Senspeed: Estimation of Vehical Speed in Urban Areas

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DESIGN AND FABRICAION OF LARGE CONSOLIDOMETER APPARATUS ATHIRA M.1, SREEDEVI P.S.2 1

PG Scholar, Dept. of civil Engineering, IES College of Engineering,chittilapilly, Thrissur Assistant professor, Dept. of civil Engineering, IES College of Engineering, chittilapilly, Thrissur ---------------------------------------------------------------------***--------------------------------------------------------------------2

Abstract - Studying the settlement behaviour of soil under loads exerted due to construction of structures and equipment on the soil is one of the most important issues in geotechnical engineering and a major problem for the safe design and stability of any structure that is to be constructed. The load−deformation characteristics of homogeneous finegrained soils can be determined by a Casagrande-type oedometer. The size of the Casagrande-type oedometer cell is 76 mm in diameter and 19 mm in height. studying load deformation characteristics of granular materials or municipal solid wastes materials cannot determined by standard oedometer .This paper presents the development of large consolidation apparatus which include a floating ring confining cell and prefabricated vertical drain to measure the settlement response and stimulate the radial displacement of organic soil under increasing effective stress respectively .

Key Words: Consolidation, Casagrande-Type Oedometer, Prefabricated Vertical, Floating Ring Consolidometer, Three Dimensional Consolidation.

1.INTRODUCTION Studying the settlement behavior of soil under loads exerted due to construction of structures and equipment on the soil is one of the most important issues in geotechnical engineering. The load−deformation characteristics of homogeneous fine-grained soils can be determined by a Casagrande-type oedometer. The size of the Casagrande-type oedometer cell is 76 mm in diameter and 19 mm in height.

The previous studies revealed that the parameters such as compression index swelling index,coefficient of consolidation, pre-consolidation stress, and compression modulus are strongly affected by sample size. Furthermore, the typical Casagrandetype oedometer specimen size is often too small to capture the compression behavior on a field scale.

the direction of the pore water flow is not in accordance with direction of the settlement. Therefore, it needs to clarify the internal behavior of clayey ground improved by the vertical drain system.

2. TEST SETUP Fig.1 shows the new consolidometer. The large consolidometer consists of water reservoir, outer guide gauge, loading piston, top plate, tie rod, consolidation cell, loading hanger, bottom plate, loading bench, reaction piston, and second class lever arm system. The confining cell is the smooth UPVC tubing (inner and outer diameters of 152 and 160 mm; 200 mm in length) that is sealed at both ends by mild steel cover plates. The confining cells are completely bolted together with four 12-mm diameter stainless-steel tie rods. The 20-mm deep boss on the cover plates incorporates a rubber O-ring seal. The O-ring seal push-fits inside the ends of the UPVC tubing. The 5-mm thick, steel top and bottom platens comfortably fit inside the UPVC tubing and the platens contact against the ends of the test specimen. The stainless-steel loading and reaction pistons, each 300 mm in length, are fastened to the top and bottom platens, respectively. The Vertical movement of the floatingring cell is guided by an outer cage consist of four 15-mm diameter vertical steel bars, which are bolted to the loading bench.

Finally a loading mechanism can be fitted to the rectangular load-frame. A second-class type lever system is used to apply stress to the specimen. A seating stress as low as 0.5 kN can be applied to the top end of the specimen. The deadweight of the confining cell itself applies a mean shear stress of about 1 kN/m2 over the specimen wall-surface area. A counterbalance system is used when the boundary shear stress is considered excess.

When a vertical stress increment is applied to the soil surface or below the surface, an increment in total stresses will occur in the three axis directions. Thus the settlement will not only occur from vertical strains but also radially.

