Consolidation Test 6gj6j
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GEOTECHNICAL LABS 2014 CONSOLIDATION TEST DETERMINATION OF ONE DIMENSIONAL CONSOLIDATION PROPERTIES
ODOMETER TEST INTRODUCTION This method covers the determination of the magnitude and rate of consolidation of a saturated or near saturated soil sample in the form of a disc confined laterally, subjected to vertical axial pressure and allowed to drain freely from top and bottom surfaces. THEORY When a saturated clay-water system is subjected to an external pressure, the pressure applied is initially taken by the water in the pores resulting thereby in an excess pore water pressure. If drainage is permitted, the resulting hydraulic gradients initiate a flow of water out of the clay mass and the mass begins to compress. A portion of the applied stress is transferred to the soil skeleton which in turn causes a reduction in the in the excess pore pressure. This process involving a gradual compression occurring simultaneously with flow of water out of the mass and with a gradual transfer of the applied pressure from the pore water to the soil skeleton is called consolidation . The total compression of a saturated soil under excess effective pressure may be considered as the sum of 1. Immediate consolidation, 2. Primary consolidation, and 3. Secondary consolidation. St=si+sp+ss The portion of the settlement of a structure which occurs more or less simultaneously with the applied loads is referred to as the initial or immediate settlement. This settlement is due to the immediate compression of the soil layer under undrained condition and is calculated by assuming the soil mass to behave as an elastic soil. If the rate of compression of the soil layer is controlled solely by the resistance of the flow of water under the induced hydraulic gradients, the process is referred to as primary consolidation. The portion of the settlement that is due to the primary consolidation is called primary consolidation settlement or compression. At the present time the only theory of practical value for estimating time-dependent settlement due to volume changes, that is under primary consolidation is the one-dimensional theory. The third part of the settlement is due to secondary consolidation or compression of the clay layer. This compression is supposed to start after the primary consolidation ceases, that is after the excess pore water pressure approaches zero. It is often assumed that secondary compression proceeds linearly with the logarithm of time. However, a
F16/1334/2010
Page 1
GEOTECHNICAL LABS 2014 satisfactory treatment of this phenomenon has not been formulated for computing settlement under this category. The process opposite to consolidation is called swelling which involves an increase in the water content due an increase in the voids.
In this method the procedure depends on the soil specification classification Fine silts and clays are classified as type A soils, and coarse soils with numerous inclusions such as small stones which break or deform badly on extrusion from the sample tube are classified as type B soils. APPARATUS 1. Fixed ring type apparatus: with metal consolidation ring, bottom and top porous plates, consolidation cell, micro-meter dial gauge and a rigid device for ing the consolidation cell. 2. Apparatus for preparation and testing specimens: A jack and frame to extrude soil from sampling tube, a jig to hold the consolidation ring, a sharp thin palette/ blade, wire saws, metal straight edges, flat glass plate, vernier callipers, tins for moisture content, filter papers, stop watch, tap water, thermometer, a watch glass and specific gravity apparatus. PROCEDURE 1. SPECIMEN PREPARATION A short length of the soil sample was extruded from sample tube by means of the jack and frame and examined for soil type. A consolidation ring of suitable dimensions and the watch glass were cleaned, dried and weighed. The ring was lubricated with grease. 2. SAMPLE A representative sample for testing was extruded from the sample tube and cut off carefully to ensure the two plane surfaces of the disc of soil were parallel to each other. The thickness of the soil disc was a little greater than the height of the consolidation ring. Using the consolidation ring as the template, the disc was trimmed until it could just slid into the ring with the last fraction of soil being pared away by the cutting edge of the ring as it was pushed into the ring carefully. Any voids created were filled with the parings. The
F16/1334/2010
Page 2
GEOTECHNICAL LABS 2014 projecting bottom and top edges were then trimmed using the sharp edge to achieve level flash surfaces. Loss of moisture and soil grains was avoided at all stages. A sample of the same soil sample was set aside for specific gravity test. The thickness of the consolidation specimen was measured and the cell placed in a metal tray and weighed. 3. ASSEMBLY OF APPARATUS AND TEST PROCEDURE The dry bottom porous plate was centred in the consolidation cell and the ring complete with the specimen placed centrally on top of it with a filter paper against each face of the specimen. The top porous plate and the loading cap were then placed centrally on top. The consolidation cell complete with specimen was then placed in the bed of the loading apparatus. The counterbalanced loading beam was adjusted carefully into a loading position with the appropriate load transmitting member in with the loading cap. The gauge was clamped into position to record the relative movement between the base of the consolidation cell and the loading cap.
