Abstract
This paper investigates the skin friction transfer characteristics of the rock‐socketed section of a rock‐socketed pile resting on thick sediment by conducting in situ core‐drilling tests and static loading tests. Test results show that when using the impact hole‐forming method in weakly cemented soil, a layer of sediment is deposited at the pile bottom. Due to the existence of sediment, when the load reaches a certain value, sudden and large subsidence is observed. This indicates that the end resistance does not contribute to the bearing capacity. Thus, it is not appropriate to consider both end resistance and side resistance in the existing design method of a rock‐socketed pile. The bearing capacity of a single rock‐socketed pile should be determined according to the side resistance of the soil layer and rock‐socketed section only. Numerical analysis is performed to determine the deformation and load‐carrying capacity of the pile and the distribution of friction on the sides of the rock‐socketed segment. Under a given applied load, small settlement is observed when socketed thickness and rock strength are relatively large. The distribution of side friction of the socketed segment along the vertical direction shows a double‐peak saddle shape. When the socketed thickness and rock strength are relatively smaller, the lower peak is higher than the upper peak, and conversely, when the socketed thickness and rock strength are relatively larger, the lower peak is smaller than the upper peak. For a given applied load on the pile top, smaller socketed thickness results in larger settlement and side friction. Due to the thick layer of sediment, the axial force of the rock‐socketed segment of the pile gradually decreases along the vertical direction from the applied load on the pile top to zero at the bottom. According to the mechanical properties at different shear stages, a function is derived for the complete constitutive model for a pile‐rock interface. Analytical solutions for the friction of a single pile are obtained under the conditions of failure and elasticity deformation of the surrounding rock. Its load transfer equation is derived as well. Accordingly, an equation is proposed for calculating the bearing capacity of rock‐socketed piles resting on sediment at the bottom.
Highlights
Rock-socketed pile is a special type of pile foundation that is widely used in the construction of multistoried buildings and bridges
Most rock-socketed piles are constructed by the method of manual excavation or impact drilling. e bottom of manual excavation is clean and easy to check, and the prediction of bearing capacity is reliable, so the manual holeforming method is the most widely used method in engineering construction
As many factors influence the performance of a pile and a rocksocketed cast-in-place pile has the characteristics of strong concealment, its bearing mechanism is complex [10]. rough extensive engineering practice and numerical analysis, scholars have found that the roughness of the wall of the bored hole has the greatest influence on the bearing capacity of rock-socketed piles [11, 12]
Summary
Rock-socketed pile is a special type of pile foundation that is widely used in the construction of multistoried buildings and bridges. Barrett and Prendergast summarized the empirical relationship between the compressive strength of the surrounding rock in the rock-socketed section and the bearing capacity of a single pile based on a large number of field load tests of rocksocketed piles [7]. Rough extensive engineering practice and numerical analysis, scholars have found that the roughness of the wall of the bored hole has the greatest influence on the bearing capacity of rock-socketed piles [11, 12]. Seol et al analyzed the coupling effect of soil resistance in the rock-socketed shaft by the elastic-plastic finite element method and studied the slip and shear load transfer characteristics of the pile-soil interface [22]. To overcome the current design flaws, this study conducts on-site tests to analyze the sediment thickness and bearing capacity of rock-socketed piles with impact hole forming. To overcome the current design flaws, this study conducts on-site tests to analyze the sediment thickness and bearing capacity of rock-socketed piles with impact hole forming. e sediment thickness, rock strength, pile-rock interface differences, and other factors are considered. e bearing performance of rocksocketed piles is analyzed numerically, and the influence of various factors on the bearing performance of rocksocketed piles with thick sediments is discussed. is paper proposes a method for calculating the bearing capacity and demonstrates the method through a design calculation for the rock-socketed pile for theoretical understanding
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