Study of Bearing Capacity Ratio and Settlement Ratio of Rectangular Footing Resting on Dune Sand Reinforced with Porcelain Insulator Waste.

Study of Bearing Capacity Ratio and Settlement Ratio of Rectangular Footing Resting on Dune Sand Reinforced with Porcelain Insulator Waste.

Kiran Bhoot

Department of Civil Engg. JIET Jodhpur, India

Abstract -Large part of worlds desert covers with wind deposited , non plastic, uniformly graded fine sand known as Dune Sand. 6.3% of area of India as a whole covers with dune sand. Dune sand possesses many geotechnical problems such as it has low bearing capacity, high permeability, low shear strength etc. Here an attempt has been made to study two parameters Bearing Capacity Ratio and Settlement Ratio of dune sand reinforced with varying percentage of porcelain insulator. The present paper deals with the laboratory tests on the use of porcelain insulators waste to enhance bearing capacity ratio and to lower the settlement ratio.

Keywords – Dune sand, bearing capacity ratio, settlement ratio

was determined by pycnometer according to IS 2720 (Part- II) 1980.

Reinforcement:

The porcelain insulator used for the study was collected from new power house, Jodhpur The Porcelain insulators were broken in to small pieces and 2mm-1.18mm size was used for the testing. The porcelain insulators particles 2%, 4%, 6%, 8%, 10% by volume, were uniformly mixed with the dune sand up to the depth of pressure bulb. From the analogy of pressure bulb, it is inferred that the soil is significantly affected to a depth of 2 to 2.5 times the width of footing, so the depth of reinforced zone was assumed here to be 3 times the width of footing.

1. INTRODUCTION

   The reinforcement improves the earth by increasing the bearing capacity of the soil and reduces the settlement. It also reduce the liquefaction behaviour of the soil. The construction of reinforced earth structure has become wide spread in Geotechnical engineering practice in the last two to three decades owing to their ease of construction and economy compared to those of conventional methods. Reinforcement of soil, is practiced to improve the mechanical properties of the soil being reinforced by the inclusion of structural element such as granular piles, lime/cement mixed soil, metallic bars or strips (Akinmusuru and Akinbolade) shredded tyres (Hataf, N. and Baziar, A.), synthetic sheet (P.K Kolay), grids,(Omar,M.T )cells etc.

   A series of load tests were conducted on a mixture of dune sand and insulators waste to determine various factors, which influence the bearing capacity of dune sand- porcelain mixture. The density of the mixture was kept as

   1. g/cc throughout the test program.

2. MATERIALS USED

   Dune Sand:

   The Dune Sand used in the present study was brought from location near Ossian, at about 45-48 km away from Jodhpur on Jodhpur- Jaisalmer road..The grain size distribution was done by performing dry sieve analysis according to IS 2720 (Part IV) 1965. The specific gravity

   Model footings :

   Rectangular footings made of alluminium alloy having sizes 4.5×5.9 sq.cm, 5.5×7.7 sq.cm, 6.5×9.8 sq.cm were used for the tests. The L/B ratio for 4.5×5.9 sq.cm, 5.5×7.7 sq.cm and 6.5×9.8 sq.cm footings were 1.3 ,1.4 and 1.5 respectively. The base of the footings was made rough by pasting sand paper of zero grades. The footings were given a semi circular groove in the centre for resting a steel ball.

   Testing Tank :

   A series of model loading tests were conducted in a test tank that had dimensions 1.00mx0.50m in plan and 0.50m in depth. The tank was made of sufficiently thick steel sheet to withstand lateral expansion under loads. The dimensions of tank were kept more than five times the largest dimension of footings so that it may not induce boundary effects (IS 1888-1962).

3. TEST PROCEDURE

   Total 18 tests were carried out to study Bearing Capacity Ratio and Settlement Ratio of dune sand mixed with varying percentage of porcelain insulator. The density of reinforced/ unreinforced dune sand was kept constant equal to 1.60 g/cc throughout the test program by compacting it with the help of tamper. Compaction through vibrators is ineffective (Ahmed and Lovell, 1993).

   Load was applied through lever arm device and recorded

   through proving ring. The settlement for each load increment was recorded through mean of the two dial gauges readings. Load Intensity versus settlement graphs were drawn for each footing having different percentage of porcelain insulators. Ultimate bearing capacity of dune sand having different percentage of porcelain reinforcement for all the three model footings was calculated by using tangent intersection method.

