scholarly journals Effect of Morphology Parameter Determination on Contact Behavior of Rock Joints under Compressive Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Feng Tian Tang ◽  
Zhi Cheng Tang
Keyword(s):  
Compressive Loading ◽  
Rock Joint ◽  
Jointed Rock ◽  
Rock Joints ◽  
Parameter Determination ◽  
Input Parameters ◽  
Contact Models ◽  
Moment Approach ◽  
Definition Of ◽  
Morphology Parameters

The closure behavior of rock joints is of critical importance to the study of hydromechanical behaviors and geophysical properties of jointed rock masses. Theoretical contact models, used to predict the relations of normal stress versus closure deformation, rely on morphology parameters of rock joint as the input parameters. The relevance of the contact models depends on the inherent assumptions and the accuracy with which the input parameters are determined. In the present study, morphology parameters of three rock joints are determined by the spectral moment approach and peak identification method, respectively. The differences are found to vary significantly depending on the selected method. The phenomenon would be related to the definition of an asperity peak on joint profile. The spectral method only considers the so-called asperity peaks, while the deterministic approach further accounts for the asperity shoulders. Finally, the morphology parameters determined by the two methods are treated as the input parameters of a validated theoretical model. The comparisons between the theoretical curves and the experimental results indicate that parameters determined by the deterministic method would be more reliable.

A Constitutive Model for Rock Joints under Cyclic Loading

2011 ◽  
Vol 243-249 ◽  
pp. 2211-2215
Author(s):  
Dong Mei Yang ◽  
Xiang Bo Qiu
Keyword(s):  
Constitutive Model ◽  
Mechanical Behaviour ◽  
Rock Joint ◽  
Joint Stiffness ◽  
Constitutive Models ◽  
Jointed Rock ◽  
Rock Joints ◽  
Cyclic Loads ◽  
Loaded Rock ◽  
Good Agreement

Cyclic loads are commonly encountered in geotechnical engineering; however most constitutive models do not account for the effect that such loads can have on the mechanical behaviour of soils and rocks. This work is concerned with the behaviour of jointed rock and, as the overall mechanical behaviour of jointed rock is usually dominated by the mechanical behaviour of the joints, it is focused on the behaviour of rock joints under cyclic loads. In particular, an extension of the existed constitutive model for cyclically loaded rock joints is presented. Variations of rock joint stiffness in both the normal and the shear directions of loading due to surface degradation are taken into account. The degradation of asperities of first and second order is considered, while a new relation is proposed for the joint stiffness in the normal direction during unloading. Numerical simulation results show good agreement of model predictions with existing experimental results.

scholarly journals Effects of Gouge Fill on Elastic Wave Propagation in Equivalent Continuum Jointed Rock Mass

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3173
Author(s):  
Ji-Won Kim ◽  
Song-Hun Chong ◽  
Gye-Chun Cho
Keyword(s):  
Wave Propagation ◽  
Rock Mass ◽  
Rock Joint ◽  
Physical And Mechanical Properties ◽  
Jointed Rock ◽  
Rock Joints ◽  
Shear Joint ◽  
Equivalent Continuum Model ◽  
Particulate Soil ◽  
Equivalent Continuum

The presence of gouge in rock joints significantly affects the physical and mechanical properties of the host rock mass. Wave-based exploration techniques have been widely used to investigate the effects of gouge fill on rock mass properties. Previous research on wave propagation in gouge-filled joints focused on analytical and theoretical methods. The lack of experimental methods for multiple rock joint systems, however, has limited the verification potential of the proposed models. In this study, the effects of gouge material and thickness on wave propagation in equivalent continuum jointed rocks are investigated using a quasi-static resonant column test. Gouge-filled rock specimens are simulated using stacked granite rock discs. Sand and clay gouge fills of 2 and 5 mm thicknesses are tested to investigate the effects of gouge material and thickness. Comprehensive analyses of the effects of gouge thickness are conducted using homogeneous isotropic acetal gouge fills of known thickness. The results show that gouge fill leads to changes in wave velocity, which depend on the characteristics of the gouge fill. The results also show that particulate soil gouge is susceptible to preloading effects that cause permanent changes in the soil fabric and contact geometry and that increased gouge thickness causes a more significant stiffness contribution of the gouge material properties to the overall stiffness of the equivalent continuum specimen. The normal and shear joint stiffnesses for different gouge fill conditions are calculated from the experimental results using the equivalent continuum model and suggested as input parameters for numerical analysis.

