Permanent Lining Research Articles

Application of Hyperstatic Reaction Method for Designing of Tunnel Permanent Lining, Part II: 3D Numerical Modelling

Underground structures often have abrupt changes in structural stiffness or ground conditions such as junctions of tunnels, tunnel portal in slopes, and niches in road tunnels. At these locations, stiffness differences may subject the structure to differential movements and generate stress concentrations. Because of adversity in these issues, they need a three dimensional analysis. This paper proposes a numerical approach to the hyperstatic reaction method (HRM) for three dimensional analysis of permanent tunnel linings. In this paper, three dimensional numerical modelling is performed by considering hyperstatic reaction concepts. Designing is done for Manjil-Rudabar freeway project, Tunnel No. 2. The numerical analyses performed for Operational Design Earthquake (ODE) and Maximum Design Earthquake (MDE) loading conditions. Then interaction diagram between axial force and bending moment used for investigating the capacity of tunnel lining. The numerical results show that although more axial forces are created in tunnel lining for ODE condition, but the points in the P-M diagrams are located in the furthest distance to the diagram border (tunnel supporting system); because of less bending moment in this condition. Therefore, the safety factor in ODE condition is more than MDE condition. This numerical processing presented that the HRM is a proper, fast, and practical method for tunnel designers.

Design of Tundish Ladle Refractories Used by Železiarne Podbrezová Based on Products from Žiaromat

This article describes the innovative design of tundish ladles using refractory products manufactured by Žiaromat a.s. Work on tundish ladle solutions was proposed and realised after 2004, when Žiaromat a.s. was acquired by Železiarne Podbrezova a.s. The acquisition led to innovation and development of new refractory products for tundish linings and their component unit modules. Tundish linings have continuously evolved at the company since 2004, leading to their current form. The permanent lining uses self-flowing low cement castable. Gunning castable is used for repairs. The working tundish lining is created with sprayed mix. High demands are placed on the properties of working linings because they affect not only the operating life of the permanent lining, but also a number of other factors, including heat loss and the micro-purity of cast steel. The current tundish ladle solutions also use castable prefabricates for impact pad, skimmer block and upper and lower nozzles, and fast hardening mastic for joining refractory materials.

Time-dependent ground movements induced by shield tunneling in soft clay: a parametric study

In this work, the effects of coupled hydromechanical (consolidation) processes associated with shield tunneling excavation in soft clays are investigated with particular attention to the prediction of ground movements at the ground surface. A series of 2d FE analyses have been carried out in parametric form in order to investigate the effects of tunnel excavation velocity relative to the soil consolidation rate and the hydraulic boundary conditions at the tunnel boundary. The shield advancement process has been simulated with a simplified procedure incorporating both volume loss and ovalization of the tunnel section. In order to investigate the relative importance of soil consolidation during the excavation process, different characteristic times for the tunnel face advancement and for the consolidation process around the tunnel have been considered, for the two limiting conditions of fully permeable liner and impervious liner. The potential damage induced by the tunnel excavation on existing structures, based on computed ground surface distortions and horizontal deformations, has been found to vary significantly with time during the consolidation process. The results of the simulations allowed to obtain useful information on the minimum tunnel face advancement speed for which the assumption of fully undrained conditions for the soil during the excavations is acceptable, as well as on the speed range for which solving the fully coupled hydromechanical problem is necessary.

Long‐term deformation of mountain tunnel lining and ground under swelling rock condition

AbstractTo monitor deformation in a road tunnel in service, periodical inspections are performed and countermeasures are taken as needed. Cracking of the permanent lining and heaving of the road surface often occur, however, so it is difficult to assess the development of such deformation features from data acquired during the construction and service stages. In this paper, the deformation mechanism and the effect of countermeasures are discussed based on the results of in situ measurements over a six‐year period and of numerical analysis. The relationship between tunnel deformation and the occurrence of defects is examined using boring data. The mechanism of tunnel deformation when the characteristics of the ground indicates a swelling condition, and the relationship between the load acting on tunnel lining and the behaviour of countermeasures are also mentioned.

