Search Results (4)

The Wave Equation Analysis of Pile Driving (WEAP) has been widely used to determine drivability, predict static resistance, and assure the integrity of piles in soils. Assigning static and dynamic properties of Soil-based Intermediate Geomaterials (S-IGMs) remains a challenge in WEAP, partly attributed to IGMs that act as transition geomaterials between soil and hard rock. Furthermore, reliable static analysis methods for unit resistance predictions are rarely available for driven piles in S-IGMs in the default WEAP method. To alleviate these challenges, this study presents improved WEAP methods for steel piles driven in S-IGMs, including proposed damping parameters and Load and Resistance Factor Design (LRFD) recommendations based on newly developed static analysis methods and the classification of S-IGMs. A back calculation approach is used to generate the appropriate damping parameters for S-IGMs for three distinct subsurface conditions utilizing a database of 34 steel H- and pipe piles. Newly developed WEAP and LRFD procedures are also recommended. Additional independent 22 test pile data are used to compare and evaluate the accuracy and efficiency of the proposed WEAP methods with the default WEAP method. Compared with the default WEAP, bearing graph analysis results revealed that the selected proposed WEAP method, on average, reduces the underprediction of pile resistances by 6% and improves the reliability with a 43% reduction in the coefficient of variation (COV). Calibrated resistance factors for the proposed WEAP method increase to as high as 0.75 compared to the current AASHTO recommendation of 0.50. An economic impact assessment reveals that the proposed WEAP method is more efficient than the default WEAP method as the average difference in steel weight for 32 test piles is 0.06 kg/kN, almost close to zero, reducing the construction challenges in the current engineering practice. Full article

For a guarantee of perpendicularity and stiffness in piles in Karst areas, full rotary cast-in-place piles are often utilized, steel pipes are rotarily driven into a stratum, and inner-steel pile casing is positioned. With the engineering background of the bridge piles of Guinan high-speed railway in Guangxi autonomous region, the space between steel drive pipe is filled with rice stones, the load-transfer mechanism of which was studied. An apparatus was designed for pullout of the drive pipe, rice stones are replaced with coarse stones, a simplified organic glass-pipe model is put forward, another similar indoor stratigraphic model is also pre-cast, and the movement of coarse sands and load transfer is studied with two models. The quantity of sands is calculated using back analysis through reappearance and the Rhino model: the first one is estimated using a reproduction of the pullout procedure, the second is calculated through the Rhino model based on the observation of the shape of sand in caves. When the drive pipe is pulled out, some coarse sand flows into the Karst caves and becomes loose, while load is applied on the top of the pile. The movement of coarse sand develops further, and more coarse sand flows into caves close to the bottom; this leads to a reduction its frictional resistance, and the axial force of the pile increases closer to the upper position of the cave, whereas the axial force of the pile is concentrated almost constantly close to the bottom of the cave. Comparing the end resistance and the frictional resistance, coarse sand can bear pile load to a great extent. Full article

In order to study the characteristics of pile–rock action of steel pipe driven pile in coral reef limestone stratum, coral reef limestone at the China–Maldives Friendship Bridge site was selected to carry out indoor physical and model tests with red sandstone as the control group. The test outcomes indicate the following: (1) when substantial deformation is permitted, the coral reef limestone has a considerable strength dispersion, a low post-peak stress decrease rate, and a high residual strength, roughly 30% of the peak strength; (2) when the steel pipe pile penetrates the coral reef limestone, the pile top load shows an obvious sawtooth shape, and with the increase in penetration depth, the pile end load of the high-porosity rock sample gradually decreases, and the pile end load of the low-porosity rock sample gradually increases; (3) when the steel pipe pile is penetrated, the strain value of the red sandstone is about twice that of the coral reef limestone at the same position from the steel pipe pile. These findings indicate that the high porosity and heterogeneity cementation characteristics of the coral reef limestone make the extrusion effect during piling significantly less than that of the red sandstone. In addition, the steel pipe pile penetration process is numerically simulated using a four-dimensional discrete spring model method based on the multi-body damage criterion. The numerical simulation results further demonstrate that the pile-side rock fragmentation during steel pipe pile penetration is the primary reason for the lower bearing capacity of steel pipe piles in coral reef limestone stratums. This method provides a novel approach for studying the mechanical properties of reef limestone. The findings can serve as a guide for the design and construction of steel pipe piles in the reef limestone stratum. Full article

This paper proposes the penetration displacement solutions of large-diameter open-ended steel pipe piles (LOSPs) with the diameter exceeding 2 m subjected to hammering load. The ultimate forcing equilibrium relationships between LOSP and soil are analyzed, and the calculated formula for self-sinking depth is derived. Next, a partial differential equation of pile hammering by single blow in soft soil is developed based on wave equation incorporating the kinematic method. A dynamic coefficient of frictional resistance (DCFR) is implemented in the process of derivation, and then the displacement Fourier analytical expression of LOSP under hammering load is presented. The parameters sensitivity of the analytical solution is investigated, and the displacement curve is compared with the numerical result. The new method presented in this paper could be used to assess the penetration development of driven piles under impact loading to predict the punching through or hammer refusal during penetration. Full article