Analytical Study of Cylindrical P-Wave Propagation across Jointed Rock Masses

2014 ◽  
Vol 988 ◽  
pp. 502-507 ◽  
Author(s):  
Shao Bo Chai ◽  
Jian Chun Li ◽  
Hai Bo Li ◽  
Ya Qun Liu
Keyword(s):  
Wave Propagation ◽  
Rock Joint ◽  
Jointed Rock ◽  
P Wave ◽  
Displacement Discontinuity ◽  
Linear Elastic ◽  
Transmission And Reflection Coefficients ◽  
Conservation Of Momentum ◽  
Elastic Rock ◽  
Transmission And Reflection

According to the displacement discontinuity method and the conservation of momentum at the wave fronts, analysis for cylindrical P-wave propagation across a linear elastic rock joint is carried out. Considering the energy variation for wave propagation in one medium, the wave propagation equation was derived and expressed in an iterative form. The transmission and reflection coefficients are then obtained from the equation. By verification, the results agree very well with those from the existing results.

Analytical Model for Rockfall Protection Galleries - a Blind Prediction of Test Results and Conclusion

2011 ◽  
Vol 82 ◽  
pp. 722-727 ◽  
Author(s):  
Kristian Schellenberg ◽  
Norimitsu Kishi ◽  
Hisashi Kon-No
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Test Results ◽  
Blind Prediction ◽  
Proposed Model ◽  
Input Parameters ◽  
Scale Test ◽  
Definition Of ◽  
Protective Structures ◽  
Cushion Layer

A system of multiple degrees of freedom composed out of three masses and three springs has been presented in 2008 for analyzing rockfall impacts on protective structures covered by a cushion layer. The model has then been used for a blind prediction of a large-scale test carried out in Sapporo, Japan, in November 2009. The test results showed substantial deviations from the blind predictions, which led to a deeper evaluation of the model input parameters showing a significant influence of the modeling properties for the cushion layer on the overall results. The cushion properties include also assumptions for the loading geometry and the definition of the parameters can be challenging. This paper introduces the test setup and the selected parameters in the proposed model for the blind prediction. After comparison with the test results, adjustments in the input parameters in order to match the test results have been evaluated. Conclusions for the application of the model as well as for further model improvements are drawn.

scholarly journals Reply to Nicholson's comment on "Consistent calculation of aquatic gross production from oxygen triple isotope measurements" by Kaiser (2011)

2012 ◽  
Vol 9 (8) ◽  
pp. 2921-2933 ◽  
Author(s):  
J. Kaiser ◽  
O. Abe
Keyword(s):  
Isotope Fractionation ◽  
Direct Calculation ◽  
Original Data ◽  
Delta Method ◽  
Base Case ◽  
Calculation Methods ◽  
Input Parameters ◽  
Net To Gross ◽  
Number Of Publications ◽  
Definition Of

Abstract. The comment by Nicholson (2011a) questions the "consistency" of the "definition" of the "biological end-member" used by Kaiser (2011a) in the calculation of oxygen gross production. "Biological end-member" refers to the relative oxygen isotope ratio difference between photosynthetic oxygen and Air-O2 (abbreviated 17δP and 18δP for 17O/16O and 18O/16O, respectively). The comment claims that this leads to an overestimate of the discrepancy between previous studies and that the resulting gross production rates are "30% too high". Nicholson recognises the improved accuracy of Kaiser's direct calculation ("dual-delta") method compared to previous approximate approaches based on 17O excess (17Δ) and its simplicity compared to previous iterative calculation methods. Although he correctly points out that differences in the normalised gross production rate (g) are largely due to different input parameters used in Kaiser's "base case" and previous studies, he does not acknowledge Kaiser's observation that iterative and dual-delta calculation methods give exactly the same g for the same input parameters (disregarding kinetic isotope fractionation during air-sea exchange). The comment is based on misunderstandings with respect to the "base case" 17δP and 18δP values. Since direct measurements of 17δP and 18δPdo not exist or have been lost, Kaiser constructed the "base case" in a way that was consistent and compatible with literature data. Nicholson showed that an alternative reconstruction of 17δP gives g values closer to previous studies. However, unlike Nicholson, we refrain from interpreting either reconstruction as a benchmark for the accuracy of g. A number of publications over the last 12 months have tried to establish which of these two reconstructions is more accurate. Nicholson draws on recently revised measurements of the relative 17O/16O difference between VSMOW and Air-O2 (17δVSMOW; Barkan and Luz, 2011), together with new measurements of photosynthetic isotope fractionation, to support his comment. However, our own measurements disagree with these revised 17δVSMOW values. If scaled for differences in 18δVSMOW, they are actually in good agreement with the original data (Barkan and Luz, 2005) and support Kaiser's "base case" g values. The statement that Kaiser's g values are "30% too high" can therefore not be accepted, pending future work to reconcile different 17δVSMOW measurements. Nicholson also suggests that approximated calculations of gross production should be performed with a triple isotope excess defined as 17Δ#≡ ln (1+17δ)–λ ln(1+18δ), with λ = θR = ln(1+17ϵR ) / ln(1+18ϵR). However, this only improves the approximation for certain 17δP and 18δP values, for certain net to gross production ratios (f) and for certain ratios of gross production to gross Air-O2 invasion (g). In other cases, the approximated calculation based on 17Δ† ≡17δ – κ 18δ with κ = γR = 17ϵR/18ϵR (Kaiser, 2011a) gives more accurate results.

