AU2013213724A1

AU2013213724A1 - Rapid load capacity test

Info

Publication number: AU2013213724A1
Application number: AU2013213724A
Authority: AU
Inventors: Justin Williamson
Original assignee: PATENTED FOUNDATIONS Pty Ltd
Current assignee: PATENTED FOUNDATIONS Pty Ltd
Priority date: 2012-08-14
Filing date: 2013-08-07
Publication date: 2014-03-06
Anticipated expiration: 2033-08-07
Also published as: AU2013213724B2

Abstract

A rapid load capacity test method for piles (including screw piles, blade piles and in-situ cast piles) employs a test apparatus with a mobile test rig locatable 5 about the pile to be tested. A lifting rod is connected to a load-applying jack and is releasably connected to the shaft of the pile. An up-lift load is applied to the pile shaft, and from the force applied, the load-bearing capacity of the pile can be calculated. It (0

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "RAPID LOAD CAPACITY TEST" The following statement is a full description of this invention, including the best method of performing it known to me/us: 1 TITLE: RAPID LOAD CAPACITY TEST BACKGROUND OF THE INVENTION; 1. Field of the invention: 5 [0001] This invention relates to a rapid load capacity test. [0002] The invention relates, but is not limited to, a load capacity test for the foundations of buildings; and more particularly, to the load capacity of piers or piles supporting the foundations. [0003] Through out the specification, the term "piles" will be used to include 10 both piers or piles, whether driven into the ground (e.g. by a pile-driving machine), screwed into the ground, or cast in-situ. 2. Prior art: [0004] Piles, having (typically hollow) steel shafts, are used to support building constructions, more typically building slabs, and are screw-driven into the soils 15 below the slabs to be constructed. [0005] Screw piles have at least one helical screw- or flyte around the shafts, usually adjacent the digging point at the lower end of the shafts. The helical screws- or flytes may be provided at spaced locations along the shafts, to spread the load transfer from the piles to the surrounding soil. 20 [0006] Engineers are always concerned that the load-bearing strength of the piles is sufficient to support the building constructions, in both static- and dynamic-load conditions. In cyclonic areas, wind forces can apply both lateral and vertical-uplift loads on a building construction, and so the load-bearing strength of the piles is not the only factor to be taken into account when 25 specifying the piles and their locations under the building. [0007] To enable the engineers to establish the load bearing capacity of the piles at a particular site, they typically have at least one test hole drilled to determine the soil profile and load capacity. However, as the soil structure may markedly vary within 30 cm (or less) of the test hole e.g. with an 30 increased sand or clay content, the engineer must assume the soil structure is uniform over the site. [0008] As structural failure is a greater concern than structural cost to the 2 engineer, the resultant specification of the piles, and their location, is likely to be much greater than is necessary to achieve the desired load bearing capacity. [0009] Alternatively, if the test hole indicated the soil structure is stronger / 5 more stable than the remainder of the site, the "over-specification" based in the test hole may actually result in "under-specification" for the balance of the site. [0010] Many geographical areas in Australia, including Adelaide, have reactive soils, typically containing an high clay content. It is not unknown for 10 such reactive soils to be liable to vertical "heave" exceeding 30cm between fully dry and fully wet. [0011] The 'heave" of the reactive soils has resulted in damage to building foundations, and to vertical displacement of a building relative to adjacent facilities / utilities. 15 [0012] It has been known, however, that the "heave" of the reactive soils e.g. following rain after a long period of drought, has been so large as to raise the piles in the soil. OBJECTS OF THE PRESENT INVENTION: 20 [0013] It is an object of the present invention to overcome, or at least ameliorate, the problems of the prior art. [0014] Other preferred objects will become apparent from the following description. 25 SUMMARY OF THE PRESENT INVENTION; [0015] In one aspect, the present invention resides in a method fortesting the load-bearing capacity of piles driven into the ground, the method including the steps of: a) placing a frame of a load capacity test rig, supportable on the ground, in 30 substantially co-axial alignment with a pile driven into the ground; b) connecting an hydraulic jack, as a load-applicator on the test rig, to the pile by a connection apparatus having one end connected to the load applicator 3 and the other end connected to the pile; c) applying an up-lifting load to the pile by the load-applicator; d) measuring or indicating the up-lifting load; and e) calculating and/or indicating the load-bearing capacity of the pile from the 5 up-lifting load. [0016] Preferably, the other end of the coupling apparatus is releasably coupled to the shaft of the pile, at or adjacent the upper end of the shaft. [0017] Preferably, the other end is releasably coupled to the shaft by a screw threaded connection, a bayonet-type connection, a wedge-type connection, or 10 other releasable connection. [0018] In a second aspect, the present invention resides in an apparatus for testing the load-bearing capacity of piles driven into the ground, the apparatus including: a test rig having a frame supportable on the ground substantially coaxially 15 aligned with the pile to be tested; a hollow ram hydraulic jack, as a load-applicator, on the frame; a connection apparatus to connect the load-applicator to the pile, the connection apparatus including at least one lifting rod or bar passing through the hydraulic jack and connected at one end to a piston rod of the hydraulic 20 jack and connected at the other end to the pile; and measuring and/or indication apparatus to measure an up-lifting load applied to the pile by the load-applicator and/or to enable calculation, or indication, of the load-capacity of the pile. [0019] Preferably, the frame substantially surrounds a shaft of the pile to be 25 tested; and the hydraulic jack is connected via a lifting-head or lifting-yoke at an upper end of the at least one lifting rod or bar. [0020] Preferably, a lower end of the at least one lifting rod or bar is releasably coupled to the shaft of the pile, at or adjacent the upper end of the 30 shaft. [0021] Preferably, the at least one lifting rod or bar is coupled to the shaft by a screw-threaded connection, a bayonet-type connection, a wedge-type 4 connection, or other releasable connection. [0022] Preferably, the measuring and/or indication apparatus includes a sensor to measure the hydraulic pressure applied to the load-applicator; and a gauge or indicator connected to the sensor indicates the hydraulic pressure, 5 the measured up-lift force applied to the pile and/or the calculated load-bearing capacity of the pile. BRIEF DESCRIPTION OF THE DRAWING: [0023] To enable the skilled workman to fully understand the invention, and to 10 enable that person to put the invention into practice, preferred embodiments will now be described with reference to the accompanying drawing, in which: FIG. 1 is a schematic side view of the testing of a blade pile in accordance with a first embodiment of the present invention. [0024] Any annotations on FIG. 1 are by way of illustration only, and are not 15 limiting to the scope of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS: [0025] The blade pile 10 schematically illustrated in FIG. 1 is representative of all screw- or blade piles, where a hollow steel shaft 11 is terminated at a 20 digging point or tip 12, and one or more pairs of screws or blades 13 are provided on the shaft. The skilled addressee will be aware that the pairs of screws or blades 13 may be provided at spaced intervals up the shaft 11; and that stabilising fins (not shown) may be provided about the shaft 11 to increase the lateral stability of the pile 10. 25 [0026] A load-bearing capacity test apparatus 20, to test the load-bearing capacity of the pile 10, has a transportable test rig 30 which can be moved from pile to pile 10 to be tested on-site. [0027] The test rig 30 has a frame 31, with a substantially annular base plate, or feet 32, at the lower end of a plurality of spaced steel struts 33, which 30 support a substantially annular pad 34 at their upper ends. The base plate, or feet 32, are arranged to enable the test rig 30 to be slid laterally into co-axial alignment with the pile shaft 11.

