Analysis of shotcrete lining of underground tunnels

Shotcrete is a process where concrete is projected or "shot" under pressure, using a feeder or a "gun" onto a surface to form structural shapes including walls, floors, and roofs. The surface can be wood, steel, polystyrene, or any other surfaces that concrete can be projected onto. The surface can be trowel led smooth while the concrete is still wet. Shotcrete has high strength, durability, low permeability, excellent bond, and limitless shape possibilities. These properties allow shotcrete to be used as a structural material in most cases. Although the hardened properties of shotcrete are similar to conventional cast-in-place concrete, the nature of the placement process provides additional benefits, such as excellent bond with most substrates and instant or rapid capabilities, particularly on complex forms or shapes. In addition to building homes, shotcrete can also be used to build pools. The practice of underground tunneling shows that the degree of stability of tunnels is dependent on the state of the soil, rock mass, and shotcrete around the tunnel contour. The development in the urban or suburban areas leads to the construction of tunnels in all kinds of soil and rock. Meanwhile, the construction of tunnels in shallow depth or soft soils causes the ground to displace. The determination of soil and rock mechanical properties to assess the stability of New Austrian Tunnelling Method (NATM) tunnels and design the support system is one of the most important steps in tunnelling. This paper provides information pertaining to the safety and increase the stability of NATM tunnel before, during and after the operation of the tunnel. Therefore, the shotcrete process is a recognized method for cemented sandy silt stabilization, with the aid of high pressure shot concrete to increase the stability of tunnels

A study of the weathering of the Seremban granite

This paper presented the weathering profile, modulus of elasticity and compressive strength of weathered granite in Seremban, Malaysia. The granite of Seremban is found to exhibit a full range of weathering grades. With increased weathering, the modulus of elasticity and uniaxial compressive strength of the granite is found to decrease

Geopolymer vs ordinary portland cement: review of the 3-d printing of concrete

Due to the need of the construction industry to implement structures with special and complex designs, mass customization with the lowest cost, especially reducing the labor cost as well as the amount of waste and materials used, the use of concrete 3D printing can be the appropriate solution to these requirements fulfill these options. As a result, a comprehensive and practical study of the major 3D printing methods and their development in the construction industry was carried out in this study. In addition, the use of OPC-based materials and geopolymer-based materials was reviewed and compared due to the development of the materials industry and the advantages and disadvantages of using different types of cementitious materials in the 3D printing of concrete

Effect of cement on compressibility and microstructure of tropical peat

Peats are geotechnically problematic soil due to their high compressibility and low shear strength. Cement is widely used for the stabilization of peat by deep mixing method (DMM). This paper presents the results of the model study of compressibility property of peats stabilized with cement columns formed by DMM. The results of consolidation test, scanning electron micrographs (SEM) and energy dispersive x-ray spectrometer (EDX) showed that the compressibility of peats can be improved significantly by the installation of cement stabilized columns. The amount of cement used to form the column was observed to influence the engineering behaviour of treated tropical peats and it had more influence on sapric peat than on hemic and fibrous peats

Optimization of Invasive Weed for Optimal Dimensions of Concrete Gravity Dams

Dam construction projects among the most extensive and most expensive projects are considered. It is always appropriate and optimal for such concrete structures to reduce the volume of concrete and consequently reduce construction costs is essential. In this study, invasive weed optimization software GNU octave, dimensions of concrete gravity dam Koyna located in India optimized stability constraints. For this purpose, a cross-section with a length unit consists of eight geometric parameters as input variables, and other geometric parameters were defined using these variables. The result showed that invasive weeds are well-optimized dimensions of the dam as the volume of concrete in the construction of the dam at the current level measures 3633 cubic meters that optimal dropped 3353 cubic meters, which is a mean of 7.7% of the value of the objective function (the volume of concrete in dams) is reduced. This amount of concrete decreased the construction of the dam, saving the cost and is more economical

The effect of soil cohesion and friction angles on reverse faults

Severe faults have caused many earthquakes around the world throughout history. More recently, earthquakes have occurred in Taiwan, China (Chi-Chi fault), and elsewhere, causing loss of lives and destroying many buildings and structures. These tectonic movements have gained attention from engineers, and in the past 15 years, the focus has been on faulting mechanisms. In this study, a physical model (1 g) was fabricated and used to evaluate the impact of a reverse fault in a field with a tunnel. In the 1 g model, researchers installed additional gauges on the tunnel, so that all the displacements could be adjusted, and all the responses could be monitored during faulting. An experimental study of various soil properties (cohesion and friction angles) in reverse faults on the tunnel lining were carried out and are described herein. A comparison of results for different levels of soil cohesion revealed that it can dramatically reduce the displacement by as much as 40%, and that friction angles of 27° can record approximately 60% more displacements than at 37°. Furthermore, a comparison of fault angles of 30° and 60° indicates that the displacements can be different by more than 43% in cohesionless soil and about 64% for a friction angle of 27°

