Behaviour of an Ice Sheet under Heavy Loading

摘要

Floating ice covers have been used successfully as a temporary working platform in the past. Ice bridges, ice roads and ice runways are generally subjected to short term loads. Long term loads can be found on ice platforms, which have to support drill rigs for days or weeks. Regardless of the loading scenario, under "normal" operating conditions, a designer has to consider two basic criteria when determining the bearing capacity of an ice cover: a) maximum flexural stresses are not allowed to exceed a predetermined strength level; and b) the maximum ice sheet deflection has to remain below the available freeboard. This paper presents cases of "abnormal" conditions or heavily loaded ice covers where at least one of the two criteria - exceeding the available freeboard - had been violated. Floating lake ice had been loaded at 14 places with up to 2,0001 of Run of Mine (ROM) rock material at each shoal location at the two mine sites in the Canadian Territory of Nunavut. The material was dumped on the ice using 60 tonne trucks. The purpose of this project was to construct fish rock shoals. With spring approaching, the rock piles fell to the bottom of the lake creating fish habitats. Despite extensive crack formations and "abnormal" large deflections, failure of the ice cover did not take place until later in spring due to flooding. The objective of this paper is to present a challenging project, safely been executed through high level monitoring.