Md. Nafiul Haque

Field Investigation of Pile Setup in Mixed Soil

An instrumented test pile was installed at the Bayou Zourie bridge reconstruction site as part of a Louisiana Department of Transportation and Development (LADOTD) research initiative to study the setup phenomenon of piles driven in Louisiana soils. Pile instrumentation included pressure cells to measure the total pressure at the pile face, piezometers to monitor the excess pore water pressure at the pile face, and “sister bar” strain gauges to measure the strain distribution along the pile. Additional instrumentation consisted of multilevel piezometers installed within soils at different locations/depths from the pile and accelerometers attached to the piles during dynamic load testing. A total of two static load tests and four dynamic load tests were conducted on the test pile. During the static load tests, the strains within the pile were measured by the strain gauges, which were used to calculate the distribution of load transfer along the pile. Both static and dynamic load tests demonstrated the increase in pile resistance with time (setup). Results of dynamic load tests confirmed that pile setup occurs at a logarithmic rate after the end of driving (EOD) and is mainly attributed to the increase in side resistance. Good correlation was observed in this study between the pile setup and the percentage of dissipated excess pore water pressure with time. The measured excess pore water pressure suggested that the surrounding soil, along the pile (within distance 2B), is significantly influenced during pile driving. Results indicated that the changes in side resistance are directly related to the changes in the horizontal effective stress acting on the pile face.

Load-Testing Program to Evaluate Pile-Setup Behavior for Individual Soil Layers and Correlation of Setup with Soil Properties

AbstractSix instrumented static-load test piles driven at four different locations along the LA-1 highway alignment in coastal Louisiana provided the opportunity to study the soil-setup behavior in relation to the soil properties. The instrumented piles consisted of six square prestressed-concrete (PSC) test piles of different sizes and different lengths. Both soil boring and piezocone penetration tests (PCPT) were conducted at each test-pile location to characterize the subsurface soil conditions. The testing program consisted of performing dynamic-load tests (DLTs) at predetermined time intervals, followed by one static-load test (SLT) at the end. These piles were instrumented with vibrating-wire sister-bar strain gauges along their length. Case pile-wave analyses were performed on the DLT data to calculate the soil-resistance distributions along test piles. Design parameters such as the adhesion factor α and the effective stress coefficient β were also backcalculated. The α values ranged from 0.68 to 1...

Field Investigation to Evaluate the Effects of Pile Installation Sequence on Pile Setup Behavior for Instrumented Test Piles

This paper examined the setup behavior of two 0.61-m (24 in.) test piles (with 44.2-m and 51.8-m lengths) that were installed within 3.05-m (10-ft) center-to-center or 5D (D = Pile Diameter) spacing. The piles were instrumented with strain gauges to measure the load transfer and setup per individual soil layers. The 44.2-m pile was installed 2 h after the 51.8-m pile. Several dynamic load tests (DLT) and one static load test (SLT) were conducted on the test piles to measure the increase in piles resistances with time. The effect of pile installation sequence on setup behavior was also investigated. The test results showed that both test piles exhibited significant increase in pile resistances or setup with time. However, the initial side resistance for the 44.2-m pile (installed 2 h later) was about half the side resistance for the 51.8-m pile; and the rate of side resistance increase with time for the 44.2-m pile was much higher than the 51.8-m pile. This behavior can be attributed to the sequence of pile driving in clayey soils. The driving of the 51.8-m pile caused the development of excess pore water pressure in the surrounding soils that affected the initial pile resistance and the setup rate of the 44.2-m pile. The CAPWAP analysis of DLT and the load distribution plots from SLTs were used to compute the resistance of individual soil layers along the piles’ length with time, which showed that clayey soil layers exhibited higher amount of setup compared to sandy-silty soil layers. The results of this study showed that the time, to, to when the setup curves become log linear with respect to time can be as early as 2 h after end of driving. The results of the testing program also indicated that the setup rate parameter “A” is independent of the depth.