scholarly journals Experimental Study on Hydromechanical Behavior of an Artificial Rock Joint with Controlled Roughness

2019 ◽  
Vol 11 (4) ◽  
pp. 1014
Author(s):  
Seungbeom Choi ◽  
Byungkyu Jeon ◽  
Sudeuk Lee ◽  
Seokwon Jeon
Keyword(s):  
Rock Mass ◽  
Rock Joint ◽  
Great Influence ◽  
Rock Joints ◽  
In Situ Tests ◽  
Joint Roughness ◽  
Artificial Rock ◽  
Geometric Conditions ◽  
Bedding Planes ◽  
Hydraulic Aperture

Rock mass contains various discontinuities, such as faults, joints, and bedding planes. Among them, a joint is one of the most frequently encountered discontinuities in rock engineering applications. Generally, a joint exerts great influence on the mechanical and hydraulic behavior of rock mass, since it acts as a weak plane and as a fluid path in the rock mass. Therefore, an accurate understanding on joint characteristics is important in many projects. In-situ tests on joints are sometimes consumptive in terms of time and expenses so that the features are investigated by laboratory tests, providing fundamental properties for rock mass analyses. Although the behavior of a joint is affected by both mechanical and geometric conditions, the latter are often limited, since quantitative control on the conditions is quite complicated. In this study, artificial rock joints with various geometric conditions, i.e., joint roughness, were prepared in a quantitative manner and the hydromechanical characteristics were investigated by several laboratory experiments. Based on the results, a prediction model for hydraulic aperture was proposed in the form of ( e h / e m ) 3 = exp ( − 0.0462 c ) × ( 0.8864 ) J R C , which was a function of the mechanical aperture, joint roughness, and contact area. Relatively good agreement between the experimental results and predicted value indicated that the model is capable of estimating the hydraulic aperture properly.

Verification of UDEC Modeling 1-D Wave Propagation in Rocks

2011 ◽  
Vol 90-93 ◽  
pp. 1998-2001
Author(s):  
Wei Dong Lei ◽  
Xue Feng He ◽  
Rui Chen
Keyword(s):  
Wave Propagation ◽  
Analytical Solution ◽  
Transmission Coefficient ◽  
Method Of Characteristics ◽  
Rock Joint ◽  
Rock Joints ◽  
Dynamic Problems ◽  
The Method Of Characteristics ◽  
Elastic Rock ◽  
D Wave

Three cases for 1-D wave propagation in ideal elastic rock, through single rock joint and multiple parallel rock joints are used to verify 1-D wave propagation in rocks. For the case for 1-D wave propagation through single rock joint, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the analytical solution. For 1-D wave propagation through multiple parallel joints, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the method of characteristics. For all these cases, UDEC results agree well with results from the analytical solutions and the method of characteristics. From these verification studies, it can be concluded that UDEC is capable of modeling 1-D dynamic problems in rocks.

scholarly journals Scale Dependence of Waviness and Unevenness of Natural Rock Joints through Fractal Analysis

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Yingchun Li ◽  
Shengyue Sun ◽  
Hongwei Yang
Keyword(s):  
Surface Roughness ◽  
Rock Joint ◽  
Fractal Dimensions ◽  
Window Size ◽  
Scale Dependence ◽  
Rock Joints ◽  
Joint Surface ◽  
Triangular Prism ◽  
Natural Rock ◽  
Waviness And Unevenness

The scale dependence of surface roughness is critical in characterising the hydromechanical properties of field-scale rock joints but is still not well understood, particularly when different orders of roughness are considered. We experimentally reveal the scale dependence of two-order roughness, i.e., waviness and unevenness through fractal parameters using the triangular prism surface area method (TPM). The surfaces of three natural joints of granite with the same dimension of 1000 mm×1000 mm are digitised using a 3D laser scanner at three different measurement resolutions. Waviness and unevenness are quantitatively separated by considering the area variation of joint surface as grid size changes. The corresponding fractal dimensions of waviness and unevenness in sampling window sizes ranging from 100 mm×100 mm to 1000 mm×1000 mm at an interval of 100 mm×100 mm are determined. We find that both the fractal dimensions of waviness and unevenness vary as the window size increases. No obvious stationarity threshold has been found for the three rock joint samples, indicating the surface roughness of natural rock joints should be quantified at the scale of the rock mass in the field.

Numerical Modeling of Jointed Rock Under Compressive Loading Using X-ray Computerized Tomography

2015 ◽  
Vol 49 (3) ◽  
pp. 877-891 ◽  
Author(s):  
Qinglei Yu ◽  
Shengqi Yang ◽  
P. G. Ranjith ◽  
Wancheng Zhu ◽  
Tianhong Yang
Keyword(s):  
Numerical Modeling ◽  
Computerized Tomography ◽  
Compressive Loading ◽  
Jointed Rock ◽  
X Ray
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