Sprayed concrete for underground excavations - A status report

Synopsis Commencement of the next phase of the Lesotho Highlands Water Project is a year or so away from becoming reality. Some 50 km of tunnels in the form of access adits, shafts, diversion tunnels, and main waterways will be constructed. Sprayed concrete will form an integral part of the temporary and permanent rock support systems that will be installed. Furthermore, the use of sprayed concrete as a final tunnel lining solution was proposed as a viable alternative to concrete linings in the feasibility studies that preceded the forthcoming implementation phase. The aim of this paper is to make the reader aware of all the sprayed concrete related issues that engineers tend to grapple with during the design and construction of tunnel projects and other underground works. Primarily, these issues would include selection of applicable design parameters, technical specifications, construction application methods, quality control and, most importantly in the context of final or permanent linings, the durability of sprayed concrete. The International Tunnelling Association (ITA) Working Group (WG) 12 has been tasked specifically to publish a set of recommendations on the Quality and Control of the Application of Sprayed Concrete and the Testing of Sprayed Concrete for Durability. These tasks were also further explored at the recent World Tunnel Congress (WTC 2015) that was held in Dubrovnik, Croatia at the end of May 2015.

Outstanding issues in excavation of deep and long rock tunnels: a case study

Excavation of deep and long tunnels faces several distinctive challenges such as unknown geological structures, high groundwater pressure, and high in situ stress, as compared with conventional tunnels. The deep and long Taining tunnel in Fujian Province, South China, was excavated in complex geological settings. This tunnel had to pass through various squeezing fault zones and intensely jointed zones. Large deformations and high-pressure groundwater were frequently encountered during excavation. To predict the potential adverse geological structures, a comprehensive method, which included tunnel seismic prediction and ground penetration radar detection as well as horizontal drilling, was developed. Energy release and pressure reduction, as well as timely sealing, pre-excavation curtain grouting, and radial grouting were adopted to control the high-pressure groundwater. Countermeasures including improvement of support stiffness, double-layered primary support, and pre-support, increase of preset deformation, grouting reinforcement, and timely installation of permanent lining were taken to ensure safe construction in the surrounding rock masses under high in situ stress.

Conservative approach for the treatment of geriatric edentulous patient with grossly resorbed mandibular ridge

The construction of complete denture prosthesis for a geriatric patient with grossly resorbed mandible has always been a challenge to our profession. Poor mandibular ridges accompanied by thin and atrophic oral mucous membrane leads to increased bruising and damage under occlusal loading. Nutrition and diet play an important role in all edentulous patients, but particularly with the geriatric patient. This case report presents a conservative prosthodontic option that includes a modifi ed fi nal impression technique using admixed compound followed by permanent lining of the mandibular denture with a heat-cure silicone-based resilient soft liner along with dietary counseling.

투수시트를 적용하여 잉여수를 탈수한 콘크리트의 강도 특성

투수시트를 적용하여 잉여수를 탈수한 콘크리트의 강도 특성

Design of shaft linings to resist time dependent deformation in evaporite rocks

Potash, a fertiliser currently in demand worldwide, lies beneath beds of salt and other evaporites deep within the ground. The ground support challenge encountered when excavating through these strata is that of time dependent (creep) deformation control. The deformation is radial, causing the shaft excavation to close up over time, eventually loading the permanent lining with the full geostatic pressure and causing lining failure. In order to achieve a significant design life for an economical shaft lining in creeping rocksalt strata, a deformation zone filled with a compressible material is employed between the excavation and permanent lining. This helps resist the ground pressure, and reduce the magnitude and velocity of creep deformation. Optimum lining designs have been developed by predicting the creep deformation at a given time and by considering the behaviour of different compressible materials available to fill the deformation zone. Foamed concrete is the favoured material for an intermediate compressible lining.

