Low strain pile integrity test is a common nondestructive test (NDT) procedure for quality control and quality assurance (QC/QA) in deep foundation construction. The test can be used to identify physical defects (voids or discontinuity, referred to as pile integrity) in piles, or determine unknown length of existing deep foundations.
Low Strain Pile Integrity Test belongs to the family of shaft head impact tests, where the response of an impact made on the head of pile head is recorded by a motion transducer (i.e. accelerometer), and used for analysis. Alternatively, engineers can use other tests such as crosshole or down-hole tests for the purpose of integrity test.
Pile Integrity Test Principle
The general principle behind the pile integrity test is relatively simple. By Assuming that the stress wave travels at the speed of C inside the pile shaft, the pile depth can be determined by measuring the time lapse, T, between striking pile head and receiving reflections on pile head.
How To Perform Low Strain Pile Integrity Test?
Pile Integrity Test (PIT) is normally performed by striking the pile head with a light hand-held hammer and recording the response of the pile using a motion transducer (i.e. accelerometer) coupled to the pile head. The hammer strike (blows) generate compressive stress wave that will travel through the pile. This wave is partly reflected from the pile toe or other anomalies within the pile in its way back to pile head. Any change in impedance (due to change in pile cross section, concrete density, or shaft-soil properties) within the pile can impact the reflecting signal.
1- When To Perform Pile Integrity Test?
The integrity testing should be performed no sooner than 7 days after casting or after concrete strength achieves at least 3/4 of its design strength, whichever occurs earlier.
2- How to Prepare The Surface?
The surface of the pile head should be prepared ahead of the test. The pile surface should be accessible, and above water. All loose concrete, soil or other foreign materials resulting from construction should be removed from pile surface. If there is any type of contamination on the surface, it should be removed (using a grinder) to reach to solid and sound concrete surface.
3- How To Couple Transducer and Pile Head?
A firm connection between the sensor’s tip and concrete surface (pile tip) is needed for successful application of the test method. A thin layer of Vaselin, or putty is normally used to make a firm connection between the sensor and the pile head.
4- What type of hammer should you use?
Low strain impact integrity testing is performed using a hand held hammer. The hammer can be as light as couple of hundred grams, to relatively heavier options. The impacts induced by smaller hammer have higher frequency content, and shorter rise time. Larger hammers on the other hand, induce higher energy. Sharp and narrow input pulses are reported to be better than wider ones. However, when the size is reduced, the frequencies contained in the impact increases; these waves attenuate faster, and are tend to decrease the ability of investigating longer piles. Hammers less than 1 Kg with a plastic impact tip are ideal for most cases. When pile diameter is larger than 1 m (1000 mm), heavier hammers will be more suitable. The hammer tip should be made of material that does not damage concrete during the impact, as this will impact the test results.
5- Striking Pile Head: Where, How, How Many?
The low strain impact should be applied to the pile head within a distance of 300 mm from the sensor. It is also important to place the transducer far from the pile edge to reduce the effect of edge. Make sure that the impact is applied axially. For inclined piles, make sure the transducer is place perpendicular to the pile surface (parallel to pile longitudinal axis), and the strike direction is parallel to this direction.
For circular (diameter less than 500 mm) and rectangular cross sections, place the sensor near the center of the pile and strike several times around the pile head (i.e. 10 impacts). Increasing the number of impacts will reduce the effect of background noise, and helps enhance repeatable parts, which will make interpretation easier. For piles with larger diameter (i.e. Diameter > 500 mm) additional locations should be considered to obtain useful integrity information about the pile.
How to interpret Pile Integrity Test Results
The motion transducer collects reflection on the pile head. The measurements can be either acceleration (accelerometer), or velocity (geophone). A typical reflection from a sound pile is displayed in the following graph.
