Soil Penetration Test Quiz and Flashcards: SPT Drilling Exam Prep

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Questions and Answers

What is the purpose of driving the sampler into the soil using hammer blows in the Standard Penetration Test?

To compact the soil layers

To create a borehole for sampling (correct)

To determine the angle of internal friction of the soil

To measure the moisture content of the soil

Why is the first 15 cm drive in the SPT considered as seating load and ignored?

To calculate the moisture content of the soil

To reduce the total number of blows required for testing

To measure the density of the soil

To account for the initial compression and disturbance of the soil (correct)

Why are split spoon samples taken at intervals of 1.5 m during soil sampling?

To prevent disturbance in deeper layers during sampling (correct)

To estimate the groundwater level in the soil

To assess the compressibility of the soil layers

To measure the electrical resistivity of the soil

What parameter is determined by taking the average N-value from each 1.5 m in the Standard Penetration Test?

Final SPT N-value Signup and view all the answers

In the 2V:1H method, what does '2V' represent?

Vertical effective stress Signup and view all the answers

What is a key advantage of using site investigation techniques like the Standard Penetration Test?

Identifying potential foundation issues Signup and view all the answers

What is the purpose of using test pits in site investigation?

To visually inspect subsurface conditions in their natural state Signup and view all the answers

In foundation engineering, what is the maximum depth limit for test pits?

18-20 feet Signup and view all the answers

When is auger boring considered suitable for site investigation?

Only in cohesive soils below the groundwater table Signup and view all the answers

What is the function of hollow stem augers in site investigation?

To use for sampling or conducting tests Signup and view all the answers

Which technique permits sampling/testing on exposed surfaces during site investigation?

Test pits Signup and view all the answers

What is the main advantage of using test pits over boreholes during site investigation?

Permits visual inspection of natural conditions Signup and view all the answers

What is the primary objective of wash boring in foundation engineering?

To create a borehole by using a casing and drilling with water or mud. Signup and view all the answers

What is the main difference between mud rotary drilling and core drilling?

Mud rotary drilling uses a core barrel with a drill bit, while core drilling is used for rock cores. Signup and view all the answers

Which method involves grinding the soil by lifting and dropping heavy chisels or bits?

Percussion Drilling Signup and view all the answers

What tool is commonly used for obtaining rock cores in foundation engineering?

Tricone drill bit Signup and view all the answers

In wash boring, how is soil loosened and removed from the borehole?

By jetting water or drilling mud under pressure and allowing it to settle at ground level. Signup and view all the answers

Which site investigation technique involves hollow drill rods with a rotating drill bit and continuous pumping of drilling mud?

Mud rotary drilling Signup and view all the answers

Study Notes

Standard Penetration Test (SPT)

1.5 m are drilled using a drilling machine
The sampler is driven into the soil by hammer blows to the top of the drill rod
Standard weight of the hammer is 622.72 N (63.48 kg), and for each blow, the hammer drops at a distance of 76.2 cm
Number of blows required for a spoon penetration of three 15 cm intervals are recorded
First 15 cm drive is considered as seating load and is ignored
Number of blows required for the last two intervals are added to give the SPT N-value at that depth

Site Investigation and Borehole Depth

Site investigation is necessary for a structure of 100 m length and 70 m width
Soil profile is required to determine the approximate depth of borehole
Assuming a uniform pressure of 200 kPa on the surface of the soil and γw = 10 kN/m3, the approximate depth of borehole can be calculated

Methods of Boring

Test Pits: permits visual inspection of subsurface conditions in natural state
- Maximum depth limited to 18-20 ft
- Especially useful for gravelly soil where boreholes may be difficult
- Sampling/testing done on exposed surfaces
Auger Boring: simplest method of exploration and sampling
- Power-driven or hand-operated
- Maximum depth of 10 m
- Suitable in all soils above ground water table but only in cohesive soil below ground water table
- Hollow stem augers used for sampling or conducting Standard Penetration Tests
Wash Boring: uses a casing driven with a drop hammer and a hollow drill rod with chopping bit
- Soil is loosened and removed from the borehole using water or a drilling mud jetted under pressure
- Also known as mud rotary drilling (soil) or core drilling (rock)
Percussion Drilling: grinding the soil by repeated lifting and dropping of heavy chisels or drilling bits
- Water is added to form slurry of cuttings

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Description

Test your knowledge on the Standard Penetration Test (SPT) used in foundation engineering. Learn about the process of driving a sampler into soil using hammer blows and understand the significance of the results obtained.

In-Situ Tests for Soils: Standard Penetration Test (SPT)

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