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

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.

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REEVALUATION OF THE EFFECT OF COVERING SHEETS FOR REDUCING BUGHOLES ON TUNNEL LINING CONCRETE

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2016.53 ◽

2016 ◽

Vol 3 (1) ◽

Author(s):

Tomoyuki Maeda ◽

Sari Harada ◽

Mai Moriuchi ◽

Isamu Yoshitake

Keyword(s):

Previous Investigation ◽

Concrete Surface ◽

Tunnel Lining ◽

Generation Mechanism ◽

Concrete Construction ◽

Model Form ◽

Entrapped Air

Most tunnel lining concretes have sidewall of negative angle, so bugholes on the concrete surface frequently appear. The bugholes are caused from entrapped air in concrete placing; the part of bugholes remains on concrete surface even after adequate vibrating for consolidation. In the previous investigation, the authors have studied on the generation mechanism of bugholes in a visible test and examined the reducing effects by covering sheet for concrete forms. According to the investigation, it was found that the water-permeable sheet causes color irregularity of concrete surface while the sheet is effective to decrease the bugholes. Hence, the present study also focuses on the effect of sheets reducing bugholes. The foci of this study are to develop an effective sheet for aesthetic of concrete surface and to reevaluate the effectiveness for reduction of bugholes. Fundamental test using a model form and various covering sheets was performed by referring to the previous investigation. The test confirms that the developed sheet adequately contributes on decrease of bugholes without the color irregularity of concrete. The observations may be useful for most concrete construction as well as tunnel lining concrete.

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VISIBLE TEST ON BUGHOLE GENERATION OF FLUIDITY CONCRETES FOR TUNNEL LINING

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2019.190 ◽

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.

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Experimental Investigation on Composite Deck Slab Made of Cold-Formed Profiled Steel Sheeting

Metals ◽

10.3390/met11020229 ◽

2021 ◽

Vol 11 (2) ◽

pp. 229

Author(s):

Siva Avudaiappan ◽

Erick I. Saavedra Flores ◽

Gerardo Araya-Letelier ◽

Walter Jonathan Thomas ◽

Sudharshan N. Raman ◽

...

Keyword(s):

Experimental Investigation ◽

Test Results ◽

Shear Connectors ◽

Modes Of Failure ◽

Deck Slabs ◽

Load Carrying ◽

Composite Slabs ◽

Ultimate Load Carrying Capacity ◽

Ductility Ratio ◽

Deck Slab

An experimental investigation is performed on various cold-formed profiled sheets to study the connection behavior of composite deck slab actions using bolted shear connectors. Various profiles like dovetailed (or) re-entrant profiles, rectangular profiles and trapezoidal profiles are used in the present investigation. This experimental investigation deals with the evaluation of various parameters such as the ultimate load carrying capacity versus deflection, load versus slip, ductility ratio, strain energy and modes of failure in composite slab specimens with varying profiles. From the test results the performance of dovetailed profiled composite slabs’ resistance is significantly higher than the other two profiled composite deck slabs.

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Absorption and Strength Properties of Short Carbon Fiber Reinforced Mortar Composite

Buildings ◽

10.3390/buildings11070300 ◽

2021 ◽

Vol 11 (7) ◽

pp. 300

Author(s):

Md. Safiuddin ◽

George Abdel-Sayed ◽

Nataliya Hearn

Keyword(s):

Tensile Strength ◽

Carbon Fiber ◽

Water Absorption ◽

Carbon Fibers ◽

Strength Properties ◽

Fiber Content ◽

Test Results ◽

Air Content ◽

Entrapped Air ◽

Short Carbon

This paper presents the water absorption and strength properties of short carbon fiber reinforced mortar (CFRM) composite. Four CFRM composites with 1%, 2%, 3%, and 4% short pitch-based carbon fibers were produced in this study. Normal Portland cement mortar (NCPM) was also prepared for use as the control mortar. The freshly mixed mortar composites were tested for workability, wet density, and entrapped air content. In addition, the hardened mortar composites were examined for compressive strength, splitting tensile strength, flexural strength, and water absorption at the ages of 7 and 28 days. The effects of different carbon fiber contents on the tested properties were observed. Test results showed that the incorporation of carbon fibers decreased the workability and wet density, but increased the entrapped air content in mortar composite. Most interestingly, the compressive strength of CFRM composite increased up to 3% carbon fiber content and then it declined significantly for 4% fiber content, depending on the workability and compaction of the mortar. In contrast, the splitting tensile strength and flexural strength of the CFRM composite increased for all fiber contents due to the greater cracking resistance and improved bond strength of the carbon fibers in the mortar. The presence of short pitch-based carbon fibers significantly strengthened the mortar by bridging the microcracks, resisting the propagation of these minute cracks, and impeding the growth of macrocracks. Furthermore, the water absorption of CFRM composite decreased up to 3% carbon fiber content and then it increased substantially for 4% fiber content, depending on the entrapped air content of the mortar. The overall test results suggest that the mortar with 3% carbon fibers is the optimum CFRM composite based on the tested properties.

