Using Thermal Monitoring and Fibre Optic Measurements to Verify Numerical Models, Soil Parameters and to Determine the Impact of the Implemented Investment on Neighbouring Structures

Abstract

Numerical modelling using Finite Element Method (FEM) is currently a standard procedure for engineering complex structures and determining structure–subsoil cooperation conditions. It is used for, among others, forecasting displacements, which are the calculation results most easily verified. Numerical modelling is also used to identify the impact on neighbouring structures and design a monitoring system and determine expected values, e.g., displacements. A numerical model enables one to optimally design the monitoring system for a facility under construction and the neighbouring structures through selecting a measurement technology, matching the scope of obtained results or choosing sensor and measurement point locations. The implemented monitoring may be based on various technologies, from thermal monitoring, laser scanning, fibre optic measurements, to classic surveying measurements. The walls must protect the soil from excessive displacement and protect the excavation against groundwater inflow. If the wall is not watertight, deepening the excavation may cause a sudden water inflow. Leak and erosion process thermal monitoring is a proven leak detection method. It is based on the tests utilizing heat and water transfer process relations, which are coupled processes. Another tool for verifying numerical models is the installation of DFOS (Distributed Fibre Optic Sensors) at the stage of executing structural elements (e.g., diaphragm walls, barrettes, foundation slab). It allows one to permanently monitor both temperature and displacements during element execution (concrete curing), and following facility construction and operation stages. The paper presents methods for designing selected monitoring elements of engineering objects, based on calculations using the Finite Element Method. The verification of numerical models, based on data obtained from DFOS, classic surveying measurements and thermal monitoring, is also presented.