Project Background

This is a project of dam reinforced by soil nail. It is located on the Hongnongjian River downstream of the Hanguguan Scenic Spot in Lingbao City, Sanmenxia City. The hydraulic dam foundation is located in the riverbed of the Hongnongjian River, which is part of the Hongnongjian River ecological water transfer and Liuhe ecological restoration project. The total length of the weir is 744.4m, of which the hydraulic dam section is 150m long, and the upstream reinforced concrete pavement is 10m long in the direction of the water flow. In order to improve the integrity and bearing capacity of the foundation of the hydraulic dam body, the hydraulic dam foundation needs to be consolidated and grouted. The construction party finally used self-drilling hollow bolts to drill holes and use them as grouting pipes.

Project Overview

Questions and Challenges

According to the geological conditions, the designer reserved a grouting hole with a diameter of 100mm in the dam body for consolidation grouting. The construction party planned to use a down-the-hole drilling machine to drill holes and then insert the steel pipe, but due to the too-small hole diameter reserved on-site and the geological conditions of the cement cushion and sand and pebble of the dam foundation, the down-the-hole drilling machine on the site could not carry out the drilling, and the construction was once stopped.

Solution

The construction party learned that the self-drilling hollow bolt can complete drilling and grouting in one drilling, without pulling out the drill pipe and then inserting the bolt, which is very suitable for the cement cushion of the dam foundation and the geological conditions of sand and pebble, so invited We went to the site to conduct drilling tests. We provide self-drilling bolt products and anchor drilling rigs and supporting implementation solutions.
The self-drilling hollow anchoring system consists of a hollow bolt body, a connecting sleeve, and a drill bit. The hollow bolt body can be used as a drill pipe for drilling and as a grouting pipe. The project adopts an R32/19 bolt, R32/51 ball tooth all-steel drill bit, the length of the bolt body is 3m and 4m, and the bolt body is connected to the design length through the connecting sleeve. When drilling, use our company’s self-drilling bolt special drilling rig to perform rotary impact to form holes, and then consolidate and grout after water-flushing drilling. The structure of the bolt is shown in the following figure:
Hollow anchor rod R32, length 3/4m, single hole drilling depth 7-8.3m, a total of 650 drilling holes, the drilling length is about 5000m.

Construction Process

Material preparation → drilling rig in place → connecting hollow bolt and drill bit → impact rotary drilling → lengthening bolt → repeat drilling → drilling completion → hole sealing → grouting pipe connection → consolidation grouting → installation completed

Construction Equipment

Drilling rig: HZY133-100A special drilling rig for self-drilling bolt

Grouting machine: screw grouting pump GLZ-5C Construction efficiency: The average drilling time of a single hole (7-8.3m deep) is 22.8min, and the drilling of the bench is more than 130m.

Project Test

After more than one month of construction, the dam reinforced by soil nail successfully completed the drilling in the cement cushion and sand and pebble channel conditions on June 15. Compared with ordinary steel pipe, the self-drilling rock bolt body can be used as both a drill pipe and an anchor rod for anchoring. There is no need to pull out the drill pipe and then insert the steel pipe, and an appropriate drill bit can be selected according to the geological conditions. The high efficiency of drilling ensures the construction progress of the project and reduces the labor intensity of the construction personnel. The smooth implementation of self-drilling bolts in this project has been highly recognized by technicians and construction personnel.