2023-12

University of Duhok (Issue : 2) (Volume : 26)

Geographically, northern Iraq, specifically on the border between Iraq, Turkey, and Iran, is considered a complex geological area consisting of different types of rocks, including sedimentary, igneous, and metamorphic. The height of the mountains in these areas ranges between 2,000 and 4,000 meters. Recently, many changes occurred in the region as a result of natural disasters such as earthquakes, random drilling of wells, and the rapid development of multi-story buildings, which led to many modifications in the geology of the Kurdistan Region. In order to construct any tunnel, the geological plan and profiles should be formed by evaluating the site investigations, and the boreholes should be drilled through the tunnel route. Accurate investigations about the geological structure and nature of the ground can be conducted during the excavation. Also, essential laboratory tests are done on core samples extracted from boreholes along the tunnel. The behaviors of the geological and geotechnical situation of the tunnel are presented, focused on the inlet of the tunnel. This work relied on previous geological investigation surveys that were conducted in the region and related to this subject, the results of geological field mapping and laboratory tests, and the geological and geotechnical parameters used for the design and construction of the tunnel. The best excavation method that can be used in this area is the New Austrian Tunneling Method (NATM), based on the economic and area conditions.

2022-11

University of Duhok (Issue : 1) (Volume : 2660)

Several factors influence the design and construction of twin tunnels, including the distance between the twin tunnels, their location, and the method of construction, among others. Surface and sub-surface structure are affected by tunnel failures. Geotechnical and geological conditions, design, and appropriate construction procedures are the main causes of failures. Understanding the distributions of various stresses on tunnels is important for tunnel stability. After construction, the findings of static and dynamic analysis were concentrated at (stress and displacement). To analyze the behavior of position and construction process of twin tunnels, a series of three-dimensional numerical analysis were performed. New geotechnical software called MIDAS GTS NX (v. 2015) was utilized to model the twin tunnel. Collecting data from a variety of studies on this issue that have been done by prior authors. Linear elastic behavior is one of a well-known method of tunnel analysis and modeling that assumes the material is linear, isotropic, and homogenous. Usually, the first tunnel (for example, the upper tunnel) is construct first, followed by the second. The present study is a particular case, both twin tunnels were excavated at the same time. The purpose of this research is to compare the impacts of tunnel position and construction procedure on the tunnel structure and surrounding ground.

2018-05

Lecture Notes in Civil Engineering, Springer (Volume : 9)

The major design parameters related in tunnel engineering are loads, tunnel dimensions, geological and geotechnical properties of the ground surrounding the tunnel, which controls stresses and deformation of this underground structure. The effects of static loads during tunneling with shield Tunnel Boring Machine (TBM) on the rock mass and segmental concrete lining are considered. Applied static loads are (self-weight, drilling or excavation pressure, jack thrust, shield external pressure and segment external pressure). A comparison of the results of maximum total displacement and principal stresses of soft rock for different tunnel diameters including (D = 4, 6, 8, 10, 12 and 14 m) is performed. Tunnel lining of a circle tunnel were assumed to behave in a simple linear elastic way. Rock mass is assumed to be Isotropic, homogeneous and elastic rock in this modelling. The numerical analysis has been simulated and evaluated for each models separately. The thickness of tunnel lining for all models was assumed as 30 cm. The main concluding points of this study are to analyze the behavior of tunnel lining and the surrounding rock under static loads during the construction processes using numerical modeling.