Loads on Sprayed Waterproof Tunnel Linings in Jointed Hard Rock: A Study Based on Norwegian Cases

A composite tunnel lining system based on a sprayed waterproofing membrane combined with sprayed concrete is currently being considered for future Norwegian rail and road tunnels. Possible loading of the tunnel linings caused by water pressure is being investigated. This tunnel lining system consists of a waterproof membrane which, during application on the sprayed concrete lining, bonds mechanically to the sprayed concrete on either side. Hence, a continuous, sealing, and non-draining structure from the rock mass to the interior tunnel surface is formed in the walls and crown. Experiences from some successful recent projects with this lining system in Europe are reviewed. However, these experiences are not directly comparable to the Scandinavian hard rock tunnel lining approach, which utilizes a relatively thin sprayed and irregular concrete layer for permanent lining. When considering the sprayed membrane and sprayed concrete composite lining concept, introducing a partially sealing and undrained element in the lining, the experiences with the traditionally used lining systems in Norway need to be reconsidered and fully understood. A review of several hard rock tunnels with adverse conditions, in which the tunnel lining has been subject to load monitoring, shows that only very small loads in the tunnel linings occur. Recent investigations with in situ water pressure testing, including two sites with the composite sprayed membrane in a partially drained waterproof tunnel lining, are discussed. In a case with a cavern located in a hydraulically saturated rock mass subjected to approximately 8 bar hydrostatic pressure, a negative pressure gradient towards the tunnel lining has been measured. The investigation results from the Norwegian test sites indicate that no significant loading of the tunnel lining takes place in a hydraulically saturated rock when applying this composite waterproof tunnel lining in parts of the tunnel perimeter.

Study on Design of Working Shaft for Oil and Natural Gas Pipe in Cross River Slurry Shield Tunnel

In terms of oil and natural gas pipe to be installed in working shaft, and in light of basic dimension of slurry shield machine and its supporting system, required parameters of working shaft, such as its diameter, lining structure, building envelope have been presented in this paper. Meanwhile, the thickness of building envelope and permanent concrete lining for working shaft is also proposed through the analysis of its elastic stability and anti-buoyancy under influence of earth and ground water pressure.

투수시트를 활용한 투수거푸집의 특성

굳지않은 콘크리트에는 항상 일정량의 잉여수가 발생하게 된다. 이러한 잉여수는 콘크리트 내부에서 갇힌공기로 남게 되어 내구성을 저하시키는 요인이 되므로 잉여수를 제거할 수 있다면 구조물의 내구성 향상에 큰 도움이 될 것이다. 기존에 많은 연구가 있었지만 투수시트의 특성에 대한 상세한 검토는 부족한 상태이며, 거푸집의 천공에 따른 시공성 저하는 여전히 의문이 있다. 따라서, 본 논문에서는 투수거푸집 시스템에서 직포 및 부직포 투수시트를 적용할 경우의 기초적인 특성을 실험을 통하여 검토하고 시공성 향상을 위해 거푸집에 천공을 하지 않는 투수거푸집에 대한 연구를 진행하였다. 그 결과 투수거푸집에서 직포와 부직포 투수시트를 사용한 경우 직포의 조밀성 및 부직포의 두께 등에 따라 일부 차이가 있었지만 W/C 감소, 표면 평탄성 증가, 표면부 강도 향상이 있었으며, 시멘트손실은 미미하여 적용성이 우수한 것으로 나타났다. 또한, 투수시트 내부에 탈수된 잉여수의 배수통로를 가지고 있는 배수 부직포 투수시트를 적용한 경우 거푸집에 천공을 하지 않고서도 필요한 탈수성능을 발휘할 수 있어 시공성 향상에 기여할 것으로 판단된다. Fresh concrete has 10~20% extra water in it. As those water remain entrapped air in the concrete, life span of structures is reduced. For that reason, if extra water is eliminated, it will be useful to improve the durability of the structures. Though there were many reports about permeable formwork, the study on the properties of permeable liner itself has been insufficient. In addition, making holes on the form causes lowering of workability. Therefore, this study reviewed the properties of woven and non-woven permeable liner and formwork which has no holes on the form. For the woven and non-woven permeable liner, they showed great application with W/C decrease, lowering roughness, increased compressive strength of surface area and slight loss of cement paste, when the were applied to concrete. In addition, they showed different performance according to the density of woven liner or thickness of non-woven liner. Furthermore, when using the draining non-woven permeable liner which has drainage path inside, concrete surface showed required performance with high workability, without drilling the holes on the form.