5 [0028] A hollow hydraulic ram jack 40 is mounted co-axially on the annular pad 34. The ram jack 40 is connected to a (high-pressure) hydraulic pump 50 via hydraulic hoses 51, 52 and pressure gauge 53. [0029] The hydraulic ram jack 40 has an annular cylinder 41 and an annular 5 piston rod 42. [0030] A lifting rod 60 is received co-axially within a central passage 43 through the piston rod 42 (and cylinder 41 ). The lifting rod 60 is screw threaded at least at its respective upper and lower ends 61, 62. [0031] The upper end 61 of the lifting rod 60 is secured to the distal end of the 10 piston rod 42 by an abutment washer 63 and high tensile nut 64. [0032] The lower end 62 of the lifting rod 60 is connected to the upper end 14 of the pile shaft 11 by a releasable coupling apparatus 70. [0033] In the embodiment illustrated in FIG. 1, the coupling apparatus 70 includes a screw-threaded nut insert 71 secured in the upper end 14 of the 15 pile shaft 11. [0034] In an alternative embodiment, not shown, lugs or fingers may be provide on the exterior of the upper end 14 of the pile shaft 11, or internally in the upper end 14 of the pile shaft 11, and be releasably engaged by a complementary bayonet-type coupling at the lower end 62 of the lifting rod 20 60; or vice versa. [0035] In other alternative embodiments, one or more transverse locking pins may releasably connect the lower end 62 of the lifting rod 60 to the upper end 14 of the pile shaft 11; the lifting rod 60 and pile shaft 11 may be screw threadably coupled together; or a wedge-type connection e.g. with balls or 25 rollers in an annular coupling head, may couple the lifting rod 60 and the pile shaft 11. [0036] The skilled addressee will appreciate that there are many possible releasable coupling methods to connect the lifting rod 60 to the pile shaft 11. [0037] The skilled addressee will also appreciate that the hollow hydraulic ram 30 jack 40 may be substituted by one or more hydraulic-, pneumatic- or mechanical screw jack(s), which may be connected to the upper end 61 of the lifting rod 60 by a lifting-head, lifting-yoke or like device to spread the load 6 between the jacks. [0038] The skilled addressee will further appreciate that two or more lifting rods may interconnect the lifting-head, lifting-yoke or like device to a coupling apparatus connectable to the upper end 14 of the pile shaft 11. With this 5 arrangement, it is preferable that the coupling apparatus be releasably connectable to the exterior of the pile shaft 11. [0039] In a further alternative embodiment not illustrated, the lifting rod (or rods) may be connected to (e.g. the distal end of) a lever arm, or rocker arm, pivotally mounted on the frame 31 and selective raised by one or more jacks. 10 [0040] In use, the test rig 30 is located with the lifting rod 60 co-axially aligned with the pile shaft 11. The lower end 62 of the lifting rod 60 is coupled to the upper end 14 of the pile shaft 11 by screw-threaded engagement between the lower end 62 of the lifting rod 60 and the nut insert 71. [0041] The hydraulic pump 50 is operated to supply hydraulic fluid, of 15 increasing pressure, to the hydraulic lift jack 40, causing the piston rod 42 to apply a lifting load to the lifting rod 60, which transfers the lifting load to the pile shaft 11. [0042] The operator monitors the hydraulic pressure via the gauge 53, and can calculate the lifting force being applied to the pile 10. By use of the 20 conversion uplift-force = 70% (load-bearing capacity), the operator can calculate the load-bearing capacity of the pile 10. (The skilled addressee will appreciate that the gauge can be calibrated to directly indicate the uplift force applied to pile 10 and/or the load-bearing capacity of the pile 10; or that the hydraulic pressure may be measured by a sensor, where the output is fed to a 25 computer for calculation / display / recordal of the load-bearing capacity for each specific pile. [0043] The operator can either determine the absolute load-bearing capacity of the pile 10; or test to ensure the load-bearing capacity of the pile is within design limits e.g. 8 tonnes. 30 [0044] When the particular pile 10 has been tested, the hydraulic pressure is reduced and the test rig 30 is disconnected from the pile. It can now be easily moved about the site to test another selected pile 10. This means that several 7 piles 0 can be quickly tested on a site to determine the soil structure(s) on the site, and their load-bearing characteristics. [0045] By use of the test method and apparatus of the present invention, the engineer can quickly, and accurately, establish the load-bearing capabilities of 5 the soil structures at multiple locations across a site, rather than simply relying on a single test result as representative of the whole site. This means that an engineer may be able to specify lighter-construction piles and/or fewer piles to achieve the design load for the piles supporting the building construction. [0046] In addition, if the testing method provides markedly varying measured 10 load-bearing capacities, the engineer can immediately request that additional piles be tested e.g. in a location where the largest variations occur. The additional tests can be quickly, and relatively inexpensively, carried out. [0047] The engineer is more confident that the foundation design, supported by the piles, is appropriate for the building construction, as changes in the 15 soils structure / characteristics can be compensated for e.g. where the site covers both reactive and no-reactive soils. [0048] Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention. 20 25 30