Construction regulations along metro alignment

The purpose of the current study was to determine construction regulations along subway alignment. The study aims to expand the underground tunnelling technique, comparison of different tunnel excavation techniques, tunnelling machines. The aim of this study was to evaluate and validate construction hazards and mitigation measures, shafts sinking, tunnel, excavated material determination. In recent years, there has been an increasing interest in subway construction. The paper opted for an exploratory study using different method for metro tunnel construction regulation. In this paper we argue about tunnel and station compatibility, TBM drive before station construction, TBM drive after station construction, construction cost and duration comparison for different tunnel construction techniques, segment plant design, segment structural design, dump site, safety factors, affecting the segment plant design are some approach to achieve construction regulations along subway alignment. One of the more significant findings to emerge from this study is that this paper is so useful for tunnel designer and also the paper provides tunnelling methods, ground and underground conditions, methods of support and stabilizations, tunnelling machine, advantages and disadvantages of methods and materials are discussed. The current investigation was limited by empirical method for construction tunnel alignments. Because of the chosen research approach, the research results may lack generalisability. Therefore, researchers are encouraged to update the proposed propositions further. The implications of the anticipated ground conditions on machine and ground support selection as well as the field observation of the actual conditions will be discussed in this paper. Designing tunnels and subway stations are usually based on underground investigations. More broadly, the paper includes implications for the development of tunnels and underground designing also designers need to determine standards and coeds. This study is a precise and concise construction regulation along metro alignment. The present study confirms previous findings and contributes additional evidence that suggests that there are many studies conducted using laboratory and field test results for tunnel structures. This paper fulfils an identified need to study construction regulations along metro alignment can be enabled

Subway station seismic consideration based on geotechnical study: a case study approach

Iran is a vast country with 1.6 million square kilometer area and more than 70 million inhabitants. Tehran, the capital of Iran, together with its satellite townships is home to more than one sixth of the country's population which make over 13 million, and mostly make motorized daily journeys. This work is based on the case study geotechnical investigation of a metro station in Tehran. The access gallery and tunnel inter-section problem is very sensitive and dangerous in critical zones and the necessity of the provision of tunnel lining has been discussed in this paper. This study is a concise case study which highlights the important soil parameters for designing of deep and shallow tunnels and substations. It shows the critical area for performance of tunnel intersection of and access galleries and the method to avoid collapse of the tunnel and access galleries while tunneling with a high safety. If boring of the access gallery and tunnel station, is made at the same time or the boring of the access gallery is carried out before the tunneling lining, the tunnel will be overburdened with loads leading to weakening of the access galleries crown, and its immediate collapse. One of the objectives of this paper is defining the seismic modeling of tunnel. Specifying the differences in seismic modeling using two softwares, PLAXIS and FLAC is another aim of this paper

Risk management overview of tunnels using numerical modeling

Purpose: The purpose of this paper is to introduce the numerical methods in tunnel engineering and their capabilities to indicate the fracture and failure in all kinds of tunneling methods such as New Austrian Tunneling Method, tunnel boring machine and cut-cover. An essential definition of numerical modeling of tunnels to determine the interaction between geo-material (soil and rock) surrounding the tunnel structure is discussed. Design/methodology/approach: Tunnel geo-material (soil and rock) interaction requires advanced constitutive models for the numerical simulation of linear, nonlinear, time-dependent, anisotropic, isotropic, homogenous and nonhomogeneous behaviors. The numerical models discussed in this paper are developed in finite element method (FEM), finite deference method (FDM), boundary element method and discrete element method and these tools are used to illustrate the behavior of tunnel structure deformation under different loads and in complicated conditions. The disadvantage of this method is the tunnel lining assumed an independent structure under fixed load which is unable to model soil-lining interaction. Predicting the effect of all natural factors on tunnels is the most difficult method. The above-mentioned numerical methods are very simple and quick to use and the results are conservative and practical for users. One of the most significant advantages of the numerical method is in predicting the critical area surrounding the tunnel and the tunnel structure before making the tunnel construction due to different loads. Findings: Numerical modeling is used as control method in reducing the risk of tunnel construction failures. Since some factors such as settlement and deformation are not completely predictable in rock and soil surrounding the tunnel, using numerical modeling is a very economical and capable method in predicting the behavior of tunnel structures in various complicated conditions of loading. Another benefit of using numerical simulation is in the colorful illustrations predicting the tunnel behavior before, during and after construction and operation. Originality/value: There are not many conducted studies using numerical models to tunnel structures that estimate the critical zones. As some of the methods available have limitation in simulating and modeling the whole tunnel design factors, numerical modeling seems to be the best option, because it is fast, economical, accurate and more interesting in predicating critical zones in tunnel. However, what softwares predict are not always the same as real ground nature conditions in which there is tunnel

Design criteria of subway tunnels

This paper is dedicated to present criteria and rules for design of metro path including tunnel geometrical sections and choosing parameters, loads applied to tunnels, fundamentals of static and seismic analysis, and primaries of structural design, structural joints, and control criteria, behavior measuring and sensitive devices. Design criteria of shallow and semi-deep tunnels are presented in this paper