Why self-drilling anchor bolts can replace ordinary mortar anchor and friction bolts for support in soft and water-rich geology?

Affected by the COVID-19, most people can only stay at home and cannot work normally. But there were also some people who sticked to their posts and worked overtime. For example, the “model couple” of China Huaneng Cambodia ’s Sanghe II Hydropower Station took the initiative to take on more work when other employees could not return to work. They fought against epidemic in Cambodia and contributed to the local economic and social development.

As a key project of “B & R” construction and Cambodian energy construction, the Sanghe II Hydropower Station constructed by China Huaneng Group has made a great contribution to the Cambodian economy since completed in December 2018.

Many difficulties were encountered during the initial construction of the hydropower station. Such as complex geological conditions, tight construction period, high-risk of construction, etc. According the construction site proposal, it utilized ordinary mortar anchor, friction bolt, and self-drilling rock anchor as experiment, in order to select the efficient and economical product.

Ordinary mortar anchor bolts needed to be put in after the hole was formed. During the process, it was found that the hole collapsed seriously after the drill rod was pulled out, so it was not suitable. The Friction bolt may cause a permeable passage after driving into the surrounding rock because of the hollow structure, and it was prone to water corrosion, so it was not suitable either. The self-drilling anchor bar combined drilling, grouting and anchoring functions together. The anchor bar did not need to be taken out after drilling, which avoided the phenomenon of hole collapse. When drilling, the cement slurry could be injected into the hollow channel of the anchor bar, and it solidified quickly after pouring out, which made the quick connection of the anchor bar and the rock. The integrated function effectively controlled the deformation and displacement of the surrounding rock, ensuring the integrity and stability to the greatest extent. And it can greatly improve the construction efficiency without casing pipe, and thus reducing the composite cost. Construction unit finally decided to use self-drilling anchor bolts because of its feature of convenient, safe and efficient.

It is rich in groundwater under the hydropower station. In order to prevent the affect by groundwater, seawater or chemical media, duplex coating rock bolt can be selected. It combines two different protecting ways together: hot-dip galvanizing and epoxy coating. Hot-dip galvanizing involves dipping the article with a chemically clean surface into a bath of molten zinc which reacts with the iron and forms a coating and to prevent rusting; Epoxy coating doesn’t react with acid, alkali. It has good chemical stability. And it can separate water, oxygen, chloride, and another corrosive medium. Meanwhile, it also creates an electric insulation layer that can insulate the electric current between steel bar and outside conditions, which can reach the good result of corrosion prevention. The combination of double coatings achieves the effect of permanent support of the anchor. It is the choice of most engineers and a good helper for tunnel engineering construction.

Sinorock® has always adhered to the concept of "matching specific products for special geology" in the geotechnical anchoring industry. Through in-depth analysis of different geological conditions, Sinorock® develop self-drilling anchor products with different characteristics. We devote to provide targeted system solutions for customers, so that the project construction is no longer a problem.

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