Numerical investigation on rigid and flexible pipelines embedded in granular and self-compacting materials
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TECHNICAL PAPER
Numerical investigation on rigid and flexible pipelines embedded in granular and self‑compacting materials Khalid Abdel‑Rahman1 · Tim Gerlach1 · Martin Achmus1 Received: 3 April 2020 / Accepted: 12 June 2020 © The Author(s) 2020
Abstract Self-compacting filling material or controlled low-strength material (CLSM) is a cementitious material which is liquid during filling, and it is used primarily as backfill, e.g., in trenches. Several products are currently used as CLSM such as flowable fill, controlled density fill, flowable mortar and low-strength plastic soil–cement. The low-strength requirement is necessary to allow for future excavation of CLSM. A two-dimensional numerical model was developed using the finite element system ABAQUS. In this model, the material behavior of granular soil and CLSM is described using an elasto-plastic constitutive model with Mohr–Coulomb failure criterion. Rigid and flexible pipes were modeled once embedded in sandy soil and once embedded in self-compacting material. The numerical model allows the modeling of the effect of hardening process on the overall behavior of the pipe–soil system. The main objective of this study is to investigate the behavior of rigid and flexible pipelines embedded in CLSM as a filling material numerically and to show advantages and disadvantages in comparison with the presently widely used filling materials like sand. Keywords Self-compacting material (CLSM) · Finite element method · Mohr–Coulomb material model · Hardening process · Pipelines
Introduction Controlled low-strength material (CLSM) is a self-compacted cementitious material used primarily as a backfill as an alternative to compacted fill. CLSM should not be considered as a type of low-strength concrete, but rather a self-compacted material with features similar to soil. At some sites, the use of self-compacting materials has proven to be beneficial in providing adequate support to flexible structures, especially in tight spaces where placement and compaction of more traditional backfill material would be problematic. Challenging situations such as placing bedding under haunches and backfilling between closely spaced parallel structures can be simplified or enhanced by using selfcompacting materials. The most common materials used are either open-graded, angular aggregates or specially proportioned cementitious mixtures. Conventional CLSM mixtures usually consist of * Khalid Abdel‑Rahman [email protected]‑hannover.de 1
Institute for Geotechnical Engineering, Leibniz University of Hannover, Appelstr 9A, 30167 Hannover, Germany
water, cement, fly ash or other similar products and fine or coarse aggregates or both. Selection of materials should be based on availability, cost, specific application and the necessary characteristics of the mixture, including flowability, strength, excavatability and density. The main purpose of the investigations presented here is the comparison of bending moments of rigid and flexible pipes in sand or CLSM, taking the effect of hardening of
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