Results can be displayed in time domain (where horizontal axis shows the arrival time of echoes on pile head). Alternatively, time stamps can be converted to depth values. Results can be presented in negative or positive formats. The first peak is usually from the surface wave triggering the motion transducer. In a sound pile, the next major peak is usually the one associated with pile toe. A minimum sampling rate of 25 kHz, and time array length of 100 ms is generally good for evaluating most piles. In the event of using an accelerometer, integration of test results are used to show the measurements in velocity format.
1. Wave Speed Adjustment
The speed of stress wave can be adjusted based on the type and condition of pile material. A number of researchers and engineers have developed correlation tables between the quality of material, and the compression wave speed in the material. For example, wave speed in sound concrete is approximately 4,000 m/s (~13,000 ft/s).
2. Low Pass Filter
Low pass filter is used to reduce the effect of high frequency reflections caused by shear wave influence at the top of the pile and steel reinforcement inside the pile.
The reflecting signal can get attenuated for several reasons. High impedance, and longer pile length can attenuate the returning signal, making it difficult to identify pile toe. In this case, an exponential amplification function is used across the pile length to amplify the low energy reflections from the pile toe and other internal anomalies. This function is applied if the reflection of the pile toe is not apparent. This function increases the amplitude of signal exponentially with time along the recorded signal. Application of this function should be handled with care, as it also amplifies background noise.
Pile Integrity Test Standards
The test has been adapted by many standards and codes around the globe. The most commonly used standard that is used for performing pile integrity test and reporting is the ASTM D5882-16, Standard Test Method for Low Strain Impact Integrity Testing of Deep Foundations, ASTM International, West Conshohocken, PA, 2016, www.astm.org
We are very excited to announce that we have signed with FPrimeC Solutions Inc. a partnership agreement to expand sales network and support centres for iPile™ | Pile Integrity Testing-PIT in Europe and the Middle East. Great times ahead for your concrete testing.
Concrete piles and drilled shafts are an important category of foundations. Despite their relatively high cost, they become necessary when we want to transfer the loads of a a heavy superstructure (bridge, high rise building, etc.) to the lower layers of soil. Quality control and quality assurance has been a popular, yet challenging task for geotechnical engineers, inspectors, and piling contractors, mainly because these elements are generally buried under ground, with only pile head being accessible most of the time. Different intrusive and non-intrusive methods have been developed over the past decades to help engineers with easy, reliable and cost-effective evaluation of quality in these elements. Pile Integrity test is referred to a group of nondestructive tests that aim to provide quantitative data on physical dimensions of pile elements, their continuity, and last but not least, consistency of the pile material.
Pile integrity test (PIT), or as ASTM D5882 refers to it as "low strain impact integrity testing of deep foundation is a widely used nondestructive test method for the evaluation of pile quality, integrity and to help estimate the unknown length of existing piles and foundations. Pile integrity test can be either used for for forensic evaluations on existing piles, or quality assurance in the new construction. The integrity test is applicable to driven concrete piles and cast-in-place piles. The following image provides a visual summary of major integrity issues in deep foundations.
Low strain impact integrity testing provides acceleration or velocity and force (optional) data on slender structural elements (ASTM D5882). Sonic Echo (SE) and Impulse Response (IR) are employed for the integrity test on deep foundation and piles. The test results can be used for evaluation of the pile cross-sectional area and length, the pile integrity and continuity, as well as consistency of the pile material; It is noted that this evaluation practice is approximate. The PIT method works best for column type foundations, such as piles and drilled shafts. The method provides a rapid and simple tool for evaluation of a number of piles in a single working day.
How to Perform PIT?