The OEDOMETER Loads were applied in sequence of 50, 100, 200, 400 kN/m2 The initial pressure for each loading was applied and the compression observed to ensure it was large enough to prevent swelling. The compression readings in the intervals were observed at sequence 0,0.25, 0.5, 1,2.25,4.00,6.25,9.00,12.25,16.00,20.25,25,36,49,64,81,100minutes and then up to 24 hrs, time sufficient for full consolidation.
F16/1334/2010
Page 3
GEOTECHNICAL LABS 2014 The gauge reading, time and √
were recorded to facilitate the plotting of the readings.
After each application of loading, the consolidation cell was filled with water to allow for swelling and saturation of specimen before increasing the pressure to the next higher value in the sequence. After the sample had fully consolidated under the full load increment, the pressure was released and the sample moisture content recorded. RESULTS TYPE OF SOIL : Red coffee soil SPECIFIC GRAVITY OF SOIL: 2.66 Sample thickness :19mm Moisture content at end of test: Wet soil= 136g Dry soil =100g Moisture content= 36% The results of the test Time in √time log time 50kN/m2 100kN/m2 200kN/m2 400kN/m2 min min 0 0 #NUM! 2800 2302 2155 1983 0.25 0.5 -0.60206 2725 2210 2055 1866 1 1 0 2700 2198 2045 1854 2.25 1.5 0.352183 2570 2192 2037 1846 4 2 0.60206 2360 2188 2031 1844 6.25 2.5 0.79588 2335 2185 2028 1838 9 3 0.954243 2330 2183 2026 1835 12.25 3.5 1.088136 2323 2180 2024 1833 16 4 1.20412 2320 2178 2020 1830 20.25 4.5 1.306425 2317 2176 2018 1829 25 5 1.39794 2314 2174 2016 1827 36 6 1.556303 2311 2171 2015 1825 49 7 1.690196 2308 2168 2012 1820 64 8 1.80618 2306 2165 2010 1818 81 9 1.908485 2304 2163 2008 1816 100 10 2 2303 2161 2006 1815
F16/1334/2010
Page 4
GEOTECHNICAL LABS 2014 1440
37.94733
3.158362
2302
2155
1983
1810
ANALYSIS GRAPHs OF VOID RATIO AGAINST PRESSURE The pressure void ratio curve can be obtained if the void ratio at the end of each increment of load is determined. A typical void ration pressure curve resembles the one shown below
PHASE DIAGRAM
Compressibility characteristics
Water content at end of test, w =36% Void ratio at end of test =e1=wGs(assuming saturation =100% Thickness of specimen at start of test= h0=19mm Change of thickness during test, dH= 1.98mm Void ratio at start of test=e0=e1+de, de is change in void ratio Where de = dH (
F16/1334/2010
)
Page 5
GEOTECHNICAL LABS 2014 In the test e1= 0.36x2.66 =0.9576 de = 1.98x(
)
de= 0.2277 e0=0.9576+0.2277 =1.185 de= 0.103dH ANALYSIS: COMPRESSIBILITY CHARACTERISTICS
Pressure (kN/m2)
dial gauge reading 24hr
0 50 100 200
log pressure
2800 2302
0 1.69897
2155 1983
2 2.30103
change dH in height
400 1810 2.60206 1.VOID RATIO AGAINST PRESSURE CURVE
F16/1334/2010
Total thickness de e = e0chang of sample de e in mm dH 0 0 19 0 1.185 0.996 0.996 18.004 0.10258 1.08241 8 2 0.294 1.29 17.71 0.13287 1.05213 0.344 1.634 17.366 0.16830 1.01669 2 8 0.346 1.98 17.02 0.20394 0.98106
Page 6
GEOTECHNICAL LABS 2014 1.4 1.2
void ratio,e
1 0.8 void ratiopressure curve
0.6 0.4 0.2 0 0
100
200 300 Pressure in kN/m^2
400
500
2.VOID RATIO AGAIST LOG PRESSURE
1.4
1.2
VOID RATIO, e
1
0.8 void ratio against log p
0.6
0.4
0.2
0 0
F16/1334/2010
0.5
1
LOG PRESSURE 1.5
2
2.5
3
Page 7
GEOTECHNICAL LABS 2014 DISCUSSION OF COMPRESSIBILITY CHARACTERISTICS A typical curves for void ratio against pressure and log pressure resemble the one below:
Void ratio pressure curve
void ratio log pressure curve
From the curves it can be deduced that the voids in any soil sample reduce with increased pressure loading on the soil sample. The voids at any given pressure in the regime of loading can therefore be deduced.
