Basic Soil Test on Sub-grade Soil Material and Flexible Pavement Design on Road Linking – Ugwuaji and Campus M, IMT; Enugu
Chapter One
Objectives of the Study
The objectives of the laboratory testing program were
- To obtain a piece of general information regarding the nature of the soil and its variation with depth throughout the length of the road under consideration.
- To obtain information regarding the strength characteristics of the soil.
- To obtain information which will enable engineers to group soils according to their appearances of the purposes of complying different soils.
CHAPTER TWO
MECHANICAL ANALYSIS
(Sieve Analysis)
AIM: To get the particle size distribution of the soil sample. This is universally used in engineering soil classification.
Apparatus:
- Weighting Balance
- Iron Brush
- Oven
- Set of Bs Sieves
13.2mm, 6.3mm, 5.9mm, 4.75, 2.4mm (No 7)
1.2mm, 600
MICRONS, 420m (No 36) .300m, .210m, .120m and .75m (No 200).
PROCEDURE
100kg of the material is weighted out and put into a bowl for washing using the .75m sieve to decant. The essence of the decanting is to remove clay, dust and silt. Several buckets of water are used for the water until the sample become less turbid. The residue after the dry sample is then removed from the oven and put into the arranged set off sieves and retainer. The set of sieves are then taken to the sieve shaker for 10 minutes.
The percentage weight passing through each sieve is plotted against the sieve size.
CHAPTER THREE
COMPACTION TEST
AIM: To determine the optimum moisture content
(OMC) and maximum dry density (MDD) of the soil sample.
APPARATUS:
Mould, moisture content cans 2.5kg, rammer, a straight edge, weighing balance, pan, electric oven, oil for out letting the mould, mixing pan and standard proctor compaction mould with collar.
PROCEDURE:
3000gm of the sample is measured out using the weighing balance.
The weighted sample is put into the large mixing pan where 8% water of the soil mass is added
8% water = 240cc
The mixed sample is divided into three portions and each portion is put into the mould in three layers each with a compaction of 25 blows with the 2.5kg rammer falling through a height of 300mm.before the last layer, the collar is fitting and after the compaction the collar is removed with the straight edge used to trim off the excess soil to flush with the mould.
The weight of the wet sample is recorded ad subtracted from the weight of the empty mould t o get the weight of the wet soil sample. Samples are taken from the top and bottom of the mould and put into moisture cans to obtain the moisture content after being placed in the oven. The procedure is repeated for additional 2% water content = 60cc up to some 18% when the buck weight of the soil and compacted with soil starts to decrease.
The dry densities obtained are plotted against the moisture contents.
CHAPTER FOUR
ATTERBERG LIMIT TEST
This test comprises of two test viz;
- Liquid limit test
- Plastic limit test
AIM: The aim of the atterberg limit test is for the classification and identification of granular materials according to their liquidity and plasticity characteristics.
APPARATUS:
The apparatus for both test are: Liquid limit device, grooving tool, moisture content can, soil mixing equipment (porcelain and spatulas) desiccators sieve no 420m with pan and lid.
LIQUID LIMIT TEST
PROCEDURE
A sample of at least 100gm is taken from the material passing BS sieve No. 36 (.42m). it is placed on glass plate and thoroughly mixed with distilled water, using a spatula until the mass becomes a thick paste of putting consistency.
A portion of the mixture is placed in the atterberg test – cup and levelled with the spatula 70 a maximum depth of 1cm. The grooving tool is then used to divide the soil pat along the diameter through the centre of the linge. By turning the handle of the machine at the rate of about 2 rotations per second, the cup is lifted and dropped repeatedly until the two parts of the soil sample come into contact at the bottom of the groove along a distance of 12mm. The no of blows, which have been given, is noted.
CHAPTER FIVE
CALIFORNIA BEARING RATIO
AIM:
To determine the shear strength of soil sample.
APPARATUS
– Cylindrical mould – Diameter = 15cm, depth = 12.5cm.