Excess pore water will also flow in lateral directions. This paper presents the development of large consolidation apparatus which incorporates a lubricated floating ring confining cell and prefabricated vertical drain in order to accurately measure the settlement response and simulate the radial displacement of organic soil under increasing effective stress. Three dimensional deformations occur when © 2017, IRJET

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International Research Journal of Engineering and Technology (IRJET)

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Volume: 04 Issue: 05 | May -2017

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1

2.2 ASSEMBLY OF THE APPARATUS

2

The outer guide cage was bolted to the loading bench. Then the bottom cover plate was located and temporarily clamped in position. The reaction platen was guided down into the UPVC tube to contact against the bottom end of the test specimen. The system was then carefully inverted after which the top platen assembly was guided inside the other end of the tube to contact the top end of the specimen. A layer of sand separated the specimen ends from the top and bottom platens. Fine wire gauze is used to prevent the sand from falling through the perforations in the bottom reaction platen. Then the assembly was located around the outer cage, and guided by the top cover plate, was lowered into position above the bottom cover plate. The cell was completely sealed by bolting the two cover plates together by four tie rods. The water from the constant-head reservoir was allowed to enter the cell via valve A in the top cover plate (Fig-3) in order to bleed any air, which may have been contained in the air bubbles above the specimen, via valve B.

3 34 5 6 7 8 9 10 11

Fig-1.New consolidometer apparatus; 1. Water reservoir; 2. Outer guide gauge; 3.Loading piston; 4. Top plate; 5. Tie rod; 6.Consolidation cell; 7.Loading hanger; 8.Bottom plate; 9. Loading bench; 10.Reaction piston; 11.Second class lever arm system

In the case of three dimensional consolidation, a vertical drain with diameter of 30mm is installed at the center of the specimen to stimulate consolidation of a hollow UPVC cylinder body with the radial flow of the pore water towards the center.

2

1

Fig-3.water reservoir system; 1.Valve A; 2.Valve C

Fig.3.3. Front view of lever arm system

Fig.3.4.side view of lever arm system

An adjustable constant-head water reservoir, which was located at an elevation of 1.15 m above the bottom platen level. The water enters and exits the confining cell via the valves A, B and C that are located in the top and bottom cover plates. Perforations at the top and bottom platens allow uniform downward seepage to occur through the test specimen. Š 2017, IRJET

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2.3. EXPERIMENTAL PROGRAMME The medium plastic clay was collected from Arayadathupalam, Kozhikode, Kerala state at a depth of 1.5m from the ground level and it was blackish in colour. The soil was initially air dried in open atmosphere prior to the testing.

A series of maintained-load compression tests were conducted on a specimen, 200 mm in length using floatingring in the consolidometer apparatus. The specimens were loaded in the new apparatus by releasing the piston clamps.

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The clamps were released from both pistons so that the UPVC tube could move relative to both platens. Only the floating-ring test incorporated the lubricated membrane wrapped around the specimen wall surface. Valve A was closed. Valves B and C in the cover plates were opened to allow both ends of the specimen to drain freely to atmosphere. A stress increment ratio of two was adopted and each load stage was about three to four days in duration.

Table -1: Basic properties of soft soil Properties of Soft soil Specific gravity

2.54

Clay (%)

48

Silt (%)

26

Sand (%)

26

Liquid limit

41

Plastic limit

20

Shrinkage limit

12

Plasticity Index

21

Soil type

CI

Maximum dry density

1.81

Optimum moisture content

15

Unconfined compressive strength

33.33

Coefficient of consolidation (cm2/s)

1.6x10-4

Fig-4.void ratio verses logarithm effective stress curve of one dimensional consolidation of soft soil.

Fig.5.22.shows the void ratio verse stress curve of soft soil in three dimensional consolidation condition

Effective sress (kPa) Fig-5.void ratio verses logarithm effective stress curve of three dimensional consolidation of soft soil

2.4. RESULTS AND DISCUSSIONS a) Determination of primary compression index Fig-4 shows the void ratio verse stress curve of soft soil in one dimensional consolidation condition. The onedimensional coefficients of volume compressibility and compression modulus of soft soil in large consolidometer are less than the one-dimensional coefficients of volume compressibility and compression modulus of soft soil in standard oedometer in the order of 40 %and 27 % respectively.