COEFFICIENT OF CONSOLIDATION 1. Square root of time fitting method. Curves for individual load increments were as plotted. 50 kN /m2 CURVE
F16/1334/2010
Page 8
GEOTECHNICAL LABS 2014 3000
gauge reading
2500 2000 50 kN/m^2 pressure
1500
Linear (50 kN/m^2 pressure)
1000 500 0 0
2
4
6
8
10
12
root time
2. 100kN/m2 CURVE 2320 2300 2280
gauge reading
2260 2240 2220
100kN/m^2 Linear (100kN/m^2)
2200 2180 2160 2140 2120 0
2
4
6
8
10
12
root time
F16/1334/2010
Page 9
GEOTECHNICAL LABS 2014 3 200kN/m2 curve 2180 2160 2140
gauge reading
2120 2100 2080 100kN/m^2
2060
Linear (100kN/m^2)
2040 2020 2000 1980 1960 0
2
4
6 root time
8
10
12
4.400kN/m2 curve 2000
gauge reading
1950
1900 400kN/m^2 Linear (400kN/m^2) 1850
1800
1750 0
F16/1334/2010
2
4
root6time
8
10
12
Page 10
GEOTECHNICAL LABS 2014 METHOD TWO: LOG T FITTING METHOD 1.50 kN/m2 PRESSURE
2750 2700 2650
gauge reading
2600 2550 50 kn pressure
2500 2450 2400 2350 2300 2250 0
0.5
1
1.5 log t
2
2.5
3
3.5
2.100kN/m2 pressure
2205 2200 2195
gauge reading
2190 2185 2180 2175 100kN pressure
2170 2165 2160 2155 2150
F16/1334/2010 0 0.5
1
1.5 log t
2
2.5
3
3.5
Page 11
GEOTECHNICAL LABS 2014 3. 200 kN/m2 pressure loading
2050 2040
gauge reading
2030 2020 2010 200kn pressure
2000 1990 1980 1970 0
1
2
3
4
log time
4.400kN/m2 pressure load 1860 1855 1850
gauge reading
1845 1840 1835 1830
400 pressure
1825 1820 1815 1810 1805 0
1
2
3
4
log t
F16/1334/2010
Page 12
GEOTECHNICAL LABS 2014 ANALYSIS OF THE GRAPHS USING ROOT TIME FITTING METHOD AND LOG TIME FITTING METHOD Values read from the above tables PRESSURE RANGE INITIAL COMPRESSION GAUGE READING FINAL COMPRESSION GAUGE READING THICKNESS OF SPECIMEN BEFORE INCREMENT IS APPLIED CHANGE OF THICKNESS OF SPECIMEN FINAL THICKNESS OF SPECIMEN (H1-dH) AVERAGE THICKNESS OF SPECIMEN 0.5(H1+Hf) TIME FITTING METHOD CORRECTED INITIAL COMPRESSION GAUGE READING COMPRESSION GAUGE READING AT 90% CONSOLIDATION EQUIVALENT TIME FOR d90 FROM CURVE COEFFICIENT OF CONSOLIDATION (0.111H^2/t90)M^2PER YEAR (d0-ds) in mm 10(ds-d90)/9 in mm INITIAL COMPRESSION RATIO(A/dH) PRIMARY COMPRESSION RATIO(B/dH) SECONDARY COMPRESSION RATIO(1-(ᵞo+ᵞP))
LOG t FITTING METHOD COMPRESSION GAUGE READING AT ARBTRARY TIME t COMPRESSION GAUGE READING AT 4 t CORRECTED COMPRESSION GAUGE READING(2d1d2) COMPRESSION GAUGE READING AT 100%CONSOLIDATION MEAN COMPRESSION GAUGE READING 0.5(ds+d100) EQUIVALENT TIME FOR d50 FROM CURVE COEFFICIENT OF CONSOLIDATION= 0.026H^2/t50 m^2/year d0-ds F16/1334/2010
KN/m2 d0 df H1 in mm dH Hf H in mm
50 2800 2302 19
100 2302 2155 18.004
200 2155 1983 17.71
400 1983 1810 17.366
0.996 18.004 18.502
0.294 17.71 17.857
0.344 17.366 17.538
0.346 17.02 17.193
ds
2590
2217
2065
1877
d90
2300
2216
2060
1876
t90 Cv
49 0.000775
44.89 0.000788
43.56 0.000784
46.24 0.00071
A B ᵞo ᵞp ᵞs
0.42 0.644444 0.421687 0.647033 -0.06872
0.17 0.002222 0.578231 0.007559 0.41421
0.18 0.011111 0.523256 0.0323 0.444444
0.212 0.002222 0.612717 0.006423 0.380861
d1
2450
2190
2033
1845
d2 Ds
2300 2600
2161 2219
2006 2060
1815 1875
d100
2300
2161
2012
1816
d50
2450
2190
2036
1845.5
t50 Cv A
0.5 0.5 0.4 0.4 0.0077801 0.0076581 0.0079993 0.0079214 0.4
0.166
0.19 Page 13
0.216
GEOTECHNICAL LABS 2014 ds-d100 INITIAL COMPRESSION RATIO A/dH PRIMARY COMPRESSION RATIO B/dH SECONDARY COMPRESSION RATIO 1-(ᵞo-ᵞp)
B Ro Rp Rs
0.6 0.401606 0.60241 1.200803
0.116 0.564626 0.394558 0.829932
0.096 0.552326 0.27907 0.726744
