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Rock excavation using drill and blast method is commonly used in tunneling world-wide. Drill and blast method has inherent disadvantage of deteriorating surrounding rock mass due to development of a blast-induced damage zone with reduced strength and stiffness parameters and increased permeability. Traditional tunnel analysis adopts same parameters for the entire rock mass, leading to the underestimation of tunnel stability. The blast damage zone with finite thickness is significant in tunnel stability. Tunneling below the groundwater table affects the hydraulic equilibrium. This will, in turn, cause seepage into the tunnel through the pores and discontinuities in the rock masses. The developed seepage force should be considered as an additional body force acting on both damaged and undamaged rock masses. This study presents a new analytical closed-form solution for the determination of stresses, strains, and displacements around a circular deep underwater tunnel with the consideration of the seepage forces and the damaged zone. The solutions are presented for tunnels excavated in pervious elastic–brittle–plastic rock masses with Mohr–Coulomb failure criterion. The damaged zone is assumed to have cylindrical shape with finite radius. The plastic zones may be formed in both damaged and undamaged rock masses, independently. In order to solve the proposed problem, three different paths for plasticity evolution including six different states that can possibly be encountered in the problem are considered. The results indicate that the seepage and the damaged zone have significant effects on the tunnel convergence and the distribution of stresses in the rock mass.

In tunnels, convergences of sidewalls, roof and floor may be different, because of weight of the failed or plastic rock mass. In this paper, a closed-form analytical solution for a deep tunnel excavated in an elastoplastic rock mass is proposed. Using the proposed solution, the effects of the weight of the plastic or failed region developed around the tunnel are investigated. In the proposed method, brittle–plastic or elastic–perfectly plastic behavior and Mohr–Coulomb yield criterion and plastic potential function are used for the ground medium. The gravitational loading is considered as a radial body force being applied to the ground medium. Illustrative examples are given to demonstrate the performance of the proposed method and to examine the effects of the gravity loads. The results obtained by the proposed method show that the gravity loading may affect the tunnel convergence, considerably.

In definition of the ground response curve for a tunnel, convergences of side wall, roof and floor may be different, because of the weight of the failed or plastic rock mass. In this paper, an anal...

The drill and blast method is one of the most widely used techniques for excavation of tunnels in rock masses. The most worrying issue in this method is unfavorable damage induced by blast...

In a pressure tunnel with a permeable lining, development of flow from the tunnel induces seepage stresses in the surrounding ground and the lining. In this paper, an analytical solution for analysis and design of pressure tunnels is presented, based on a generalized effective stress principle. The problem is considered as axial-symmetric, and the lining and the rock mass are assumed to be poroelastic, homogeneous and isotropic. The proposed method covers various types of pressure tunnels, such as unlined, shotcrete lined, concrete lined, reinforced concrete lined and prestressed concrete lined pressure tunnels. For unlined and uncracked lined pressure tunnels, the hydraulic analysis is independent of mechanical responses; thus, closed-form expressions for stresses, strains and pore pressure are derived. On the other hand, in cracked reinforced concrete linings, the development of cracks are considered in the mechanical and hydraulic responses. In this case, the hydraulic and mechanical analyses are coupled; therefore, the hydraulic and mechanical analyses are carried out by an iterative procedure. The applicability of the proposed solution for the design of pressure tunnels is illustrated and discussed by using an illustrative example problem.

The excavation impact (e.g. due to blasting, TBM drilling, etc.) induces an excavation damaged or disturbed zone around a tunnel. In this regard, in drill and blast method, the damage to the rock mass is more significant. In this zone, the stiffness and strength parameters of the surrounding rock mass are different. The real effect of a damage zone developed by an excavation impact around a tunnel, and its influence on the overall response of the tunnel is of interest to be quantified. In this paper, a fully analytical solution is proposed, for stresses and displacements around a tunnel, excavated in an elastic–brittle–plastic rock material compatible with linear Mohr–Coulomb criterion or a nonlinear Hoek–Brown failure criterion considering the effect of the damaged zone induced by the excavation impact. The initial stress state is assumed to be hydrostatic, and the damaged zone is assumed to have a cylindrical shape with varied parameters; thus, the problem is considered axial-symmetric. The proposed solution is used to explain the behavior of tunnels under different damage conditions. Illustrative examples are given to demonstrate the performance of the proposed method, and also to examine the effect of the damaged zone induced by the excavation impact. The results obtained by the proposed solution indicate that, the effects of the alteration of rock mass properties in the damaged zone may be considerable.

