为充分研究超前小导管参数对其超前支护的 影响程度，通过三维数值模拟计算，重点研究超前小导 管管径和小导管长度对其超前支护“棚架”效应的影响 规律。研究结果表明: 超前小导管管径的改变对超前 支护的影响较小，增大管径不能明显控制围岩变形，超 前小导管长度的增加对超前支护的影响趋势由强而趋 于平缓，从而得出小导管的最优长度。

The influence on advanced support due to the parameters of advanced small pipes is studied via threedimensional numerical simulation. The research focued on the effect of the advanced support with the change of small pipes’ diameter and length. Results showed the pipe diameter has little influence on the advanced support and increasing pipe diameter cannot markedly alleviate surrounding rock deformation, and the impact of the pipes ' length of advanced support on the rock reinforcement reduced from the strong to gentle scales. The optimal length of pipes was obtained.

U455． 49

为充分研究超前小导管参数对其超前支护的影响程度，通过三维数值模拟计算，重点研究超前小导管管径和小导管长度对其超前支护“棚架”效应的影响规律。研究结果表明：超前小导管管径的改变对超前支护的影响较小，增大管径不能明显控制围岩变形，超前小导管长度的增加对超前支护的影响趋势由强而趋于平缓，从而得出小导管的最优长度。