From the articles below - I would assume they are what we call bar ditches.
From ASK.com
Eric Koch wrote on 2000-06-11 09:47:19.0
Comments: FIST member assign to 2/17 FA but attached to 1st Plt B Co 1/9th Inf from Nov 85 to Nov 86. Looking for other Fist'ers (Buckey, Rosso, McCrory, Lt J.M. Collins, Hutchinson, Rodriguez, Commisso) as well other manchus (D. Silva, L. Bird, M. Best, LLavin, etc.) to catch up with. Great reading through some of these stories about the ROK and some of the "incidents" during the mission.
We did the tour from Dec 85 to Feb 86. Biggest memories for me were the first SR-71 sonic boom I heard while in the barracks at Oulette (took off out the door from a dead sleep), our Katusa Hong puking in my boots after a night of drinking soju (we tried to get him to morning formation but ended up sticking him in a turtle ditch which worked fine until he started moaning during formation), and taking our laser range finders and aiming for the faces of the N. Koreans across the MDL. Does that sign still say "WECOME To The NORTH"? By far the best time I spent in the service was that tour.
Dietrich Grabau wrote on 2003-11-22 20:37:10.0
Comments: Looking for anyone how served with me in the JSA. Empie,Lester,Mac,Smith,Berryhil,SGT Brown, you know how you are there are to many names. But Joe Butcher should have told you that him and Huebner were standing on cordon row watching a north korean tour when the Chinese JDO defected. Yes I know that 1 PLT had the duty that day but there were five or six maddogs augmented that day.Butcher,Huebner,Vanover,Empie,and Collins. As for X-Mas 1989 The maddogs and some members from 4 PLT were useing any thing we could find to sledding down the hill from the JSF orderly room and ditching just before we ran into the building at the end or the escort car that some one droped in to the turtle ditch. We also used one of the CUCV's to instruct the fine art of bumper skiing. It was truly a great time and I would not give it up for anything.