中交二公局承建的昭通至樂山高速公路串佛段轎頂隧道長12615米（左洞6318米，右洞6307米），為本條線路控制性工程。隧道圍巖裂隙發(fā)育、復雜多變、涌水頻發(fā)、巖爆突出，并穿越煤系地層，瓦斯多段落溢出，施工難度大、安全風險高。
　　The 12615m long (6,318m of the left hole and 6307m of the right hole) Zhaotong-Leshan Expressway Chuansi-Foeryan Mt. Jiaoding Tunnel was constructed by CCCC Second Highway Engineering Co., Ltd. and is the controling project of this line. Thanks to the complex and changeable tunnel surrounding rock fissure development, frequent water gushing, rock burst outburst through the coal stratum, gas overflow in many sections, thus, the construction is difficult, and in a high safety risk.