4.2 Project Works Activites
4.2.4 On Site Practice Works
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determination of the CBR value. The design CBR can also be determined through this CBR test, namely by using the relationship curve between the CBR and the dry density of each test object.
In the Yogyakarta - Bawen Toll Road Construction project, CBR testing was carried out at the Quality Control Laboratory. The CBR test itself is carried out before the construction of a new layer embankment is carried out.
a. Preparation Works
Prepare 3 test samples weighing about 7 kg, which have been compacted in a cylinder with 10, 35, 65 collisions on each layer in each different test sample. After compaction remove the collar and level the surface. Take sample for determination of moisture content. Weight of mold and compacted test sample. Soak the mold in water for 3 days.
b. Test Works
After 4 days do a swell reading and find a swell percentage. Remove the mold from the test sample and allow the water to dry. Then place the test sample on the penetration piston and place a surcharge load of 4.53 kg. Apply pressure and note how much pressure. Draw a graph between the penetration and penetration load and find the value of CBR. Draw the graph between the CBR percentage and dry density, and find the CBR at the required degree of compaction.
Figure 4.6 CBR Soaking Process
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Apply regular loading so that the penetration rate approaches 1.27 mm/min (0.05")/min. Record the load readings at 0.312 mm (0.0125"), 0.62 mm (0.025"), 1.25 penetration mm (0.05"), 0.187 mm (0.075"), 2.5 mm (0.10"), 3.75 mm (0.15"), 5 mm (0.20"), 7.5 mm (0 .30"), 10 mm (0.40") and 12.5 mm (0.50"). Record the maximum load and penetration if the maximum loading occurs before 12.50 mm (0.5") of penetration. Remove the specimen from the mold and determine the moisture content of the top layer of the specimen 25.4 mm thick.
c. Result
Using the corrected load values for 2.54 mm (0.1") and 5.08 mm (0.2") penetration, calculate the CBR value by dividing the standard load by 70.31 kg/cm2 each ( 1000 psi) and 105.47 kg/cm2(1500 psi) and multiply by 100 the CBR value is taken at a penetration of 0.1". .
If this repeated experiment still produces a CBR value at 5.08 mm penetration greater than the CBR value at 2.54 mm (0.1") penetration, then the CBR value is taken at 5.08 mm (0.2") penetration. If the maximum load is reached at penetration before 5.08 mm (0.2") then the CBR value is taken from the maximum load with the appropriate standards.
Figure 4.7 CBR Reading Process
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4.2.4.2 Proctor Standard
Soil compaction test or Proctor Standard is a laboratory method for experimentally determining the optimal moisture content where a certain type of soil will be the densest and achieve maximum dry density. There are four soil compaction variables, namely compaction effort or compaction energy, soil type (gradation, cohesive or non-cohesive, particle size, etc.), moisture content, and dry unit weight. Standard compaction is an attempt to compact with standard compaction equipment.
The relationship between dry unit weight (γd) and wet unit weight (γw) and water content (ω) is expressed in the equation:
γd = γw 1 + ω a. Tools preparation
Prepare a cylindrical concrete mold with a diameter of 101.6 mm and a volume of 943.3 cm³ which has been lubricated on the inside to make it easier to release the soil sample later.
Figure 4.8 Result of CBR Test
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43 b. Make soil sample
Make soil mix with the same quality as used in the construction project, then the soil mixture that has been made will be put into the mould. Add in 3 layers each 1/3 layer, 2/3 layer, and until the top is full. The soil in the mold is compacted using a ram which weighs 2.5 kg with a fall height of 30.5 cm. Soil compaction was carried out in 10, 35, 65 blows on 3 different soil samples.
Figure 4.9 Load Plate Installation for Mold
Figure 4.10 CBR Blows
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44 c. Test Works
In Proctor's test, the soil is compacted in a 1/30 ft3 (=943.3 cm3) cylindrical mold. The diameter of the mold is 4 in. (=101.6mm). During experiments in the laboratory, the mold was glued to a base plate and extended (also cylindrical) on top. The soil is mixed with water at different levels and then compacted using a special pounder. The compaction of the soil is carried out in 3 (three) layers (with a thickness of each layer approximately 1.0 in.) and the number of impacts is 25 times for each layer. The impactor weighs 5.5 lb (mass = 2.5 kg) and has a drop height of 12 in. (=304.8 mm) (Standard Proctor Test, ASTMD-698).
4.2.4.3 DCP Test
The DCP (Dynamic Cone Penetration) Test aims to quickly and practically determine the CBR value of a sub grade, sub base or base course of a system. The test provides the strength of a layer of material to a depth of 90 cm below the existing surface without excavating to the depth of the desired reading.
The test is carried out by recording the number of blows and penetration of the cone (metal cone) embedded in the soil/foundation layer due to the impact of the pounder then using graphs and formulas, the penetrometer reading is converted to a reading which is equivalent to the CBR value.