4. RESULTS AND DISCUSSIONS

   The bearing capacity ratio is the ratio of ultimate bearing capacity of reinforced soil to the ultimate bearing capacity of unreinforced soil. Graph-1 , graph-2 and graph-3 represents the bearing capacity ratio of 4.5×5.9 sq.cm, 5.5×7.7 sq.cm, 6.6×9.8 sq.cm respectively.

   Bearing Capacity Ratio

   Bearing Capacity Ratio

   Graph 1.

   BCR FOR 5.5×7.7 SQ.CM FOOTING

   BCR FOR 5.5×7.7 SQ.CM FOOTING

   2

   1.5

   1

   0.5

   0

   2

   1.5

   1

   0.5

   0

   0

   2

   4

   6

   8

   10

   12

   0

   2

   4

   6

   8

   10

   12

   Percentage Reinforcement

   Percentage Reinforcement

   Graph 2.

   BCR FOR 6.5X9.8 SQ.CM FOOTING

   BCR FOR 6.5X9.8 SQ.CM FOOTING

   2

   1.5

   1

   0.5

   0

   2

   1.5

   1

   0.5

   0

   0

   2

   4

   6

   8 10 12

   0

   2

   4

   6

   8 10 12

   Percentage reinforcement %

   Percentage reinforcement %

   Bearing Capacity Ratio

   Bearing Capacity Ratio

   Graph 3.

   Settlement ratio is the ratio of settlement of a footing placed on reinforced soil to the settlement of the footing placed on unreinforced soil. Graph-4 , graph-5 and graph-6 represents the settlement ratio of 4.5×5.9 sq.cm, 5.5×7.7 sq.cm, 6.6×9.8 sq.cm footings respectively.

   Graph 4.

   Graph 5.

   Graph 6.

5. CONCLUSIONS

   • Experimental study on porcelain reinforced dune sand under rectangular footings shows sufficient increase in bearing capacity.

   • Result analysis shows higher the Bearing Capacity Ratio and smaller Settlemet Ratio for smaller footings therefore porcelain reinforced soil technique appeared to be efficient for smaller rectangular footing.

   • Maximum Bearing capacity Ratio obtained for 10% of porcelain insulator for each footing in this experimental study.

   • Minimum Settlement Ratio obtained for 10% porcelain insulator for each footing in this experimental study.

6. REFERENCES

1. Akinmusuru and Akinbolade (1981) Stability of Loaded Footing on Reinforced Soil, Journal of Geotechnical Engineering, 107(GT6), pp.819-827

2. Ingold, T.S., Reinforced Earth, Pub. Thomas Telford Ltd, London 1982.

3. Jha K and Mandal J.N. (1988), A review of research and literature on the use of Geosynthetics in the modern Geosynthetical World. First Indian Geotextile conference on reinfoced soil and Geotextiles, 1988.

4. Omar, M.T., el al (1993), Ultimate bearing capacity of shallow foundations on sand with geogrid reinforcement Can. J. Geotechnical Engineering 30 (3) pp, 545-549.

5. Yetimoglu et al, (1994) The bearing Capacity of Rectangular footings on reinforced sand, PhD, Thesis

6. Hataf, N. and Baziar, A., (2000) Use of Tire shreds for Bearing Capacity Improvement of Shallow Footing on Sand, Proc. Of the 3rd Int. Conf. on Ground Improvement Techniques, Singapore, pp.189-194

7. Nand Kishore Executive director Geotech RDSO, Concept and Design of Reinforced Earth structure Report No. GE: R-73 June 2005, Geotechnical Engineering Directorate (Research designs and standards Organisation Lucknow).

8. M.Y. Al-Aghbari , (2007)Settlement of Shallow Circular Fondations with structural skirts Resting on Sand , The Journal of Engineering Research Vol. 4, No.1, 11-16

9. MadhaviLatha, G., AmitSomwanshi, S.(2009) Bearing Capacity of square footings on geosynthetic reinforced sand, Geotextiles and Geomembranes 27(4), pp. 281-294

10. Arora K.R. Soil Mechanics and Foundation Engineering Standard publishers.2011

11. P.K Kolay, S.Kumar and D.Tiwari Deptt. Of Civil and Environmental Engg. Southern Illinois University, Carbondale,

U.S.A. Improvement of Bearing capacity of shallow foundation on Geogrid Reinforced silty clay and sand Journal of construction Engg. Vol. 2013 Article ID-293809