A Modified Stress-Displacement Solution for a Pressure Tunnel with a Permeable Liner in an Elastic Porous Medium Based on a New Model

Referring to previous literature, the elastic problem for a deep pressure tunnel with a permeable liner in a saturated elastic porous medium that obeys Terzaghi’s effective stress principle is further investigated. In the analysis, the influences of the changes of the pore water pressure around the opening, the construction sequence of the tunnel, and the interaction between the liner and the surrounding geomaterial on the mechanical response of the tunnel are appropriately considered. Also, the influences of the relative liner thickness and rigidity and the relative distance of the point under investigation from the tunnel axis on the stress-displacement fields for various combinations of the mechanical and geometric parameters are numerically evaluated and discussed. The results indicate that both the support pressure and displacement increase monotonically with increasing liner rigidity and thickness. The influence of the tunnel excavation upon the displacement field is significantly larger than upon the stress field. Either too high or too low values for the relative rigidity and thickness of the liner are unfavorable for structural stability.

Effect of Refractory᾽s Thermal Expansion Coefficient on the Stress Field of the Top of Gasifier

The top of COREX-C3000 gasifier was simulated with a finite element analysis technique. It is studied of the influence of thermal expansion coefficient of the refractories on the temperature field and stress field and the function discipline with different parameters. The results of the simulation indicated that when the coefficient of thermal expansion of working lining and permanent lining are respectively 3.5×10-6/K and 4.5×10-6/K, the distortion and initial stress of the gasifier top are much less.

Effect of Refractory᾽s Thermal Conductivity on the Thermal Stress Field of the COREX Gasifier Top

The top of COREX-3000 gasifier was numerical simulated and investigated the relationship between thermal conductivity and the thermal-stress field. It is concluded that when the thermal conductivity of the working lining and permanent lining is respectively 0.95W / (m•K) and 0.5 W / (m•K), the change rate of the top stress along radical direction is minimum.

Low intensity continuous copper smelting

As current advanced copper smelting processes are judged to be inherently inefficient, a case is made for a radical rethink of more appropriate technology to capture the energy content of high energy sulphides, such as chalcopyrite. Generic melt circulation employing non-oxygen enriched air top blowing in the non-splash mode with permanent linings of solidified copper matte is proposed. Two melt circulation loops are interconnected by a siphon to maintain automatically a continuous flow of high grade matte from the first melt circulation loop with a low copper metal activity into a copper saturated matte loop, which takes the place of traditional Peirce–Smith converters. Copper is removed continuously from the converting loop into two countercurrent packed bed gas–liquid contactors. The first packed bed employs controlled air oxidation of residual sulphur, followed then by the second packed bed using an excess of reformed natural gas for copper deoxidation in advance of continuous anode casting.

Sprayed tunnel linings: a comparison between several reinforcement solutions

In tunnel construction the use of sprayed concrete coupled with steel mesh or added with steel fibres for temporary and permanent linings is a well known and used solution. The paper investigates the use of A/R glass fabric reinforcement for temporary linings in order to estimate its competitiveness in terms of mechanical performance, costs and placing time. The mechanical performance of three different solutions (steel mesh, steel fibre and glass fabric) were compared by means of bending tests on slabs (600 × 600 × 100 mm). After a careful mechanical characterization of the material, the average maximum loads reached in the experimental investigation on slabs are compared with the values predicted by a limit analysis kinematic approach. A proper geometrical description of the specimens was also performed by means of laser-scanner technique in order to justify the scattering induced by the non-uniform thickness of the tested slabs due to a material hardening too fast induced by silicate addition.

Effects of fruit bagging on coloring and related physiology, and qualities of red Chinese sand pears during fruit maturation

