In water conservancy and hydropower engineering, it is often difficult to construct elbow in underground caverns rapidly due to its complex structure. Aiming at problems of slow speed, difficulty in fine control and prominent safety contradiction in traditional construction methods, the innovative technology named convertible slip-form of 90° elbow and shaft inclined traction-pouring is put forward. A convertible slip-form on cambered surface is designed, combining with multi-point traction control system and pouring technology by layer after layer with aslop surface, which solves key problems such as inclined coaxial traction, cylindrical and cambered surface sliding transition of the form, and realizes automatic construction of elbow structure. For the stability of caverns in construction, according to interaction between surrounding rock and lining, based on PFC-FLAC discrete continuous coupling analysis method and acoustic emission technology, the stress and damage evolution process of them are studied, according to crack distribution of structure, weak positions of lining is determined, which reveal meso-damage mechanism under macro-mechanical behavior. According to the development law of concrete strength and numerical calculation results, the empirical control model of convertible slip-form construction is proposed, and it can obtain recommended slipping time of slip-form under arbitrary construction load. In summary, the safety and feasibility of the key technology have been clear demonstrated in the thesis, which provides certain references for similar projects in years to come.

1. Introduction

In hydropower and water diversion projects, the flow pattern transition of elbow section is often required due to the flow pattern and water pressure. At present, traditional construction method of allround scaffold+set-shaped formwork is often adopted for construction of elbow. In the large underground cavern, due to numbers of formwork, this method causes serious bubbles, water marks and surface flaws on concrete surface after construction. At the same time, this method requires more manpower, a longer construction period, and has lower resource utilization. At present, the construction of large-scale hydro-junctions is becoming more and more common at home and abroad. China's Baihetan, Wudongde and other giant water conservancy projects are rapidly developing and constructing like a raging fire. Therefore, an efficient construction technology for large-scale underground cavern elbow structure is proposed, which plays an important role in promoting construction level of water conservancy projects.

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