(k) IS: Code of Practice for design and construction of well foundation. (l) IS: Code of Practice for determination of allowable bearing. Page 1. Page 2. Page 3. Page 4. Page 5. Page 6. Page 7. Page 8. Page 9. Page Page Page Page Page Page Page Page Page portal7.info - Download as PDF File .pdf), Text File of the penetration test results as given in IS: and reproduced below: Q = 9.

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download BIS IS CODE OF PRACTICE FOR DESIGN AND CONSTRUCTION OF WELL FOUNDATIONS from SAI Global. k IS Code of Practice for design and construction of well foundation from SAAS 45 pages WSA_ADB NCRPB_FR_Vol V B-3 Detailed portal7.info . So, IS has given an expression for the allowable bearing pressure, which is represented by Q a, and it is given by N square B plus 16 times

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This must be added to the load. Piles may also be further divided into the following categories. For end-bearing piles passing through relatively compressible strata. Bearing-cum-frication piles: These piles transfer the load both by bearing and friction. This judgment is employed in selecting appropriate multiplying factors. Driven piles require large areas and head room since it needs larger and heavier driving rigs. In case of piles of non-circular section.

Precast driven piles ensure good quality of material.

The spacing is also decided by group behavior for total carrying capacity and settlement. In cast-in-situ piles.

Selection of type of pile. Driving causes vibration of the ground which may damage nearby structures. When piles are installed through compressible fill or sensitive clay into underlying hard stratum. The depth is termed as critical depth. Angle of internal friction. The average ultimate unit skin friction.

The semi-empirical relationships between the bearing capacity factor. The underlying hard stratum shall not be considered for assessing the downward drag and the skin friction expected to be mobilised by the strata will be assessed on the basis of para 2. This can be roughly estimated as cohesion of the remoulded clay multiplied by the surface area of pile shaft. Load Carrying Capacity. O in degrees Fig. Static Formula: Piles in non-cohesive Soil: The maximum value of qL is to be equal to 0.

The extant methods of evaluation of ultimate bearing capacity indicate that both point resistance and average skin friction of a pile would increase with greater depth of penetration. Nq factors. The unit point resistance shall preferably be estimated from static cone penetration results. While the pile point is above the critical depth. For bored piles one third to one half values as applicable to driven piles shall be used. The conventional shaft capacity theory in terms of Ks cannot be used for piles longer than about 15 to 20 pile diameter because the corresponding value of fs in case of such long piles does not exceed the critical value f1.

Soil strata Type of pile The value of N shall be corrected for overburden pressures to determine unit point resistance and not for frictional resistance. For piles driven into non-plastic silt.

Given data. Embedded Depth below the deepest scour level Problem —To work out the ultimate bearing capacity of a single pile. Diameter of the pile In the case of bored piles. Better reliance may be placed on results of load tests on piles. Ap cm toe. Static Formulae may be used as a guide only for bearing capacity estimates.

Note 1. The factor of safety shall be judiciously chosen after considering the following: N is Note 2. Loose sandy soil 3.

The ultimate capacity of the IIB The bearing capacity of a pile group may be worked out as under: For a group of piles. The bearing capacity of a group of piles is generally evaluated by multiplying with efficiency factor. A minimum factor of safety shall be 2.

Full scale trials have shown that for piles driven into soft and medium clays with 3 to 4d spacing. The ultimate capacity of the group may be computed taking into account the friction capacity along the sides of the column of soil and the end bearing of the soil column.

A large number of equations giving the efficiency factor are in use and it is very difficult to establish the accuracy of these equations as the behaviour of pile group is dependent on many complex factors.

In the case of loads and moments arising out of earthquake effects. This overloading shall not be allowed at the initial design stage. A group of piles deriving their support mainly from friction and connected at the top by a rigid pile cap may be visualised to transmit load to the soil from a column of soil enclosed between the piles.

It is. The factor of safety based on load tests shall be increased in unfavourable conditions such as: The final selection of the factor of safety shall take into consideration the total settlement and differential settlement of the structure. For transient loading arising out of superimposed loads. This additional capacity along with the individual capacity of the piles multiplied by the number of piles in the group shall not be more than the capacity worked out as per Para 2.

Pneumatic Sinking of Wells. Types of piles. Spacing of piles. Load carrying capacity of a pile. Factor of Safety for pile foundations. Pile grouping. Settlement of pile foundations. Load test. Capacity of Pile against lateral loadings. Depth Of Foundations The depth of deep foundations below the high flood level shall be determined as indicated in clause 6. The choice of type and shape of well foundation will depend upon the soil, type, the size and shape of pier or abutment, depth of foundation and available construction material.

Where major obstructions such as uneven rocky strata are likely to be encountered, provision for pneumatic sinking may be made. Small obstructions can be removed either with the help of divers or by chiselling.

Shape And Cross-Section Of Wells: The horizontal cross-section should satisfy the following requirements: a The dredge hole should be large enough to permit dredging.

The well steining should also be designed to withstand the earth pressures acting only on two opposite sides or only on diametrically opposite quadrants under conditions of sand blowing. The effect of heap of earth dumped near the well during sinking shall also be taken into account. IIB-iv1 Explanation Of The Diagram: The intention of the diagram is to offer something definite in place of the rather fortuious method now centrally practiced.

OC-Represents depth to which foundation should be sunk.

Note: 1. The diagram applies only to sandy bottom. If the river bed is soft, a greater depth is necessary. Piers are always presumed to have enough stone around them to prevent local pier formed swirls from scooping pot-holes at pier base. The shapes normally used are circular, double D.

Dumb-bell, hexagonal or octagonal, square, rectangular and any of the above shapes with multiple dredge holes. For clayey strata settlement should be worked out for full load based on consolidation test results. For wells constructed in cohesion less soils where full settlement due to dead load will take place by the time construction is completed and the necessary adjustments in the final level can be made before erection of girder, dead load due to well and the substructure can be ignored.

In such cases, settlement shall be evaluated only for superstructure, live load and loss of friction in the well due to scour. The passive pressure and skin friction shall be taken only for soil below the level of scour. Well curb. Well steining. Bottom Plug. Top Plug.

Well cap. Pneumatic Sinking of Wells. Types of piles. Spacing of piles. Load carrying capacity of a pile. Factor of Safety for pile foundations. Pile grouping. Settlement of pile foundations. Load test. Capacity of Pile against lateral loadings.

Depth Of Foundations The depth of deep foundations below the high flood level shall be determined as indicated in clause 6. The choice of type and shape of well foundation will depend upon the soil, type, the size and shape of pier or abutment, depth of foundation and available construction material.

Where major obstructions such as uneven rocky strata are likely to be encountered, provision for pneumatic sinking may be made. Small obstructions can be removed either with the help of divers or by chiselling.

Shape And Cross-Section Of Wells: The horizontal cross-section should satisfy the following requirements: a The dredge hole should be large enough to permit dredging.

The well steining should also be designed to withstand the earth pressures acting only on two opposite sides or only on diametrically opposite quadrants under conditions of sand blowing. The effect of heap of earth dumped near the well during sinking shall also be taken into account. IIB-iv1 Explanation Of The Diagram: The intention of the diagram is to offer something definite in place of the rather fortuious method now centrally practiced. OC-Represents depth to which foundation should be sunk.

Note: 1. The diagram applies only to sandy bottom. If the river bed is soft, a greater depth is necessary. Piers are always presumed to have enough stone around them to prevent local pier formed swirls from scooping pot-holes at pier base. The shapes normally used are circular, double D.