simulate the influence of fracture location on the seepage field of rock mass. As the excavation direction of the shaft is vertically downward, the surrounding strata are symmetrical around the plane of the shaft axis, which is different from the horizontal tunnel. Taking the auxiliary shaft of the No.1 Shaft in HighLiGongshan as the engineering background, combined with Monte Carlo methods and DFN generator built in FLAC3D5.01, a discrete fracture network is generated. Based on the dual medium theory, MIDAS is used to optimize the modeling of each fracture group. At the same time, the concept of “Fracture Weakening area” is introduced, and the simulation is carried out based on a fluid–solid coupling method. It is found that the simulation effect is close to the reality. The water inflow increases with the increase of shaft excavation depth, and the water inflow at the end of excavation is nearly three times larger than the initial value. Combined with Legendre equation, a new analytical formula of water inflow prediction is proposed. It is found that this analytical formula is more sensitive to permeability and has a greater safety reserve.

scholarly journals A methodology of re-generating a representative element volume of fractured rock mass

2020 ◽  
Vol 71 (4) ◽  
pp. 347-358
Author(s):  
DANG Hong-Lam ◽  
THINH Phi Hong
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Fracture Network ◽  
Hydraulic Calculation ◽  
Fractured Rock Mass ◽  
Fracture Characteristics ◽  
Mechanical Calculation ◽  
Representative Element ◽  
Representative Element Volume ◽  
Actual Fracture

In simulation of fractured rock mass such as mechanical calculation, hydraulic calculation or coupled hydro-mechanical calculation, the representative element volume of fractured rock mass in the simulating code is very important and give the success of simulation works. The difficulties of how to make a representative element volume are come from the numerous fractures distributed in different orientation, length, location of the actual fracture network. Based on study of fracture characteristics of some fractured sites in the world, the paper presented some main items concerning to the fracture properties. A methodology of re-generating a representative element volume of fractured rock mass by DEAL.II code was presented in this paper. Finally, some applications were introduced to highlight the performance as well as efficiency of this methodology.

Analysis of Coupled Three-Dimensional Seepage and Temperature Fields in Fracture Network of Rock Mass

2019 ◽  
Vol 17 (04) ◽  
pp. 1950005 ◽  
Author(s):  
Zengguang Xu ◽  
Yang Liu ◽  
Yaping Wang ◽  
Junrui Chai ◽  
Yanlong Li
Keyword(s):  
Rock Mass ◽  
Coupling Effect ◽  
Fractured Rock ◽  
Seepage Flow ◽  
Fracture Network ◽  
Temperature Fields ◽  
Fractured Rock Mass ◽  
Flow Temperature ◽  
Geothermal Resources ◽  
Mass Temperature

The coupling effect of seepage and temperature fields in fractured rock mass is a hot topic in the area of water conservancy, nuclear waste disposal and geothermal resources development. A coupling mathematical model of the seepage, flow temperature and rock mass temperature fields in the fracture network of rock mass is established based on the seepage and temperature interaction. A calculation program is developed and applied to calculate the seepage and temperature fields of the dam foundation of a water conservancy project. The interaction mechanism of the seepage, flow temperature and rock mass temperature fields is analyzed in this paper. Results show that the seepage field largely influences the temperature field, which can provide several suggestions for the deep underground disposal of nuclear waste, geothermal resources development and fractured rock mass in dam foundations. Considering the coupling effect of the seepage, flow temperature and rock mass temperature fields by the fracture network method is necessary.