In this paper, an analytical method, for calculating seepage induced stresses and displacements in underwater lined circular pressure tunnels, is developed on the basis of a generalized effective stress law. The problem is considered as axisymmetric, and the lining and rock mass are assumed to be elastic, homogeneous and isotropic. The solution accounts for the seepage forces with the steady-state flow and hydro-mechanical pressures between adjacent zones. The proposed method can be applied for the analysis and design of pressure tunnels with concrete lining, prestressed concrete lining, grouted rock mass, as well as for the analysis of pressure tunnels considering the effects of the surrounding fractured or damaged zone. Illustrative examples are given to demonstrate the performance of the proposed method, and also to examine the effect of seepage forces on stability of pressure tunnels. It is concluded that, the classic solutions (Lame’s solution), that is based on considering the internal pressure as a mechanical load applied to the tunnel surface, is not applicable to pervious media and results in unsafe designs.

Drill and blast method is mostly used method for excavation of tunnels throughout the world. This tunneling method involves the use of explosives. Compared with bored tunneling by Tunnel Boring Machine, blasting generally results in the development of a blast-induced damaged zone around the tunnel boundary. Theoretically, the presence of this zone, with its reduced strength and stiffness, will affect the overall performance of the tunnel, as well as its construction and maintenance. In fact, the extent of the damaged zone is finite. However, the effect of this zone is traditionally considered by a damage factor D applied to the entire rock mass surrounding the tunnel. This is a common modeling method which can greatly underestimate the strength and stability of the overall rock mass. In this paper, a semi-analytical solution is proposed for analysis of tunnels considering the damaged zone. The solution is presented for circular tunnels excavated in rock masses obeying a new proposed non-linear strain-softening behavior and the non- linear Hoek–Brown failure criterion. The damaged zone is assumed to have a cylindrical shape with reduced strength and deformability parameters.

Shredded cabbage (50 % v/v) and Daikon radish cubes (57 % v/v) with different salt concentrations (0.15, 0.5, 1, 1.5, and 1.85 %) were heated from 30 to 70 °C in a static ohmic heating cell at different voltages (65, 80, 100, 120, and 135 V) and frequencies (60, 2070, 5030, 7990, and 10,000 Hz) to evaluate their ohmic heating behaviour. Radish heated under 1.5 % salt, 120 V and 7990 Hz or 1 % salt, 135 V and 5030 Hz conditions gave the shortest heating time of 6 min from 30 to 70 °C, and cabbage gave the longest time of 128 min at 0.15 % salt, 100 V, and 5030 Hz. Regression models of heating rate as a quadratic function of the sample temperature gave R2 >0.98. The general trend observed was that the magnitude of the heating rate increased with frequency at high voltage but decreased at low voltage for cabbage, while the opposite trend was observed for radish. Heating was more efficient at higher salt concentration and applied voltage. Radish heated more rapidly than cabbage. A slight slope change was observed in all cases between 50 and 60 °C. The response surface models revealed linear, cross products and quadratic effects to be significant with R 2 over 0.98.

When an opening is excavated below groundwater table, the groundwater flows into the excavated zone and seepage forces apply to the rock mass surrounding the opening. Such seepage forces significantly affect the elasto-plastic responses of the rock mass based on effective stress law. In this regard, it is recognised that the failure criterion of a rock mass is a function of Terzaghi’s effective stress, while its elastic deformations are a function of Biot’s effective stress. Based on this generalised effective stress law, seepage forces arising from the groundwater flow into a cylindrical opening are estimated quantitatively, in the present study. An elastic–brittle–plastic analysis of deep circular openings in an infinite Hoek–Brown medium with consideration of the seepage forces under steady-state flow and the generalised effective stress law is derived. The proposed solution can be effectively used for the actual design of underwater openings below deep groundwater table. It is shown that, in openings ...

