Summary of Density Methods for Preparing Building Underground (nfm) |
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soil group |
soil types |
degree of compaction |
typical equipment and procedure for compaction |
field control |
Deep foundation methods |
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equipment |
n° of passes or coverages |
comp. lift thick in. |
placement water content |
compaction methods |
field control |
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Pervious - free draining |
GW
GP
SW
SP |
com -pac -ted |
90 - 95% of CE 55 maximum density 75 - 80% of relative density |
vibratory rollers and compacters |
indefinite |
indefinite |
saturate by flooding |
control sample at intervals to determine degree of compaction or relative density |
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rubber tired roller |
2 - 5 coverages |
12 |
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crawler type tractor |
2 - 5 coverages |
8 |
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power hand tasper |
indefinite |
6 |
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semi- com -pac -ted |
85 - 90% of CE 55 maximum density
65 - 75% of relative density |
rubber tired roller |
2 - 5 coverages |
14 |
saturate by flooding |
control sample as above, if needed
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vibro-flotation compaction piles, sand piles, explosives surface compaction as noted above |
undisturbed samples from borings or test pits to determine degree of compaction or relative density |
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crawler type tractor |
1 - 2 coverages |
10 |
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power band tasper |
indefinite |
8 |
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controlled routing of construction equipment |
indefinite |
8 - 10 |
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semi pervious and imper -vious |
GM GC SM SC ML CL OL OK MH CH OH |
com -pac -terd |
90 - 95% of CE 55 maximum density |
rubber tired roller |
2 - 5 coverages |
8 |
optimum water content based on CE 55 test with 12 blows per layer |
control samples at intervals to determine degree of compaction |
1) surface compaction by equipment and procedures is feasible only if material is at proper water content 2) Densification of soil is controlled by consolidation process: - pre-load fills - lowering of groundwater table - drying Consolidation may be accelerated by means of sand drains Field control exercised by observation of pore pressure ans surface settlement |
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sheep foot roller |
4 - 8 passes |
6 |
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power hand tasper |
indefinite |
4 |
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semi- com -pac -ted |
85- 90% of CE 55 maximum density |
rubber tired roller |
2 - 4 coverages |
10 |
1) optimum water content based on CE 55 test with 7 blows per layer; 2) by obser -vation side maximum water content at which material can operate, dry- side minimum water content require to bond particles with no voids or honeycombed material |
1) control samples as noted above if needed 2) field control exercised by visual inspection of action of compacting equipment |
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sheeps foot roller |
4 - 8 passes |
8 |
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crawler type tractor |
3 coverages |
6 |
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power hand tasper |
indefinite |
6 |
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controlled routing of construction equipment |
indefinite |
6 - 8 |
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Typical Engineering Properties of Compacted Material |
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group symbol |
soil type |
range of maximum dry unit weight pcf |
range of optimum water content % |
compression typical value |
typical strength characteristics |
typical coeffi-cient of permeability ft/min |
range of CBR values |
range of sub-grade mo-dulus lb/cu inc |
potential frost action |
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at 2.5 kgf |
at 7.5 kgf |
cohesion (as compacted pcf) |
cohesion (saturated pcf) |
effective stress envelop deg |
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GW |
well graded clean gravels, gravel sand mixture |
125 - 135 |
11 - 8 |
0.3 |
0.6 |
0 |
0 |
> 38 |
5. 10 |
40 - 80 |
300 - 500 |
none to very light |
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GP |
poorly graded clean gravels, gravel sand mix. |
115 - 125 |
14 - 11 |
0.4 |
0.9 |
0 |
0 |
> 37 |
10 |
30 - 60 |
250 -400 |
none to very light |
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GM |
silty gravels, poorly graded gravel sand silt |
120 - 135 |
12 - 8 |
0.5 |
1.1 |
- |
- |
> 34 |
> 10 |
20 - 60 |
100 - 400 |
slight to medium |
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CG |
clayey gravels, poorly graded gravel sand clay |
115 - 130 |
14 - 9 |
0.7 |
1.6 |
- |
- |
> 31 |
> 10 |
20 - 40 |
100 - 300 |
slight to medium |
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SW |
well graded clean sand, gravelly sands |
110 - 130 |
16- 9 |
0.6 |
1.2 |
0 |
0 |
38 |
> 10 |
20 - 40 |
200 - 300 |
none to slight |
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SP |
poorly graded clean sands, gravel mix |
100 - 120 |
21- 12 |
0.8 |
1.4 |
0 |
0 |
37 |
> 10 |
10 - 40 |
200 - 300 |
none to slight |
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SM |
silty sands, poorly graded sand silt mix |
110 - 125 |
16- 11 |
0.8 |
1.6 |
1050 |
420 |
34 |
5. 10 |
10 - 40 |
100 - 300 |
slight to medium |
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SM - SC |
sand silt, clay mix with slightly plastic fines |
110 - 130 |
15- 11 |
0.8 |
1.4 |
1050 |
300 |
33 |
2. 10 |
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SC |
clayey sands, poorly graded sand clay mix |
105 - 125 |
19- 11 |
1.1 |
2.2 |
1550 |
230 |
31 |
2. 10 |
5 - 20 |
100 - 300 |
slight to high |
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ML |
inorganic silts and clayey silts |
95 - 120 |
24- 12 |
0.9 |
1.7 |
1400 |
190 |
32 |
10 |
15 or less |
100 - 200 |
medium - very high |
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ML-CL |
mixture of inorganic silt and clay |
100 - 120 |
22- 12 |
1.0 |
2.2 |
1350 |
460 |
32 |
5.10 |
- |
100 - 200 |
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CL |
inorganic clays of low to medium plasticity |
95 - 120 |
24- 12 |
1.3 |
2.5 |
1800 |
270 |
28 |
10 |
15 or less |
50 - 200 |
medium to high |
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OL |
organic silt and silt-clays of low plasticity |
80 - 100 |
33- 21 |
- |
- |
- |
- |
- |
- |
5 or less |
50 - 100 |
medium to high |
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MH |
inorganic clayey silts elastic silts |
75 - 95 |
40 - 24 |
2.0 |
3.8 |
1500 |
420 |
25 |
5. 10 |
10 or less |
50 - 100 |
medium - very high |
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CH |
inorganic clays of high plasticity |
80 - 105 |
36 - 19 |
2.6 |
3.9 |
2150 |
230 |
19 |
10 |
15 or less |
50 - 150 |
medium |
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OH |
organic clays and silty clays |
75 - 100 |
45 - 21 |
- |
- |
- |
- |
- |
- |
5 or less |
25 - 100 |
medium |
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