Metro systems : Construction, operation and impacts

Peer reviewedPublisher PD

New Method of Full-Field Stress Analysis and Measurement Using Photoelasticity

Photoelastic measurements provide a means to obtain a meaningful representation of the stress state in a granular material over the full area of a plane-strain sample without the need to place stress transducers inside the sample. This method uses the property of non-crystalline materials to become optically anisotropic when put under stress. To measure the resultant relative retardation of a light beam transmitted through a model built from glass grains and a liquid with a matching refractive index in the pores, a full-field polariscope has been built. This setup is able to characterize the stress state in the full-field of the sample with only seven intensity measurements. A plane-strain pile penetration test is used as an example

An efficient transient‐state algorithm for evaluation of leakage through defective cutoff walls

Artificial barriers are widely used to prevent leakages. However, due to construction errors during the wall installation, passages with small dimensions may occasionally penetrate through the barrier, undermining its tightness. A three‐dimensional discretized algorithm (TDA) is proposed for quantitatively estimating the transient‐state discharge rate through defective cutoff walls. By discretizing the wall into a three‐dimensional refined mesh grid, the algorithm enables an examination of penetrating passages, an evaluation of defect dimensions, and an estimation of discharge rate through the penetrating passages. A rigorous realization‐by‐realization comparison between the TDA and the finite element method (FEM) was made, and it was found that the TDA results show strong correlations with the FEM results, but at a remarkably lower (1/103‐1/104) computational cost. The TDA generally gives a discharge rate that is 0.1‐1.0 times greater than its FEM counterpart, as the lengthened seepage distance due to random corrugations in the penetrating untreated zone cannot be replicated by the TDA

A two-stage numerical analysis approach for the assessment of the settlement response of the pre-damaged historic Hoca Pasha Mosque

The current article presents a case study of the settlement response of the historic Hoca Pasha Mosque that involves uncertainties arising from the complex excavation activities, soil properties, building materials, and geometry and the presence of pre-existing cracks in the mosque’s walls. The objective is to demonstrate the added value of a two-stage numerical analysis approach for the assessment of the settlement response of the building. The first stage comprises analyses of the structural behavior using the monitored settlements for each wall. The second stage examines the behavior of the complete building as a whole. The effects of soil-structure interaction and the pre-existing cracks are considered through discrete interface elements. It is shown that executed simulations can reasonably reproduce the overall settlement response, resulting stresses and the pre-existing crack activities. The parametric analyses in the second stage also produce generalizable results, of use beyond the specific case. Namely, as the soil/structure stiffness ratio increases the settlement-induced vulnerability increases. Including soil-structure interaction in the analyses reduces tensile strains due to differential settlements. Including pre-existing cracks reduces tensile strains in the vicinity of the cracks but results in an increase of stresses in neighboring sections

Distributed Temperature Sensing applied during diaphragm wall construction

Distributed Temperature Sensing (DTS) can be used to monitor the production process of diaphragm walls. DTS is able to differentiate between already present and fresh bentonite suspensions during refreshing of the bentonite slurry and excavation bentonite remaining in the trench can be observed. During concrete casting, DTS is able to differentiate between bentonite suspension and concrete. As a result, the continuity of the casting process and the arrival of good grade concrete at crucial locations in the trench can be monitored. Tests conducted on laboratory models provided reference information for interpretation of field data. Field experiences have shown the benefits of the DTS tests and the predictive value of the reference measurements. Finally, the results are compared with CSL measurements at the same location.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author