scholarly journals SHEARD CLAYEY SHALES OF FLYSCH. THEIR BEHAVIOR DURING THE EXCAVATION OF THE DIVERSION TUNNEL OF GADOURA DAM IN RHODES (GREECE)

2004 ◽  
Vol 36 (4) ◽  
pp. 1773
Author(s):  
Π. Μαρίνος ◽  
T. Χριστοδουλοπούλου ◽  
Β. Περλέρος
Keyword(s):  
Engineering Geology ◽  
Groundwater Table ◽  
Fiber Glass ◽  
Pressure Relief ◽  
Tunnel Face ◽  
Diversion Tunnel ◽  
Geotechnical Parameters ◽  
Temporary Support ◽  
The Face ◽  
Geological Formation

This paper deals with the particular geological-geotechnical conditions that predominate in the construction area of the diversion tunnel of Gadoura dam (in Rhodes) and the way these conditions were taken under consideration during the construction of the temporary support system. The intensely sheared geological formation of flysch that is encountered in the construction area of the tunnel, is characterised by the predomination of clayey shales against siltstones and other lithological members (sandstone horizons, occasional gypsum lenses and limited limestone intercalations) and by the absence of a groundwater table. The main features of this argillaceous facies of flysch are: the schistosity-foliation due to tectonic compression and the chaotic structure, in places where it occurs in alternations with sandstone and siltstone, due to differential deformation of the strata. As a result, squeezing phenomena occured during the tunnel advance. According to the engineering geology model, which was proposed after the first excavation works, sheared clayey shales compose a "soil type" rockmass specified by very low geotechnical parameters (GSI=15-20, ITIJ=6, Oci=5-10 MPa, E m =30r>500 MPa, c'=150+250 kPa, φ=13°+18° και oCm=0,400,60 MPa). Performing a declined surface on the tunnel face, shotcrete and fiber glass anchoring, this weak rockmass was behaved well on the face. The applying of a light forpoling system has contributed to the stabilization of the face and of the cylindrical "core" of rock immediately ahead of the advancing face, although it was a conservative measure. Steel ribs incorporated into shotcrete were used for the support of the tunnel behind the face. Lateral forces were further stabilized by the closure of the invert using reinforced concrete. Weep holes were locally opened for the pore pressure relief.

scholarly journals A New Evaluation Method for the Uniaxial Compressive Strength ahead of the Tunnel Face Based on the Driving Data and Specification Parameters of TBM

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Yuexiu Wu ◽  
Chishuai Ma ◽  
Xianjun Tan ◽  
Dianseng Yang ◽  
Hongming Tian ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Evaluation Method ◽  
Hard Rock ◽  
Rock Type ◽  
Soft Rock ◽  
Tunnel Face ◽  
Diversion Tunnel ◽  
Proposed Model ◽  
High Prediction

Uniaxial compressive strength (UCS) is a very important fundamental mechanical parameter for TBM construction. In this work, a predictive model of UCS was proposed according to the TBM parameters including torque, penetration, cutter number, and cutter diameter. The parameter of the new proposed model was established by fourteen existed TBM tunnels’ construction data. To describe the relationships of UCS with PLSI of the Murree tertiary hard rocks, regression analyses have been conducted and a fitting equation with high-prediction performance was developed. Validation from the data of Neelum–Jhelum (NJ) TBM diversion tunnel were carried out. The absolute errors between predictive UCS and experimental UCS were presented. Through comparison, it can be concluded that the proposed calculation equation of UCS has a high accuracy for a certain rock type with UCS from 50 MPa to 200 MPa. For special hard rock or soft rock, a new calculation equation between UCS and TBM parameters should be studied furthermore.

Liquefaction Susceptibility Assessment Using Geotechnical and Geological Manners of Northern Thailand

2020 ◽  
Vol 11 (2) ◽  
pp. 50-71
Author(s):  
Yayat Kusumahadi ◽  
Suttisak Soralump ◽  
Montri Jinagoolwipat
Keyword(s):  
Spectral Analysis ◽  
Groundwater Table ◽  
Soil Resistance ◽  
Susceptibility Assessment ◽  
Liquefaction Potential ◽  
Liquefaction Susceptibility ◽  
Site Investigations ◽  
Geological Formation ◽  
Soil Site ◽  
High Seismicity

Soil site investigations such as boring logs, basic soil properties, spectral analysis of surface wave, and the examinations of geologic and geomorphologic were performed in Mae Lao area to investigate the susceptibility of liquefaction after the 6.2 Mw Chiang Rai Earthquake 2014. The study area was found to lay on a complex geological formation and geotechnical behavior with a condition of the high groundwater table. Being located on a high seismicity area (intensity V-VII Mercalli) governs the study area as a concern for high liquefaction hazards. Liquefaction susceptibility-based compositional criteria, soil resistance, and geologic criteria have been established, and consequently, the character of liquefaction potential is defined.

scholarly journals Hydro-mechanical response of excavating tunnel in deep saturated ground

