RailwaymonitoringMONITORING SOLUTIONS FOR THE RAIL INDUSTRY

PiletestingPILE MONITORING & TESTING SPECIALISTS

Strainstall

The Bi-Directional Static Load Test is a well-known static load testing method that uses a time and space

saving approach by loading the pile resistance from the mid-pile of near-toe position instead of top loading.

The BDSLT has gained world wide acceptance for larger diameter (> mm) cast in-situ concrete piles.800

Bi-Directional Static Load Testing (BDSLT)

expertise

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Widely adopted in the US, Europe and Asia, engineers and piling contractors are increasingly turning to the Bi-Directional Static Load Test method due to its effectiveness and the breadth of information provided.

Hydraulically driven, high capacity, sacrificial bi-directional jacks are pre-installed in the pile with the rebar cage, prior to concreting. After casting, loading is applied in equal and opposite directions - upwards against upper skin friction and downward against lower skin friction and end bearing.

Since the upward skin friction and end-bearing are measured separately, there is no guesswork as to how much load was carried by each section. Testing is typically performed until the ultimate capacity in either shear or end baring is reached to determine the maximum pile capacity.

Pile Testing and Monitoring Specialists

By using multiple bi-direction jacks on a single horizontal plane, the available test capacity can be increased to more than 10,000 tonnes, and by using multiple jacks on different planes, distinct elements within a shaft can be isolated for testing.

Using this method, scaling errors can be totally eliminated by testing the full size production piles, and installing the testing apparatus within the pile shaft means the Bi-Directional Static Load Test is not restricted by the limits of kentledge weight, reaction piles or overhead

Automated Data Acquisition and LoggingStrainstall’s pileSENTINEL package is used for automated and continuous monitoring of static loads. The advanced electronic recording system is configured to provide real-time data recording at defined intervals (that can be as frequent as every minute), and features easy to use PC-based software that interfaces with Microsoft Excel.

Mobility and Space Efficiency

Benefits and advantages

Eliminates the need for overhead beams or reaction piles.

Time EfficiencyIt only takes a few days of preparation for the installation of the pre-manufactured bi-directionalhydraulic jack(s).

Precision TestingProvides engineers with separatedata on the end-bearing and frictionresistance of the shaft

Cost EfficiencyHas been proven to be more cost effective than traditional load testingmethods.

VersatilityCan be applied to barrette, bored piles (compression or tension),inclined piles or belled shafts. Thetest pile can be reused to carryworking loads after testing bygrouting the pile.

structural beams. Ground and not the test method determine the weight of load that can be

The incorporation of strain gauges within the pile helps to determine the distribution of load throughout the shaft length, and the use of embedment strain gauges can provide detailed analysis of soil properties.

In summery, the speed and accuracy of testing makes the Bi-Directional Static Load Test a highly useful tool for value engineering and project redesign.

conditconditions

used.

Pile Testing and Monitoring Specialists

Crosshole sonic logging is a method of verifying the quality and consistency of

piles with the objective of locating defects. Selected bored piles are pre-installed with steel tubes

that span the whole axial length before casting.

drilled shafts and other

concrete

A transmitter lowered down into one tube sends a high frequency signal that travels through the concrete and is detected by a receiver in the second tube. As these transmitters are raised and lowered along the length of the pile, a cross hole analyser (CHA) records the signals at regular depth intervals, and the time that the signal takes to travel from the transmitter to the receiver (first arrival time), as well as the signal energy.

These two parameters will indicate the concrete quality between the

pair of tubes at a particular depth. The entire shaft length is logged and the test is then repeated for each pair of tubes, allowing for a full and thorough investigation of faults both along the length and by its quadrant.

The results are mapped and presented in graphical format to provide qualitative data once testing is complete. By comparing the graphs from the various combinations of access tubes, the structural soundness of the concrete throughout the pile can be established .

Cross-Hole Sonic Logging

3D TomoSonic SoftwareTomoSonic is a 3D tomography imaging tool that supplements the cross hole analyser output. This analysis is useful in cases where cross hole sonic tests reveal a defect, but does not give a precise indication of its extent.

