Abstract:In water conservancy and hydropower engineering, prestressed anchor cables (or bars) are commonly used to reinforce unstable slopes and improve their stability. However, the design of prestressed anchorage has so far been mostly over-conservative, resulting in excessive waste. The anchorage design theory and method need further study. Through analysis of factors affecting rock-anchor design parameters and by applying optimization and decision theory, this paper proposes a method for determining rock-anchor design parameters and establishes the rock-anchor support design decision-support system RSASYS, providing designers with a new analysis approach. Practice proves the method feasible and of great economic benefit.

Abstract:To further improve the design and calculation theory of prestressed anchor-cable piles and save investment, a graded calculation method and subgrade coefficient method are adopted. Based on the deformation theory of cantilever-beam bearing strata and the elastic foundation-beam theory, the pile deformation and internal forces under anchor-pile deformation compatibility are computed, so as to control deformation at the pile anchorage face and optimize pile diameter, anchor prestress and anchor length. According to pile internal-force variation and by the limit-state method, double-face reinforcement is designed for positive/negative bending moments. Engineering practice shows the theory reflects site conditions well.

Abstract:The effectiveness of reinforcing rock mass with prestressed anchor cables depends on the magnitude of prestress. To keep the rock mass stable in the long term, sufficient prestress must be maintained. Factors such as time-dependent rock deformation, anchor relaxation/corrosion and anchorage differences cause prestress loss, adversely affecting reinforcement. This paper focuses on prestress loss due to time-dependent rock deformation. The loss can be expressed as σ_L=σ_0+σ_a+…; based on the viscoelastic properties of rock, formulas for σ_a and σ_… are derived, and the influence of bond and free lengths on reducing prestress loss is discussed.

Abstract:Based on study of the action principle and mechanical mechanism of prestressed anchor cables, the advantages of anchor-cable support are clarified. The factors affecting anchor prestress loss are analyzed in depth; according to mechanical properties, new domestic materials suited to prestressed anchor cables are selected, and compensation measures for anchor prestress are proposed, improving the overall anchorage effect of the prestressed anchor-cable system.

Abstract:Through large-scale field testing and mathematical analysis, first-hand data on the subgrade reaction of unbonded prestressed raft foundations are obtained, revealing distribution laws of subgrade reaction and the influence of unbonded prestress thereon. The results verify the design of the building foundation and may serve as reference for similar designs. A comprehensive calibration method combining laboratory and field calibration of large-diameter earth-pressure cells is also discussed.

Abstract:Based on tests, this paper proposes a composite anchorage type between the traditional tension-type and compression-type, adopting double-layer anticorrosion protection, and puts forward improvements to the design and construction of coarse-steel-wire rock anchor-cable systems.

Abstract:By comparing anchor cables of different strengths, this paper demonstrates the reliability and superiority of 2000 MPa ultra-high-strength anchor cables applied to geotechnical engineering.

Abstract:The vertical-slope anchorage of the main section of the Three Gorges Permanent Ship Lock involves large quantities, complex structure, high technical difficulty, strict quality requirements, short schedule and poor construction conditions. During construction the relationship between anchorage and excavation was well handled; technical problems of hole making, hole inspection, strand threading, high-level scaffolding erection and safety management were solved, achieving good results.

Abstract:The high slopes of the Three Gorges Permanent Ship Lock are equipped with 4,367 prestressed anchor bundles, on which 101 prestressed anchor load cells have been installed, covering 91 bundles. This paper presents the installation and monitoring results of the prestressed anchor load cells, analyzes the load loss during locking and the variation patterns during operation of the prestressed anchor bundles, and evaluates the anchoring effectiveness of the installed anchor bundles.

Abstract:Unbonded prestressed anchor cables were widely used to reinforce the Maya high slope, the diversion-tunnel portal slopes, the scour-protection wall and the underground powerhouse of the Shuibuya Project. The structure is a two-stage-grouting full-length bonded type with multi-layer anticorrosion protection. Targeting the karst-fissured rock characteristics, consolidation grouting of anchor holes was strengthened, simplifying the grouting procedure and realizing true full-length single grouting. Structural optimization ensures construction quality and improves corrosion resistance and durability, providing useful experience for anchor construction in strongly karst-fissured limestone strata.