Calculation of Bearing Capacity of Augercast Tapered Piles in Clayey Soils
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SOIL MECHANICS CALCULATION OF BEARING CAPACITY OF AUGERCAST TAPERED PILES IN CLAYEY SOILS
UDC 624.154.54 A. I. Polischuk,* D. A. Chernyavskii Department of foundation engineering, Kuban State Agrarian University (KubSAU), Krasnodar, Russia, *Corresponding author Email: [email protected].
The article presents a new method for determining the bearing capacity of augercast tapered piles in clayey soils by considering the various factors such as the level of external load, the sequence of operations in the installation of piles, and variations in the physical and mechanical characteristics of soils in the pile space that are responsible for effective performance of piles. This method is also recommended for designing free-standing pile and girder foundations.
Introduction Augercast tapered piles are a type of pile foundations constructed by injecting fine-grained concrete mixture into drilled wells under high pressure. Such piles are installed with a flight auger or using unextractable drill rods [1]. The design solution for augercast tapered piles was developed at KubSAU in 2010-2017 [2, 3] and is currently adapted in various construction industries and design organizations. These piles can be classified as spacer piles (wedge-shaped, pyramidal, etc.). Their bearing capacity Fd is greater than that of augercast cylindrical piles in the same working conditions. The main reasons for higher bearing capacity is due to effective soil compaction around the pile shaft during their installation (achieved by the pressure injection of concrete mixture into a conical well) and additional soil passive resistance around the pile shaft during loading of piles with an external load N in operation. Currently, there are many methods for calculating the bearing capacity Fd of rammed, driven tapered, pyramidal piles during the designing the foundations of buildings and structures. A significant contribution to the development of these methods was made by B.V. Bakholdin, A.L. Gotman, and A.B. Ponomarev et al. [4-11]. However, the methods for calculating the bearing capacity of augercast tapered piles in clayey soils have not been studied and developed so far. Tapered Pile Installation Technology The structural scheme of the augercast tapered pile [2, 3] is explained by the sequence of operations presented here (Fig. 1). First, a well (4) with a constant diameter is drilled up to a length 1-3 m (depends upon the length of the rods) (Fig. 1a). At that time, a drilling bit (3), which is as a cutting tool, is attached to a hollow metallic cylindrical pipe (1) with various components and special couplings (2). But in the proposed method, we used the so-called crown couplings equipped with metal cutting edges (blades) instead of conventional couplings (5) (Fig. 1b). The important characteristic of crown coupling in the process is the increase in diameter of the cutting edges when there is
Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 2-7, July-August, 2020. 0038-0741/20/5704-0273
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