A simplified approach to directly consider intact rock anisotropy in Hoek——Brown failure criterion

Many rock types have naturally occurring inherent anisotropic planes, such as bedding planes, foliation,or flow structures. Such characteristic induces directional features and anisotropy in rocks＇ strength anddeformational properties. The HoekeBrown （HeB） failure criterion is an empirical strength criterionwidely applied to rock mechanics and engineering. A direct modification to HeB failure criterion toaccount for rock anisotropy is considered as the base of the research. Such modification introduced a newdefinition of the anisotropy as direct parameter named the anisotropic parameter （Kb）. However, thecomputation of this parameter takes much experimental work and cannot be calculated in a simple way.The aim of this paper is to study the trend of the relation between the degree of anisotropy （Rc） and theminimum value of anisotropic parameter （Kmin）, and to predict the Kmin directly from the uniaxialcompression tests instead of triaxial tests, and also to decrease the amount of experimental work. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Limit analysis of supporting pressure in tunnels with regard to surface settlement

The proliferation of Hoek-Brown nonlinear failure criterion and upper bound theorem makes it possible to evaluate the stability of circular tunnels with an original curved collapsing mechanism. The arch effect of shallow circle tunnel is not taken into consideration so that the mechanical characteristics can be easily described. Based on the mechanism, the upper bound solution of supporting pressure of tunnels under the condition of surface settlements and overloads on the ground surface is derived. The objective function is formed from virtual work equations under the variational principle, and solutions are presented by the optimum theory. Comparisons with previous works are made. The numerical results of the present method show great agreement with those of existing ones. With regard to the surface settlement and overloads, the influence of different rock parameters on the collapsing shape is analyzed.

Upper bound limit analysis of roof collapse in shallow tunnels with arbitrary cross sections under condition of seepage force

The analytical solutions for predicting the exact shape of collapse mechanisms in shallow tunnels with arbitrary excavation profiles were obtained by virtue of the upper bound theorem of limit analysis and variation principle according to Hoek-Brown failure criterion. The seepage force was included in the upper bound limit analysis, and it was computed from the gradient of excess pore pressure distribution. The seepage was regarded as a work rate of external force. The numerical results of roof collapse in square and circular tunnels with different rock parameters were derived and discussed, which proves to be valid in comparison with the previous work. The influences of different parameters on the shape of collapsing blocks were also discussed.

THEORETICAL ANALYSIS ON THE LOCAL CRITICAL STRESS AND SIZE EFFECT FOR INTERFACIAL DEBONDING IN PARTICLE REINFORCED RHEOLOGICAL MATERIALS

The mechanisms of interfacial debonding of particle reinforcedrheological materials are studied. Based on an energy criterion, asimple formula of local critical stress for interfacial debonding isderived and expressed in terms of the interfacial energy. Theparticle size effect on interface debond- ing can then be analyzedeasily owing to the fact that critical stress is inverselyproportional to the square root of particle radius. By takingPP/CaCO_3 system as an example, the present energy criterion iscompared with the mechanical debonding criterion, and it is foundthat under the condition that bond strength is equal to matrixstrength and particle radius not over 0.2μm, the mechanicaldebonding cri- terion can be automatically satisfied if the energycirterion is satisfied.

Network Coding-Aware Routing Protocol in Wireless Mesh Networks

Network coding mechanisms, such as COPE, can improve network throughput effectively in Wireless Mesh Networks（WMN）. While the Hybrid Wireless Mesh Protocol（HWMP） is suitable for WMN, its extension with COPE does not provide any added benefits; specifically, HWMP cannot establish paths with more coding opportunities. As a result, the advantages of network coding cannot be exploited sufficiently. This paper proposes improvements upon HWMP with a new, network Coding-Aware routing protocol（CAHWMP） for WMN. In the CAHWMP protocol, we propose a coding criterion based on data streams to devise an algorithm for actively detecting coding opportunities during path discovery. CAHWMP subsequently establishes paths using the codingaware routing metric, which can balance channel resource consumption and the gain due to sharing resources introduced by network coding. Simulation results show that CAHWMP can establish paths with more coding opportunities; as a result, it improves network performance such as network throughput.