Figure 4.11 Weigh the Mold
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45 a. Preparation Works
Prepare all parts of the equipment by connecting all parts of the equipment and make sure the connection of the upper rod with the base as well as the lower rod and steel cone are securely attached. After the tool is ready, determine the test point and then note where the test point is located.
b. Test Works
The blow is carried out with the tool in a vertical position on a flat surface. Then record the initial reading on the depth gauge ruler. Impact results are read every five times the collision by recording how deep it is reached in the fifth blow until the depth measuring bar is exactly at one hundred. Then add up the total number of collisions until it reaches one hundred. If the results do not meet the requirements of the laboratory test, a re-test is carried out. After treatment on the tested soil.
Figure 4.12 DCP Test Process
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Tests using DCP produce data that can be analyzed to produce accurate information on the thickness and strength of pavement or airfields. Tests can be carried out quickly and test sites can be easily tidied up. One of the advantages of using the DCP Test is that it is effective in terms of processing time as well as inexpensive in cost.
4.2.4.4 Sandcone Test
This test is a method of testing the density of soil in place (field) using a sand cone. The apparatus described herein is limited to testing soils containing granular particles not more than 50 mm in diameter. This test is generally carried out to evaluate the results of field compaction performance which is determined in terms of degree of compaction, namely the ratio between gd in the field and gd maximum results of compaction trials in the laboratory in percentage of the field.
a. Preparation Work
Prepare a test bottle by filling Otawa sand until it is full. Then weigh the fully filled test vial. As well as prepare other tools such as a hammer, sand spoon, brush, chisel, nails, container and Speedy Moisture
Figure 4.13 Result of DCP Test
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Tester.
b. Test Works
Do the excavation at the test location by installing a boundary plate as deep as 12 – 15 cm. Then take the used aggregate until it is clean, then transfer it to a container and weigh it. For coarse aggregates such as granular, a filtering process is carried out with a filter size of ¾". For fine aggregates such as soil is not filtered. After that, weigh the aggregate.
After weighing, test the moisture content using the Speedy Moisture Tester. Place the test bottle into the excavation hole with the funnel facing down. Open the test bottle faucet and let the sand fill the excavation hole then close the test bottle faucet. After that, weigh the test bottles that have been used to fill the dug holes. Testing the water content and filling the excavation with test bottles can be done in parallel to shorten the time.
Then cover the excavation hole with the remaining aggregate.
4.2.4.5 Speedy Moisture Test
Testing the water content with the Speedy tool is a test in the field (on site) by reading the moving indicator dial based on the pressure of acetylene gas in the Speedy tool. Acetylene gas in the Speedy tool is caused by a chemical reaction between the test object and Calcium
Figure 4.14 Sandcone Test Process
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Carbide (CaC2).
a. Preparation Works
Prepare a set of Speedy Moisture Test tools. Then clean the Speedy Moisture tool using a cleaning brush so that there is no residue from the previous sample test mixture.
b. Test Works
Weigh the test sample weighing approximately 50 grams or speedy scales in a balanced state. Then enter the test sample into the Speedy tool. After that, insert 2 steel balls into the speedy tool. Turn the lid on the speedy tool and add 2 measuring spoons of calcium carbide. Close the speedy tool tightly then shake the speedy tool 10 times forward and then 10 times backward. Take a dial reading when the dial indicator stops moving. Then clean the speedy tool and take out the steel ball. The reading is carried out according to the laboratory water content, if it is not appropriate, a re-test will be carried out after the location of the soil sample is treated.
Figure 4.15 Speedy Test
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4.2.4.6 Trial Compaction Test
The process of soil compaction or Trial Compaction Test for road embankments and subgrades is a very important process to know. In this compaction process the end result determines the quality of the construction, this is where the life of the pavement construction is determined and good compaction results will save construction costs on it. The results of compaction are largely determined by the type of material used as backfill, the procedure for compaction and the compactor used. All material backfilled for highway construction must be compacted. The purpose of this compaction is:
1. To increase the density of soil.
2. To increase the bearing strength of soil.
3. To reduce the permeability of the soil.
The trial compaction test is carried out as follows: spread the soil 1.5 to 2 times the width of the wheel of the compactor for a length of 50 m to 75 m. Then grind it with a vibro roller for 8 passes, 1 pass is one movement of the compactor back and forth.
Figure 4.16 Land Flattering
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4.2.4.7 Soil Sampling
Soil sampling is an important step for determining soil physical properties in the laboratory. After taking the soil sample, it will be taken to the laboratory for testing. In principle, the results of the analysis of the physical properties of the soil in the laboratory must be able to describe the actual state of the physical properties of the soil in the field. The advantage of determining soil physical properties in the laboratory can be done more quickly, and the number of soil samples is relatively large. The disadvantage is that soil samples taken in the field are destructive, because they can damage the soil surface.
Figure 4.17 Compaction Process
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