Testing of sealing and consolidation technology with polyurethane resins at one railway tunnel

Abstract

This paper presents the results of polyurethane resins testing for sealing and consolidation of the railway tunnel lining affected by infiltration. In the first part the main causes of tunnel ageing are presented. Water infiltration is the most important cause of tunnels alterations and damages. Performing of sealing systems at extrados or within the lining itself may improve behavior of tunnels against the water action. If the tunnel lining present a high porosity due to water leakage a restoration of the structural integrity and consolidation of the lining is recommended. The method to create such sealing system is grouting. Injections based on chemical materials are the most efficient method of stopping the water infiltration inside the tunnel structure. Polyurethane resins injections and its applications are briefly presented. With a view to introduce the new technology with PUR in tunnels, a demonstration testing was performed at ring 12 of Predeal tunnel, which was selected because it showed the highest infiltrations on vault, appearing as moisture and leakages in summer and icicles and ice blocks in winter. The following works have been made: (1) Drilling of grouting holes (D = 29 mm) through the structure of existing vault; (2) Injection via holes of two component polyurethane resins, Bevedan Bevedol WFA type, into the wet masonry and country rock at extrados of lining, for void filling and sealing. (3) Injection with high pressure of two components PUR into the mass of lining, near the joint between ring 12 and 13 (row 1 and 2) for consolidation of damaged concrete and sealing of joint. (4) Filling of joint between ring 12 and 13 with elastic PUR for maintaining the sealing in conditions of joint opening. With a view to know the technical state (damages, defects, infiltrations, cavities) of lining at intrados, within its mass and at extrados, both before and after injections, an investigations program was performed, consisting of: Monitoring of infiltrations and apparent defects at intrados of lining in several periods; Taking out of core samples from consolidated lining body and their testing before and after injections; Investigation of lining and surrounding ground in three sections by Georadar method before and after injections. The experiment was a success as confirmed by the following arguments: The actual state of intrados of lining without infiltrations; The results of Georadar investigations which shows the removal of water from lining and its removal from extrados proving the efficiency of treatment by injections with polyurethane resins; The usefulness of the information obtained, regarding the technical state of existing lining (thickness, damages, caverns) and also the way of behavior at the pressure given by injections; The results of core samples testing which reveal the important increase of compressive strength and decrease of permeability by realization of consolidation injection. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.