CASTING AND TESTING OF A BORED PILE FOUNDATIONS

Transcription

1 CASTING AND TESTING OF A BORED PILE FOUNDATIONS J.Naga Shiva jyothi, M. David nagasivajyoyhi95@gmail.com,mogiidavid352@gmail.com ABSTRACT This project titled BORED CAST IN- SITU PILE FOUNDATIONS done in Visakhapatnam Steel Plant is conducted for a period of 15 days to have knowledge of various techniques, apparatus and equipment used in Bored Pile casting and testing. A wide range of topics like field investigations, soil classification, setting out of the works, construction of piles and pile load tests are included. carried out by C & C Consulting Firm. From the detailed soil investigation report submitted by C & C Consulting Firm to VSP is used for the analysis of foundation. The investigation comprised of sinking boreholes / drill holes at different locations of the proposed structures, conducting different field investigation and laboratory tests together with the analysis of sub-soil data and submission of the reports in phases indicating the types of foundation to be adopted for the proposed structure Overview: RashtriyaIspat Nigam Limitedenvisaged the expansion of Visakhapatnam Steel Plant at Visakhapatnam, A n d h r a Pradesh. T h i s p r o j e c t i s a b o u t t h e constructions of Wire Rod Mills and Seamless Tube Plant, and for the expansion of Steel Melting Shop. In order to facilitate design and construction of structures on the proposed site, a detailed soil investigation was All the field investigations and laboratory tests were made according to the prescribed set of rules given in the standard IS codes. For example, a total of thirty boreholes were investigated as decided by VSP and all the boreholes were sunk according to the provisions made in IS: 1892 (1980). 2.1.Geology of the site: The site is a part of Eastern Ghats in India, Eastern Ghats-a series of detached hill IJCSIET-ISSUE7-VOLUME1-SERIES4 Page 1

2 ranges of heterogeneous composition, which stretches from Northern border of Orissa through Coastal regions of Andhra Pradesh. The major rock type in this area is Khondalite; a typical metamorphic rock composed of quartz-garnet-sillimanite etc. of Achaean / Precambrian age. This rock formation is either underlines or intruded by quartzite formation-a younger formation of Proterozoic age. Dolerite-dykes also occur in some places. 2.2.Ground Water Table: The standing Ground Water Table was observed in each borehole after 24 hours of termination of boreholes and is presented in a tabular form by C & C Consulting Firm. The average Ground Water Table lies at a depth of about 1.68 m from the data obtained. A part of the Borehole data (14 out of 30) is presented here in the next page. 3.Foundation Consideration and Bearing Capacity: All the calculations for bearing capacity and load carrying capacities for different types of foundation that can be laid was done by C & C Consulting Firm and the same is presented here. Foundation for different utilities for the construction ofmelting Shop would depend on the load of different structures. In order to design the foundation for these structures, it is essential to consider sub-soil condition. From the sub-soil condition, two necessary design criteria are to be satisfied. a) There should be adequate factor of safety against bearing capacity failure. b) The settlement should be within the serviceable limit of the structure / equipment. 3.1.Shallow Foundation: Now from the consideration of functional requirement of the structures, it is envisaged that the depth of shallow foundation (RL=+ 7.00m) will be either in residual soil of stratum-i or in highly weathered rock of stratum-ii. Based on this, the bearin g capacit y for different siz es of shallow IJCSIET-ISSUE7-VOLUME1-SERIES4 Page 2

3 foundation has been investigated at a depth of 2.00m to 4.00m below finished ground level of been +7.00m in the residual soil. ground surface is highly compressible and very weak to support the load transmitted by the structure Pile A pile is a slender structural member made up of steel, concrete or wood. A pile is either driven into the soil or formed in-situ by excavating a hole and fitting it with concrete. A brief discussion about piles and the necessity to use them as foundation will be done before explaining the method of their construction for a better understanding. 2. When the plan of the structure is irregular relative to its outline and load distribution. It would cause nonuniform settlement if a shallow foundation is constructed. A pile foundation is required to reduce differential settlement. 3. Pile foundations are required for the transmission of structural loads through deep water to firm stratum. When the soil at or near the ground surface is not capable of supporting a structure, deep foundations are required to transfer the load to deeper strata. The most common types of foundations are piles, piers and caissons. 4. Pile foundations are used to resist horizontal forces in addition to support the vertical loads in earthretaining structures and tall structures that are subjected tohorizontal forces due to wind and earthquake. 4.2 Pile foundations are used in the following conditions: 1. When the strata at or just below the 5. Piles are required such that when the soils are such that wash out, erosion or scour of soil may occur from IJCSIET-ISSUE7-VOLUME1-SERIES4 Page 3

