Interface shear box tests for assessing axial pipe–soil resistance

Abstract

The clay-interface shear resistance is an important parameter for the design of offshore pipelines, which slide on the seabed as a result of thermally-induced expansion, contraction and lateral buckling. This paper presents a methodology for characterising the clay-interface resistance and quantifying the effect of drainage and consolidation during or in between shearing episodes. Models for describing the clay-interface resistance during planar shearing are presented and compared to test data for a range of drainage conditions from drained to undrained and including the case of episodic consolidation. The test data are from two series of interface shear box (ISB) tests carried out on marine clays. The effects of normal stress level (in the low stress range), over-consolidation and interface roughness are also examined. 1 INTRODUCTION Soil-interface resistance is a relevant design parameter for a range of geotechnical structures, e.g., piles, retaining walls, submarine pipelines, skirted foundations, offshore gravity structures and mat foundations. Studies of soil-interface behaviour have been conducted for a variety of soil types (e.g., Potyondy 1961, Yoshimi & Kishida 1981, Lemos & Vaughan 2000). These studies are based on experimental investigations using interface shear box (ISB) tests or interface ring shear tests, which have historically been performed as drained tests. Databases of results have been assembled by Ramsey et al. (1998), Jardine & Chow (2005) and Eid et al. (2014) (with the latter focusing on low stress levels) with the aim of identifying correlations between soil index properties and soil-interface shearing characteristics. Some studies have considered tests conducted at different rates of shearing, corresponding to various drainage conditions (e.g, Lehane and Jardine 1992, Tika et al. 1996, Ganesan et al.

Apparatus for Measuring Pipe-Soil Interaction Behavior Using Shallow ‘Pipe-like’ Penetrometers

“…In order for the shallow penetrometers to be able to measure the drained friction angle during slow sustained rotation, the penetrometer surface must be sufficiently rough. To identify a suitable surface finish, low stress drained interface shear box tests (σ'n ∼8-12 kPa; 82 mm diameter interface; see also Boukpeti & White, 2017) were conducted on normally consolidated kaolin clay using machined and shot-blasted plastic inserts (Polyoxymethylene).…”

Shear‐Rate‐Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels

“…Studies on the shear behavior of bimaterial interfaces between soil and concrete, steel, geotextiles, and other manufactured materials, especially under low normal stresses ( σ n = 1–100 kPa), are abundant in the literature (e.g., Boukpeti & White, ; Eid et al, ; Ganesan et al, ; Ho et al, ; Lemos & Vaughan, ; Potyondy, ; Tsubakihara & Kishida, ; Wijewickreme et al, ; Zhang & Zhang, ). Equally, in fault mechanics, many researchers have been focusing on the slip‐ and rate‐dependent behavior of rock interfaces and thin gouge layers under high normal stresses ( σ n = 1–20 MPa) to understand the behavior of faults under subseismic and coseismic slip rates (e.g., Di Toro et al, , , ; Hirose & Shimamoto, ; Perfettini & Ampuero, ; Kitajima et al, ; Togo et al, ; Yao et al, , Ma et al, ; Yao et al, ).…”

Soil‐structure interface modeling with the nonlinear incremental approach

“…Figure 18 shows a schematic representation of the influence of shearing rate on the strength of normally consolidated clay, according to Quinn et al 66 . It was observed that, in soil‐on‐soil or interface shear tests, when increasing the shear rate, the drainage condition shifts progressively from “drained” with the volumetric change, to “partially drained” with slight volumetric change and to “undrained” with no volumetric change in the localized shear zone 67,68 . Under experimental CNL condition, the total normal stress is kept constant, while the effective normal stress evolves differently due to the generation of excess pore‐water pressures under different shearing rates.…”