Is Bi-Directional Load Test Future for Static Pile Test in India?
Sarathy Geotech & Engineering Services Pvt Ltd.
Geotechnical & Geophysical integrated approach for both Offshore, Nearshore & On-land projects.
Partha Sarathi Parhi, Ph.D. , Our Senior Geotechnical Engineer is writing,
In recent years, the construction industry of India has witnessed significant growth with the inclusion of several mega projects like metro railways, Bharatmala Pariyojna, Sea links, etc., and it is expected to grow exponentially. This has led to an increase in demand for foundation testing, particularly pile foundation, to ensure the safety and reliability of any project. Traditionally, static pile testing has been the go-to method for testing pile capacity, but recently, there has been an increasing interest in bidirectional load testing as an alternative method with significant advantages.
Static pile testing involves measuring the load capacity of a pile by applying a static load to the pile and monitoring its behavior. This method is reliable but can be time-consuming and expensive. Bidirectional load testing, on the other hand, is a relatively new method that involves applying both upward and downward loads to a pile using a reaction frame, which can provide accurate results within a shorter time frame.
One of the significant advantages of bidirectional load testing is its ability to measure the load-deflection response of a pile. This allows engineers to determine the ultimate load capacity of the pile, as well as the load-displacement behavior of the pile during the loading cycle.
The test results can separate out soil/rock resistance and movement data for shaft and toe individually and hence can give information on the magnitude of mobilized shaft and toe resistances. Additionally, if strain gauges are used at different depths during the foundation casting, data from these strain gauges during the testing can give valuable information about soil/ rock resistance distribution along the foundation length.??
The cost of load testing is a significant consideration for construction projects in India. Bidirectional load testing is generally less expensive than traditional static pile testing, mainly because it requires fewer resources and can be performed in a shorter period. The time and cost savings provided by bidirectional load testing can be particularly beneficial for projects with tight schedules or budget constraints.?
Furthermore, bidirectional load testing can be performed using a smaller reaction frame compared to static pile testing. This means that it can be performed in locations with limited space or challenging access. This is particularly important in densely populated urban areas where construction sites are often located in tight spaces.?
Despite its advantages, bidirectional load testing is not without its limitations. One of the significant concerns is the lack of standardization of testing procedures. Additionally, bidirectional load testing is relatively new in India, and there is a lack of trained personnel who can perform the tests accurately and safely.
The bidirectional load test is an alternative to the static pile test that offers several advantages, including faster testing times, lower costs, and more accurate results.
Although the use of this test is growing in India, the static pile test remains the most used method of foundation testing. The future of the bidirectional load test in India will depend on several factors, including the availability of specialized equipment, the cost of the test, and the availability of skilled personnel to perform the test.
Regardless, the Bidirectional load test is a promising alternative that offers significant advantages and should be considered for use in construction projects.
Comment your thoughts!
Visit us Today: www.sarathygeotech.com
Contact Us: +91 91640 00080
CGM, LEA Associates, New Delhi || M. Tech.(Geotechnical Eng./IIT KGP), B.E.(Civil) || P. Eng.(India) & C. Eng.(India) || FIE, LMIGS, MISSMGE, MISRM, LMISRMTT, LMISET, LMIRC, LMICI, LMISH, MDFI, LMISEG, MIAEG, LMIIBE
9 个月Another limitations of the BDSPLT are the following. 1. The pile shaft having uncleaned base or bottom specially for long pile in alluvial soil deposit with or without having weak concrete along the bottom part below the "Loading Cells" can't be loaded till up to its desired theoretical ultimate load due to excessive deflection of the bottom part of shaft consuming the “Travel Run” of the “loading Jacks” at lower level of applied test load. In this case the test becomes incomplete due to the mobilisation of end-bearing resistance of the bottom part of shaft prior to the mobilisation of the available skin friction of the top part of pile shaft. 2. The interpretation of the BDSPLT is NOT straight forward and independent of theoretical evaluation. The evaluation of the loads corresponding to the deflection needs special expertise from the interpretation of the top and bottom load deflection curve. So all these aspects truly need careful practice and expertise in the relevant field. Thanks N Regards.
CGM, LEA Associates, New Delhi || M. Tech.(Geotechnical Eng./IIT KGP), B.E.(Civil) || P. Eng.(India) & C. Eng.(India) || FIE, LMIGS, MISSMGE, MISRM, LMISRMTT, LMISET, LMIRC, LMICI, LMISH, MDFI, LMISEG, MIAEG, LMIIBE
9 个月The "Bidirectional Load Test (BDSPLT) " is found mostly suitable for larger value of "Test Load" say 1500 ton & above. Even though BDSPLT has several advantages specially to test the large diameter long shaft to examine the load-deflection behaviour till up to the "Ultimate Load", but the BDSPLT has several factors to become successful. The following important aspects need special attention. 1. The pile is to be preselected and needs all the required preparation during its installation itself as this is the instrumented pile load test. So based on the pile construction history, the pile having some doubtful installation record can not be selected for test. 2. The position of the "Load Cell Assembly" is very important to continue the test till up to the desired ultimate load. The balancing position "Load Cell/Jack" is completely depends on the available "Theoretical Assessment of Pile Load Carrying Capacity and its distribution along the shaft from top to toe level" based on the reliable "Geotechnical Investigation Data". In absence of adequate and appropriate investigation data, the position of the "Load Jack Assembly" cannot be placed at the balancing point of capacity of the top and bottom part of the pile shaft. Regards.
Geotechnical Engineer || GeoStructures || Tata Consulting Engineers Limited || IIT Bhubaneswar ||
9 个月Absolutely. But as this test is very much sensitive to the location of the load cell inside the pile, accurate geotechnical parameters are required to predict its location which can only be obtained from good quality Investigation. So, the better Quality of Geotechnical Investigation scenario in India only can boost the success rate of BDSLT Test.
Bi-Directional Pile Load Test Specialist
9 个月Good explanation and sharing of Bi-directional Static Load Test from Partha Sarathi Parhi, Ph.D. Just few things to add on here, the jacks used are specific with a cone shape which can prevent the issue of blockage for sediment around the steel plates and formation of the soft layer concrete that will lead to inaccurate testing results. Thanks Regards, Wang