4 underneath a shallow foundation. 6. Piles are used for the foundations of some structures, such as transmission towers, off-shore platforms, which are subjected to uplift. 7. In case of expansive soils, such as black cotton soil, which swell or shrink as the weather content changes, piles are used to transfer the load below the active zone. 8. Collapsible soils, such as loess, have a breakdown of structure accompanied by a sudden decrease in void ratio when there is an increase in water content. Piles are used to transfer the load beyond the zone of possible moisture changes in such soils. 5. Pile Load Test 5.1. Vertical Load Test: This figure shows a Routine vertical load test being carried out on a pile.a load of 183 tons is placed on the pile through the hydraulic jack arrangement. The load for which the pile is designed is 120tons. The test was done for 1.5 times the safe load of 120 tons, i.e., 180 tons. But the extra 3 tons came from the lateral beam on which the actual load is resting. The actual load that could act on each pile after construction is 25tons.Hence the piles laid by are safer. There are two types of load tests carried out. One is called Initial Load Test and is carried out during the soil investigation. The Routine Load Test is done on selected piles after 28 days of concreting in accordance with the specification and relevant IS codes. Procedure: Loading should be carried up to one and half (1.5) times the safe load or up to the load at which total settlement attains a value of 12 mm, whichever is earlier. The pile head should be chipped off carefully till sound concrete is met. The projecting reinforcement should be cutoff or bent suitably and the top surface IJCSIET-ISSUE7-VOLUME1-SERIES4 Page 4

5 finished smooth and leveled with Plaster of Paris when required. A mild steel (M.S.) bearing plate Figure: 5.1. Vertical loading (181 tons) on piles to test load bearing capacity CONCLUSION: should be placed on pile head for the jack to rest. The test should be carried out by applying a series of vertical downward incremental loads on test pile. The loading should be applied by reaction from kentledge of adequate capacity for the full test load. The test pit should be excavated by open excavation through all types of soils to required depth. This mini project BORED CAST IN-SITU PILE FOUNDATION gave us knowledge about pile foundation and helped us getting practical experience.problems during construction of pile foundation and their remedial measures were learnt. Some of those problems are 1. Bore hole collapse 2. Pile foundation failure due to manual errors in design. We observed the installation of Pile foundation and Vertical Pile Load Test. The result obtained in the Vertical Pile Load Test is 1.62mm (Net Settlement) which is far less than the maximum allowable settlement (12mm). Hence, Pile foundation is safe. IJCSIET-ISSUE7-VOLUME1-SERIES4 Page 5

6 BIBILOGRAPHY Publications of Bureau of Indian Standards 1. IS: Code of Practice for Plain Reinforced Concrete. 2. IS: (Part 1/ section-2) -- Code of practice for Design and Construction of Pile Foundations-- Load test on Piles. 3. IS: (Part 1/ section-2) -- Code of practice for Design and Construction of Pile Foundations-- Load test on Piles. 4. IS: (Part-1/section 2) Appendix-A Bentonite properties. 5. IS: Methods of sampling of aggregates for concrete. 6. IS 2386(P.1)-1963 Methods of test for aggregates of concrete. 7. IS: Mild steel and medium tensile steel bars and high tensile bars. 8. IS: Spec. for high strength deformed steel bars & wire. 9. IS: Methods of tests for strength of concrete. 10. IS: Methods of sampling and analysis of concrete. 11. IS: Code of Practice for Plain Reinforced Concrete tests on concretes. 12. IS: Methods of tests for strength of concrete. 13. IS: Code of practice for subsurface investigations. 14. IRC: IS: Specification for 53 grade ordinary Portland cement. 16. IS: Portland slag cement Specification. 17. IS: Specification for coarse and fine aggregates from natural sources for concrete. 18. IS:2720 (Part 9F) Liquid limit of Bentonite. 19. Soil Mechanics and Foundation by B.C.Punmia, Ashok Kumar Jain and Arun Kumar Jain, Laxmi, publications Pvt.Ltd., New Delhi- 16 th Edition, Soil Mechanics and Foundation Engg. By K.R. Arora, Standard Publishers and Distributors, Delhi-5 th Edition, Geotechnical Engineering by C.Venkataramaiah, New Age International (P) Limited Publishers, New Delhi- 3 rd Edition, IJCSIET-ISSUE7-VOLUME1-SERIES4 Page 6