Enhancing Slope Stabilization at the Left Bank of Xiluodu Hydropower Station with Self-Drilling Anchor Bolts

Time:2015-08-20View:

Introduction

Slope stabilization in challenging geological conditions has always been a daunting task for engineers and construction experts. In the case of the Left Bank of Xiluodu Hydropower Station, where complex geological stratifications and a short construction period posed significant challenges, the innovative application of self-drilling anchor bolts emerged as a game-changer.

Enhancing Slope Stabilization at the Left Bank of Xiluodu Hydropower Station with Self-Drilling Anchor Bolts

Enhancing Slope Stabilization at the Left Bank of Xiluodu Hydropower Station with Self-Drilling Anchor Bolts

Geological Complexity Unveiled

At the heart of the Xiluodu Hydropower Station project lies the Left Bank, a region characterized by a geological landscape of unparalleled complexity. To comprehend the magnitude of this complexity, we must first understand the three distinct geological stratifications encountered during the project's execution:

1. Diluvial Deposit (plQ3): The topmost layer comprised diluvial deposits, featuring an inhomogeneous structure that posed a constant threat of shaft collapse.

2. Glacier Deposit (fgl+glQ2): Directly beneath the diluvial deposit, this layer exhibited poor autostability, adding to the challenges faced during construction.

3. Ancient Landslide Deposit: At the deepest level, the ancient landslide deposit consisted of Triassic system amaranth sandstone and limestone macadam, further complicating the project's geological intricacies.

Project Overview

The scope of this project encompassed the construction of two outlet shafts, NO.1 and NO.2, both reaching an impressive depth of 251 meters. Each shaft had distinct characteristics and requirements based on the surrounding rock conditions.

1. NO.1 Shaft: The covering stratification extended to a depth of 115 meters, with an excavation diameter ranging from 14.0 to 14.6 meters. Given the relatively weak nature of the surrounding rock in this layer, support became crucial when digging to depths between 3.0 and 4.5 meters. Self-drilling anchor bolts, each measuring 6 meters in length, were employed at an interval spacing of 1.2 meters by 1.0 meter. The drilling depth reached 5.5 meters, ensuring a robust anchor for the subsequent construction of a long inclined shaft.

2. NO.2 Shaft: The covering stratification extended to a depth of 126 meters, with similar excavation dimensions as NO.1 Shaft. Similarly, self-drilling anchor bolts, mirroring the specifications used in the NO.1 Shaft, were employed to bolster the surrounding rock.

The Remarkable Role of Self-Drilling Anchor Bolts

In the face of the formidable geological challenges at the Left Bank of Xiluodu Hydropower Station, the decision to employ self-drilling anchor bolts proved to be a pivotal one. This innovative technology offers several advantages over traditional methods, which became evident during the project's execution:

1. Simultaneous Drilling, Grouting, and Anchoring: Self-drilling anchor bolts are engineered to perform drilling, grouting, and anchoring these 3 steps in a single operation. This feature significantly expedited the construction process, ensuring that work proceeded swiftly even in the presence of complex geological stratifications.

2. Hollow Bore for Flushing: The hollow bore of the self-drilling anchor bar allowed for efficient flushing during drilling, minimizing the risk of clogging with sediment, and debris. This ensured that the anchor bolts were securely embedded in the rock, enhancing stability.

3. Adaptability to Weak Rock and Unconsolidated Ground: The hollow anchor bar used in self-drilling anchor bolts can be cut arbitrarily and can also be lengthened by the coupler. It can be used in narrow spaces where large equipment cannot enter. Compared with the traditional casing drilling method, self-drilling anchor greatly improves the construction efficiency and reduces the construction cost. Self-drilling anchor bolts excel in conditions where weak rocks, loose soil, weathered layers, or sand with stone layers. This adaptability was crucial for the Left Bank project, where the surrounding rock conditions varied significantly.

4. Enhanced Safety: Given the dangerous nature of the project's overall conditions, ensuring the safety of the construction team was paramount. The self-drilling anchor bolt can be reinforced by installing plates and nuts on the exposed section of the self-drilling hollow anchor bar close to the surface of the rock body. When the rock body deforms, the deformation force is transmitted to the anchor bars and anchorages through the pads and nuts to stabilize the rock body. This method of reinforcement makes self-drilling anchor bolts more direct and safer than other traditional cable anchors.

Results and Conclusion

The application of self-drilling anchor bolts in the Vertical Shaft at the Left Bank of Xiluodu Hydropower Station delivered remarkable results. Despite the daunting geological complexities, the project was completed within the stipulated timeframe, and safety standards were upheld throughout.

The success of this project serves as a testament to the efficacy of self-drilling anchor bolts in slope stabilization, particularly in challenging geological conditions. By seamlessly combining drilling, grouting, and anchoring, these anchor bolts offer a robust and efficient solution for similar projects worldwide.

Conclusion

The Left Bank of Xiluodu Hydropower Station project stands as a shining example of innovative engineering solutions that can overcome even the most formidable geological obstacles. The strategic use of self-drilling anchor bolts has not only enhanced the stability of the slope but also paved the way for future projects to tackle similar challenges with confidence and efficiency.

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