ANALYSES discussion The coefficient of consolidation, cv generally decreases as the liquid limit of soil increases. The two methods above are commonly used for determining this coefficient for each load increment from one dimension consolidation tests. The forms of theoretical and experimental curves are as shown below
1.Root time fitting method
F16/1334/2010
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0.118 0.624277 0.34104 0.716763
GEOTECHNICAL LABS 2014 2. Log Time fitting method
Hence from these curves, initial, primary and secondary consolidation can be derived as well as the consolidation coefficients for a given soil at given loadings. Compression ratios can also be deduced as on the table.
F16/1334/2010
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GEOTECHNICAL LABS 2014
From above the ranges of consolidation coefficients for different soil types is given. From the experimental results, the soil was red earth. CONCLUSION The soil can be classified as red earth. F16/1334/2010
Page 16
ODOMETER TEST INTRODUCTION This method covers the determination of the magnitude and rate of consolidation of a saturated or near saturated soil sample in the form of a disc confined laterally, subjected to vertical axial pressure and allowed to drain freely from top and bottom surfaces. THEORY When a saturated clay-water system is subjected to an external pressure, the pressure applied is initially taken by the water in the pores resulting thereby in an excess pore water pressure. If drainage is permitted, the resulting hydraulic gradients initiate a flow of water out of the clay mass and the mass begins to compress. A portion of the applied stress is transferred to the soil skeleton which in turn causes a reduction in the in the excess pore pressure. This process involving a gradual compression occurring simultaneously with flow of water out of the mass and with a gradual transfer of the applied pressure from the pore water to the soil skeleton is called consolidation . The total compression of a saturated soil under excess effective pressure may be considered as the sum of 1. Immediate consolidation, 2. Primary consolidation, and 3. Secondary consolidation. St=si+sp+ss The portion of the settlement of a structure which occurs more or less simultaneously with the applied loads is referred to as the initial or immediate settlement. This settlement is due to the immediate compression of the soil layer under undrained condition and is calculated by assuming the soil mass to behave as an elastic soil. If the rate of compression of the soil layer is controlled solely by the resistance of the flow of water under the induced hydraulic gradients, the process is referred to as primary consolidation. The portion of the settlement that is due to the primary consolidation is called primary consolidation settlement or compression. At the present time the only theory of practical value for estimating time-dependent settlement due to volume changes, that is under primary consolidation is the one-dimensional theory. The third part of the settlement is due to secondary consolidation or compression of the clay layer. This compression is supposed to start after the primary consolidation ceases, that is after the excess pore water pressure approaches zero. It is often assumed that secondary compression proceeds linearly with the logarithm of time. However, a
F16/1334/2010
Page 1
GEOTECHNICAL LABS 2014 satisfactory treatment of this phenomenon has not been formulated for computing settlement under this category. The process opposite to consolidation is called swelling which involves an increase in the water content due an increase in the voids.
