VISIBLE TEST ON BUGHOLE GENERATION OF FLUIDITY CONCRETES FOR TUNNEL LINING

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Isamu Yoshitake ◽  
Masahiro Hieda ◽  
Kenta Okamoto ◽  
Tomoyuki Maeda
Keyword(s):  
Experimental Study ◽  
Image Analysis ◽  
Concrete Surface ◽  
Strength Properties ◽  
Area Ratio ◽  
Tunnel Lining ◽  
Conventional Concrete ◽  
Construction Methods ◽  
Natm Tunnel ◽  
Air Void

Bughole (surface air-void) is a concern for surface quality though it rarely decreases strength properties of the concrete structure. In particular, sidewall of NATM tunnel lining which generally has negative angle is a significant concern in the bughole problem. To reduce the surface imperfection of concrete, the authors examined the bughole properties and discussed on construction methods in previous investigations. The present study focuses on the relation of bughole generation and concrete viscosity. A visible test of bughole generation was conducted using high and medium fluidity concretes in addition to the conventional concrete. Bughole distribution and properties were analyzed by the image analysis which was developed in our previous study. This paper reports the effect of concrete fluidity on decrease of bugholes on concrete surface. A remarkable observation in the experimental study is that number and area-ratio of bugholes increased with concrete viscosity while large voids can be decreased by using high/medium fluidity concrete.

REDUCING BUG-HOLES ON TUNNEL LINING CONCRETE BY USING COVERING SHEETS

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Sari Harada ◽  
Tomoyuki Maeda ◽  
Masayuki Hirano ◽  
Isamu Yoshitake
Keyword(s):  
Experimental Investigation ◽  
Image Analysis ◽  
Concrete Surface ◽  
Tunnel Lining ◽  
Coated Steel ◽  
Test Results ◽  
Sheet Materials ◽  
Tunneling Method ◽  
Experimental Parameters ◽  
Entrapped Air

This study focused on bug-holes on sidewalls of tunnel lining concrete. The bug-holes of lining concrete may negatively affect aesthetics and durability of NATM (New Austrian Tunneling Method) tunnels. Most bug-holes appeared on concrete surface are generated from entrapped air during consolidating concrete. In particular, the sidewall of tunnel lining is constructed with negative angles, so bug-holes are often observed on the sidewall. Seven concrete specimens were prepared to simulate conventional tunnel lining. In the experimental investigation, breathable-waterproof material sheets and permeable sheets were used. The primary experimental parameters are (a) covering-sheet materials and (b) form surfaces such as ceramic-coated steel with grooves. The study examined bug-hole distributions in the concrete specimens using the various sheets. The bug-hole distributions were quantified by using an image analysis developed in this study. The test results show that quantity of bug-holes of concrete using the sheets is lower than the quantity of concrete without sheets. It was noteworthy that the bug-holes were hardly observed in the test using the form covered with the permeable sheets.

The effect of pore-water pressure on NATM tunnel linings in decomposed granite soil

2005 ◽  
Vol 42 (6) ◽  
pp. 1585-1599 ◽  
Author(s):  
J H Shin ◽  
D M Potts ◽  
L Zdravkovic
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Drainage System ◽  
Tunnel Lining ◽  
Natm Tunnel ◽  
Decomposed Granite ◽  
Secondary Lining ◽  
Granite Soil ◽  
Functional Components

Tunnelling in a water bearing soil often produces a long-term interaction between the tunnel lining and the surrounding soil. With respect to lining design, infiltration and external pore-water pressures are often one of the most important factors to be considered. Development of pore-water pressure may accelerate leakage and cause deterioration of the lining. This can be particularly troublesome to structural and functional components of the tunnel and can often lead to structural failure. However, as a result of the complicated hydraulic boundary conditions and the long times often required for pore pressure equilibration, research on this subject is scarce. Consequently, most design approaches deal with the effects of pore-water pressure on the tunnel lining in a qualitative manner. In this paper, the development of pore-water pressure and its potential effects on the tunnel lining are investigated using the finite element method. In particular, the deterioration of a drainage system caused by clogging is considered. It is shown that the development of pore-water pressure on the lining is dependent on the lining permeability and the deterioration of the drainage system, particularly for a tunnel with both a primary and a secondary lining. The magnitude of pore-water pressure on a new Austrian tunnelling method (NATM) tunnel constructed in decomposed granite soil and the effect of tunnel shape are investigated. Design curves for estimating pore-water pressure loads on a secondary lining are proposed.Key words: numerical analysis, tunnel lining, decomposed granite.

