High in the Never Summer Mountains of Colorado sits a critical piece of infrastructure for the city of Fort Collins Utilities Dept. known as the Michigan Ditch. The 5.2-mile-long ditch was originally constructed in the early 1900s to convey water from the west side of the mountain range to the east. The city purchased the ditch system 40 years ago and has maintained it ever since, placing a $150-million to $300-million value on the collected water it provides.
尽管斜坡不稳定在整个历史上困扰着沟渠，但在2014 - 15年度冬季，沟渠先前的沟渠先前沟渠中的一个沟渠中的一个沟渠横向横向沟通，水平的“泥石流”水平21英尺，垂直移动了7英尺。由于大多数收集的水以每秒100立方英尺的速度流过滑坡区域，因此密歇根州的沟渠将在可预见的将来停止使用，并且需要永久解决方案。
Degree of Difficulty
Site logistics at 10,300 ft above sea level make for a challenging and short construction season. The city of Fort Collins used its alternative product delivery system (APDS) in a design-build, team-oriented approach to solve the problem. The program allows the city to quickly move forward on assembling a team.
Picking from a number of pre-qualified and pre-approved designers and contractors in July 2015, the city assembled a design-build team and began discussing options for permanent repairs to the ditch. Ultimately, the construction of a tunnel behind the landslide in competent rock was deemed the best long-term solution.
2015年夏末进行了彻底的岩土研究证实了隧道对齐。船员拿了八个垂直钻孔，以及三个水平钻孔。地下调查表明，滑坡的一个矮小的部分比以前预期的。这些发现，结合了现场的几何形状，意味着弯曲的隧道比对最好将沟渠保持在实心基岩中。
关于隧道方法和载波选择的其他考虑因素产生了最终计划，该计划要求建造在630英尺半径曲线上的765英尺长，直径为8英尺的隧道。这允许安装直径60英寸的霍巴斯载体管。另外200英尺的开放切割，60英寸。管道也将被制成以绑在现有沟渠中。
Key Challenges
The first challenge was to pick a tunneling machine that the team could transport up to the jobsite. The project is located two miles up a single-track dirt road with a small launch and retrieval site on the side of a mountain, so getting a crane there to unload equipment was not an option.
设计建造团队与多个供应商进行了交谈，并决定了明尼苏达州Akkkerman Inc.的定制隧道无聊机（TBM）。直径为96英寸的Akkkerman 720系列II TBM配备了混合式刀具，该刀具使用了13张圆盘切割机，40个刮刀牙齿和4个刮刀杆。
刀头建造到98英寸。为了提供足够的过度切割以使630英尺半径曲线。
此外，TBM的重量少于50,000磅，设置相对较小和检索足迹，可以在开始施工所需的六个月时间内制造。如果TBM可以处理隧道驱动器的地质，则建筑团队相对有信心将其从现场传递和检索。
第二个挑战是准确，安全地建造隧道。VMT技术测量Solutions Inc.的最先进的指导系统，再加上两个不同的调查团队的常规调查检查，向TBM操作员和现场施工检查员提供了对隧道施工位置的不断反馈。
The tunnel was built within 0.01 in. horizontally and 1 in. vertically of the design. Building the job safely was a large task for the field supervisory team. Every work shift included a morning and afternoon safety briefing with an open discussion of the upcoming tasks and hazards involved in the work. The project was completed with zero-recordable injuries.
Completing the tunnel within the 2016 summer construction window was the goal from the beginning. Typically, the site is accessible from mid-May through mid-October. The as-expected, mixed-face geology encountered during the tunnel construction resulted in slower than anticipated production and higher tooling changes.
设计建造团队在9月份进行了额外的夜班，并于2016年9月29日完成了隧道。最后60英寸的安装。在整个10月，在整个10月27日，载货管和搭配的沟渠都发生在整个密歇根州沟渠后面的密歇根州沟渠。柯林斯堡市回到网上的一大批基础设施。
John Beckos is a project manager with BT Construction Inc. in Henderson, Colo.
项目团队
所有者：柯林斯堡市，欧文·兰德尔（Owen Randall），首席工程师
设计建造（APD）团队：Stantec Consulting (prime engineer), Lithos Engineering (geotechnical and tunnel engineer), BTrenchless (tunnel contractor), Hydro Construction (general contractor)
