Change of temperature field around different drainage structures in cold region tunnel based on model testing

Improper layout of drainage structures and inadequate insulation measures in cold tunnels can result in varying degrees of frost formation during operation. This study focuses on the Hongtoushan highway tunnel as an example, where the distribution characteristics of the temperature field around the lower drainage structure under different arrangements are investigated through indoor model testing. The results indicate that there is a significant hysteresis phenomenon in temperature changes across the cross-section as the burial depth increases. With an increase in the burial depth of the surrounding rock, the hysteresis time of temperature changes gradually elongates. The temperature variation pattern can be approximated by a cubic polynomial. In the vertical section, as the tunnel depth increases, the temperature of the surrounding rock in the lower part of the tunnel gradually rises while the amplitude of temperature change diminishes. The temperature near the centerline is relatively lower compared to the sides, where the temperature gradually increases moving away from the centerline.

Diagnosing decay: the value of medical analogy in understanding the weathering of building stones

This paper represents the first element of the introduction to this volume, and as such investigates its principal underlying rationale; namely the importance of accurate diagnosis of stone decay in the formulation of effective conservation strategies. It does this by exploring ways in which perceived similarities between stone decay and human disease have influenced attitudes towards conservation, and how refinements within medical diagnostic strategies can inform future condition assessments of building stones. In doing so, it identifies the importance of looking beyond obvious symptoms to the isolation of the fundamental causes of decay and the factors that control them. These controls are strongly conditioned by accumulated stresses within the stonework. In many buildings these are the product of a complex history involving exposure to a variety of environmental conditions and successive human intervention. Only by understanding these memory effects is it possible to explain current decay phenomena, attempt any prediction of future behaviour or recommend appropriate intervention. The concept of appropriateness is further developed through an examination of the TNM (Tumours, Nodes and Metastases) Staging System for cancer diagnosis. This holistic scheme embodies a progressive approach to diagnosis that begins with a clinical assessment based on how the patient presents, and leads on to more detailed pathological investigations involving sampling, testing and analysis. The scheme also requires an assessment of the certainty of the diagnosis and proposed treatments must be viewed in terms of a cost benefit analysis. A modified version of this staging system has already been developed for use in the physical assessment of buildings. It is suggested that the next stage in its development, and that of any other condition assessment procedure that deals solely with the fabric of a building, is the inclusion of a value-based appraisal of its cultural significance.