The purpose of foundation is to carry a load and then transfer and spread over the loads of the structure to the greater area of the ground. Foundation is one of the important elements for all types of building whether for the tall building or common building in order to make sure the building is stable and strong enough to carry load. The most important of foundation is to transfer the load to the ground, prevent sedimentation, and also to maintain the position of the building. In deciding to make a selection of type of foundation is to know the important factors before the construction of foundation occurs such as load, types of soil, and also cost involved when construction occur. For the load factors such as live load, dead load and also wind load need to be taken into account. This is important to make sure the foundation can carry out double of overall load of building. A part from that, the geotechnic factor also plays a vital role in order to prevent any settlements. Any site investigation should be done carefully to make sure the foundation which is want to build up is strong enough to carry the load. Besides, the cost factor must be considered to make sure the construction of foundation more economical, strong and stable. The types of foundations that is usually used for construction such as pad foundation, pile foundation and many more but the mostly used in construction is pad foundation because of it is more economic and highly strength with the combination of reinforcement bar. Pad foundation are usually combined with the pile foundation to construct a building especially in a high area.
24 Feb 2009
sub structure
Compaction test
Compaction test
Testing Objectives
Determination of maximum dry unit weight which can be used for specification of field compaction
Relationship between the moisture content and density of soils.
Need and Scope
The knowledge of maximum dry density enables to improve the in situ ground conditions which otherwise may be unsuitable for construction. This value ensures maximum density (number of soil particles) accommodated at the most optimum moisture level to ensure enhanced strength.
Apparatus Required
Proctor mould with a detachable collar assembly and base plate.
Rammer weighing of 2.5 kg and equipped to provide a height of drop to a free fall of 30 cm.
Sample extruder.
A sensitive balance.
Straight edge.
Squeeze bottle
Mixing tools such as mixing pan, spoon, towel, spatula etc.
Moisture tins.
Drying Oven
Test Procedure
1. Obtain approximately 10 lb (4.5 kg) of soil breaking all the lumps and passing US No. 4 sieve.
2. Add approximate amount of water to increase the moisture content by about 5%.
3. Determine the weight of empty proctor mould without the base plate and collar. W1, (lb).
4. Fix the collar and base plate. Distribute the soil into three equal parts.
5. Place the first part in the Proctor mould and compact the layer giving 25 blows.
6. Scratch the layer with a spatula forming a grid to ensure uniformity in distribution of compaction energy to the subsequent layer. Place the parts 2 & 3 repeating the above two steps.
7. The final layer should ensure that the compacted soil is just above the rim of the compaction mould when the collar is still attached.
8. Detach the collar carefully without disturbing the compacted soil inside the mould and using a straight edge trim the excess soil leveling to the mould.
9. Determine the weight of the mould with the moist soil W2, (lb). Extrude the sample and break it to collect the sample for water content determination preferably from
the middle of the specimen.
10. Weigh an empty moisture can, W3, (g) and weigh again with the moist soil obtained from the extruded sample in step9, W4, (g). Keep this can in the oven for water
content determination.
11. Break the rest of the compacted soil with hand (visually ensure that it passes US Sieve No.4). Add more water to increase the moisture content by 2%.
12. Repeat steps 4 to 11. During this process the weight W2 increases for some time with the increase in moisture and drops suddenly. Take two moisture increments
after the weights starts reducing. Obtain at least six points to plot the dry unit wt, moisture content variation.
13. After 24 hrs recover the sample in the oven and determine the weight W5, (g).
The Modified compaction procedure is similar to the above with a change in the compactive effort. The rammer used in the modified compaction is a 10 lb with a
height of drop of 18".
Reporting the results
The results shall be the maximum dry unit eight and the optimum moisture content at which this value is obtained
Calculations
| Test | 1 | 2 | 3 | 4 | 5 | 6 |
| 1. Weight of the mold, W1, (lb) | | | | | | |
| 2. Weight if the mold + moist soil, W2 (lb) | | | | | | |
| 3.Weight of the moist soil, W2-W1, (lb) | | | | | | |
| 4. Moist unit weight, γb = [(W2-W1)/(1/30)], (lb/ft3) | | | | | | |
| 5. Moisture can number | | | | | | |
| 6. Weight of moisture can, W3, (g) | | | | | | |
| 7. Mass of can + moist soil, W4, (g) | | | | | | |
| 8. Mass of can + dry soil, W5, (g) | | | | | | |
| 9. Moisture content, w(%)= [(W4-W5)/(W5-W3)] x 100 | | | | | | |
| 10. Dry unit weight of compaction γd (lb/ft3) = γb/[1+(w/100)] | | | | | | |
