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Volume 6, Number 3, March 2014

The present paper is dealing with the investigation of the stress field around the infinitely long cylindrical cavity, of a circular cross section, contained in the transversally isotropic elastic continuum. Investigation is based upon the determination of the stress function that satisfies the biharmonic equation, for the given boundary conditions and for rotationaly symmetric loading. The solution of the partial differential equation of the problem is given in the form of infinite series of Bessel's functions. Determination of the stress-strain field around cavities is a common requirement for estimation of safety of underground rock excavations.

Key Words
cylindrical cavity; stress state; rotationally symmetric loading; functions of loading; transversally isotropic medium

(1) Dragan Č. Lukić:
Faculty of Civil Engineering Subotica, University of Novi Sad, Subotica, Serbia;
(2) Aleksandar D. Prokić and Stanko V. Brčić;
Faculty of Civil Engineering, University of Belgrade, Belgrade, Serbia.

Population increase and economic developments can lead to construction as well as demolition of infrastructures such as buildings, bridges, roads, etc resulting in used concrete as a primary waste product. Recycling of waste concrete to obtain the recycled concrete aggregates (RCA) for base and/or sub-base materials in road construction is a foremost application to be promoted to gain economical and sustainability benefits. As the mortar, bricks, glass and reclaimed asphalt pavement (RAP) present as constituents in RCA, it exhibits inconsistent properties and performance. In this study, six different types of RCA samples were subjected classification tests such as particle size distribution, plasticity, compaction test, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. Results were compared with those of the standard road materials used in Queensland, Australia. It was found that material type 'RM1-100/RM3-0' and 'RM1-80/RM3-20' samples are in the margin of the minimum required specifications of base materials used for high volume unbound granular roads while others are lower than that the minimum requirement.

Key Words
recycling; waste concrete; road materials; classification tests

Shiran Jayakody, Chaminda Gallage and Arun KumarSchool of Urban Development, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Australia.

Tire chips and tire chips-soil mixtures can be used as alternative fill material in many civil engineering applications. In this study, the potential benefits of using tire chips as lightweight material to improve the bearing capacity and the settlement behavior of sand slope was investigated experimentally. For this aim, a series of direct shear and model loading tests were conducted. In direct shear tests, the effect of contents of the tire chips on the shear strength parameters of sand was investigated. Different mixing ratios of 0, 5, 10, 15 and 20% by volume were used and the optimum mixing ratio was obtained. Then, laboratory model tests were performed on a model strip footing on sand slope reinforced with randomly distributed tire chips. The loading tests were carried out on sand slope with relative density of 65% and the slope angle of 30

Key Words
tire chips; sand slope; bearing capacity; model test

(1) Mehmet Salih Keskin:
Department of Civil Engineering, Dicle University, Diyarbakir, 21280, Turkey;
(2) Mustafa Laman:
Department of Civil Engineering, Cukurova University, Adana, 01330, Turkey.

The development of transportation in large cities requires the construction of twin tunnels located at shallow depth. As far as twin tunnels excavated in parallel are concerned, most of the cases reported in literature focused on considering the effect of the ground condition, tunnel size, depth, surface loads, the relative position between two tunnels, and construction process on the structural lining forces. However, the effect of the segment joints was not taken into account. Numerical investigation performed in this study using the FLAC3D finite difference element program made it possible to include considerable influences of the segment joints and tunnel distance on the structural lining forces induced in twin tunnels. The structural lining forces induced in the first tunnel through various phases are considerably affected by the second tunnel construction process. Their values induced in a segmental lining are always lower than those obtained in a continuous lining. However, the influence of joint distribution in the second tunnel on the structural forces induced in the first tunnel is insignificant. The critical influence distance between two tunnels is about two tunnel diameters.

Key Words
tunnel; twin tunnels; segmental lining; structural forces; segmental joint; tunnel distance; numerical model

(1) Ngoc Anh Do and Irini Djeran-Maigre:
Laboratory LGCIE, University of Lyon, INSA of Lyon, Villeurbanne, France;
(2) Daniel Dias:
Laboratory LTHE, Grenoble Alpes University, Grenoble, France;
(3) Pierpaolo Oreste:
Department of Environmental, Land and Infrastructural Engineering, Politecnico of Torino, Torino, Italy;
(4) Ngoc Anh Do:
Department of Underground and Mining Construction, Faculty of Civil Engineering, Hanoi University of Mining and Geology, Vietnam.

Soil nailing, as an effective stabilizing method for slopes and excavations, has been widely used worldwide. However, the interaction mechanism of a soil nail and the surrounding soil and its influential factors are not well understood. A pullout model using a hyperbolic shear stress-shear strain relationship is proposed to describe the load-deformation behavior of a cement grouted soil nail. Numerical analysis has been conducted to solve the governing equation and the distribution of tensile force along the nail length is investigated through a parametric study. The simulation results are highly consistent with laboratory soil nail pullout test results in the literature, indicating that the proposed model is efficient and accurate. Furthermore, the effects of key parameters, including normal stress, degree of saturation of soil, and surface roughness of soil nail, on the model parameters are studied in detail.

Key Words
soil nail; hyperbolic stress-strain relationship; pullout test; interface shear resistance

(1) Cheng-Cheng Zhang, Hong-Hu Zhu and Bin Shi:
School of Earth Sciences and Engineering, Nanjing University, Nanjing, China;
(2) Qiang Xu and Hong-Hu Zhu:
State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu, China;
(3) Jian-Hua Yin:
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China.

In this study, in order to evaluate adequacy of considering local site effect, excluding soil-structure interaction (SSI) effects in inelastic dynamic analysis and design of mid-rise moment resisting building frames, three structural models including 5, 10, and 15 storey buildings are simulated in conjunction with two soil types with the shear wave velocities less than 600 m/s, representing soil classes De and Ee according to the classification of AS1170.4-2007 (Earthquake actions in Australia) having 30 m bedrock depth. Structural sections of the selected frames were designed according to AS3600:2009 (Australian Standard for Concrete Structures) after undertaking inelastic dynamic analysis under the influence of four different earthquake ground motions. Then the above mentioned frames were analysed under three different boundary conditions: (i) fixed base under direct influence of earthquake records; (ii) fixed base considering local site effect modifying the earthquake record only; and (iii) flexible-base (considering full soil-structure interaction). The results of the analyses in terms of base shears and structural drifts for the above mentioned boundary conditions are compared and discussed. It is concluded that the conventional inelastic design procedure by only including the local site effect excluding SSI cannot adequately guarantee the structural safety for mid-rise moment resisting buildings higher than 5 storeys resting on soft soil deposits.

Key Words
soil-structure interaction; local site effect; inelastic dynamic analysis; mid-rise moment resisting building frames

Behzad Fatahi, S. Hamid Reza Tabatabaiefar and Bijan Samali:
Centre for Built Infrastructure Research, School of Civil and Environmental Engineering, University of Technology Sydney (UTS), Australia.

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