The three-dimensional coefficients of volume compressibility of soft soil in large consolidometer is less than the three-dimensional coefficients of volume compressibility of soft soil in standard oedometer in the order of 33.33%.Similarly three dimensional compression modulus of soft soil in large consolidometer is 34% less than that of standard oedometer. b) Determination of coefficient of compressibility and coefficient of volume compressibility Coefficient of compressibility is the amount by which a stratum of given thickness will compress under increasing

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load pressure. It is measured as the change in void ratio per unit increase in pressure and it is given by: av= If e0 is the initial void ratio of the consolidating layer, another useful parameter is the coefficient of volume compressibility, mv which is expressed as mv =

the void ratio and effective stress curve of standard oedometer apparatus and large consolidometer apparatus were 1.35x10-3 and 0.9x10-3 m2/KN respectively. Similarly the coefficient of volume compressibility of soft soil in standard oedometer and large consolidometer were 0.79x10-3 and 0.52x10-3 respectively.

C) Determination of Cumulative stain Fig-8.shows the cumulative strain versus logarithm of elapsed time responses for the soft soil of one dimensional consolidation measured using large consolidometer setups and the standard oedometer apparatus. As expected, the test materials were medium compressible, deforming at slow but steady rates.

Cumulative strain (%)

A. One dimensional consolidation

Time (min)

Fig-6.void ratio–effective stress plot of soft soil for one dimensional Fig-6 shows the void ratio versus effective stress responses for the soft soil measured using the large consolidometer setups and the standard oedometer apparatus. The slope of the void ratio and effective stress curve of standard oedometer apparatus and large consolidometer apparatus were 1.83x10-3 and 1x10-3 m2/kN respectively. Similarly the coefficient of volume compressibility of soft soil in standard oedometer and large consolidometer were 0.483x10-3 and 0.0967x10-3 respectively.

Fig-7.cumulaive strain – time plot of soft soil 3. CONCLUSIONS The development of a new consolidometer to accurately measure the consolidation response. The new apparatus incorporates a lubricated, floating-ring confining cell in order to minimize the boundary effects during large-strain consolidation conditions. Large, first-class quality, undisturbed core samples are obtained by pushing the UPVC tubing of the confining cell directly into the soft ground.

Maintained-load compression tests were carried out in the large floating-ring consolidometer.

Proving tests on saturated, undisturbed Soil specimens indicates that when benchmarked against the standard fixed-ring oedometer apparatus, practically identical strain responses were measured using the large floating ring consolidometer (indicating similar boundary effects).However, the main advantage of the consolidometer is that the much larger specimen size is more representative of the inherently heterogeneous and anisotropic soft soil deposit. Following are the main conclusions 

Fig-7 void ratio – effective stress plot of soft soil for three dimensional  Fig-7 shows the void ratio versus effective stress responses for the soft soil measured using the large consolidometer setups and the standard oedometer apparatus. The slope of © 2017, IRJET

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one dimensional Primary compression index of soft soil was 0.122 and 0.089 in standard oedometer and large consolidometer respectively One dimensional Primary compression index of soft soil was 28% less than standard oedometer

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International Research Journal of Engineering and Technology (IRJET)

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Three dimensional Primary compression index of soft soil was 0.0897 and 0.06in standard oedometer and large consolidometer respectively Three dimensional Primary compression index of soft soil was 37% less than standard oedometer The Strain difference between standard oedometer and large consolidometer were 4.84% in soft soil.

ACKNOWLEDGEMENT The author wish to acknowledge the help and support of the staff of civil engineering department, the APJ Abdul Kalam University, for the permission to publish this paper. I articulate my sincere thanks to all teaching and non teaching faculty of Department of Civil Engineering, IES College for providing necessary facilities for the completion of this work REFERENCES [1]

[2]

[3] [4]

[5]

Brendan C. O’Kelly, “Development of a large consolidometer apparatus for testing peat and other highly organic soils”,Suoseura-Finnish Peat land Society Helsinki 2009 ,ISSN 0039-5471,Suo 60(1–2): 23– 36,(2009).

Maryam Mokhtari., and Nader Shariatmadari., “Design and fabrication of large scale oedometer”, Journal of Central South University, 931−936. (2015) Peter W. Rowe.“A new consolidation cell”, Geotechnique, 162-170, (1966) Zulkifli Bin Ahamad,“Compressibility and shear strength behavior of peat soil”, University of Malaysia Sarawak, (2005) G.sridhar.,andRentmony G.Robinson, “Determinatio of radial coefficient of consolidation using log t method”, International Journal of Geotechnical Engineering, 5(4):373-381 · October 2011

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