Some Problems When Supporting Tunnels by Self Drilling Hollow Rock Bolts

by Simone S. sinorockco

The problems existing in tunnel construction supported by self-drilling anchor rock bolts are mainly divided into three categories: preparation, construction, and acceptance, including the allocation of quality management personnel, the inspection of raw materials and equipment, the positioning, angle, installation, and grouting problems of bolt construction, and acceptance and drawing. test questions.

In tunnel construction, hollow rock bolts are often used to maintain the stability of surrounding rock and ensure construction safety. With the increase in the use of bolts in tunnel engineering, construction safety, and quality problems are also common. The angle and length of the bolt, as well as the installation and grouting of the bolt, are relatively common problems. Sinorock will show you some problems existing in the tunnel construction supported by rock bolts and how to prevent them.

The Preparation Before the Construction

Staffing of Quality Management Personnel

The tunnel construction supported by the rock bolts process is relatively complicated. In order to ensure the construction quality, it is necessary to provide monitoring personnel during the construction to monitor the drilling positioning, drilling angle, drilling depth, grouting, and inspection of the bolt construction.

Raw material inspection

The tunnel construction quality supported by rock bolts is closely related to the quality of raw materials. It is necessary to control the quality of raw materials, plan the inspection items and sampling ratios of raw materials, control the quality of raw materials from the source of manufacturers, and choose manufacturers with reliable quality.

Inspection of construction equipment

The tunnel construction supported by rock bolts mainly relies on labor and drilling rigs. The bolting rigs need to be selected according to the construction environment and construction design. The construction environment determines the area of ​​the construction rig and the convenience of construction. The design of construction drawings determines the drilling depth requirements that the rig needs to meet.

Problems in The Process of Anchor Construction

Anchor Rod Positioning

The rock bolt positioning includes steps such as laying out, marking, and fixing points. It cannot be positioned intuitively. If the anchor rod positioning deviates, the construction effect will not meet the requirements. Therefore, the construction site should strictly require the construction process of self-drilling hollow grouting bolts, and checking the positioning of the bolts for 10% of the number of bolts.

Drilling Angle

When designing, the drilling angle of the rock bolts will be set according to the geological and rock formation. During construction, due to the environmental conditions of the tunnel and the limitation of equipment adjustment, the drilling angle often deviates. Before drilling, manual observation and checking are required to ensure the accuracy of construction.

Anchor Rod Installation

When purchasing rock bolts, it is necessary to take into account the occurrence of unexpected situations, and purchase bolts that exceed the required amount, including their accessories. The purpose is to prevent the length, specification, and appearance of the rock bolt do not meet the requirements, and if the accessories are not complete during the installation of the bolt, which can be replaced immediately. When installing the stopper, if it is found to be loose or the distance from the orifice is too large or too small, it should be corrected immediately.

Grouting Problem

In tunnel construction, if hollow rock bolts are used, attention should be paid to grouting and grouting. When inspecting, it is necessary to pay attention to whether there is an overflowing slurry near the orifice stopper, and whether it is intentionally plugged with an anchoring agent at the grouting port, which is a false grouting phenomenon. If the steps of grouting and grouting are not done well, the slurry will not be full, resulting in excessive pores and affecting the anchoring effect.

Problems of Acceptance And Acceptance of Anchor Bolt Construction

Construction Effect of Anchor Rock Bolt

After the rock bolt grouting construction is completed, the length and grouting degree of the bolt needs to be checked. Unqualified bolts belong to failed bolts and need to be re-struck or grouted. The number of re-struck bolts is the same as the number of failed bolts, and the length should be 1.5 times that of the failed bolts.

Pull-out Test

According to relevant regulations, it is necessary to test the pull-out force value of the bolt after the construction of the bolt to check whether it meets the design value of the pull-out force. In the test, no less than 3 bolts should be randomly checked for pull-out force test in every 300 bolts in the operation area.

The above is the explanation of the problems existing in the construction of tunnel bolts. The bolts are to ensure the safety of construction and the safety of later support, and it is necessary to strictly control and manage the quality. 

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Created on May 10th 2022 04:02. Viewed 141 times.

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