Innovation structures of very lean roller compacted concrete dams

Yury P. Lyapichev

doi:10.22363/1815-5235-2021-17-3-248-260

Yury P. Lyapichev

Open Access

https://doi.org/10.22363/1815-5235-2021-17-3-248-260

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Abstract

Over the past 20 years, rolled compacted concrete (RCC) dams have continued to be built in many countries because of their technical and economic advantages over conventional dams of vibrating concrete and embankment dams. The aim of this study is the development of new structural and technological solutions in RCC dams in order to reduce the consumption of cement and expand their use on non-rock foundations, which will allow them to successfully compete with concrete face rockfill dams. The numerical analyses of static and seismic stress-strain state (SST) of gravitational dams in roller compacted very lean concrete dams have been made, as well as their stability, strength and cost have been assessed. For rock and dense sandy-gravel foundations the most economical is the concrete face rockfill dam and symmetrical RCC dam of very lean concrete with bases (0.5-0.7) of both slopes and outer zones of conventional concrete and central zone of rockfill strengthened by cement-ash mortar. Taking into account that the cost of diversion and spillway tunnels for very lean RCC dam will be less and the construction period - shorter than for the concrete face rockfill dam, it can be concluded that variant of symmetrical RCC dam of very lean concrete is the technically and economically effective. Symmetrical RCC dams of very lean concrete with 1V/(0.5-0.7)H slopes have more seismic resistance and technical and economic efficiency as compared with conventional gravitational RCC dams and other types of dams. These dams up to 200 m high can be built on rock foundations and up to 100 m high - on dense sandy gravel foundations.

Highlights

In most countries of the world when designing gravity dams from conventional and rolled compacted concrete (RCC) use two main conditions of strength
Symmetrical RCC dams of very lean concrete with 1V/(0.5–0.7)H slopes have more seismic resistance and technical and economic efficiency as compared with conventional gravitational RCC dams and other types of dams. These dams up to 200 m high can be built on rock foundations and up to 100 m high – on dense sandy gravel foundations
Are given results of analyses of stability and strength of 4 types of dams h = 100 m: gravity dam from RCC-3rd type (Figure 6), rockfill dam with reinforced concrete face, dam from very lean RCC (Figure 3) and dam from RCC and rockfill enriched with cement-ash mortar (Figure 4)

Summary

Introduction

In most countries of the world when designing gravity dams from conventional and RCC use two main conditions of strength According to the theory of eccentric compression, which is not applicable, especially for the contact section, the distribution of total vertical stresses will be linear from point B to the downstream face, i.e. in closed (work) zone of RCC seam (Figure 1, b) For this RCC dam profile and the operating loads, the stress in point B depends on coefficient α of relative depth of crack propagation (α = AB / AC). With increase of α coefficient the moment from dam own weight relatively to point B increases, which leads to decrease of normal stress, while uplift water pressure increases, which leads to increase of normal stress The balance between these two counteractions is expressed by Hoffman condition (2). There may be value of α coefficient greater than given αo for which Levy condition will be held

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