An analytical–numerical solution is proposed in this paper for calculating the mechanical and hydraulic characteristics of underwater tunnels, excavated in an elasto-plastic strain-softening and Hoek–Brown rock material considering strain-dependent permeability. The problem is considered with axial-symmetry condition and thus, the initial stress state is assumed to be hydrostatic. Hydraulic and mechanical differential equations governing the plastic and the elastic rock mass around the tunnel are derived. As the derived equations do not have closed-form solutions, a computer program has been prepared, in order to solve the corresponding equations numerically and to examine the analysis. The results obtained are compared with the results obtained using a commercial finite difference code for investigating the effects of utilised simplifying assumptions. The proposed approach is also used to analyse the response of tunnels under different hydro-mechanical conditions. The results show that the proposed solut...

SUMMARY In this study, a simplified analytical closed-form solution, considering plane strain and axial symmetry conditions, for analysis of a circular pressure tunnel excavated underwater table, is developed. The method accounts for the seepage forces with the steady-state flow and is based on the generalized effective stress law. To examine the effect of pore pressure variations and also the boundary conditions at the ground surface, the formulations are derived for different directions around the tunnel. The proposed method can be applied for analysis and design of pressure tunnels. Illustrative examples are given to demonstrate the performance of the proposed solution and also to examine the effect of seepage forces on the stability of tunnels. The simplified analytical solution derived in this study is compared with numerical analyses. It is concluded that the classic solutions (Lame's thick-walled solution), considering the internal pressure as a mechanical load applied to the tunnel surface, are not applicable to pervious media and can result in an unsafe design. Copyright © 2012 John Wiley & Sons, Ltd.

In a drained underwater cavity, seepage forces and pore-water pressure that develop around the cavity may affect the response of the rock mass. In this paper, a fully analytical solution is proposed for analysis of underwater cavities excavated in elastic–brittle–plastic and Mohr-Coulomb rock material, considering the induced seepage forces under steady-state flow. The initial stress state is assumed to be hydrostatic, and the seepage flow is assumed to be radial; thus, the problem is considered axisymmetric. In the proposed solution, in contrast to the failure processes that are represented as a function of Terzaghi’s effective stresses, the induced deformations are considered as a function of Biot’s effective stresses. The proposed solution is used to explain the behavior of cavities under different hydromechanical conditions. The results show that, in the case of drained cavities, seepage flow causes the induced radial displacements to increase and the stability of the cavity to decrease. From ...

The typical food chain steps start at the farm, then go through more or less complex transformation, distribution, and retail before reaching the consumer, each step using natural resources and generating pollution. It is generally believed that processors and transporters are the worst offenders. It is not surprising, therefore, that the first Life Cycle Assessment (LCA) reported came from food processors. But those early studies focused on reducing packaging and energy inputs simply because organic wastes were not considered as serious a threat as in other industrial sectors (e.g., chemical, pulp and paper or mining). However, since the mid-1980s, investigations of environmental impacts of food products became gradually more widespread, and the first published LCAs on food production and processing showed the food chain to be a very large contributor to most LCA impacts parameters. Surprisingly, most impacts are generally located at the farm level, but processing is a major contributor in some sectors. The purpose of this chapter is not to get into highly technical considerations related to LCA, because it is not directed primarily to the LCA practitioner. It is intended rather to arouse the interest of professionals in food processing, such as engineers and technologists, and people working in the food industry who would like to opt for an environmental holistic approach to support decision-making, and for accounting and monitoring purpose using a life cycle perspective. The chapter first discusses some methodological considerations specific to the food processing industry, then lists some limitations and perspective of LCA. The last section will describe briefly the main food transformation processes used, focusing on required natural resources needed (land, water, energy, fertilizers, and pesticides) and on generated outputs (food, by-products and wastes). LCA will help quantify the different impacts and will show the relative influence of each food step in order to provide a clearer global picture of the situation.