In this method the procedure depends on the soil specification classification Fine silts and clays are classified as type A soils, and coarse soils with numerous inclusions such as small stones which break or deform badly on extrusion from the sample tube are classified as type B soils. APPARATUS 1. Fixed ring type apparatus: with metal consolidation ring, bottom and top porous plates, consolidation cell, micro-meter dial gauge and a rigid device for ing the consolidation cell. 2. Apparatus for preparation and testing specimens: A jack and frame to extrude soil from sampling tube, a jig to hold the consolidation ring, a sharp thin palette/ blade, wire saws, metal straight edges, flat glass plate, vernier callipers, tins for moisture content, filter papers, stop watch, tap water, thermometer, a watch glass and specific gravity apparatus. PROCEDURE 1. SPECIMEN PREPARATION A short length of the soil sample was extruded from sample tube by means of the jack and frame and examined for soil type. A consolidation ring of suitable dimensions and the watch glass were cleaned, dried and weighed. The ring was lubricated with grease. 2. SAMPLE A representative sample for testing was extruded from the sample tube and cut off carefully to ensure the two plane surfaces of the disc of soil were parallel to each other. The thickness of the soil disc was a little greater than the height of the consolidation ring. Using the consolidation ring as the template, the disc was trimmed until it could just slid into the ring with the last fraction of soil being pared away by the cutting edge of the ring as it was pushed into the ring carefully. Any voids created were filled with the parings. The
F16/1334/2010
Page 2
GEOTECHNICAL LABS 2014 projecting bottom and top edges were then trimmed using the sharp edge to achieve level flash surfaces. Loss of moisture and soil grains was avoided at all stages. A sample of the same soil sample was set aside for specific gravity test. The thickness of the consolidation specimen was measured and the cell placed in a metal tray and weighed. 3. ASSEMBLY OF APPARATUS AND TEST PROCEDURE The dry bottom porous plate was centred in the consolidation cell and the ring complete with the specimen placed centrally on top of it with a filter paper against each face of the specimen. The top porous plate and the loading cap were then placed centrally on top. The consolidation cell complete with specimen was then placed in the bed of the loading apparatus. The counterbalanced loading beam was adjusted carefully into a loading position with the appropriate load transmitting member in with the loading cap. The gauge was clamped into position to record the relative movement between the base of the consolidation cell and the loading cap.
The OEDOMETER Loads were applied in sequence of 50, 100, 200, 400 kN/m2 The initial pressure for each loading was applied and the compression observed to ensure it was large enough to prevent swelling. The compression readings in the intervals were observed at sequence 0,0.25, 0.5, 1,2.25,4.00,6.25,9.00,12.25,16.00,20.25,25,36,49,64,81,100minutes and then up to 24 hrs, time sufficient for full consolidation.
F16/1334/2010
Page 3
GEOTECHNICAL LABS 2014 The gauge reading, time and √
were recorded to facilitate the plotting of the readings.