Evaluation of pile capacity from CPT and pile setup phenomenon

Abstract Piles driven in cohesive soils usually experience a large increase in capacity over time, known as setup or freeze. This paper presents the field results of two test piles that were driven in two different locations of Louisiana to evaluate the pile setup behavior. Laboratory and in situ soil testings (cone penetration test, CPT) were conducted to characterize the subsurface soil properties. Several dynamic load tests (DLTs) and one static load test (SLT) were conducted on each test pile at different times after end of driving (EOD) to quantify the magnitude and rate of setup. The test pile in one site was instrumented with vibrating wire strain gages to calculate the load-distribution along the length of the pile during the static load test. With the aid of Case Pile Wave Analysis Program (CAPWAP®) analyses and load distribution plots from strain gages, skin friction and end-bearing capacities were measured separately. The load test results showed that the setup was mainly attributed to increase in skin friction with time and end-bearing capacity remained almost constant. The load test results also showed that setup behavior was more significant in soft cohesive soil. The pile capacity of one test pile was also evaluated using different CPT methods (such as Schmertmann, De Ruiter and Beringen, LCPC). The result showed that all the methods can estimate the pile capacity with good accuracy.

A Load-Testing Program on Large-Diameter (66-Inch) Open-Ended and PSC-Instrumented Test Piles to Evaluate Design Parameters and Pile Setup:

This paper presents the results from a pile load testing program for a bridge construction project at Chalmette, Louisiana. The load testing includes three 66-in. spun-cast post-tensioned open-ended cylinder piles and one 30-in. square prestressed concrete (PSC) pile driven at four different locations along the bridge site in clayey-dominant soil. Both cone penetration tests and soil borings/laboratory testing were used to characterize the subsurface soil conditions. All test piles (TP) were instrumented with strain gauges to measure the load distribution along the length of the TPs and to measure the side and tip resistances, separately. Dynamic load tests (DLT) were performed on all TPs at different waiting periods after pile installations to quantify the amount of setup (i.e., increase in pile resistance with time). Case Pile Wave Analysis Program (CAPWAP®) analyses were performed on the DLT data to calculate the resistance distributions along the TPs. A static load test was performed only on the PSC pile and statnamic load tests (SNLT) were conducted on both pile types. Design parameters such as the total stress adhesion factor, α, and the effective stress coefficient, β, were back-calculated. The α values ranged from 0.41 to 0.86, and the β values ranged from 0.13 to 0.29. The load test results showed that SNLT overestimated the tip resistance as compared with dynamic and static load tests. Moreover, the pile tip resistance was almost constant during the testing period, and setup was mainly attributed to increase in pile side resistance with time.

Analytical Models to Estimate the Time Dependent Increase in Pile Capacity (Pile Set-Up)

This paper presents the analyses of twelve prestressed concrete (PSC) instrumented test piles that were driven in different locations of Louisiana in order to develop analytical models to estimate the increase in pile capacity with time or pile set-up. The twelve test piles were driven mainly in cohesive soils. Detailed soil characterizations including laboratory and in-situ tests were conducted to determine the different soil properties. The test piles were instrumented with vibrating wire strain gauges, piezometers and pressure cells. Several static load tests (SLT) and dynamic load tests (DLT) were conducted on each test pile at different times after end of driving (EOD) to quantify the magnitude and rate of set-up. Measurements of load tests confirmed that pile capacity increases almost linearly with the logarithm of time elapsed after EOD. Case Pile Wave Analysis Program (CAPWAP) were performed on the restrikes data and were used along with the load distribution plots from the SLTs to evaluate the increase of skin friction capacity of individual soil layers along the length of the piles. The logarithmic set-up parameter “A” for unit skin friction was calculated of the 70 individual clayey soil layers, and were correlated with different soil properties. Nonlinear multivariable regression analyses were performed and three different empirical models are proposed to predict the pile set-up parameter “A” as a function of soil properties.