Surface preparation is the first thing to do when performing a pile integrity test. Any type of contamination should be removed (using a grinder) to reach to solid and sound concrete surface. The pile head surface should be accessible, above water, and clean of loose concrete, soil or other foreign materials resulting from construction. This step is so vital, because then connection between the sensor and concrete should be solid (firm contact). The acceleration sensor should be placed on concrete firmly. To do so, a couplant material should be used to attach the acceleration sensor the pile head. An impactor (usually a hand-held hammer) is used for impacting pile head; the impact should be applied axially with the pile. Motion transducer should be capable of detecting and recording the reflected echos over the pile top. Acceleration, velocity, or displacement transducers can be used for this purpose. At the minimum, acceleration transducer should have an Analog to Digital Converter with 12 bit resolution; and a Sample Frequency of at least 25 KHz. The location of the sensor should be selected away from the edges of the pile. The integrity testing should be performed no sooner than 7 days after casting or after concrete strength achieves at least 3/4 of its design strength, whichever occurs earlier.
The distance between the impact location and the sensor should be no larger than 300 mm. Several impacts are applied to the top of the pile. The reflected echos are then recorded for each individual impact. As an alternative, the average can be determined and used. As mentioned earlier, acceleration transducer can be used for the purpose of this test. In this case, the apparatus shall provide signal conditioning and integrate acceleration to obtain velocity. The apparatus shall balance the velocity signal to zero between impact events.
What Information Does Pile Integrity Test Provide?
The Pile Integrity Test (PIT) provides information about:
+ Evaluate integrity and consistency of pile material (concrete, timber);
+ Evaluate pile cross-sectional area and length;
Limitations of Pile Integrity TestThe PIT provide an indication of soundness of concrete; however, the test has certain limitations:
+ PIT can not be used over pile caps.
+ It does not provide information regarding the pile bearing capacity.
+ Test should be undertaken by persons experienced in the method and capable of interpreting the results with specific regard to piling.
+ This test is not effective in piles with highly variable cross sections
+ It is not effective in evaluating sections of piles below cracks that crosses the entire cross sectional area of the pile.
Geomorph Instruments is very happy to announce a new, strategic partnership with RTUTec and the appointment of the latter as our representative in Israel.
RTUTec was founded for the purpose of identifying innovative technologies. Ron Pincu and Dr. Amos Frishling founded RTUTec in 2014.
Ron was a member of the founding team of the NDT lab in the Israeli air-force. He holds NDT Level II certifications, has a first degree in Engineering and an MBA from Hartford University in England. Over the years, Ron has specialized in finding original solutions for testing requirements. If in Aerospace industry, Oil & Gas, research and more. Ron has been instrumental in developing cutting edge portable X-ray systems for field NDT requirements.
RTUTec is currently offering a variety of products in different technologies among which are portable digital radiography systems, mobile cabinet X-ray and tomosynthesis equipment, Dosimeters & Survey meters, portable X-ray sources, thermographic devices and Ultrasonic & Radio-frequency based solutions.
We are very happy to announce that we are DUNS registered.
The Dun & Bradstreet D‑U‑N‑S Number is a unique nine-digit identifier for businesses. This number, identifies a company as being unique from any other in the Dun & Bradstreet Data Cloud. The D‑U‑N‑S Number is used as the starting point for any company's Live Business Identity, the most comprehensive and continually updated view of any company in the Data Cloud.
D‑U‑N‑S Numbers are often referenced by lenders and potential business partners to help predict the reliability and/or financial stability of the company in question. D‑U‑N‑S, which stands for data universal numbering system, is used to maintain up-to-date and timely information on more than 300 million global businesses. The D‑U‑N‑S Number also enables identification of relationships between corporate entities (hierarchies and linkages), another key element of Live Business Identity and commercial risk assessment practices.
The need to detect and assess jellyfish is driven by a variety of interests and concerns. Certainly most of us are aware that the sting from some species of jellyfish may cause painful wounds or even death, prompting the use of warning flag systems, barrier nets, and advanced sonar systems to protect swimmers at public beaches. Compounding this threat of physical harm, jellyfish populations in many of the world's oceans are know to dramatically and suddenly fluctuate, and often without cause or explanation. Despite the significant hazards posed by contact with jellyfish, the mechanisms controlling their movements and population dynamics are not well understood. Scientific echosounders are a proven, reliable instrument for the detection and measurement of jellyfish, and these specialized sonar systems are used by researchers worldwide for a wide range of studies. Their body structure of a jellyfish is dense enough to reflect pulses of sound (pings) emitted by sonar, and thus jellyfish are quite well-suited for the use of hydroacoustics. Over recent years, researchers around the globe have developed a wide range of interesting sonar methods and equipment for their study and this article documents just a few of these projects and case studies.