Claims

1. A method for testing the load-bearing capacity of piles driven into the ground, the method including the steps of: 5 a) placing a frame of a load capacity test rig, supportable on the ground, in substantially co-axial alignment with a pile driven into the ground; b) connecting an hydraulic jack, as a load-applicator on the test rig, to the pile by a connection apparatus having one end connected to the load applicator and the other end connected to the pile; 10 c) applying an up-lifting load to the pile by the load-applicator; d) measuring or indicating the up-lifting load; and e) calculating and/or indicating the load-bearing capacity of the pile from the up-lifting load. 15

2. A method as claimed in claim 1, wherein: the other end of the coupling apparatus is releasably coupled to the shaft of the pile, at or adjacent the upper end of the shaft.

3. The method of claim 2, wherein: 20 the other end is releasably coupled to the shaft by a screw-threaded connection, a bayonet-type connection, a wedge-type connection, or other releasable connection.

4. An apparatus for testing the load-bearing capacity of piles driven into the 25 ground, the apparatus including: a test rig having a frame supportable on the ground substantially coaxially aligned with the pile to be tested; a hollow ram hydraulic jack, as a load-applicator, on the frame; a connection apparatus to connect the load-applicator to the pile, the 30 connection apparatus including at least one lifting rod or bar passing through the hydraulic jack and connected at one end to a piston rod of the hydraulic jack and connected at the other end to the pile; and 9 measuring and/or indication apparatus to measure an up-lifting load applied to the pile by the load-applicator and/or to enable calculation, or indication, of the load-capacity of the pile.

5 5. The apparatus of claim 4, wherein: the frame substantially surrounds a shaft of the pile to be tested; and the hydraulic jack is connected via a lifting-head or lifting-yoke at an upper end of the at least one lifting rod or bar. 10

6. The apparatus of claim 4 or claim 5, wherein: a lower end of the at least one lifting rod or bar is releasably coupled to the shaft of the pile, at or adjacent the upper end of the shaft.

7. The apparatus of claim 6, wherein: 15 the at least one lifting rod or bar is coupled to the shaft by a screw-threaded connection, a bayonet-type connection, a wedge-type connection, or other releasable connection.

8. The apparatus of any one of claims 4 to 7, wherein: 20 the measuring and/or indication apparatus includes a sensor to measure the hydraulic pressure applied to the load-applicator; and a gauge or indicator connected to the sensor indicates the hydraulic pressure, the measured up-lift force applied to the pile and/or the calculated load-bearing capacity of the pile. 25 30