After each application of loading, the consolidation cell was filled with water to allow for swelling and saturation of specimen before increasing the pressure to the next higher value in the sequence. After the sample had fully consolidated under the full load increment, the pressure was released and the sample moisture content recorded. RESULTS TYPE OF SOIL : Red coffee soil SPECIFIC GRAVITY OF SOIL: 2.66 Sample thickness :19mm Moisture content at end of test: Wet soil= 136g Dry soil =100g Moisture content= 36% The results of the test Time in √time log time 50kN/m2 100kN/m2 200kN/m2 400kN/m2 min min 0 0 #NUM! 2800 2302 2155 1983 0.25 0.5 -0.60206 2725 2210 2055 1866 1 1 0 2700 2198 2045 1854 2.25 1.5 0.352183 2570 2192 2037 1846 4 2 0.60206 2360 2188 2031 1844 6.25 2.5 0.79588 2335 2185 2028 1838 9 3 0.954243 2330 2183 2026 1835 12.25 3.5 1.088136 2323 2180 2024 1833 16 4 1.20412 2320 2178 2020 1830 20.25 4.5 1.306425 2317 2176 2018 1829 25 5 1.39794 2314 2174 2016 1827 36 6 1.556303 2311 2171 2015 1825 49 7 1.690196 2308 2168 2012 1820 64 8 1.80618 2306 2165 2010 1818 81 9 1.908485 2304 2163 2008 1816 100 10 2 2303 2161 2006 1815
F16/1334/2010
Page 4
GEOTECHNICAL LABS 2014 1440
37.94733
3.158362
2302
2155
1983
1810
ANALYSIS GRAPHs OF VOID RATIO AGAINST PRESSURE The pressure void ratio curve can be obtained if the void ratio at the end of each increment of load is determined. A typical void ration pressure curve resembles the one shown below
PHASE DIAGRAM
Compressibility characteristics
Water content at end of test, w =36% Void ratio at end of test =e1=wGs(assuming saturation =100% Thickness of specimen at start of test= h0=19mm Change of thickness during test, dH= 1.98mm Void ratio at start of test=e0=e1+de, de is change in void ratio Where de = dH (
F16/1334/2010
)
Page 5
GEOTECHNICAL LABS 2014 In the test e1= 0.36x2.66 =0.9576 de = 1.98x(
)
de= 0.2277 e0=0.9576+0.2277 =1.185 de= 0.103dH ANALYSIS: COMPRESSIBILITY CHARACTERISTICS
Pressure (kN/m2)
dial gauge reading 24hr
0 50 100 200
log pressure
2800 2302
0 1.69897
2155 1983
2 2.30103
change dH in height
400 1810 2.60206 1.VOID RATIO AGAINST PRESSURE CURVE
F16/1334/2010
Total thickness de e = e0chang of sample de e in mm dH 0 0 19 0 1.185 0.996 0.996 18.004 0.10258 1.08241 8 2 0.294 1.29 17.71 0.13287 1.05213 0.344 1.634 17.366 0.16830 1.01669 2 8 0.346 1.98 17.02 0.20394 0.98106
Page 6
GEOTECHNICAL LABS 2014 1.4 1.2
void ratio,e
1 0.8 void ratiopressure curve
0.6 0.4 0.2 0 0
100
200 300 Pressure in kN/m^2
400
500
2.VOID RATIO AGAIST LOG PRESSURE
1.4
1.2
VOID RATIO, e
1
0.8 void ratio against log p
0.6
0.4
0.2
0 0
F16/1334/2010
0.5
1
LOG PRESSURE 1.5
2
2.5
3
Page 7
GEOTECHNICAL LABS 2014 DISCUSSION OF COMPRESSIBILITY CHARACTERISTICS A typical curves for void ratio against pressure and log pressure resemble the one below:
Void ratio pressure curve
void ratio log pressure curve
From the curves it can be deduced that the voids in any soil sample reduce with increased pressure loading on the soil sample. The voids at any given pressure in the regime of loading can therefore be deduced.
COEFFICIENT OF CONSOLIDATION 1. Square root of time fitting method. Curves for individual load increments were as plotted. 50 kN /m2 CURVE
F16/1334/2010
Page 8
GEOTECHNICAL LABS 2014 3000
gauge reading
2500 2000 50 kN/m^2 pressure
1500
Linear (50 kN/m^2 pressure)
1000 500 0 0
2
4
6
8
10
12
root time
2. 100kN/m2 CURVE 2320 2300 2280
gauge reading
2260 2240 2220
100kN/m^2 Linear (100kN/m^2)
2200 2180 2160 2140 2120 0
2
4
6
8
10
12
root time
F16/1334/2010
Page 9
GEOTECHNICAL LABS 2014 3 200kN/m2 curve 2180 2160 2140
gauge reading
2120 2100 2080 100kN/m^2
2060
Linear (100kN/m^2)
2040 2020 2000 1980 1960 0
2
4
6 root time
8
10
12
4.400kN/m2 curve 2000
gauge reading
1950
1900 400kN/m^2 Linear (400kN/m^2) 1850
1800
1750 0
F16/1334/2010
2
4
root6time
8
10
12
Page 10