Due to shifts in ocean temperatures and currents, populations of so called “giant jellyfish” can rapidly increase or “bloom” and spread to new areas. Blooms of these massive creatures wreak havoc on commercial fishing operations by fouling nets and reducing fish catches. Predicting the movements and locations of giant jellyfish can help fishermen avoid the animals, and thereby increase fishing catch rates and efficiencies.
Dr. Kyounghoon Lee, of Chonnam National University in South Korea, has extensively studied the giant jellyfish, Nemopilema nomurai, using a split beam echosounder integrated with an acoustic camera and CTD sensor deployed from research vessels while conducting mobile surveys. Results from Dr. Lee’s work provide information about the sizing distribution and migration patterns of the animals in the Yellow Sea and East China Sea. Below you can see images of the giant jellyfish
Another Korean researcher, Dr. Kang Do-Hyung with the Korean Institute of Ocean Science and Technology (KIOST) has done extensive work using a multi-frequency BioSonics split beam echosounder studying the acoustic target strength (TS) of several jellyfish species, including the giant jellyfish Nemopilema nomurai Kishinouye. Some of Dr. Kang’s work involved using tethered jellyfish in net cages with the echosounder transducer affixed to the top of the cage. TS data derived from this research can be used for developing acoustic scattering models, and surveying giant jellyfish distributions and biomasses. Below, you can see a diagram of Dr. Kang's experiment with tethered jellyfish and a sonar echogram showing the jellyfish
Jellyfish increasingly cause significant problems for power plants, and other industrial facilities that intake large amounts of cooling water, when swarms of the organisms enter the water intakes and clog intake screens. Clogging events due to jellyfish blooms require laborious clean-up efforts and have caused total shutdowns of nuclear power plants in the United States, Scotland, Sweden, Japan, and Israel. Financial losses from such unplanned, sudden shutdowns can exceed 1 million USD per day. Below you can see power plant employees working to remove tons of jellyfish from water intake structures.
As a solution for power plant operators, BioSonics Automated Monitoring System (AMS) can be specifically configured for the detection of jellyfish, either for single, larger animals or dense aggregations of smaller individuals. Similar BioSonics systems are already in use at nuclear power plants in the US and Europe. The BioSonics AMS consists of a DT-X split beam echosounder coupled with a heavy duty PC running specialized software that processes hydroacoustic data in real time. Split beam transducers are fix-mounted in a horizontal or up-looking orientation and provide an acoustic curtain or “trip wire” to detect and classify objects in the water column at ranges exceeding 500m.
We are glad to present our customer’s find of a numismatic treasure – a witness to early currency reforms and noticeable effects on present world currencies: Several silver coins identified as Spanish Dollars were detected with the ground scanner Rover C II in northern Peru and can be dated back to the late 16th century.
Reverse of the silver coin: The coat of arms of Castile shows two lions and two castles, divided by a cross and surrounded by the letters ‘ET INDIARVM REX’. The coin can be dated back to the late 16th century – approx. 1580. The Spanish Dollar was very common and widespread, occurrences with perfectly intact motifs are rather seldom.
Pieces of Eight: The Basic Concept of World Currencies
The numismatic value of this find is fascinating in many respects: The coins became a popular trade currency of the Spanish Empire and still have impact on the designation of the present dollar. The discovery and conquest of mineral wealth in Peru and Mexico in the 15th and 16th century empowered the Spanish Empire and initiated early monetary reforms. One of the most famous silver coins of that time is the ‘Piece of Eight’, named after its divisibility into several bits. This concept is still common for breaking down currency values such as the US-Dollar into Half Dollar and Quarter Dollar.
