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CONTENTS
Volume 18, Number 1, May20 2019
 

Abstract
In this study, both 2D and 3D failure shapes of rock mass above the water-filled cavity are put forward when the surrounding rock mass cannot bear the pressure caused by the water-filled cavity. Based on the analytical expressions derived by kinematic approach, the profiles of active and passive failure patterns are plotted. The sensitivity analysis is conducted to explore the influences of different rock parameters on the failure profiles. During the excavation of the deep tunnels above the karst cavity, the water table always changes because of progressive failure of cavity roof. Therefore, it is meaningful to discuss the effects of varying water level on the failure patterns of horizontal rock layers. The changing laws of the scope of the failure pattern obtained in this work show good consistency with the fact, which could be used to provide a guide in engineering.

Key Words
water-filled karst cavity; 3D failure mechanism; deep tunnel; pore-water pressure

Address
R. Zhang: 1.) School of Civil Engineering, Central South University, Hunan, 410075, China
2.) Department of Civil and Structural Engineering, University of Sheffield, U.K.

X.L. Yang: School of Civil Engineering, Central South University, Hunan, 410075, China


Abstract
The purpose of this study was to propose a new approach for quantifying in situ rock mass damage, which would include a degree-of-damage and the degraded strength of a rock mass, along with its prediction based on real-time Acoustic Emission (AE) observations. The basic approach for quantifying in-situ rock mass damage is to derive the normalized value of measured AE energy with the maximum AE energy, called the degree-of-damage in this study. With regard to estimation of the AE energy, an AE crack source location algorithm of the Wigner-Ville Distribution combined with Biot\'s wave dispersion model, was applied for more reliable AE crack source localization in a rock mass. In situ AE wave attenuation was also taken into account for AE energy correction in accordance with the propagation distance of an AE wave. To infer the maximum AE energy, fractal theory was used for scale-independent AE energy estimation. In addition, the Weibull model was also applied to determine statistically the AE crack size under a jointed rock mass. Subsequently, the proposed methodology was calibrated using an in situ test carried out in the Underground Research Tunnel at the Korea Atomic Energy Research Institute. This was done under a condition of controlled incremental cyclic loading, which had been performed as part of a preceding study. It was found that the inferred degree-of-damage agreed quite well with the results from the in situ test. The methodology proposed in this study can be regarded as a reasonable approach for quantifying rock mass damage.

Key Words
acoustic emission; quantitative damage; rock mass; wave attenuation; fractal theory; Wigner-Ville distribution; Weibull model

Address
Jin-Seop Kim, Geon-Young Kim and Min-Hoon Baik: Radioactive Waste Technology Development Division, Korea Atomic Energy Research Institute, Daejeon 305-353, Korea

Stefan Finsterle: Finsterle GeoConsulting, Kensington, CA 94708, U.S.A.

Gye-Chun Cho: Department of Civil & Environmental Engineering, Korean Advanced Institute for Science and Technology, Daejeon 305-701, Korea

Abstract
Rockburst disasters pose serious threat to mining safety and underground excavation, especially in China, resulting in massive life-wealth loss and even compulsive closed-down of some coal mines. To investigate the mechanism of rockbursts that occur under a state of static forces, a stress model with sidewall as prototype was developed and verified by a group of laboratory experiments and numerical simulations. In this model, roadway sidewall was simplified as a square plate with axial compression and end (horizontal) restraints. The stress field was solved via the Airy stress function. To track the \"closeness degree\" of the stress state approaching the yield limit, an unbalanced force F was defined based on the Mohr-Coulomb yield criterion. The distribution of the unbalanced force in the plane model indicated that only the friction angle above a critical value could cause the first failure on the coal in the deeper of the sidewall, inducing the occurrence of rockbursts. The laboratory tests reproduced the rockburst process, which was similar to the prediction from the theoretical model, numerical simulation and some disaster scenes.

Key Words
failure; numerical analyses; plasticity; rock; triaxial tests

Address
Jinyang Fan: 1.) State Key Laboratory for the Coal Mine Disaster Dynamics and Controls, Chongqing University, 400044 Chongqing, China
2.) Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d\'Azur, Géoazur, 250 rue Einstein, 06560 Valbonne, France

Jie Chen, Deyi Jiang,Cai Shu and Wei Liu: State Key Laboratory for the Coal Mine Disaster Dynamics and Controls, Chongqing University, 400044 Chongqing, China

Jianxun Wu: 1.)State Key Laboratory for the Coal Mine Disaster Dynamics and Controls, Chongqing University, 400044 Chongqing, China
2.) Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, 78712-0273 Austin Texas, U.S.A.

