Richard J. Jardine's research while affiliated with Imperial College London and other places

... The latter prevented the tests from continuing up to the strain levels ( a>20%) at 10 which final 'ultimate' strengths are expected to develop. However, it was possible to progress to 11 larger strains in triaxial tests conducted after consolidation to in-situ p'0 levels more than 500 kPa 12 above in-situ values, which tended towards ductile barrelling behaviours as pressures increased, 13 see The triaxial tests referred to in Figure 3, as well as other triaxial tests involving the application of 1 p'0>500 kPa (Liu et al., 2023), were conducted because pile driving and lateral loading raises local 2 p' values far above in-situ levels, making it important to address pressure-level dependency. Liu et 3 al. ...

... The surrounding intact chalk provides stiff radial containment to the reconsolidated putty annuli formed around the pile shafts and constrains any dilation that develops as the putty fails monotonically or degrades under cycling. Ahmadi-Naghadeh et al. (2022) investigated intact SNW chalk's undrained cyclic triaxial behaviour under in-situ stress conditions. High quality samples could withstand one-way deviator stress amplitudes, q cyc = Δσ 1 -Δσ 3 , up to 700 kPa in a fully stable manner. ...

... The programme supported the joint industry project 'axial-lateral pile analysis for chalk applying multi-scale field and laboratory testing' (ALPACA), which investigated how 37 tubular steel piles, such as those driven in offshore low-to medium-density chalk, behaved under axial and lateral, monotonic and cyclic loading at the research site at St Nicholas-at-Wade (SNW), Kent, UK . Vinck (2021) and Vinck et al. (2022) describe the SNW ground conditions and report the site's characterisation by comprehensive in situ profiling and monotonic laboratory testing. Sample variability posed a significant challenge, as with calcarenites, and testing focused on 20 low-to medium-density 'structured' (Leroueil & Vaughan, 1990) high-quality specimens from a single location and depth. ...

... In the undrained condition, the mechanical properties (i.e., strength and stiffness) of clay are significantly dependent on the principal stress direction, which is further dominated by the loading/unloading direction. This characteristic is called stress-induced anisotropy, differing from the inherent anisotropy formed by directional sedimentation of granular soil particles (i.e., sand, gravel soil) [18,19]. The prominent impact of clay anisotropy on geotechnical constructions was confirmed in previous excavation analyses [7,8,11,13]. ...

... Table 1 summarises the axial-cyclic subset of eight nominally identical 508mm OD open-tubular 'LD' piles driven to 10.15m tip depths, with 41% of their shaft lengths below the water table and L p /D ≈ 20. The piles' 20.6mm wall thicknesses (giving relatively low D/t w ≈ 25) were instrumented with opposing strings of optical fibre Bragg grating (FBG) strain gauges (Buckley et al., 2020b). Axial-cyclic tests were also conducted on six new 'SD series' 139mm OD piles, one of which also carried FBG gauges. ...

... Their stress-strain loops evolved steadily, with moderately increasing cyclic stiffnesses and decreasing damping ratios, as listed in Table 3. Applying large number of such low-level cycles resulted in a stable, non-linear, but principally reversible response that enhanced the de-structured chalk's cyclic resistances. Similar outcomes were reported for silica sands (by Aghakouchak et al. (2015)) and stiff glacial till (see Ushev & Jardine (2020)). The pore water pressure ratio r u (= (p 0 ′ -p′)/p 0 ′ = Δu/p 0 ′, p 0 ′ = 200) tended to stabilise after ≈2000 cycles and eventually reached 34.5% and 67.4% in DCy-A1 and DCy-D1, respectively. ...

... • the initial monotonic response in both homogeneous and layered soils (e.g. the PISA/ PISA2 projects (Abadie et al. 2020b), Byrne et al. 2019;Burd et al. 2020). • the influence of pile installation and improved driving methods for large-diameter monopiles (e.g. ...

... Brunning and Ishak [18] calculated the SRD in carbonate rock with Stevens's method and proposed that the unit end bearing is 2-3.5 times the unconfined compressive strength for the carbonate rock. Based on the onshore and offshore dynamic test results for low-medium-density chalk, Buckley et al. [19] studied the pile driving in low-to medium-density chalk and proposed a CPT-based ICP-05-like formula to calculate SRD considering the friction fatigue and the ratio of the pile diameter to the pile wall thickness. ...

... The reduction of the radial stress with increasing ℎ∕ is more pronounced in the case of OCR 0 = 2. For the installation of piles in sand (White and Lehane, 2004;White and Bolton, 2004;Jardine et al., 2013;Yang et al., 2020), the negative excess pore water pressures tend not to be as large as in clay (or are not existent at all), for why the effective radial stress is lowest at the pile shaft. This is not the case for an installation in clay, where in particular the simulation with a higher initial value of OCR shows large values of effective stress at the pile shaft due to negative excess pore water pressure. ...

... Notably, in response to the possible inadequacy of the usual p-y approach, several authors have proposed alternative methodologies for analyzing laterally loaded monopiles installed in sandy soils Brinkgreve et al., 2020;Burd et al., 2020aBurd et al., , 2020bByrne et al., 2020;Chu and Ge, 2021;Page et al., 2021;Sayles et al., 2018;Taborda et al., 2020;Thieken et al., 2015;Velarde and Bachynski, 2017). Among these methodologies, those based on three-dimensional (3D) finite element models (FEMs) are the most complete and robust. ...