The latest issue of Dam Engineering (Volume XXX, Issue 4) has been published:
Case studies on laboratory evaluation and repair of concrete dams in Himalayan regions of India using high performance concrete
By P N Ojha, Suresh Kumar, Brijesh Singh & B N Mohapatra
Abstract: Some older concrete dams in the Himalayan region are facing acute problems of wearing of the surface of spillway glacis, roller bucket and wing walls due to the intermittent discharge of excess stored water at high velocity, along with silt and boulder impact, which leads to abrasion and damage of these structure on the downstream side. The maintenance and repair of such structures generally requires the use of high performance concrete mixes. However, the design and execution of such concrete is a major challenge when the available aggregates are alkali silica reactive (ASR), mechanically weak in nature, or a combination of both. Selection of concrete-making materials, production and placement of concrete in extreme cold weather and quality control on site are also major challenges. This paper demonstrates a systematic procedure of material evaluation, and design of high performance concrete mixes (HPC) in a laboratory, and the proper implementation of the production and placement of concrete with the required engineering properties at the site. Case studies of three existing dams in the Himalayan region are discussed. Aggregates available near the vicinity of two of the dam sites were reactive in nature, whereas at the other dam site the aggregate was found to be mechanically weak. The evaluation of high performance concrete mixes of M60, M75 and M90 grade using steel fibres, and M90 grade without steel fibres, are highlighted. This paper also covers the production and placement strategy for concreting.
Improving seismic stability of the earth dam
By Denis Krutov
Abstract: This article discusses (i) reasons to improve a dam’s seismic stability, (ii) rehabilitation options on the downstream slope of earth dams, (iii) measures to simplify rehabilitation works and (iv) analysis to verify design decisions on dam embankment stability due to accelerations in the body of dams due to seismic events. A common measure to improve earth dam embankment stability during a seismic event is to increase the volume of the bottom prism (construction of surcharge) on the downstream side of a dam. This can be complex and costly when it requires the rehabilitation of a dam’s drainage system. A less costly alternative is to locate the additional surcharge at a higher elevation on the downstream side above the drainage system. Stability analysis of the dam’s embankment under static and seismic loading for various design proposals was conducted.
PROJECT PROFILE: Comprehensive monitoring of Victoria Dam
An automated monitoring system, optical total stations, GNSS receivers and other structural monitoring instrumentation continuously monitor Sri Lanka’s tallest dam – providing a 360 degree view in real-time – of all dam movements.
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