The construction requirements of rock bolt in foundation pit support
The construction requirements of rock bolt in foundation pit support

The construction requirements of rock bolt in foundation pit support

1. The pitch error of rock bolt drilled hole in the horizontal direction should not be greater than 100mm in the vertical direction, skewness should not be greater than 3%.

2. Grouting pipe should be banding together with rock bolt, the first grouting from the bottom of the hole should be as 100-200mm, the second grouting pipe out of the hole should be filled slurry seal treatment;

3. Slurry should be prepared according to the design, selection of a filling sand ratio 1: 1-1: 2, water-cement ratio 0.38-0.45 cement mortar or grout cement ratio 0.45-0.5, the secondary high pressure grouting should be use the slurry water cement ratio of 0.45 to 0.45;

4. Secondary pressure grouting pressure should be controlled between 2.5-5.0Mpa, grouting time can be determined according to the grouting process test or a grouting intensity reached after 5MPa;

5. The tension and prestress of rock bolt should meet the following requirements: anchorage strength is greater than 15Mpa and has reached the level of 75% of the design before proceeding with tension; Bolt tension sequence should consider the impact on the adjacent anchor; Anchor should be tensioned to design load of 0.9 to 1.0 times after the lock according to design requirements;

6. Rock bolts selection shall be 1% of the total and not less than 3 ribs in accordance with relevant regulations each layer to bolt examination for rock bolt acceptance test.

Posted by Sinorock

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