توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Effects of Pore Pressure and Hydraulic– Mechanical Coupling on Stability of Under Ground Water Tunnels
نویسنده(ها): ،
اطلاعات انتشار: اولین کنفرانس بین المللی و سومین کنفرانس ملی سد و نیروگاههای برق آبی، سال
تعداد صفحات: ۱۳
In this paper an analytical–numerical method for hydraulic and mechanical analyses of tunnels below groundwater table excavated in a strain–softening Hoek–Brown rockmass is proposed. The problem is considered as axisymmetric, i.e. the initial stress state is assumed to be hydrostatic. In this method, the seepage body force and thesecondary permeability of rock mass due to the mechanical– hydraulic coupling are taken into account. As the strain dependent permeability and a nonlinear behaviormodel for the rock mass is used, the derived differential quations should be solvednumerically. Thus, the numerical method (the finite difference method) is utilized for these equations. The influence of seepage and the hydro–mechanical coupling, on the elasto–plastic solutions is also examined<\div>

۲Accurate Survay Effect of Jointing On Bearing Capacity for Rock Foundation (A Case Study of Safa Dam in Kerman Province, Iran)
اطلاعات انتشار: هفتمین کنفرانس بین المللی پیشرفتهای علوم و تکنولوژی، سال
تعداد صفحات: ۹
The effect of discontinuities in bearing capacity of the rockmass depends on its orientation, surface conditions, and infillings. This study was conducted to calculate bearing capacity of the safa dam's rockmass using analytical and numerical techniques. In analytical technique using Serrano & Olalla method and in numerical technique using ABAQUS software. In per second methods, stress analysis was performed in two states. In one state, assuming a continuous environment for the bedrocks, the analysis was performed for the bedrock considering rock mass geotechnical parameters. In the second state, the analysis was performed considering two joint set in the bedrock as weak close planes with respect to the geotechnical of the intact rock. For these two states, the stress and safety factor, compressional and tensional, in turn, ultimate and allowed bearing capacities were estimated. Finally, the ultimate and allowed bearing capacities obtained through the different approaches were compared. The difference between the obtained allowed bearing capacities in two mentioned states implies the considerable effect of joints and cracks conditions on bearing capacity of the foundation in this project.<\div>

۳An Elasto–Plastic Model for Analysis of Underwater Tunnels, Excavated in a Strain–Softening Hoek–Brown Rock Mass
اطلاعات انتشار: هفتمین کنفرانس بین المللی پیشرفتهای علوم و تکنولوژی، سال
تعداد صفحات: ۹
In this paper, an analytical method for the analysis of underwater tunnels in axisymmetric plain strain conditions is presented. A new technique has been proposed using finite difference numerical method for calculating the distribution of pore water pressure as well as stress and strain around a circular tunnel excavated in rock mass. Behavior of the rock mass around the tunnel is considered elasto–plastic in strain–softening model. Meanwhile, the effects of increment in elastic strain within plastic zone and dilatancy angle are taken into account. Seepage flow and secondary permeability due to hydraulic–mechanical coupling have also been considered in the plastic zone.A more accurate model has been provided for calculating the distribution of pore pressure in the elastic zone by modifying the previous models. Since governing equations do not have a closed form solution, a computer program has been prepared based on the proposed model. Accuracy and applicability of this method have been investigated with an example.<\div>

۴Estimation of Creep Deformations in Circular Tunnels Considering Elasto–Plastic Behavior
اطلاعات انتشار: هفتمین کنفرانس بین المللی پیشرفتهای علوم و تکنولوژی، سال
تعداد صفحات: ۷
By excavating an underground space, the state of stress and displacement in the surrounding medium are changed in comparison to the initial state. As time passes, the variation of the displacement mainly depends on the creep behavior of the hosting rock mass. In this paper, an elasto–viscoplastic creep model is proposed. In the proposed model, the main purpose is to consider plastic deformations increasing with time. The viscoplastic behavior of rocks plays a key role in the tunneling works, especially for deep tunnels subjected to large in situ stresses. Using non–linear Hoek–Brown yield criterion in a creep model is the other important aim of this paper, which eliminates estimating specific equivalent Mohr–Coulomb strength parameters from the Hoek–Brown parameters. The equations related to the proposed model are derived and then, to reach a numerical solution of the equations, the finite difference software (FLAC(2D)–FISH Editor) is used. The application of the proposed model is illustrated through an example analyzed numerically using the finite difference software FLAC(2D).<\div>

