Why Do Lubrication Systems Get Under-Specified?

Because it doesn’t look important until it’s too late. 

Most crews don’t get excited about bentonite. It’s not a cutterhead, it’s not a jacking frame, and it’s not the TBM hogging through the ground. It’s just “mud,” right? 

That mindset is part of the problem. 

As explained in Lubrication Tips & Tricks, bentonite does more than make the pipe slippery. When it is mixed correctly and fully hydrated, it creates a filter cake around the borehole and helps balance pressure in the annulus. That is what reduces skin friction and keeps jacking forces under control. 

Another reason lubrication gets shortchanged is because soil changes everything. In sticky clays, the ground can swell and grab onto your pipe hard enough to spike torque and thrust in a hurry, as highlighted in Combating Sticky Clays. Without the right mix of inhibitors, surfactants, and proper pH, jacking loads can climb fast. Once they increase, they are difficult to bring back down. 

It also gets overlooked because you cannot see it working. You see shafts. You see the machine. You see the jacking pipe. Lubrication is happening in the annulus, out of sight. Modern tunneling systems are built to meter and monitor lubrication because it directly affects jacking force. That is why systems like Akkerman’s Jacking and Lube Cans and Bentonite Injection System are used. They provide controlled and metered primary and secondary injection points into the annulus to help manage loads throughout the drive. 

On longer drives, the correct lubrication mix and delivery system can be the difference between a smooth push and watching your pressure gauges climb into the danger zone. 

Bottom line: lubrication is not just mud. It is force control. When it is treated like an afterthought, jobs get harder than they need to be, and sometimes a lot more expensive.