soil bearing capacity test report- sample report for SBC of soil

Soil Bearing Capacity

For Foundation design the Soil Bearing Capacity is very essential. Soil Bearing capacity is the term explained as, the soil strength or the soil capable enough to carry certain load. SBC of soil can be find out by using the test called Standard perpetration test (SPT) using SBC number the strength is to be determined. After find out the Soil Bearing capacity the report to be prepared and submitted to design department for foundation design.

The following report is the sample copy of soil bearing capacity report.

1. INTRODUCTION 1.1. PURPOSE AND SCOPE Geo-technical site investigation work for. “PROPOSED CONSTRUCTIONOF R.C.C ROOF GROUND INDUSTRIAL GODOWN BUILDING S.F. No: 158/2B & 158/2C OF AVINASHI VILLAGE, TIRUPUT-DT.” The primary purpose of our investigation is to obtain data to develop foundation design recommendations for the above work. At, first instance, Visit to site and chose spot for SPT. Client’s representatives choose a no of location and selected the locations of SPT. To accomplish these purposes, the following tasks were performed: 1. Detailed soil borings (Not required for this site) were done up to stratum to explore the sub surface stratigraphy and obtain soil samples for testing. 2. Field and laboratory tests were conducted to evaluate the index and engineering properties of the soils 3. Engineering analysis were performed to develop foundation design information for proposed structure 1.2. SITE ADDRESS: S.F. No: 158/2B & 158/2C OF AVINASHI VILLAGE, TIRUPUT-DT. 1.3. THE STRUCTURE As per the client information the Industrial godown building (G+1) for the above mentioned site. 2. FIELD INVESTIGATIONS 2.1. ROTARY BORING Rotary drilling technique was adapted using Calyx machine in this field. In this method, boring is effected by the cutting action of a rotating bit that is kept in firm contact with the bottom of the hole. The bit is attached to the lower end of a hollow drill rod that is rotated by a suitable chuck. Drilling mud (usually Bentonite) is continuously forced down the hollow drill rods. The mud returning upwards though the annular space between the drill rods and the side of the hold bring the cutting to the surface. 2.2. STANDARD PENETRATION TEST It is now most commonly used in site test. The test measures the penetration resistance of the split spoon sampler, when it is driven into the soil, at the bottom of a borehole in a standard manner. The N-value, which is the number of blow required to achieve 300mm penetration of the soil, indicates the relative density of sand or gravel, the consistency of other soil such as silts or clays and the strength of weak rocks. The test is described in IS 2131 - 1981. The split spoon sampler is attached to stiff drill rod and lowered to the bottom of the bore hold. A standard blow consists of dropping a mass of 63.5kg free fall through 750 mm on to an anvil at the top of the rods and ensuing that this amount of dynamic energy is transferred to the sampler as much as possible. The number of blows required to achieve each 150mm penetration is recorded for a fall penetration of 450mm. The initial 150mm penetration is referred to as seating drive and the blows required for this penetration are not considered as this zone is in disturbed soil. The next 300mm of penetration is referred to as the test drive and the number of blows required to achieve this fully is termed the penetration resistance or N-value. The total number of blows (N) required, to advance the spoon into the bore, for another two successive 15cm (a total of 30 cm) is recorded as a measure of the soil relative density or consistency as given in Table. CO – RELATION FOR SATURATED SAND/NON – PLASTIC SILT Relative Density Penetration Value (Blows/Ft) Very loose 0 to 4 Blows Loose 5 to 10 Blows Medium 11 to 30 Blows Dense 31 To 50 Blows Very Dense > 50 Blows CO – RELATION FOR SATURATED CLAY/PLASTIC SILT Relative Density Penetration Value (Blows/Ft) Very Soft 0 to 2 Blows Soft 3 to 4 Blows Medium Stiff 5 to 8 Blows Stiff 9 To 16 Blows Very Stiff 17 To 32 Blows Hard > 32 Blows Rock samples were extracted by Rotary drilling technique using double tube core barrel of 76mm diameter, filter with a diamond bit. The extracted cores for every run, not exceeding 1.0 meter were arranged in the core boxes and the T.C.R as well as R.Q.D values were measured. The appropriate estimation of the properties of the encountered rock strata can be obtained by referring to the borehole logs and the following description R.Q.D % ROCK QUALITY 90 – 100 Excellent 75 – 90 Good 50 – 75 Fair 25 – 50 Poor 0 - 25 Very Poor RECOVERY % DESCRIPTION OF ROCK 0 – 20 Rock is treated as soil 20 – 35 with SPT > 50 blows / 30 cm Soft or disintegrated rock 35 – 50 Intermediate rock 50 – 85 Medium rock > 85 Sound rock The fieldwork was carried out under the close supervision of our engineer in accordance with Indian Standard mentioned earlier. 2.3. SAMPLING Soil samples were collected through Split spoon and rock core sample were collected through single tube core barrel. 