TREATMENT MEASURES FOR A TUNNEL CAVING-IN

This paper analyzed the reason which leads to the caving in for a deep buried tunnel in soft sand layer.The most important reason was the sandy soil lens which disturbed by the blasting operation.According to the situation,treatment measures were taken.First,the cave forme by collapse was filled by shot creting;then,the surrounding rock of caving-in area was reinforced by advanced small pipe grouting;thereafter,concentrated steel rigid frame was constructed along the tunnel to support the sourrounding rock.Convergence monitoring was conducted during the treatment.The results showed this scheme was feasible.