Abstract
Because of the limits of struts, braceless retaining structures (BRS) have become a preferred option in deep excavation engineering. A type of BRS, that is, inclined retaining system, has been successfully applied in several projects. However, its performance and working mechanism have not been systematically studied. A case study and finite element results in this study show that inclined piles (IP) are more effective than vertical piles (VP), while composite inclined retaining structures (CIRSs) are more effective than IP in terms of deflection and bending moment reduction. The deformation-control mechanism of IP mainly comes from the decrease in the active earth pressure. For CIRSs, the working mechanism is governed by several combined effects, that is, the rigid frame effect, inclined strut effect, earth berm effect, and gravity wall effect. For instance, in composite vertical and inward-inclined piles (VIIP), inclined piles function as struts for the vertical piles in this rigid frame system and frictional force between the soil and the inclined piles significantly influences its retaining performance; the soil between the vertical and inclined piles plays a role similar to an earth berm; additionally, the entire retaining system is similar to a gravity retaining wall, which has relatively high overturning stability.
Highlights
In the urban area of China, an increasing number of high-rise buildings and underground utility tunnels are being constructed, and correspondingly, excavation projects are becoming progressively deeper, larger, and longer
Field Monitoring Results and Discussions. ree inclinometers, that is, M-1, M-2, and M-3, were set at profiles retained by vertical and inward-inclined piles (VIIP), vertical piles (VP), and VII2P (composite retaining structure with retaining element of two inclined piles and one vertical pile, as shown in Figure 5(c)), respectively, as shown in Figure 2(a). e inclinometers were inserted into the circular holes of the rectangular piles. en, cement
The retaining performance and working mechanism of some new braceless retaining structures, such as IP and different types of composite inclined retaining structures (CIRSs), were systematically investigated by 3D numerical simulations. e main conclusions are summarized as follows: (1) Compared with VP, normal soil stress acting on inclined piles in the active zone decreased, and the displacement and bending moment of IP were significantly reduced
Summary
In the urban area of China, an increasing number of high-rise buildings and underground utility tunnels are being constructed, and correspondingly, excavation projects are becoming progressively deeper, larger, and longer. The centrifuge model experiment based on this practical case demonstrated that the deformation of inclined piles was approximately 30% less than that of vertical piles [6]. Jeldes et al [8] introduced a new type of earth-retaining structure named piling framed retaining wall (PFRW), which consists of vertical and battered piles, walers, and tie-down anchors and is applicable for soils underlain by rock. The working mechanism of the retaining structures consisting of inclined piles used for excavations in soft soil areas has not yet been systematically investigated. E deformations, internal forces, and soil-structure interaction for different types of CIRSs were analyzed to investigate the working mechanisms of CIRSs. Based on the case study and numerical simulations, the excellent retaining performances of CIRSs and their working mechanisms were addressed
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