pilot tunnel meaning in English
超前平硐
导洞（导坑）
道洞
前探平硐
隧道导洞
Examples
- Construction of flat tunnel of large span at extra - shallow depth must be conducted on the principle that advance grouting should be strictly performed before excavation and length of pull at one time should be short , together with reinforced support , immediate closing and constant monitoring and surveying . that preceding pilot tunnels , large - volume excavation divided into small ones , excavation of flank before that of center , upper before lower , arch before wall etc is a good method which could effectively reduce surface subsidence and its adverse effect on adjacent buildings , in addition , some other measures are also taken to lessen blast - induced vibration in the ground and surrounding structures . in a word , all means and steps mentioned above have already proved effective and practicable in practice
软弱大跨超浅埋扁平隧道必须按“管超前，严注浆，多分部、短开挖、强支护、快封闭，勤量测”的施工原则进行施工，采用“眼镜超前，化大为小，先侧后中，先上后下，先拱后墙”的施工方法控制地表沉降和对周边建筑物的影响；采用“多分部，化大为小，短进尺，密布眼，弱装药，设减振槽” ，控制爆破振动，经过实践证明，这些方法都是行之有效的。 - Tensile stress field would appear in the proximity of arched vault after excavation , slacking of surrounding rock and subsequent dropping of blocks of rock from such area would possibly occur at any time in the context of extra - shallow depth . so i - steel arched support must be erected to provide against possible block dropping and be integrated into a ring with that of pilot tunnels on both sides
拱顶在核心土开挖后，在一定范围内出现拉应力区，在超浅埋情况下极容易掉块和发生围岩松驰，因此核心土必须边开挖边架设工字钢拱架，使之与左右导洞拱顶工字钢形成整体。