## Soil Nail tests

## Soil Nail tests

(OP)

Hi there,

I have a small question on soil nail test, plz help. (I would be more grateful if PEinc also comments)

for proof test FHWA says that we should calculate LBPt as greater of 3 m and 0.9*A*fy/Qall*FSproof then DTL=LBPt*Qall

for verification test is the same except FS=2.5-3 instead of 1.5

my question is if for example we have a 32mm bar with fy=4000 kg/cm2 and 9m long DTL for proof and verification would be differetnt

if we assume qall=20 kN/m

then DTL for proof=190 kN and for verification=10 kN

then if we do a proof test then 150% load=280 kN and for verification 200% (as FHWA suggests) =200 kN so verification test load is less than proof.

for most cases I mean for bar with more than about 7-8 m, qu dosnot have any effect on DTL, so can you help me with this how should I exactly choose the correct DTL for my tests?

Regards.

I have a small question on soil nail test, plz help. (I would be more grateful if PEinc also comments)

for proof test FHWA says that we should calculate LBPt as greater of 3 m and 0.9*A*fy/Qall*FSproof then DTL=LBPt*Qall

for verification test is the same except FS=2.5-3 instead of 1.5

my question is if for example we have a 32mm bar with fy=4000 kg/cm2 and 9m long DTL for proof and verification would be differetnt

if we assume qall=20 kN/m

then DTL for proof=190 kN and for verification=10 kN

then if we do a proof test then 150% load=280 kN and for verification 200% (as FHWA suggests) =200 kN so verification test load is less than proof.

for most cases I mean for bar with more than about 7-8 m, qu dosnot have any effect on DTL, so can you help me with this how should I exactly choose the correct DTL for my tests?

Regards.

## RE: Soil Nail tests

As I have mentioned before, I am strongly against proof testing of production nails. I have concerns about successfully installing and removing a temporary sheath for the unbonded length and have concerns about testing a nail with an uncased, ungrouted unbonded length. Testing a production nail with a temporary steel casing in the unbonded length is a good way to lose or ruin expensive steel casing pipe. If an uncased drill hole collapses during a production test, the nail is worthless and needs to be replaced. I prefer to do all nail testing on sacrificial nails with a bond length of 10 feet maximum. If the design ultimate bond stress is high (say for very dense soil or rock), I shorten the bond length so that I do not fail the bar. Sometimes, I will use a stronger bar for the test but care needs to be taken that the excavated face of wall or the shotcrete does not fail by punching shear. A large test load could require an unreasonably large area of cribbing beneath the test jack.

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## RE: Soil Nail tests

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## RE: Soil Nail tests

I agree with your commnets in regard to proof test, but the client has asked us to do some proof tests.

I am using the same manual you are using, but as you know in Appendix E it has introduced a formula to calculate DTL, and that's what I'm exactly confused, suppose we have 13m long nail with 32mm Dia, which is 1m is unbonded, could you please tell me what DTL we have to use for proof tests, Qu= 150 kpa, and safety factor to calculate Qall was assumed to be 2.0.

if we refer to Appendix E, the LBPTmax=0.9*8.04*4000/(1.5*10*3.14*100*1.5/2)=8.2m

so DTL=8.2 x Qall (23.55)=192 kN,

if we use 150% DTL then it would be 289 kN which is almost 0.9fy.

if we use the same procedure in appendix E for verification test, we reach the same value at max load, so what would be difference,

could you please tell me with the above parameter which DTL you use for proof test?

Thanks.

## RE: Soil Nail tests

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## RE: Soil Nail tests

## RE: Soil Nail tests

ALLnails in the project have minimum 9.0 bonded length, so as I mentioned above Qall= 23.5 kN/m, so as you cited if we choose 3.0m bondedthen, DTL would be 70 kN if we choose a value between 3m to 8.2(which is the maximum) for example 5.0m then DTL is 117 kN and ...

so then what is the difference?, if we choose 3.0m the 150% DTL is 10.5. the nail maybe acceptable at this range but if we choose 5.0m and the nail might fail at 120 kN which is about 100% of DTL we selected, as I told before all nails have minimum 9.0m length, and so choosing a value beetween 3.0m and LBPT max leads to different levels of DTL, so my question is with these nail lengths how can I satisfy this sentence of Manual?

"Proof tests are used to ascertain that the contractor’s construction methods and/or soil conditions have not changed

and that the production soil nails can safely withstand design loads without excessive movement or long-term creep over the service life"

## RE: Soil Nail tests

If you have to prove 10 psi bond, you have to stress a known bond length and diameter to the load required to give 10 psi without overstressing the bar. You can do this with a 10 foot (1m) bond length. You don't need to test a 30 foot bond length.

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## RE: Soil Nail tests

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## RE: Soil Nail tests