Red Chinese sand pears ( Pyrus pyrifolia Nakai) are particular to China. In order to determine the effects of fruit bagging treatments (including bag types, bag removal patterns and dates) on fruit qualities and to understand the mechanism of coloring of red Chinese sand pears, two experiments were carried out. In the first experiment, fruit of ‘Meirensu’ were firstly covered by light-impermeable paper bags with different levels of light permeable liners during their early development stage, then, the whole bag were/not removed or only the outer layer of bags were removed 3, 2 or 1 weeks before harvest. Thus, the fruit were/not totally re-exposed or were under different levels of sunlight transmission (80.31% or 34.71%). Non-bagged fruit were used as the control. Bagging treatments significantly affected the concentration of anthocyanin and the visual qualities of pear fruit. Compared to control, fruit re-exposed totally for 2 or 3 weeks accumulated the largest amount of anthocyanin and fruit receiving 80.31% and 34.71% of sunlight for 1–3 weeks could synthesize a little anthocyanin, indicating that high light intensity is imperative for coloring in red Chinese sand pears. Bagging treatments did not affect contents of total soluble sugars, but decreased organic acids contents in fruit. In the second experiment, fruit of ‘Meirensu’ and ‘Yunhongli No. 1’ were covered with only one type of light-impermeable bag during the early development stage and totally re-exposed after the bag removal 15 days before harvest. Fruit were then collected at different intervals to trace the time-course of coloring, and related physiology and inner qualities. With increasing time after the bag removal, the concentration of chlorophyll, carotenoid, flavonoid and total phenols changed little, but the concentration of anthocyanin accumulated extremely fast within 10 days after the bag removal in both cultivars and thereafter kept constant. ‘Yunhongli No. 1’ had higher anthocyanin contents and lower hue angle than ‘Meirensu’, indicating a higher potential of anthocyanin synthesis. After the bag removal, the sucrose contents and PAL activities increased gradually and correlation analysis revealed that they were highly correlated with anthocyanin accumulation in two cultivars. This study suggests that anthocyanin biosynthesis in red Chinese sand pears is a highly light dependent process and modified by genotypes. Based on the current results, in order to obtain red Chinese sand pear fruit with attractive appearance and good inner qualities, fruit must be covered with light-impermeable bags at the early stage of fruit development and the bag should be removed totally at least 10 days before harvest.

Analytical and numerical study of the effect of water pressure on the mechanical response of cylindrical lined tunnels in elastic and elasto-plastic porous media

This paper revisits the classical problem of excavating a deep cylindrical tunnel in a saturated elastic or elasto-plastic porous ground that obeys Terzaghi's effective stress principle. A generalized form of the classical two-dimensional analytical solution by Lamé for the problem of excavating a cylindrical tunnel in elastic medium subject to axi-symmetric loading is presented. The solution considers the long-term (i.e., post-transient) mechanical effect of changes in pore pressure due to drainage of the ground around the opening on the mechanical response of the tunnel. The proposed solution together with the analytical solution for axi-symmetric loading of an annular ring representing a liner are used to explain the fundamental differences in support loading obtained for various hydro-mechanical conditions. These conditions involve excavating the tunnel with a permeable liner, with and without removal of water from the tunnel, excavating the tunnel with an impermeable liner, with subsequent drainage of water in the ground around the tunnel, etc. The results obtained with the analytical solution are compared with results obtained with the hydro-mechanical option in a commercial finite difference code. The finite difference approach is also used to obtain results and explain the behavior of the tunnel under different hydro-mechanical conditions when the ground is assumed to behave elasto-plastically.

Beneficial Reuse of FGD Material in the Construction of Low Permeability Liners: Impacts on Inorganic Water Quality Constituents

In this paper, we examine the water quality impacts associated with the reuse of fixated flue gas desulfurization (FGD) material as a low permeability liner for agricultural applications. A 0.457-m-thick layer of fixated FGD material from a coal-fired power plant was utilized to create a 708m2 swine manure pond at the Ohio Agricultural Research and Development Center Western Branch in South Charleston, Ohio. To assess the effects of the fixated FGD material liner, water quality samples were collected over a period of 5years from the pond surface water and a sump collection system beneath the liner. Water samples collected from the sump and pond surface water met all Ohio nontoxic criteria, and in fact, generally met all national primary and secondary drinking water standards. Furthermore it was found that hazardous constituents (i.e., As, B, Cr, Cu, and Zn) and agricultural pollutants (i.e., phosphate and ammonia) were effectively retained by the FGD liner system. The retention of As, B, Cr, Cu, Zn, and ammonia was likely due to sorption to mineral components of the FGD liner, while Ca, Fe, and P retention were a result of both sorption and precipitation of Fe- and Ca-containing phosphate solids.