Abstract
In this paper, it was presented an investigation on the load-settlement and vertical stress analysis of the ring footings on the loose sand bed by conducting both laboratory model tests and numerical analyses. A total of twenty tests were conducted in geotechnical laboratory and numerical analyses of the test models were carried out using the finite element package Plaxis 3D to find the ultimate capacities of the ring footings. Moreover, the results obtained from both foregoing methods were compared with theoretical results given in the literature. The effects of the ring width on bearing capacity of the footings and vertical stresses along the depth were investigated. Consequently, the experimental observations are in a very good agreement with the numerical and theoretical results. The variation in the bearing capacity is little when ri/Ro<0.3. That means, when the ring width ratio, ri/Ro, is equal to 0.3, this option can provide more economic solutions in the applications of the ring footings. Since, this corresponds to less concrete consumption in the ring footing design.

Key Words
model test; numerical analysis; bearing capacity; vertical stress; ring foundation; loose sand

Address
Yakup Turedi and Murat Ornek: Department of Civil Engineering, Iskenderun Technical University, Hatay 31200, Turkey

Buse Emirler: Department of Civil Engineering, Cukurova University, Adana 01950, Turkey

Abdulazim Yildiz: Department of Civil Engineering, Cukurova University, Adana 01330, Turkey

Abstract
Bending moments in the raft of a pile raft system is affected by pile-pile interaction and pile-raft interaction, amongst other factors. Three-Dimensional finite element program has to be used to evaluate these bending moments. Winkler type analysis is easy to use but it however ignores these interactions. This paper proposes a very simplified and novel method for finding bending moments in raft of a piled raft based on Winkler type where raft is supported on bed of springs considering pile-pile and pile-raft interaction entitled as \"Winkler model for piled raft (WMPR)\" The pile and raft spring stiffness are based on load share between pile and raft and average pile raft settlement proposed by Randolph (1994). To verify the results of WMPR, raft bending moments are compared with those obtained from PLAXIS 3D software. A total of sixty analysis have Performed varying different parameters. It is found that raft bending moments obtained from WMPR closely match with bending moments obtained from PLAXIS 3D. A comparison of bending moments ignoring any interaction in Winkler model is also made with PLAXIS-3D, which results in large difference of bending moments. Finally, bending moment results from eight different methods are compared with WMPR for a case study. The WMPR, though, a simple method yielded comparable raft bending moments with the most accurate analysis.

Key Words
pile-raft interaction; pile-pile interaction; Winkler model; bending moment; piled raft foundation

Address
Irfan Jamil and Irshad Ahmad: Department of Civil Engineering, University of Engineering & Technology, Peshawar, Pakistan

Abstract
The effect of microstructure on the permeability of two saturated marine clays was studied through a series of falling head permeability tests and mercury intrusion porosimetry (MIP) tests. The key findings from this experimental study include the following results: (1) The permeability of undisturbed specimens is larger than that of reconstituted specimens at the same void ratio due to different soil fabrics, i.e., the pore size distributions (PSDs), even though they have the similar variation law in the permeability versus void ratio. (2) Different permeabilities of undisturbed and reconstituted specimens at the same void ratio are mainly caused by the difference in void ratio of macro-pores based on the MIP test results. (3) A high relevant relation between Ck (Ck is the permeability change index) and e*10, can be found by normalizing the measured data both on undisturbed or reconstituted specimens. Hence, the reference void ratio e*10, can be used as a reasonable parameter to identify the effect of soil fabric on the permeability of saturated soft clays.

Key Words
undisturbed specimen; reconstituted specimen; permeability; pore size distribution; soil fabric; reference void ratio

Address
Bo Chen and Pan Jin: College of Civil Engineering and Architecture, Quzhou University,78, Jiuhuabei Road, Quzhou, Zhejiang, 324000, P. R. China

De\'an Sun: Department of Civil Engineering, Shanghai University, 99, Shangda Road, Shanghai, 200444, P. R. China

Abstract
Grout injection is mainly used for permeability reduction and/or improvement of the ground by injecting grout material into pores, cracks, and joints in the ground. The oscillatory grout injection method was developed to enhance the grout penetration. In order to verify the level of enhancement of the grout, field grout injection tests, both static and oscillatory tests, were performed at three job sites. The enhancement in the permeability reduction and ground improvement effect was verified by performing a core boring, borehole image processing analysis, phenolphthalein test, scanning electron microscopy analysis, variable heat test, Lugeon test, standard penetration test, and an elastic wave test. The oscillatory grout injection increased the joint filling rate by 80% more and decreased the permeability coefficient by 33–68%, more compared to the static grout injection method. The constrained modulus of the jointed rock mass was increased by 50% more with oscillatory grout injection compared to the static grout injection, indicating that the oscillatory injection was more effective in enhancing the stiffness of the rock mass.

