Centrifuge and Real-Time Hybrid Testing of Tunneling beneath Piles and Piled Buildings

Abstract

Tunnels are constructed increasingly close to existing buried structures, including pile foundations. This poses serious concerns, especially for tunnels built beneath piles. Current understanding of the global tunnel-soil-pile-building interaction effects is lacking, which leads to designs that may be overly conservative or the adoption of expensive measures to protect buildings. This paper presents outcomes from 24 geotechnical centrifuge tests that aim to investigate the salient mechanisms that govern piled building response to tunneling. Centrifuge test data include greenfield tunneling, pile loading, and tunneling beneath single piles and piled frames, all within sand. The global tunnel-piled frame interaction scenario is investigated using a newly developed real-time hybrid testing technique, wherein a numerical model is used to simulate a building frame, a physical (centrifuge) model is used to replicate the tunnel-soil-foundation system and structural loads, and coupling of data between the numerical and physical models is achieved using a real-time load-control interface. The technique enables, for the first time, the modeling of a realistic redistribution of pile loads (based on the superstructure characteristics) in the centrifuge. The unique dataset is used to quantify the effects of several factors that have not previously been well defined, including pile installation method, initial pile safety factor, and superstructure characteristics. In particular, the results illustrate that pile settlement and failure mechanisms are highly dependent on the pretunneling loads and the load redistribution that occurs between piles during tunnel volume loss, which are related to structure weight and stiffness. The paper also provides insight as to how pile capacity should be dealt with in a tunnel-pile interaction context.

Centrifuge Study on the Influence of Tunnel Excavation on Piles in Sand

“…The central axis of the nearest pile was separated from the tunnel axis by a distance of = 75 mm; the pile tips were at a depth = 140 mm, giving a clear vertical distance to the depth of the tunnel crown of = 75 mm in all tunnelling tests, whereas was 150 mm in the pile jacking test. In the TPSI tests, labelled as test TPSI1, 2 and 3, the same geometric scenario as the TPGI test was considered, except that in these tests the load applied to the piles was adjusted during tunnel volume loss according to the load redistribution of a connected 5-story steel frame structure (accomplished using the CCNM technique (Idinyang et al, 2018;Franza and Marshall, 2018)). The three TPSI tests differed only in terms of final tunnel volume loss , : , =2.2 % for TPSI1, , =3.2 % for TPSI2, and , =2.8 % for TPSI3.…”

A global sensitivity analysis framework for hybrid simulation

“…The latter consists of exposing a single structural component to a predefined time-temperature loading curve inside a furnace and indeed does not account for the redistribution of internal forces caused, for example, by thermal expansion or partial collapse. For a similar motivation, Franza and Marshall Franza and Marshall (2018) developed an HS platform to study soil-structure interaction problems where a numerical model of a building frame (i.e., the NS) is used to mimic a realistic structural loading exerted on the physical centrifuge model of a tunnel-soil-foundation system (i.e., the PS). The use of HS in other engineering and science disciplines is growing (e.g.…”

Effects of Different Construction Sequences on Ground Surface Settlement and Displacement of Single Long Pile due to Twin Paralleled Shield Tunneling

“…In order to understand the pile-soil-tunnel interaction mechanism, many scholars have conducted centrifuge model tests and field measurement analysis [9][10][11][12][13]. Franza and Marshall [11] presented outcomes from 24 geotechnical centrifuge tests and investigated the global tunnel-piled frame interaction scenario by using a newly developed realtime hybrid testing technique.…”

“…In order to understand the pile-soil-tunnel interaction mechanism, many scholars have conducted centrifuge model tests and field measurement analysis [9][10][11][12][13]. Franza and Marshall [11] presented outcomes from 24 geotechnical centrifuge tests and investigated the global tunnel-piled frame interaction scenario by using a newly developed realtime hybrid testing technique. e results illustrated that pile settlement and failure mechanisms are highly dependent on the load redistribution that occurs between piles during tunnel volume loss, which are related to structure weight and stiffness.…”