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RE: Epoxy Grout and Rock Anchors[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: RE: Epoxy Grout and Rock Anchors
- From: James_F_Fulton(--nospam--at)RohmHaas.Com (James F Fulton)
- Date: Mon, 13 Nov 2000 09:40:12 -0500
Caution ! I have experience with a major failure of an in-ground basin floor involving epoxy grouted rebar use as rock anchors in somewhat fractured rock. According to the drawings: Number 6 rebar embedded in 2 inch diameter holes drilled 6 ft. deep into rock was grouted with "BRUTEM 15 EPOXY GROUT OR EQUAL". The 15 ft. deep basin floor is 70 ft. x 140 ft. x 14 in. thick, reinforced with #6 at 12, EWEF. The floor cracked and was (permanently) deflected up 12 in. by 7 ft. groundwater head acting on the slab bottom, giving 268 psf net pressure on the slab. Based on analysis of the possible causes of the failure, I believe it has to do with the epoxy grouted rebar. Either (1) the particular epoxy used was not suited for the constant wet condition that exists and it failed by loss of shear strength or debond, and/or (2) the two inch diameter hole is too large for epoxy grouting rebar in that over time the grout creeps under load and eventually fails in shear. Also, two inch hole diameter seems to be too large considering that all epoxy manuf. I see recommend the drill hole in concrete be only 1/8" larger on the diameter than the particular rebar size being grouted. I believe that a cementitious grout is better for rock anchors like this.
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