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Simon Heru Prassetyo ◽  
Marte Gutierrez
Keyword(s):  
Pore Pressure ◽  
Mechanical Response ◽  
Coupled Model ◽  
Computer Code ◽  
Lagrangian Analysis ◽  
Tunnel Face ◽  
Tunnel Support ◽  
Steady State Condition ◽  
Mechanical Unloading ◽  
The Face

AbstractExcavating a tunnel in a deep and saturated ground affects the short- and long-term hydro-mechanical (H-M) response in the ground surrounding the opening. However, the interactions between transient pore pressure behavior and the corresponding deformation and stresses in the ground ahead of and behind the tunnel face are still not well understood. This paper investigates the transient H-M response of excavating a tunnel in a deep and saturated ground using a two-dimensional axisymmetric coupled model in the computer code Fast Lagrangian Analysis of Continua (FLAC). The tunnel was advanced in a stepwise excavation procedure consisting of undrained excavation and drained consolidation until the final tunnel face was reached. The final excavated face was then left to consolidate toward the steady-state condition. The main results of the paper are as follows: (1) when simulating a tunnel excavation in deep saturated ground using the convergence-confinement method, the unloading factors should be nonlinear and should consists of the mechanical unloading factor in the form of excavation force and the hydraulic unloading factor in the form of excavation pore pressure. These two unloading factors are necessary because the induced H-M response near the tunnel face is a rather transient response instead of an initial or final response. Moreover, it is observed that the pore pressure dissipation is not linear either with time or with distance to the tunnel face, (2) a relationship between the unloading factors and the distance to the tunnel face should then be established. This relationship is vital because it will provide the timing for tunnel support installation, and (3) the extrusion and the convergence of the advance core could be related through the proposed equations capturing the linear relationships between the face extrusion and its convergence as well as between the core extrusion and its pre-convergence. Through these relationships, the tunnel engineer may be able to estimate the magnitude of the deformation ahead of the face, which will subsequently allow control of the deformation behind the face.

Detailed hydrogeological studies are often necessary to assess the water balance of a watershed. Understanding the hydrogeological structures makes it possible to establish the watershed boundaries, to verify the congruence of the watershed hydrographic boundaries and the boundaries of the groundwater basin (Chapter 2), to locate the aquifers at various depths, and to establish the relationship between these aquifers and the surface water. In reminder, the groundwater system is connected to the hydrological cycle by various processes: infiltration through the unsaturated zone, contribution to ground-water by percolation and leakage, evaporation from the unsaturated zone, and finally, groundwater outflow. Definitions: Aquifers and Types of Groundwater Hydrogeology is based on the analysis of two essential entities: the aquifer and the groundwater table: An is a permeable geological formation (soil or rock) with pores or cracks that interconnect and that are sufficiently large that water can freely circulate under the effect of gravity (examples: sands, gravels, fissured chalk, sandstone, etc). In this way, the aquifer constitutes a reservoir for the groundwater tables. The is all the water contained in the saturated zone of the

Hydrology ◽  
2010 ◽  
pp. 227-228
Keyword(s):  
Surface Water ◽  
Unsaturated Zone ◽  
Hydrological Cycle ◽  
Groundwater Table ◽  
Groundwater System ◽  
Geological Formation ◽  
Groundwater Basin ◽  
Hydrogeological Studies ◽  
The Relationship ◽  
Groundwater Outflow

Flexural properties of blockboard reinforced with glass fiber and various types of fabrics

BioResources ◽  
2019 ◽  
Vol 14 (4) ◽  
pp. 9882-9892
Author(s):  
Mihai Ispas ◽  
Camelia Cosereanu ◽  
Octavia Zeleniuc ◽  
Mihaela Porojan
Keyword(s):  
Picea Abies ◽  
Glass Fiber ◽  
Grain Orientation ◽  
Cotton Fabrics ◽  
Modulus Of Rupture ◽  
Flexural Properties ◽  
Fiber Glass ◽  
Strength Performance ◽  
The Face ◽  
Parallel Direction

Flexural properties were evaluated of blockboard with spruce (Picea abies Mill) core and faces made of 2.5-mm fromager (Ceiba pentandra) veneer and 3-mm high-density fiberboard (HDF). For these two types of structures, fiber glass, jute, gauze, and cotton fabrics, were separately bonded under the face layers to improve the strength performance. Flexural properties, modulus of rupture (MOR), and modulus of elasticity (MOE) were determined under laboratory conditions. Improved values were found for MOR and MOE tested in the parallel to core grain direction compared to those perpendicular-to-grain. They were 32% to 49% (MOR) and 39% to 95% (MOE) improvements in case of veneer faces and 142% to 161% (MOR) and 134% to 245% (MOE) improvements in case of HDF faces. The best results of MOR and MOE were obtained for glass fiber used as insertion material, the higher ones being reached for specimens tested in the parallel direction to grain, which were 56.1 N/mm2 (MOR) and 6704 N/mm2 (MOE) for HDF faces. Generally, the improvements were more evident on the blockboard structures with veneer faces oriented perpendicular-to-core grain (30% for MOR and 18% MOE) and for HDF faces with parallel core grain orientation (16% for MOR and 6% MOE).