Treasure Hunters’ Serendipity and our Technical Expertise
Thanks to its powerful performance and various special features, the multi-purpose metal detector Rover C II identifies hidden cavities and precious metal objects in different types of terrain: such as the silver coins which were found in the Sechura Desert approx. 60 cm (1.97 ft) deep – deeper than conventional detectors are able to explore.
The 3D ground scanner Rover C II combines metal detection with geoelectrical measurement in order to:
Source: Palawan News (www.palawan-news.com)
The Department of Environment and Natural Resources (DENR) is set to charge the management of a beach hostel in El Nido after the discovery of its “illegally installed” polymerizing vinyl chloride (PVC) pipeline within the easement zone over the weekend.
A statement sent to Palawan News Tuesday by the DENR MIMAROPA Region said the PVC pipeline was excavated from the beachfront of Outpost Beach Hostel in Barangay Corong-Corong through the use of the ground penetrating radar (GPR) by a survey team of the regional and central offices of the Mines and Geosciences Bureau (MGB).
“The pipeline measuring six inches in diameter and six meters in length was uncovered in front of Outpost Beach Hostel in Corong-Corong. It was also found discharging black and foul-smelling liquid directly into Bacuit Bay, one of the province’s ecotourism sites undergoing massive rehabilitation,” the statement said.
The DENR MIMAROPA said to confirm the source of the wastewater, the Environmental Management Bureau (EMB) used a green tracer solution into Outpost Beach Hostel’s last chamber to which the excavated pipe was connected.
The DENR regional and central offices survey team is seen in this photo using the ground penetrating radar (GPR) to detect the presence of the illegally installed sewerage pipe in front of the Outpost Beach Hostel in Corong-Corong, El Nido. (Photo courtesy of the Mines and Geosciences Bureau)
“After almost 20 minutes, the green solution drained into the said pipe, indicating that the said establishment was the one discharging wastewater from the tank. The EMB shall be conducting further investigation to determine if there are other sources of wastewater discharge aside from the hostel,” it pointed out.
Paul Sepulveda, one of the co-owners of Outpost Beach Hostel, reportedly admitted that they owned the pipe.
Nevertheless, the statement said DENR MIMAROPA regional executive director Henry Adornado ordered the immediate removal of the sewage line as it violates the provisions of Presidential Decree 1067 or the Water Code of the Philippines, which prohibits structures within the easement zones without permission from the government.
Meanwhile, the excavation site was filled with sand using the backhoe sent by the local government of El Nido. The end of the cut pipe was left open for sampling and analysis by the EMB.
“We have to remind everyone that we are preparing Bacuit Bay as Water Quality Management Area so we shall be conducting regular water sampling and analysis not only to Outpost Beach Hostel but also to other establishments to ensure they do not discharge untreated wastewater into Bacuit Bay,” EMB Regional Director Michael Drake Matias said.
Besides regular effluent sampling, the DENR and the MGB have been conducting a GPR survey of the coastal areas of El Nido since March 18 to detect buried waste pipelines. They are calling business establishments to take Outpost Beach Hostel as an example to avoid interruption in their business operations.
“You cannot hide them (pipes) forever. We will eventually uncover them so we advise you to remove your illegal sewage lines and comply with the laws for your own good,” MGB MIMAROPA regional director Roland De Jesus was also quoted in the statement.
The DENR, EMB, and MGB in MIMAROPA vowed to impose the maximum penalty to any establishments found continuously breaking environmental rules and regulations; and employ unified action to ensure environmental protection remains as a top priority.
Golden Engineering X-ray generators are based on Pulsed X-ray technology. Pulsed X-rays generate a high intensity X-ray burst (pulse) in a very short period of time (10 to 50 nanoseconds depending on the model). The output dose of each pulse is 3-6 mR measured 12 inches from the front of the X-ray generator. The operator varies the overall dose of each exposure by changing the pulse setting. The pulse rate varies from 10 pulses per second to 25 pulses per second depending on the model. The generators can fire up to 200 pulses before a four-minute rest period.