Experimental study on deformation and strength properties of microfissured rock

2013 ◽  
pp. 231-234
Author(s):  
Ronggui Deng ◽  
Zhibin Zhong ◽  
Xiaomin Fu ◽  
Weimin Xiao ◽  
Jing Yin
Keyword(s):  
Experimental Study ◽  
Strength Properties

scholarly journals Experimental Study of the Effect of Curing Mode on Concreting in Hot Weather

2021 ◽  
Vol 31 (4) ◽  
pp. 243-248
Author(s):  
Nassima Bakir
Keyword(s):  
Experimental Study ◽  
Concrete Surface ◽  
Work Conditions ◽  
Climatic Conditions ◽  
Water Evaporation ◽  
Negative Effects ◽  
Climate Conditions ◽  
Hot Climate ◽  
Hot Weather ◽  
Job Site

Most developing countries have hot climate, ordinary jobsites characterized by reduced of human resources, equipment and infrastructures. The objective of this article is to make an experimental study of the influence of the hot climate such as that of Algeria, on the different properties of concrete in the fresh state, such as excessive water evaporation from the concrete surface, increased demand for water, increased slump loss corresponding to additional water on job-site, higher plastic shrinkage cracking and difficulty in controlling air content. At the hardened state, we could mention a reduction of strength at 28 days, decreased durability resulting from cracking at long-term period. To show the problems linked to concreting under these conditions and to present the appropriate solutions concrete or mortar can withstand the conditions in which it is implemented. Thus, negative effects caused principally by hot weather concreting motivated the choice of the such study. The research experimental work conditions in which the cementitious matrix was kept concerned two different environments, namely hot and dry climate conditions (t = 40°, h = 0%) alike the climate of the region of M'sila., and that of a medium with a hot and humid environment (t = 40°, h = 100%). The output of the investigation demonstrated the crucial role of the cure method in hot regions. The comparison of results for a reference concrete kept in air without any curing measures with two curing types simulating hot weather environment of the region M’sila was undertaken. These obtained outcome results were discussed based on the influence of climatic conditions to conclude procedures for hot weather concreting and suitable cure methods.

scholarly journals Study of the structure and characteristics of autoclaved aerated concrete

2020 ◽  
pp. 23-32
Author(s):  
Veronika Aleksandrovna Alipova
Keyword(s):  
Building Material ◽  
Coefficient Of Thermal Expansion ◽  
Weight Ratio ◽  
Strength Properties ◽  
Sound Insulation ◽  
Vapor Permeability ◽  
Conventional Concrete ◽  
Autoclaved Aerated Concrete ◽  
Aerated Concrete ◽  
Manufacturing Technologies

The lightweight and porous building material has many advantages over conventional concrete, such as a higher strength-to-weight ratio, a lower coefficient of thermal expansion and good sound insulation. This article focuses on the historical periodization of the development of autoclaved aerated concrete and a literature review that focuses on the influence of porosity, vapor permeability and strength properties of a given building material. The subject of this research is the analysis of the key historical events and manufacturing technologies that influenced the creation and transformation of the structural components of autoclaved aerated concrete. In the course of research, the author revealed that although aerated concrete is a new material in construction, it appeared a long time ago. Initially, five thousand years ago, this composition of the material was used as a plaster and brickwork mortar; showing a positive effect in construction, the aerated concrete over the years took the form of a cellular block, and its characteristics continue to be discovered. The properties, composition and structure of autoclaved aerated concrete are being improved through its composition and geometry of the shape of block, which contributed to environmental friendliness of the new building material, its durability, and creation of comfortable living conditions for people. However, the material requires new rational manufacturing technologies are needed in order to improve its quality and characteristics.

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