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How can trial pits be made in slopes?

In slopes, trial pits are transformed into another method called slope surface stripping. It involves the removal of slope surface protection and vegetation to reveal the soil conditions below slope surface for inspection purpose. The strip is about 0.3m to 0.5m wide and 150mm to 300mm deep and it usually extends from the crest to the toe of slopes. Slope surface stripping is commonly used in Hong Kong.

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This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

What is the difference between trial pit, trial trench and inspection pit?

A trial pit is used for obtaining information on the subsurface soil conditions. It allows logging of the various soils types and soil sampling. Typical size of trial pits has minimum base plan area of 1.5m2. Trial trench serves the same purpose of trial pit except that they differ in size and dimension. For instance, the length of a trial trench is normally larger than its width by a certain factor (e.g. 5) to cater for its “trench” shape.

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An inspection pit is a pit used for identifying and positioning of underground utilities and structure.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

What is the application of Continuous Piezocone Penetration Test?

Continuous piezocone penetration test basically consists of standard cone penetration test and a measurement of pore water pressure. Three main parameters, namely sleeve friction, tip resistance and pore water pressure measurement are measured under this test.

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Pore water pressure generated in the soils during penetration of the cone is measured. An electrical transducer located inside the piezocone behind saturated filter is used for the measurement. By analyzing the results of pore pressure with depth, the stratigraphy of fine-gained soils with different layers is obtained readily.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

How to identify sand and clay from the results of Cone Penetration Testing?

Cone Penetration Testing measures the pressure at the end of cone (end resistance), friction on sleeve and pore water pressure. Friction ratio is defined as the ratio of friction/end resistance.

For clay, typical CPT results exhibit low end resistance, high friction ratio and high pore water pressure.

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For sand, typical CPT results exhibit high end resistance, low friction ratio and low pore water pressure.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

When would engineers use Cone Penetration Testing instead of Standard Penetration Test?

(I) Standard Penetration Test is carried out in boreholes at 1.5-2m intervals. However, Cone Penetration Testing allows a continuous record of ground resistance profile.

(II) Disturbance to ground is less by Cone Penetration Testing when compared with Standard Penetration Test.

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(III) The use of Cone Penetration Testing is faster and cheaper when compared with the combination of boring, sampling and Standard Penetration Test.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.