۵Rock Slope Stability: Comparison of Geogrid Box Method with Conventional Reinforcement Methods
اطلاعات انتشار: هفتمین کنگره ملی مهندسی عمران، سال
تعداد صفحات: ۸
This research sets out to review critically the current slope stability methods including geometry modification, rock bolt and wire mesh and to offer geogid box method as an alternative toconventional rock slope stability methods. Achieving the objectives of this research, the limit equilibrium (LE) and finite element (FE) analysis were conducted to predict the response of rock slopes to a broad range of possible scenarios, namely dry, half–saturated and saturated states; as wellas, static, quasi–static and dynamic conditions. The results indicate that the factors of safety obtainedthrough the geogrid box method are higher than those obtained through conventional reinforcement methods.<\div>

۶Analysis of the impact of various factors on ground settlement profile due to excavation Twin tunnels
نویسنده(ها): ،
اطلاعات انتشار: دومین کنفرانس بین المللی یافته های نوین پژوهشی در مهندسی عمران، معماری و مدیریت شهری، سال
تعداد صفحات: ۱۰
Constant growing of cities has caused many problems in transportation, one of the greatest ways to overcome this problem, is using underground transportation system. In urban areas, regarding the shallow depth of tunnels, the ground often consists of soil, which design and calculation of it is very important, because building new tunnels near the existing buildings is inevitable. Generally excavation tunnels in any depth of soil causes a change in the stress distribution system followed by tunnel opening divergence leading to distortions in the ground surface. In this paper the settlement resulting from the excavation of a twin tunnel is investigated using the Isfahan subway twin tunnel data and finite difference software such as Flac 3D and Flac 2D. Also, to better compare different methods of tunnel excavation, the effects of factors such as two tunnels excavation delay, circular cross–section of the tunnel and various elastic modules of the surrounding soils of the tunnels are assessed as well. The results showed that the settlements calculated by Flac 3D and Flac 2D have a 6% and 9% difference with the real values respectively. Investigating two tunnels’ excavation delay showed that simultaneous excavation increases the settlement by 3%. It was also observed that the settlement decreases by increasing the modulus of elasticity and for all the values, the ratio of the settlement of the surface ground on the top of the tunnel center to the settlement of the tunnel crown is constant and equal to 0.7.<\div>

۷Analysis of Circular Reinforced Tunnels by Analytical Approach
نویسنده(ها): ،
اطلاعات انتشار: Journal of the Structural Engineering and Geotechnics، اول،شماره۲،۲۰۱۱، سال
تعداد صفحات: ۱۲
This paper addresses the problem of quantifying the mechanical contribution of rockbolts installed systematically around tunnels (regularly spaced around the tunnel) excavated in rock masses. Assuming that the mechanical contribution of grouted rockbolts is that of increasing internal pressure within a broken rock mass, a new procedure for computation of ground response curves for a circular tunnel excavated in strain softening material and then reinforced with systematically active grouted rockbolts is presented. In this work, the equation of the ground response curve for a tunnel which has been reinforced with passive grouted rockbolts is also derived. The proposed model allows one to take into account the effect of the distance of the bolted section to the tunnel face, the effect of increasing rockbolts spacing, the influence of increasing pretension load in calculating of the ground response curve, and the effect of increasing the cross–section area of rockbolts. The results show that decreasing rockbolts spacing increases the support system stiffness rather than preloading of them.
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