Construction of 3D Discrete Fracture Network Model using Structural and Hydrogeological Data

2020 ◽  
Author(s):  
Mohammadreza Jalali ◽  
Zhen Fang ◽  
Pooya Hamdi
Keyword(s):  
Rock Mass ◽  
Network Model ◽  
Fracture Network ◽  
Crystalline Rock ◽  
Discrete Fracture Network ◽  
Seismic Survey ◽  
Discrete Fracture ◽  
Dfn Model ◽  
Hydrogeological Data

<p>The presence of fractures and discontinuities in the intact rock affects the hydraulic, thermal, chemical and mechanical behavior of the underground structures. Various techniques have been developed to provide information on the spatial distribution of these complex features. LIDAR, for instance, could provide a 2D fracture network model of the outcrop, Geophysical borehole logs such as OPTV and ATV can be used to investigate 1D geometrical data (i.e. dip and dip direction, aperture) of the intersected fractures, and seismic survey can mainly offer a large structure distribution of the deep structures. The ability to combine all the existing data collected from various resources and different scales to construct a 3D discrete fracture network (DFN) model of the rock mass allows to adequately represent the physical behavior of the interested subsurface structure.</p><p>In this study, an effort on the construction of such a 3D DFN model is carried out via combination of various structural and hydrogeological data collected in fractured crystalline rock. During the pre-characterization phase of the In-situ Stimulation and Circulation (ISC) experiment [Amann et al., 2018] at the Grimsel Test Site (GTS) in central Switzerland, a comprehensive characterization campaign was carried out to better understand the hydromechanical characteristics of the existing structures. The collected multiscale and multidisciplinary data such as OPTV, ATV, hydraulic packer testing and solute tracer tests [Jalali et al., 2018; Krietsch et al., 2018] are combined, analyzed and interpreted to form a combined stochastic and deterministic DFN model using the FracMan software [Golder Associates, 2017]. For further validation of the model, the results from in-situ hydraulic tests are used to compare the simulated and measured hydraulic responses, allowing to evaluate whether the simulated model could reasonably represent the characteristics of the fracture network in the ISC experiment.</p><p> </p><p><strong>References</strong></p><ul><li>Amann, F., Gischig, V., Evans, K., Doetsch, J., Jalali, M., Valley, B., Krietsch, H., Dutler, N., Villiger, L., Brixel, B., Klepikova, M., Kittilä, A., Madonna, C., Wiemer, S., Saar, M.O., Loew, S., Driesner, T., Maurer, H., Giardini, D., 2018. The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment. Solid Earth 9, 115–137.</li> <li>Golder Associates, 2017. FracMan User Documentation.  Golder Associates Inc, Redmond WA.</li> <li>Krietsch, H., Doetsch, J., Dutler, N., Jalali, M., Gischig, V., Loew, S., Amann, F., 2018. Comprehensive geological dataset describing a crystalline rock mass for hydraulic stimulation experiments. Scientific Data 5, 180269.</li> <li>Jalali, M., Klepikova, M., Doetsch, J., Krietsch, H., Brixel, B., Dutler, N., Gischig, V., Amann, F., 2018. A Multi-Scale Approach to Identify and Characterize the Preferential Flow Paths of a Fractured Crystalline Rock. Presented at the 2<sup>nd</sup> International Discrete Fracture Network Engineering Conference, American Rock Mechanics Association.</li> </ul>

A New Method to Determining the Strength Parameters of Fractured Rock Mass

2014 ◽  
Vol 898 ◽  
pp. 378-382
Author(s):  
Yun Hua Guo ◽  
Wei Shen Zhu
Keyword(s):  
Rock Mass ◽  
Mechanical Response ◽  
Fractured Rock ◽  
Fracture Network ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Constitutive Relationship ◽  
Hydropower Station ◽  
Rock Masses ◽  
Fractured Rock Mass

A Hydropower Station is located in the middle reach of the Dadu River in southwest China. The natural slope angles are generally 40°~65° and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. Many abutment slopes were formed during construction of the abutments. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the hydropower station. According to the statistical distribution of joints and fractures at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model which is close to the real state of the fractured rock mass are established by the Monte-Carlo method. The mechanical response of fractured rock masses with different sizes of numerical models is studied using FLAC3D. The REV characteristic scale is identified for rock masses in the slopes with stochastic fracture network. Numerical simulation is performed to obtain the stress-strain curve, the mechanical parameters and the strength of the jointed rock mass in the zone. A constitutive relationship reflecting the mechanical response of the jointed rock mass in the zone is established. The Comparison between the traditional method and the method in this paper has been made at the end.

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