1 Introduction
Instrument | Evaluation method | Test conditions | Developed/investigated | ||||
---|---|---|---|---|---|---|---|
Filtration media | Stop mechanism | Pressure (bars) | Grout volume (L) | ||||
1 | Sand column | Ra–T–V | Sand | C–F3–Re | 2.6 | 10 | Axelsson et al. (2009) |
2 | Pressure chamber | Ra | Fleece fine sand soft rock | F4 | 1.6 | N.A. | Gandais and Delmas (1987) |
3 | Filter pump | T | Wire mesh | F2 | 0.5 | 0.3 | Hansson (1995) |
4 | Penetrability meter | T | Wire mesh | F2 | 1.0/2.0 | 1.0 | Eriksson and Stille (2003) |
5 | NES method | W | Slot | F1 | 0–20 | N.A. | Sandberg (1997) |
6 | Nobuto method | W | Slot | F1 | 10–50 | Unlimited | Nobuto et al. (2008) |
7 | PenetraCone | Vt | Slot | F2 | 1.5/3.0/5.0 | Unlimited | Axelsson and Gustafson (2010) |
8 | Short slot | W | Slot | F2 | 0–15 | 1.7 | Draganovic and Stille (2011) |
9 | Long Slot | W–P | Slot | F2–Re | 0–15 | 1.7 | Draganovic and Stille (2014) |
2 Materials and Methods
2.1 Adjustment of Filter Pump
2.2 Adjustment of Penetrability Meter
2.3 Short Slot
2.4 Material Selection and Mixing
2.5 Test Plan
Test group | Pressure (bar) | Test device | Evaluation method | No. of repetitions with every mesh size | No. of repetitions with every slot size | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
26 μm | 35 μm | 43 μm | 54 μm | 61 μm | 77 μm | 90 μm | 104 μm | 122 μm | 144 μm | 200 μm | 43 μm | 50 μm | 70 μm | 84 μm | 169 μm | 177 μm | ||||
1 | 1 | OFP | WT | 1 | 4 | 4 | 4 | 3 | 3 | 2 | – | – | – | – | – | – | – | – | – | – |
2 | 1 | MFP | WT | – | 4 | 3 | 3 | 3 | 3 | 2 | 1 | 2 | 1 | – | – | – | – | – | – | – |
3 | 1 | MPM | WT | – | 2 | 2 | 2 | – | 3 | 1 | 2 | 1 | 3 | – | – | – | – | – | – | – |
4 | 1 | MPM | PT | – | 2 | 3 | 3 | – | 1 | – | 3 | – | 3 | 1 | – | – | – | – | – | – |
5 | 1 | SS | WT | – | – | – | – | – | – | – | – | – | – | – | – | – | 1 | – | 1 | 3 |
6 | 15 | SS | WT | – | – | – | – | – | – | – | – | – | – | – | 1 | 3 | 1 | – | – | – |
Sum = | 1 | 12 | 12 | 12 | 6 | 10 | 5 | 6 | 3 | 7 | 1 | 1 | 3 | 2 | – | 1 | 3 | |||
Total No. = 85 |
3 Results
Test device | Evaluation method | Pressure (bar) | bmin (µm) | bcrit (µm) |
---|---|---|---|---|
OFP | T | 1 | 35 | 77 |
OFP | W | 1 | 35 | 90 |
MFP | T | 1 | 43 | 61 |
MFP | W | 1 | 43 | 77 |
MPM | W | 1 | 43 | 200 |
MPM | P | 1 | 35 | 200 |
SS | W | 1 | 70 | 200 |
SS | W | 15 | 26 | 50 |
3.1 Penetrability Measurement Using Filter Pump
3.2 Penetrability Measurement Using Penetrability Meter
3.3 Penetrability Measurement Using Short Slot
4 Discussion
4.1 Uncertainties Induced by the Applied Pressure
4.2 Uncertainties Induced by the Grout Volume
4.3 Uncertainties Induced by the Constriction Geometry
4.4 Uncertainties Induced by the Evaluation Methods
4.5 Uncertainties Induced by a Combination of Origins
5 Conclusions
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Nonuniform and unequal applied pressure was found to be one of the main governing origins of uncertaity and contradition in the results of different penetrability measuring instruments. Evaluating b crit at both the low and the high pressures, e.g. 1 and 15 bar, was found crucial to determine the upper and the lower limits of a real fracture aperture in rock that a specific grout can penetrate without filtration.
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Difference in the designated grout volume was found the second governing origin of uncertaity and contradition in the results of penetrability measuring instruments. The experiments using modified Penetrability meter clearly illustrated that the higher the designated grout volume, the greater the value of b crit . The required grout volume for proper evaluating the grout penetrability was also estimated to be approximately 2.5 L. The results of ordinary and modified Filter pump and ordinary Penetrability meter (with the designated grout volume of 0.3 and 1 L) will therefore be less than the proper values of the grout penetrability through a real fracture in rock. This makes applicability of those instruments not recommended. However, Filter pump is still useful for quality control of the cement and the mixing process as suggested by Swedish standard SS-EN-14497.
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Diversity in the constriction geometry was found as the third governing origin of uncertainty and contradiction in the results of the penetrability measurements. The evaluated value of the b min in Short slot was greater than that in modified Penetrability meter in closely identical conditions. This was due to the remained differences in the constriction geometries. However, the similar values of the b crit obtained from both instruments inferred that evaluating the b crit is less influenced by the diversity in constriction geometry.