Mekanika Tanah : Analisa Gradasi Tanah - Hinawan T. Santoso, ST, MT

Summary

This script delves into the study of soil mechanics, focusing on gradation analysis to understand soil characteristics. The lecture covers sieve analysis for coarse soils and hydrometer tests for fine soils, explaining the different methods used to assess soil particle size distribution. It also discusses key parameters like uniformity coefficient (Cu), gradation coefficient (Cc), and effective particle size (D10, D30, D60). The analysis helps classify soil types and predict their behavior, such as drainage efficiency. Practical examples and calculations are included to demonstrate how to interpret and apply gradation results in real-world scenarios.

Takeaways

• 😀 Grading analysis (analisa gradasi) is used to study the particle size distribution of soil to understand its characteristics and classify it.
• 😀 Sieve analysis (uji saringan) is used for coarse-grained soils, where soil is passed through various sieves to separate particles based on size.
• 😀 Hydrometer analysis (uji hidrometer) is used for fine-grained soils, where sedimentation or the rate of particle settling in water is measured.
• 😀 The sieve analysis follows ASTM standards, with sieve sizes ranging from 4.75 mm (No. 4 sieve) to 0.0053 mm (No. 270 sieve), with a critical size of 0.075 mm for separating coarse and fine aggregates.
• 😀 The goal of sieve analysis is to calculate the percentage by weight of soil retained on each sieve, which can then be plotted to create a particle size distribution curve.
• 😀 Key parameters from sieve analysis include D10, D30, and D60, which represent particle sizes corresponding to 10%, 30%, and 60% passing, respectively.
• 😀 The distribution curve of soil particles can be categorized into three types: well-graded, poorly graded, and uniform, based on the shape of the graph.
• 😀 The uniformity coefficient (Cu) helps determine the grading of the soil; values less than 2 indicate uniform grading, while values greater than 6 indicate well-graded soil.
• 😀 The coefficient of gradation (Cc) is another important parameter that indicates the smoothness of the grading curve; values between 1 and 3 suggest good gradation.
• 😀 For fine-grained soils, the analysis requires precise measurements using a hydrometer and sedimentation methods, considering the impact of temperature and water viscosity on results.

Q & A

What is the purpose of gradation analysis in soil mechanics?

The purpose of gradation analysis is to evaluate the particle size distribution of soil. It helps in understanding the soil's characteristics, which is essential for soil classification and determining other parameters such as the soil's permeability and uniformity coefficient.

What types of sieve tests are used in gradation analysis?

There are two types of sieve tests used in gradation analysis: one for coarse-grained soils, which uses mechanical sieving, and another for fine-grained soils, which uses hydrometer tests to measure particle size distribution.

What is the significance of ASTM sieve sizes in soil testing?

ASTM sieve sizes are important for standardizing the particle size ranges used in soil testing. The sieves range from a size of 4.75 mm (No. 4) to 0.0053 mm (No. 270), with No. 200 typically separating coarse from fine aggregates.

How is the percentage of soil retained on a sieve calculated?

The percentage of soil retained on a sieve is calculated by dividing the weight of soil retained on a specific sieve by the total weight of the sample and then multiplying by 100 to get the percentage.

What is the difference between coarse-grained and fine-grained soil analysis?

Coarse-grained soil analysis is performed using sieve analysis, while fine-grained soil analysis uses the hydrometer method to account for the finer particles that pass through the smallest sieves.

What are the key parameters derived from a gradation curve?

The key parameters derived from a gradation curve include D10, D30, and D60, which represent the particle sizes at 10%, 30%, and 60% passing by weight, respectively. These values help define soil characteristics like uniformity and effective size.

What does a well-graded soil distribution look like on a graph?

A well-graded soil distribution graph typically shows a smooth, continuous curve that represents a soil with a good mix of particle sizes, resulting in better compaction and drainage characteristics.

What does a uniformity coefficient (Cu) value indicate about soil gradation?

The uniformity coefficient (Cu) indicates the range of particle sizes in the soil. A value of Cu less than 2 suggests uniform gradation, while a Cu between 2 and 4 indicates poor grading. A Cu greater than 6 suggests a well-graded soil with good drainage properties.

What is the role of hydrometer analysis in soil testing?

Hydrometer analysis is used to determine the particle size distribution of fine-grained soils (those passing through a sieve with a 0.075 mm opening), relying on sedimentation or settling rates of soil particles in water.

Why is the temperature of the water important in hydrometer analysis?

The temperature of the water affects its viscosity, which in turn influences the sedimentation rate of particles. Accurate temperature control is necessary to ensure reliable results in hydrometer analysis.