2018-01

Transactions of the VSB – Technical University of Ostrava, Safety Engineering Series. (Issue : 1) (Volume : 18)

This paper illustrates the use of MIDAS GTS NX to investigate the tunnel’s simulation in order to highlight the effect of static and dynamic load on the behaviour of tunnel to compare this response expressed in terms of displacement and stresses acting on the tunnel and ground. Main tunnel is located in the ground having uniform property throughout its extent, connecting gallery is located perpendicular to the main tunnel, the shotcrete and rock bolts for each tunnel will be installed

2017-01

Research Journal of Mining (Issue : 1) (Volume : 1)

The aim of this paper is to analyse the effects of internal and seismic loads on the stability of circle tunnels at different depth using response spectrum. A full 3D numerical model using the finite element software program MIDAS GTS NX is established. It is often assumed that the effect of earthquakes on underground structures such as tunnels is negligible but the results of this study show that the stress caused by seismic loads can be harmful to the tunnel stability [22].Most of the researcher explains that shallow tunnels suffer higher damage compared to deep structures. During the Shield TBM excavation, it is assumed that the excavation pressure and the Jack thrust are applied on the shield excavation face the Shield external pressure and segment external pressure are applied around that face. This work study a 3D numerical modelling was prepared to simulate the static and dynamic behavior of circular tunnels, were undertaken to investigate the seismic tunnel response conditions to compare the results in the displacement, stresses, forces and bending moments acting in the tunnel lining

2016-01

INTERNATIONAL JOURNAL OF INTERDISCIPLINARITY IN THEORY AND PRACTICE

One of the important tasks in mechanized tunneling using tunnel boring machines is to determine the required face pressure ensuring its stabilization. Calculation methods, which are used to the evaluation of face pressure, differ in their mathematical basis, calculation assumptions, the degree of conservatism of results, required computing time and calculation efficiency, which is a very important factor, particularly when practical problems is solved. Analytical calculations to determine the required stabilizing face pressure mainly rely on limit equilibrium methods and plasticity theory. The “lower bound theory” allows obtaining a statically acceptable solution which, however, is quite conservative. On the other hand, the “upper bound theory” allows obtaining kinematically acceptable non-conservative solution. Although numerical methods (finite element method, etc.) to determine the tunnel face pressure allow modelling this problem with more general calculation assumptions (inhomogeneous environment, etc.) as compared with the above analytical methods, the creation of the model and the actual calculation are more time consuming. The paper presents the comparison of the face pressure values obtained from analytical models of different authors, and from the numerical model, created by the authors of this paper in MIDAS GTS. The paper concludes comparative charts for various computational methods and analysis of the results.

2015-10

GSTF Journal of Engineering Technology (JET) (Issue : 3) (Volume : 3)

The contribution presents the results of 3D-stochastic modelling of slab-subsoil interaction. The cooperation between the centric loaded concrete foundation slab (square shape, dimension 2 m x 2 m, thickness 0.1 m) has been modeled as a contact problem using software MIDAS GTS (based on the finite element method). To take into account the stochastic character of the soil characteristics the stochastic simulation Latin Hypercube Sampling method was used. Four input stochastic parameters of soil were considered - elastic modulus, unit weight, friction angle and cohesion. From the contact modelling viewpoint two variants were modelled – first variant neglected the interface elements on the contact, in the second one the interface elements were involved into the model. The contribution presents the 90% confidence interval for the settlement in the centre of the upper surface of the slab and for the contact stresses below the slab also. The results of experimental measurements were used to the calibration of the model.

2015-07

GSTF Journal of Engineering Technology (JET) (Issue : 3) (Volume : 3)

This paper presents the results of an experimental investigation of the using of carbon fiber reinforced polymer (CFRP) to enhance the high strength reinforced concrete (RC) deep beam in case of creating a circular cutout throughout its web. A set of 5 specimens were grouped and investigated to evaluate the structural behavior in terms of shear strength capacity and deflection. The specimens were 1200mm long with rectangular cross-section of 100x500mm. Two symmetric circular cutouts of 150mm diameter were made at midpoint of each shear span. CFRP strips were installed around the cutouts in three different configurations in order to enhance the cutout zone. The results of this experimental work showed that the diagonal configuration of CFRP strips around the cutout was the best one, as the ultimate shear strength ratio with respect to control solid beam was 0.97, while it was 0.86 for control beam with cutouts. A significant positive effect was observed on the deflection for the beams that enhanced with CFRP strips. Also, CFRP sheet oriented diagonally around cutout was the most appropriate for reducing the deflection.