Arun Soil Lab Pvt.Ltd.
Geotech and Material Consultants
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Certificate No. : TC-5382
NABL Accredited as per
ISO/IEC: 17025 - 2005

PILE LOAD TESTS
PILE LOAD TEST IS : 2911 (Part IV) - 2010
SCOPE
  • Piles find application in foundation to transfer loads from a Structure to competent sub surface strata having adequate load bearing capacity. They are provided in general in soft and expansive soils. Piles transfer load either by skin friction along its shaft or by end bearing or by both. The installation of piles demand careful control on position, alignment, depth and involve specialized skill and experience. Pile Load Test is the most direct method for determining the safe load on piles including its structural capacity with respect to soil in which it is installed.
DATA
  • The following information is necessary for pile (s) on which test is proposed.

    (a) Pile type including material and reinforcement details, group of piles, if any
    (b) Method of driving with driving record or installation.
    (c) Pile depth (s) and details of cross-section (s).
    (d) Type of test desired
    (e) Layout of the pile(s), space available around and position in the group for single pile test.
    (f) Depth of water table and soil strata details with soil test results.
    (g) Safe load and ultimate load capacity, and the method (s) on which based.
    (h) Availability and provision of type of piles or anchors or kentledge for reaction.
    (i) Nature of loading/loading plan
VERTICAL LOAD TEST (COMPRESSION)
There are namely two types of vertical load Test in Compression
Initial Test
  • Initial Test is done on specifically cast pile to determine the ultimate load capacity of it and arrive at safe load by applying a factor of safety. The test is done in important/major projects and number of tests may be one or more depending on the number of piles required. In case specific information about strata and past guiding experience is not available, a minimum of two tests must be done. The Initial Load Test is generally continued up to 2.50 times the safe load or the settlement equal to 7.50% of the bulb diameter, whichever is earlier.
Routine Test
  • Routine Test is done on working pile for evaluating the design load that can be safely taken by the pile . The number of tests may be generally one-half percent of the total number of piles required. The number of tests may be increased up to2%in a particular case depending upon nature, type of structure and strata condition.
Vertical Load Test
  • In this test, compression load is applied to the pile top by means of a hydraulic jack against rolled steel joist or suitable load frame capable of providing reaction and the settlement is recorded by suitably positioned dial gauges.
  • A bearing plate with a hole at the centre is placed on finished, cleaned and smooth green top (head) of the pile for jack to rest. The test is carried out by applying a series of vertical downward incremental load each increment being of about 20% of safe load on the pile.
  • Kentledge for reaction shall be placed on a platform supported clear of the test pile. The centre of gravity of the kentledge must be on the axis of the pile and the load applied by jack shall be coaxial with this pile. The reaction to be made available for the test should be 25% more than the final test load proposed to be applied.
  • Settlement is recorded with minimum 2 dial gauges for single pile and 4 dial gauges of 0.01mmsensitivity for groups, each positioned at equal distance around the piles and normally held by datum bars resting on immovable supports at a distance of 3D (subject to minimum of 1.5 metre) from the edge of the piles, where D is the pile stem diameter of circular piles or diameter of the circumscribing circle in the case of square or non-circular piles.

    However, the safe load on group of piles for initial test shall be the least of the following:
  • Final Load at which the total displacement attains a value of 25mmunless otherwise required in a given case
  • Two-thirds of the final load at which the total displacement attains a value of 40 mm.
  • Whereas, the routine test shall be carried as above but for a maximum settlement not exceeding 25 mm.

LATERAL LOAD TEST
  • This test is carried out by introducing a hydraulic jack with gauge between two piles or pile group under test or the reaction may be suitably obtained otherwise. The loading is applied in increments of about 20 percent of the estimated safe load.
  • Displacements shall be read by using at least two dial gauges of 0.01 mm. sensitivity spaced at 30 cm. and kept horizontally one above the other on the test pile and the displacement noted/recorded at cut-off level from similar triangles where cut-off level is unapproachable and for approachable cut-off level, however, one dial gauge placed diametrically opposite to the jack directly measures the displacement.

    The safe lateral load on the pile shall be taken as the least of the following:
  • Fifty percent of the final load at which the total displacement increases to 12mm.
  • Final Load at which the total displacement corresponds to 5 mm or any other permissible displacement as per performance requirements.
  • All pile load tests being field tests, a load-deflection behaviour is bound to reflect the variation in strata and construction of the pile. Consequently, load-deflection behaviour differ from pile to pile. All the data is shown by curves drawn between load applied and deflection obtained on graphs. These curves are essential part of Pile Load Test Report.

PULL-OUT TEST
  • In this test uplift force is preferably applied by means of hydraulic jack (s) which usually rest on rolled steel joist(s) which in turn rests on two supports on the ground. The jack reacts against a frame attached to the top of the test pile such that when the jack is operated, the pile gets pulled up and the reaction is transferred to the ground through the supports which are at least 2.5 D away from the test pile periphery (where D is pile stem diameter).
  • The test pile shall have adequate steel to withstand pulling. In some cases, in order to allow for neck tension in a pull-out test, it may be necessary to provide additional reinforcement in the piles to be tested.
  • The pull-out load increments and consequent displacement readings are read similarly as in the case of vertical load test.

    The safe load shall be taken as the least of the following:
  • Two-thirds of the load at which the total displacement is 12 mm or the load corresponding to a specified permissible uplift.
  • Half of the load at which the load-displacement curve shows a clear break (downward trend).
  • The Initial Test is carried out up to twice the estimated safe load or until the load displacement curve shows a clear break (downward trend).
  • Routine Test shall be carried out to one-and-a half times the estimated safe load or 12mmtotal displacement whichever is earlier.