scholarly journals Upper Bound Solution for the Face Stability of Shield Tunnel below the Water Table

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Xilin Lu ◽  
Haoran Wang ◽  
Maosong Huang
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Fe Simulation ◽  
Shield Tunnel ◽  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Face Stability ◽  
The Face ◽  
Upper Bound Limit Analysis

By FE simulation with Mohr-Coulomb perfect elastoplasticity model, the relationship between the support pressure and displacement of the shield tunnel face was obtained. According to the plastic strain distribution at collapse state, an appropriate failure mechanism was proposed for upper bound limit analysis, and the formula to calculate the limit support pressure was deduced. The limit support pressure was rearranged to be the summation of soil cohesionc, surcharge loadq, and soil gravityγmultiplied by their corresponding coefficientsNc,Nq, andNγ, and parametric studies were carried out on these coefficients. In order to consider the influence of seepage on the face stability, the pore water pressure distribution and the seepage force on the tunnel face were obtained by FE simulation. After adding the power of seepage force into the equation of the upper bound limit analysis, the total limit support pressure for stabilizing the tunnel face under seepage condition was obtained. The total limit support pressure was shown to increase almost linearly with the water table.

Numerical Simulation of Roadway Deformation of Different Cutting Aperture

2013 ◽  
Vol 340 ◽  
pp. 892-895
Author(s):  
Xue Min Gong ◽  
Jia Yong Zhang ◽  
Li Wen Guo
Keyword(s):  
Numerical Simulation ◽  
Simulation Analysis ◽  
Wall Rock ◽  
Rock Stress ◽  
Analysis Software ◽  
Pressure Relief ◽  
Element Analysis ◽  
Gas Seepage ◽  
The Face ◽  
Roadway Deformation

Using ANSYS finite element analysis software, the crushing effect and wall rock deformation of a small high-pressure jet impacting coal were given numerical simulation analysis. It verified that impacting increased exposed area of coal in punch, providing conditions for pressure relief of internal coal seam and gas seepage. through comprehensive analysis of the rock stress and coal displacement of different roadway models after undercutting, it was determined that aperture size was 4/15 or so of roadway floor length, thus roadway fissures developed full, and maintained rock integrity, in favor of speeding up the face driving.

scholarly journals Study on the Face Stability of a Metro Tunnel in a Silty Clay Layer Constructed Using the Full-Face Method

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1069
Author(s):  
Zhien Zhang ◽  
Mingli Huang ◽  
Chunbo Yu ◽  
Xiaojian Fu
Keyword(s):  
Soft Soil ◽  
Horizontal Displacement ◽  
Silty Clay ◽  
Subway Tunnel ◽  
Tunnel Face ◽  
The Core ◽  
Cut Method ◽  
The Face ◽  
Full Face ◽  
Subway Tunnels

The horizontal displacement of the soil at the face of the subway tunnel is symmetrically distributed along the central axis of the tunnel, which is larger in the middle and smaller at both sides. The displacement is related to the size of the excavation face. If the excavation area is too great, the horizontal displacement of the tunnel face will be too large, easily leading to tunnel face collapse. For this reason, tunnel builders often use the core-keeping ring-cut method to build subway tunnels. A large section is divided into several small sections to reduce the soil displacement caused by soil excavation. With the continuous promotion and application of mechanized construction in the field of tunnels, mechanized full-section construction will gradually be performed in urban subway tunnels. Once the change in construction method from the core-keeping ring-cut method to the full-face method is made, the issue of how to maintain the stability of the tunnel working face (especially the soft soil stratum) becomes the focus of attention. Taking silty clay as the research object, this paper studies the displacement law of core soil with regard to the tunnel face under the condition of full-face excavation by using theoretical analysis, numerical simulations, and outdoor tests. According to the research results, the extrusion displacement of the tunnel face is the main cause of tunnel displacement. We optimize the construction parameters of glass fiber anchors to strengthen the tunnel face and provide theoretical guidance for the safe construction of subway tunnels.

Influence of Pipe Roof Reinforcement on Face Stability of Underwater Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1029-1033 ◽  
Author(s):  
Kai Wang ◽  
Hai Gui Kang ◽  
Hai Tao Wang
Keyword(s):  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Face Stability ◽  
Seepage Pressure ◽  
Kinematic Method ◽  
The Face ◽  
Tunnel Face Stability ◽  
Underwater Tunnel ◽  
Groundwater Flow Condition

The effect of seepage force on tunnel face stability with pipe roof reinforcement was studied based on the kinematic method of limit analysis. This method can be employed to define the safety factor and its corresponding critical failure mechanism for a given tunnel. The studies revealed that the existence of groundwater may seriously affect the face stability. Under the steady-state groundwater flow condition, most part of the total support pressure is owing to the seepage pressure acting on the tunnel face. There was a relatively large reduction in the seepage pressure by adopting the pipe roof reinforcement technique.

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