What are the components of the static load test system?
The most common static load test is the single pile vertical compressive static load test. The single pile vertical compressive static load test adopts a test method close to the actual working conditions of the vertical compressive pile to determine the vertical compressive resistance of the single pile bearing capacity. It is currently recognized as the most intuitive and reliable test method for testing the vertical compressive bearing capacity of foundation piles.
The vertical compressive static load test of a single pile is mainly to determine the vertical compressive ultimate bearing capacity of a single pile through measurement, that is, the corresponding one before the single pile reaches the failure state under the vertical load or when a deformation that is not suitable for continued bearing maximum load. It depends on the support resistance of the soil to the pile and the strength of the pile structure. It is generally controlled by the support resistance of the soil to the pile. For end-bearing piles, super-long piles and piles with defective pile quality, it may be controlled by the strength of the pile structure.
The composition of the detection system
Static load test equipment is mainly composed of loading reaction force system, load measurement system, displacement measurement system and automatic acquisition system.
loading reaction force system
Loading reaction force device composition: loading voltage stabilizing equipment, reaction force device.
Purpose: to ensure that sufficient reaction force is provided to transmit the load to the predetermined position of the pile through the loading equipment.
1. Load voltage regulator equipment
Whether it is vertical compression, pull resistance or horizontal thrust, the test load should be loaded by hydraulic jack.
Rules for the use of jacks:
(1) When two or more units are connected in parallel, the models and specifications should be the same.
(2) The force center of the jack coincides with the center of the pile.
Principle of jack selection:
(1) Parallel use requires the same specifications
(2) Jack output
(3) Jack stroke
Selection principle of oil pump
1. Oil output
2. Maximum working pressure
3. Fuel tank size
4. Double oil circuit oil pump
Common oil pumps:
Electric oil pump
Manual oil pump
2. Reaction device
The common reaction device consists of different specifications of steel beams, buttresses, counterweights (concrete blocks or steel blocks), etc.
Single pile vertical compressive static load devices often use anchor pile reaction device, weight reaction device, anchor pile pressure combined reaction device, and ground anchor reaction device.
Anchor pile reaction device
Anchor pile reaction device
Anchor pile reaction device
Ballast reaction device
Anchor pile pressure-weight combined reaction force device
Ground anchor reaction device
Load measurement system: pressure test equipment, including pressure gauges, pressure sensors, and load cells.
Load measurement system
Precision requirements: better than equal to 0.5
The pressure gauge and pressure sensor are installed between the pressure relief valve and the jack.
Pressure gauge Pressure Sensor load cell
Displacement measuring device: Displacement measuring device includes reference beam, reference pile and dial indicator or displacement sensor.
Displacement measurement system
1. Reference beam
a. Stiffness.
b. One end should be fixed and one end should be simply supported.
2. Benchmark pile
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Reaction device
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Test pile center and anchor pile center
(Or beside the buttress of the weight platform)
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Test pile center and reference pile center
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Base pile center and anchor pile center
(Or beside the buttress of the weight platform)
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Anchor pile beam
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≥4（3）D and ＞2.0m
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≥4（3）D and＞2.0m
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≥4（3）D and＞2.0m
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Weight platform
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≥4D and ＞2.0m
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≥4（3）D and＞2.0m
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≥4D and＞2.0m
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Ground anchor
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≥4D and ＞2.0m
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≥4（3）D and＞2.0m
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≥4D and＞2.0m
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(3) Dial indicator and displacement sensor
Location: The position below the top of the pile 200mm, preferably not less than 0.5 times the pile diameter.
Quantity: For piles with diameter or side width> 500mm, 4 dial indicators or displacement sensors should be installed symmetrically in two directions. For piles with diameter or side width ≤ 500mm, 2 dial indicators or displacement sensors can be installed symmetrically.
Accuracy: the error is not more than 0.1%FS, the resolution is not more than 0.01mm.
A large range dial indicator or displacement sensor should be used.
Automatic acquisition system
Due to the long test time and the harsh on-site environment for static load test, there are many static load testers on the market, which can greatly increase the on-site inspection efficiency, reduce the workload of on-site inspection staff, and can be carried out more accurately. Operations and records, etc. The use of static load tester can not only improve the work efficiency on site, ensure the safety of on-site workers, but also conduct tests more accurately.