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Experimental Investigation on Relative Crack Length For Fracture Toughness of Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.146-147.1524 ◽

2010 ◽

Vol 146-147 ◽

pp. 1524-1528 ◽

Cited By ~ 3

Author(s):

Xue Zhi Wang ◽

Zong Chao Xu ◽

Zhong Bi ◽

Hao Wang

Keyword(s):

Fracture Toughness ◽

Experimental Investigation ◽

Crack Length ◽

Fracture Toughness Test ◽

Test Results ◽

Toughness Test ◽

Wedge Splitting Test ◽

Splitting Test ◽

Wedge Splitting

The wedge splitting test specimens with three series of different relative crack length were used to study the influences of relative crack length on the fracture toughness of common concrete. The suitable formulation for fracture toughness of concrete with different relative crack length was gotten on comparing between fracture toughness test results and computation results of the model developed from Hu formula.

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Experimental Study on Sand and Cement Replacement by Termite Mound Soil

International Research Journal of Multidisciplinary Technovation ◽

10.34256/irjmtcon38 ◽

2019 ◽

pp. 279-287

Author(s):

Harish R ◽

Ramesh S ◽

Tharani A ◽

Mageshkumar P

Keyword(s):

Experimental Study ◽

Experimental Investigation ◽

Compressive Strength ◽

Natural Environment ◽

Fine Aggregate ◽

Test Results ◽

Termite Mound ◽

Cement Concrete ◽

Cement Ratio ◽

Compressive Strength Of Concrete

This paper presents the results of an experimental investigation of the compressive strength of concrete cubes containing termite mound soil. The specimens were cast using M20 grade of concrete. Two mix ratios for replacement of sand and cement are of 1:1.7:2.7 and 1:1.5:2.5 (cement: sand: aggregate) with water- cement ratio of 0.45 and varying combination of termite mound soil in equal amount ranging from 30% and 40% replacing fine aggregate (sand) and cement from 10%,15%,20% were used. A total of 27 cubes, 18 cylinders and 6 beams were cast by replacing fine aggregate, specimens were cured in water for 7,14 and 28 days. The test results showed that the compressive strength of the concrete cubes increases with age and decreases with increasing percentage replacement of cement and increases with increasing the replacement of sand with termite mound soil cured in water. The study concluded that termite mound cement concrete is adequate to use for construction purposes in natural environment.

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Experimental Investigation of Stiffened Square CFST Columns under Axial Load

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.919-921.1794 ◽

2014 ◽

Vol 919-921 ◽

pp. 1794-1800

Author(s):

Xin Zhi Zheng ◽

Xin Hua Zheng

Keyword(s):

Experimental Investigation ◽

Bearing Capacity ◽

Cross Sections ◽

Axial Load ◽

Local Buckling ◽

Test Results ◽

Tubular Columns ◽

Economical Benefit ◽

Steel Consumption ◽

Cfst Columns

Abstract: 7 square steel tubular columns were tested to discuss the ultimate axial bearing capacity, ductility performance and the steel consumption under stiffened by steel belts and binding bars of different cross-sections. Test results indicate that only by increasing fewer amounts of steel usage, stiffened square CFST columns with binding bars can not only improve the overall effects of restraint and alleviate regional local buckling between the binding bars, but also improve the bearing capacity of concrete filled square steel tubular columns. The utility benefits and the economical benefit is considerable, deserving extensive use.

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Analytical and Experimental Investigation of the Stability of the Rotor-Bearing System of a New Small Turbocharger

Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery ◽

10.1115/87-gt-110 ◽

1987 ◽

Cited By ~ 14

Author(s):

H. R. Born

Keyword(s):

Experimental Investigation ◽

Dynamic Stability ◽

Squeeze Film ◽

Test Results ◽

Flow Capacity ◽

Squeeze Film Dampers ◽

Rotor Bearing ◽

The Stability ◽

Turbine Design ◽

Bearing System

This paper presents an overview of the development of a reliable bearing system for a new line of small turbochargers where the bearing system has to be compatible with a new compressor and turbine design. The first part demonstrates how the increased weight of the turbine, due to a 40 % increase in flow capacity, influences the dynamic stability of the rotor-bearing system. The second part shows how stability can be improved by optimizing important floating ring parameters and by applying different bearing designs, such as profiled bore bearings supported on squeeze film dampers. Test results and stability analyses are included as well as the criteria which led to the decision to choose a squeeze film backed symmetrical 3-lobe bearing for this new turbocharger design.

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