GEOTECHNICAL LABS 2014 METHOD TWO: LOG T FITTING METHOD 1.50 kN/m2 PRESSURE
2750 2700 2650
gauge reading
2600 2550 50 kn pressure
2500 2450 2400 2350 2300 2250 0
0.5
1
1.5 log t
2
2.5
3
3.5
2.100kN/m2 pressure
2205 2200 2195
gauge reading
2190 2185 2180 2175 100kN pressure
2170 2165 2160 2155 2150
F16/1334/2010 0 0.5
1
1.5 log t
2
2.5
3
3.5
Page 11
GEOTECHNICAL LABS 2014 3. 200 kN/m2 pressure loading
2050 2040
gauge reading
2030 2020 2010 200kn pressure
2000 1990 1980 1970 0
1
2
3
4
log time
4.400kN/m2 pressure load 1860 1855 1850
gauge reading
1845 1840 1835 1830
400 pressure
1825 1820 1815 1810 1805 0
1
2
3
4
log t
F16/1334/2010
Page 12
GEOTECHNICAL LABS 2014 ANALYSIS OF THE GRAPHS USING ROOT TIME FITTING METHOD AND LOG TIME FITTING METHOD Values read from the above tables PRESSURE RANGE INITIAL COMPRESSION GAUGE READING FINAL COMPRESSION GAUGE READING THICKNESS OF SPECIMEN BEFORE INCREMENT IS APPLIED CHANGE OF THICKNESS OF SPECIMEN FINAL THICKNESS OF SPECIMEN (H1-dH) AVERAGE THICKNESS OF SPECIMEN 0.5(H1+Hf) TIME FITTING METHOD CORRECTED INITIAL COMPRESSION GAUGE READING COMPRESSION GAUGE READING AT 90% CONSOLIDATION EQUIVALENT TIME FOR d90 FROM CURVE COEFFICIENT OF CONSOLIDATION (0.111H^2/t90)M^2PER YEAR (d0-ds) in mm 10(ds-d90)/9 in mm INITIAL COMPRESSION RATIO(A/dH) PRIMARY COMPRESSION RATIO(B/dH) SECONDARY COMPRESSION RATIO(1-(ᵞo+ᵞP))
LOG t FITTING METHOD COMPRESSION GAUGE READING AT ARBTRARY TIME t COMPRESSION GAUGE READING AT 4 t CORRECTED COMPRESSION GAUGE READING(2d1d2) COMPRESSION GAUGE READING AT 100%CONSOLIDATION MEAN COMPRESSION GAUGE READING 0.5(ds+d100) EQUIVALENT TIME FOR d50 FROM CURVE COEFFICIENT OF CONSOLIDATION= 0.026H^2/t50 m^2/year d0-ds F16/1334/2010
KN/m2 d0 df H1 in mm dH Hf H in mm
50 2800 2302 19
100 2302 2155 18.004
200 2155 1983 17.71
400 1983 1810 17.366
0.996 18.004 18.502
0.294 17.71 17.857
0.344 17.366 17.538
0.346 17.02 17.193
ds
2590
2217
2065
1877
d90
2300
2216
2060
1876
t90 Cv
49 0.000775
44.89 0.000788
43.56 0.000784
46.24 0.00071
A B ᵞo ᵞp ᵞs
0.42 0.644444 0.421687 0.647033 -0.06872
0.17 0.002222 0.578231 0.007559 0.41421
0.18 0.011111 0.523256 0.0323 0.444444
0.212 0.002222 0.612717 0.006423 0.380861
d1
2450
2190
2033
1845
d2 Ds
2300 2600
2161 2219
2006 2060
1815 1875
d100
2300
2161
2012
1816
d50
2450
2190
2036
1845.5
t50 Cv A
0.5 0.5 0.4 0.4 0.0077801 0.0076581 0.0079993 0.0079214 0.4
0.166
0.19 Page 13
0.216
GEOTECHNICAL LABS 2014 ds-d100 INITIAL COMPRESSION RATIO A/dH PRIMARY COMPRESSION RATIO B/dH SECONDARY COMPRESSION RATIO 1-(ᵞo-ᵞp)
B Ro Rp Rs
0.6 0.401606 0.60241 1.200803
0.116 0.564626 0.394558 0.829932
0.096 0.552326 0.27907 0.726744
ANALYSES discussion The coefficient of consolidation, cv generally decreases as the liquid limit of soil increases. The two methods above are commonly used for determining this coefficient for each load increment from one dimension consolidation tests. The forms of theoretical and experimental curves are as shown below
1.Root time fitting method
F16/1334/2010
Page 14
0.118 0.624277 0.34104 0.716763
GEOTECHNICAL LABS 2014 2. Log Time fitting method
Hence from these curves, initial, primary and secondary consolidation can be derived as well as the consolidation coefficients for a given soil at given loadings. Compression ratios can also be deduced as on the table.
F16/1334/2010
Page 15
GEOTECHNICAL LABS 2014
From above the ranges of consolidation coefficients for different soil types is given. From the experimental results, the soil was red earth. CONCLUSION The soil can be classified as red earth. F16/1334/2010
Page 16
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