– 4.5kg Rammer and 450mm free fall
– Weighing balance
– Measuring cylinder, strength edge
– Oil for oiling / lubricating
– Large mixing pan
– CBR machine
PROCEDURE
600gm of the sample is measured out and mixed with water of equivalent OMC = 11.3% from the compaction test. The sample is then compacted in three layers with 62 blows each of the 45kg rammer and free fall of 450mm. The collar is flitted at the third layer and removed after the compaction.
The surface is trimmed off with the straight edge to flush with the top edge of the mould. The sample is placed in the CBR machine and surcharge loads placed to take care of the weight of pavement leading are then taken for penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 5.5, 6.0, 6.5, and 70mm.
SOAKED SAMPLE
The unsoaked sample which has been tested is put in water for four days and tested for penetration. The essence of soaking is to stimulate saturation in service.
The bottom of the mould in this faced up since the top has been tested for penetration in the unsoaked procedure.
The group index method for sample C is as follows
– % Passing sieve No 200 = 73.3%
– Liquid limit = 33.00%
– Plastic limit = 23.49%
Daily traffic intensity = 700 commercial valued per day. To design a suitable pavement by the G.I method.
LL = 33.00%
PL = 23.49%
PI = 9.51 = 10%
Passing No 200 = 73.3%
a = 72.3 – 35
a = 38.3
b = 73.3 – 15
c = 40 – 33
c = 7
d = 10 – 10
d = 0
G .I = 0.29 + 0.005ac + 0.01bd
0.2 (38.3) + 0.005 (38.3)(7) + 0.01 (58.3) (0)
= 7.66 + 1.3405 + 0
= 9.0005
G.I Number = 9
:. Thickness of sub – base = 9cm
Daily traffic intensity = 700 vehicle per day
Corresponding to 750 vehicle per day
Base = 20cm
Surfacing = 10cm
CHAPTER SIX
ANALYSIS
From the analysis of test results on the sample, it was found that sample A and B are generally made up of fine grains with a greater percentage of it passing sieve No 200, while sample C is excellent and very good for pavement design.
Sample A was collected some metres into the pathway then sample was collected about half way into the pathway (CH A – B = 124.7m), but than sample C was collected at the end of the pathway very close to the express linking Ugwuaji (CH B – C = 331m).
Since the sample C part of the pathway is okay, burrow pit material could be collected from there to cover or blanket the entire sum of the pathway, but since material will not be enough, we now collected burrow pit material from the area where it would be enough to sum for the burrow pit material was based on particle size distribution, plastic limit liquid limit, compaction and CBR test to show that the sample is okay for pavement design. The essence of sub base is to help spread and reduce the losd distribution over the sub grade.
CONCLUSION AND RECOMMENDATION
From the results of the tests, it was found that the samples A and B are generally composed of sility day, which does not allow easy drainage of water. It rather retained a lot of water, which result in the swelling of the soil with consequent collapse under load. Sample C was found to be excellent.
Further study shows that when the soils are stabilized by the mechanical stabilization method, their plasticity indices reduced this rendering the soil more stable with variations in its moisture contents.
The CBR values are consequently increased. Any type of soil can be stabilized with cement but much concern is attached on the economic implication of cement stabilization.
The stabilization with cement raises the CBR values of the soil, but from the economic point of view, unless where soil cement has an exceptional advantage, in the construction project in question. The mechanical stabilization method can always be used where it is found to be a good alternative since this will be cheaper in term of cost.
In the soil studied in this project based on experiments and past studies, it is concluded that sample C is good as sub – base material and good for pavement design.
The following recommendation are thus made regarding construction with stabilized materials.
- There should be adequate and full field control especially in the soil – cement construction.
- Careful compaction control.
- There should be adequate drainage of the road.
- Use a proper material for the base course and good placing of sealing cost to minimize water absorption from the surface.
- In embankments, the sloping should not be too steep. A slope of I vertical to 2 horizontal is recommendation
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