3. LABORATARY TESTS The operations to be performed in the laboratory depend upon the type of the nature of data required for the problem at hand. In case of cohesionless material, like sand, the laboratory tests are usually minimum and the design parameters are worked out from field test data such as form SPT- N value, Core resistance and plate load test data. In the case of cohesive soils, the programme of laboratory testing can vary from carrying out simple tests such as unconfined tests to comprehensive study of soil behaviour using triaxial shear tests and consolidation tests. Following laboratory tests are conducted. For Cohesionless soil a) Specific gravity b) Sieve analysis c) Direct shear test For Cohesive soil a) Specific gravity b) Natural moisture content c) Atterberg’s limits d) Sieve Analysis 4. FOUNDATION ANALYSIS 4.1 Safe Bearing Capacity The bearing capacity of granular soil depends upon the unit weight and angle of internal friction of the soil. These two properties of granular soils are determined by standard penetration tests. The allowable bearing pressure based on tolerable settlement has been established empirically by Terzaghi and Peck, 1948 and may be expressed by the equation. Safe bearing capacity = 1.40(N”-3) x ((B+0.3)/2B)2 xW’ x Rd x s Where, N” = Corrected N value B = Width of Foundation = constant 1 W’ = Water table correction = constant 0.5 Rd = Depth of Foundation = constant 2 s = Tolerable settlement = 25 mm 5. DESIGN CRITERIA 5.1 Design of Foundations As per the clients information the PROPOSED CONSTRUCTIONOF R.C.C ROOF GROUND INDUSTRIAL GODOWN BUILDING S.F. No: 158/2B & 158/2C OF AVINASHI VILLAGE, TIRUPUT-DT. The design of foundation depends upon the founding strata, loading intensity at the foundation level and configuration at loading points. For the above conditions, pile foundations are recommended for the proposed structure shown in the following recommendation. 5.2 Depth of Foundation Minimum depth of foundations is governed by the following factors: ·        Top loose zone. ·        Adequate depth of soil above founding level, to ensure mobilization of full safe bearing capacity. ·        Adequate depth of soil strata below founding level of requisite strength to mobilize the safe bearing capacity and at the same time restricts the total and differential settlements within the allowable limits. ·        The type and depth of foundation shall be decided by the design engineer. 6. FOUNDATION RECOMMENDATIONS ·        The engineering properties of soil and SPT N value are to be considered for the foundation recommendation The site for PROPOSED CONSTRUCTIONOF R.C.C ROOF GROUND INDUSTRIAL GODOWN BUILDING S.F. No: 158/2B & 158/2C OF AVINASHI VILLAGE, TIRUPUT-DT. The borehole investigation was conducted and SBC was determined. 7. PRECAUTIONS Entire report should be studied before implementing the recommendations. Loose pockets of soil, if encountered shall be removed and backfilled with a levelling course of concrete shall be laid and construction of foundations with IS CODE recommends can be taken up subsequently. 8. LIMITATIONS The soil investigations have been carried out at locations in the site chosen by the client so as to represent the entire site. The recommendations provided in this report are hence valid only for these test locations. However, if there is any change in sub soil conditions and properties at places between or beyond chosen test locations, JAI SHRIRAM ENGINEERING COLLEGE may be contacted for further advice. With passage of time, the recommendations may vary due to manmade and natural environmental changes. GEOTECHNICAL INVESTIGATOR 9. REFERENCES 1. IS: 6403-1981 2. IS: 2911-(part1/sec-2 0-1979) 3. IS: 2131-1980 4. IS: 8009 (Part-1) 1976 5. IS: 2720 for all laboratory tests 6. Wayne CTEng(1992)Foundation design,13th reprint, Prentice - Hall of India Pvt.Ltd., 7. Bowles J.E,(1982) Foundation Analysis and design ,3rd edition, Mc Graw Hill International Book Co. 8. Tomlinson M.J. (1995) Foundation Design and Construction, 6th edition, Longman Group. ANNEXURE – I SOIL TEST RESULTS Name of Project: GEOTECHNICAL INVESTIGATION WORK FOR PROPOSED CONSTRUCTIONOF R.C.C ROOF GROUND INDUSTRIAL GODOWN BUILDING S.F. No: 158/2B & 158/2C OF AVINASHI VILLAGE, TIRUPUT-DT. Soil Investigation done by: Jai Shriram Engineering, Avinashipalayam, Tirupur- Dt BORE HOLE NO: 01 and 02 LOCATION: Avinashi, Tirupur GROUND WATER LEVEL: Not Met WORK STARTED ON 12.12.2019 WORK COMPLETED ON 12.12.2019 INDEX PROPERTIES SIEVE ANALYSIS % SPT SOIL PROFILE AND DEPTH IN METRES DEPTH OF SAMPLING (M) IS SOIL CLASSIFICATION NATURAL WET DENSITY (g/cc) NATURAL WET UNIT WEIGHT (kN/m3) NATURAL MOISTURE CONTENT % LIQUID LIMIT % PLASTIC LIMIT % PLASTICITY INDEX SPECIFIC GRAVITY COARSE SAND % MEDIUM SAND % FINE SAND % CLAY & SILT % DEPTH OF TESTING M OBSERVED N VALUE CORRECTED N VALUE SAFE BEARING CPACITY KN/m2 1.5 S 1.44 19.4 11.2 NP NP NP 2.52 32 26 18 24 1.5 17 14 414 1.5 S 1.51 20.3 10.9 NP NP NP 2.28 31 25 21 23 1.5 16 13 384.7 SM – SILTY SAND, S - SAND, SBC is based on SPT Result. *NP – Non Plastic, N/A – Not Applicable