TomoSonic helps visualise the local defect in two or three dimension by producing a 2D or 3D colour coded images of the shaft. The TomoSonic software combines arrival time data from the scans of all pairs of tubes and analyses the data and displays it in various views.

innovation

and measurements can be provided to show lateral, tensile and compressive forces.

Static load testing is used to provide a direct measurement of pile displacement in response to a physically

applied test load and is considered to be the bench-mark of pile performance. Suitable for all pile types,

static load testing can be carried out on either production piles or sacrificial test piles.

Static Load Testing

adequately supported and that there is sufficient reserve capacity.

The test pile is subjected to loading using a hydraulic jack, and Strainstall designed and manufactured high capacity loadcells are used to measure the load. Direct measurements of pile displacement under the applied weight are logged and the test results presented in a graphical format that shows loading versus pile head displacement.

Virtually any size of load test can be performed on land and at sea,

Load testing a pile to failure identifies the maximum operating capacity of a pile and also provides valuable information to design engineers. It is recommended for load tests carried out prior to the foundation design, as the outcome of the tests are critical in verifying foundation design parameters and formulating remedial actions if needed.

Testing on production piles is used to prove that the pile will perform satisfactorily at the design load plus an overload, to demonstrate that a building or structure will be

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www.strainstallmonitoring.comPile Testing and Monitoring Specialists

High strain static load testing is a method of testing deep foundations to obtain information about their

capacity and/or to monitor their installation. A Pile Driving Analyser (PDA) is used to record, process and

display data and results.

High strain dynamic pile testing is suitable for use on all types of drilled and driven piles, and has the advantage of being conducted in a non-destructive manner. They are also less expensive to conduct that static load tests, which means they can be performed on many more piles at a much lower cost and faster speed.

Dynamic measurements of force and velocity are collected by strain sensors and accelerometers attached to the pile. The PDA monitors the strain and acceleration caused by the

hammer impact, and process thesesignals after each hammer blow during driving or restrike to give an immediate graphical visual of the loading signals for each blow.

Typical results obtained on site include mobilised static load

its size and location can be estimated by analysing the propagation and reflection of the wave induced on the foundation by the hammer impact.

A low strain pile integrity test is used to detect potential defects such as major cracks, necking, soil inclusions or voids and, in some situations, the method can determine unknown lengths of piles. The method does not require advanced planning or access tubes, which makes it the most affordable option when pile integrity is in question.

The name "low strain dynamic test" stems from the fact that when a light impact is applied to a pile it produces a low strain. The impact produces a compression wave that

Pile Testing and Monitoring Specialists

High Strain Dynamic Pile Testing

Feedback on the maximum tension and compression forces

Direct measurements of hammer input energy and efficiency

Cost effective

Instant checks on the pile integrity and the location of any damage

Instant preliminary results on site

Benefits and advantages

capacity, pile integrity (including the location and extent of any damage), the maximum compression/tension forces at the pile top and toe, and hammer performance.

Low Strain Pile Integrity Testing (also know as the sonic echo or pulse echo method) is a quick and cost

effective way of evaluating the integrity of auger cast-in-place piles, bored shafts, driven concrete piles

and concrete filled pipes.

Low Strain Dynamic Pile Testing

travels down the pile at a constant wave speed and produces wave reflections in response to changes in cross sectional area, such as a reduction in diameter or a void in the concrete.

An accelerometer attached to the top or side of the installed pile monitors the impact and resulting deflections from a small hand-held hammer. The accelerometer signal is evaluated in the field or transferred to a PC for further analysis by PIT-W, a Windows based software program. If a defect is present along the shaft,

experience

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Strainstall has over 45 years experience in the monitoring and testing of structures and components. Our team of qualified geotechnical, mechanical, electronic, civil and structural engineers are well equipped to develop solutions to most instrumentation and monitoring requirements across all engineering sectors. One such sector is the foundation engineering industry, in which we specialise in the provision of high strain dynamic pile testing and analysis, pile integrity testing, consulting services and other specialist testing services.

Operating state-of-the-art equipment and computer software, the systems used offer proven accuracy and reliability through thousands of field tests conducted every year all around the world.

Strainstall

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