Key Words
oscillatory injection; rock joint grouting; artificial joint; field test

Address
Byung-Kyu Kim, In-Mo Lee, Tae-Hwan Kim and Jee-Hee Jung: School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Abstract
This investigation presented conventional triaxial and creep-permeability tests on sandstones considering thermally-induced damage (TID). The TID had no visible effects on rock surface color, effective porosity and permeability below 300oC TID level. The permeability enlarged approximately two orders of magnitude as TID increased to 1000oC level. TID of 700oC level was a threshold where the influence of TID on the normalized mass and volume of the specimen can be divided into two linear phases. Moreover, no prominent variations in the deformation moduli and peak strength and strain appeared as TID<500oC level. It is interesting that the peak strength increased by 24.3% at 700oC level but decreased by 11.5% at 1000oC level. The time-related deformation and steady-state creep rate had positive correlations with creep loading and the TID level, whereas the instantaneous modulus showed the opposite. The strain rates under creep failure stresses raised 1-4 orders of magnitude than those at low-stress levels. The permeability was not only dependent on the TID level but also dependent on creep deformation. The TID resulted in large deformation and complexity of failure pattern for the sandstone.

Key Words
thermally-induced damage; sandstone; physical changes; creep behavior; permeability

Address
Bo Hu, Sheng-Qi Yang and Wen-Ling Tian: State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering,
China University of Mining and Technology, Xuzhou 221116, P.R. China


Abstract
A free vibration analysis and wave propagation of triclinic and orthotropic plate has been presented in this work using an efficient quasi 3D shear deformation theory. The novelty of this paper is to introducing this theory to minimize the number of unknowns which is three; instead four in other researches, to studying bulk waves in anisotropic plates, other than it can model plates with great thickness ratio, also. Another advantage of this theory is to permits us to show the effect of both bending and shear components and this is carried out by dividing the transverse displacement into the bending and shear parts. Hamilton\'s equations are a very potent formulation of the equations of analytic mechanics; it is used for the development of wave propagation equations in the anisotropic plates. The analytical dispersion relationship of this type of plate is obtained by solving an eigenvalue problem. The accuracy of the present model is verified by confronting our results with those available in open literature for anisotropic plates. Moreover Numerical examples are given to show the effects of wave number and thickness on free vibration and wave propagation in anisotropic plates.

Key Words
wave propagation; functionally graded plate; quasi 3D HSDT

Address
Soumia Bouanati and Kouider Halim Benrahou: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria

Hassen Ait Atmane: 1.)Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2.) Department of Civil Engineering, Faculty of Civil Engineering and Architecture, Univesité Hassiba Benbouali de Chlef, Algérie

Sihame Ait Yahia: 1.) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2.) Department of Civil Engineering, Faculty of Applied Science, Université Ibn Khaldoun, Tiaret, Algeria

Fabrice Bernard: INSA Rennes, Rennes, France

Abdelouahed Tounsi: 1.) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2.) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia

E.A. Adda Bedia: Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, 21589, Saudi Arabia


Abstract
Physical conditions play vital role on the mechanical properties of frozen soil, especially for the temperature and moisture content of frozen soil. Subsequently, they influence the subsidence and stress law of permafrost layer. Taking Jiangcang No. 1 Coal Mine as engineering background, combined with laboratory experiment, field measurements and empirical formula to obtain the mechanical parameters of frozen soil, the thick plate mechanical model of permafrost was established to evaluate the safety of permafrost roof. At the same time, FLAC3D was used to study the influence of temperature and moisture content on the deformation and stress law of frozen soil layer. The results show that the failure tensile stress of frozen soil is larger than the maximum tensile stress of permafrost roof occurring in the process of mining. It indicates that the permafrost roof cannot collapse under the conditions of moisture content in the range from 20% to 27% as well as temperature in the range from -35oC to -15oC. Moreover, the maximum subsidence of the upper and lower boundary of the overlying permafrost layer decreases with the increase of moisture content in the range of 15% to 27% or the decrease of temperature in the range of -35oC to -15oC if the temperature or moisture content keeps consistent with -25oC or 20%, respectively.

Key Words
frozen soil; physical conditions; failure law; subsidence and stress laws

Address
Yaning Zhang and Huayong Lv: 1.) School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
2.) Coal Industry Engineering Research Center of Top-coal Caving Mining, Beijing 100083, China

Zhanbo Cheng: 1.)School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
2.)Coal Industry Engineering Research Center of Top-coal Caving Mining, Beijing 100083, China
3.)School of Engineering, University of Warwick, Coventry CV47AL, U.K.


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