Pulsed X-ray technology has inherent advantages for field operation compared to conventional constant potential X-ray machines or radioactive sources.
Performance and Packaging: Pulsed technology generates high output voltage using minimal input voltage. The result is extremely small single package generators with significant penetrating capability.
Safety and Simplicity: Minimal side and rear X-ray leakage means the operator safety stand-off distance is 20 feet (6 m) behind the unit. The generators contain no radioactive material. Radiation is only emitted from the generator while it is pulsing. The single package design eliminates the need for connecting cables between tube head, control module, and power supply. The Golden Engineering cold cathode tube requires no warm up and one input variable (pulse setting) simplifies the operating process.
Compatibility: Golden Engineering pulsed generators are compatible with most digital imaging systems. Conventional radiographic film requires more X-ray dose than digital imaging systems and may not be a viable option for light duty, pulsed X-ray generators. Contact us for more information.
The moisture and humidity testing system for floor covering related industries has been developed to help users avoid moisture related problems in flooring and to identify the cause of problems if they do occur.
The system involves testing the subfloor using both the Tramex CME non-destructive test and in situ Relative Humidity Hygro-i probes. The ambient conditions of the building are also measured and the moisture condition of many floor coverings can be checked.
ASTM F2659: Non-destructive testing
The CME instant test for concrete is completely non-destructive and specified by many floor-covering manufacturers around the world, in part because of its simplicity and the repeatability of the results.
The ease and speed of the CMEX allows for many tests, conforming to ASTM F2659, to be carried out over a large area in a short amount of time. Simply turn on the meter and push it onto the surface being tested and read the results on the clear display. The results are calibrated to show percentage moisture content by weight.
ASTM F2659 calls for 3 to 5 readings in the same location. If there are any variations in those readings, record the highest result.
This is repeated in at least 8 locations for the first 1000sq.ft. and 5 for every 1000sq.ft. thereafter, allowing the user to build up a moisture map of the entire slab and identify when and where to test further if testing, for example, to ASTM F2170.
ASTM F2170: Hygro-i in situ testing
The reusable Hygro-i relative humidity probe has been designed specifically for measuring the potential moisture condition of a slab or screed as per ASTM F2170.
To perform this in-situ type relative humidity test, simply drill a hole in the concrete 40% of the thickness of the slab.
Push the sleeve into the hole, insert the Hygro-i probe into the sleeve and cover with the cap. Leave for the standard test period. When taking readings, plug the interface into the Hygro-i probe and instantly read the relative humidity, temperature and dew point simultaneously on the clear display. When testing is complete the Hygro-i probes can be removed with the extraction tool and used repeatedly. The user must be mindful of all the proper safety precautions as mentioned in the ASTM standard.
Ambient Conditions: Hygro-i testing
In conjunction with the Hygro-i relative humidity probe, the CMEX also functions as a digital hygrometer. The meter displays the relative humidity, temperature, dew point and mixing ratio, allowing the user to assess the environmental ambient conditions within the building, making sure they are suitable for installing a floor covering. Using an Infrared Surface Thermometer in combination with the relative humidity results it becomes easy to identify condensation problems.
Moisture Content of Wood: Pin-type wood probe
The CMEX can also be used with the hand held pin probe, for measuring moisture in wood. This is especially useful when installing wood floor coverings.
By comparing the moisture content of wood with the ambient relative humidity conditions we can determine when the wood is in balance with the ambient conditions within the building.
Another way of identifying when wood is in balance with the building, is to discreetly take moisture content readings from wood somewhere already in service within the building. By taking this in-service moisture content reading it becomes more predictable if the wood floor covering is likely to move, to shrink or expand, or if it is in balance.
Excessive moisture in concrete floor slabs and screeds or a disequilibrium between moisture content in the building and the flooring materials can lead to major problems in many types of floor coverings.