Investigation

Geotechnical Investigation

Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions.

Questions

What is reconnaisance?

List the categories of information to review during office reconnaissance?

Main purposes for field reconnaissance prior to subsurface investigation?

List the maps and other data that should be reviewed prior to subsurface investigation

To do the sursurface investigation, which work should be carried out first?

What is the main information expressed in geological map?

What are the factors to be considered to determine the number and the layout of boring?

Why do we need more borings for limestone unit than other rock types?

What are two major purposes of field reconnaissance?

List the items to observe during field reconnaissance

What are the advantages of test pits and trenches in comparison with boreholes? What are the limitations for pits and trenches?

List different methods of drilling? (Let's read to understand how each drilling method is, which method should be applied to certain ground condition. For example: wash drilling is only applicable for soil, not applicable for soil mix with gravel or rock. The main function of drilling bit and drilling mud in borehole drilling?

What is distiction between drilling and sampling?

Which type of sample, i.e. disturbed or undisturbed, is needed for determining the grain size of soil? Similar question for other properties of soil (moisture content, limit limit, shear strength)

What are the factors that can influence the degree of disturbance of soil sample?

Which method of sampling should be used for rock coring? pushed tube sampling or rotary coring?

What are factors that involve the rock core recovery?

Why do soil samples need sealing?

Can we measure the dip of joints in rock using rock core in conventional drilling?

Can we measure the dip direction of joints in rock using rock core in conventional drilling?

How SPT is accomplished?

Is the soil sample from SPT generally considered as disturbed or undisturbed sample?

In standard penetration test, the number of blows is recored for three increaments, each 150mm, but only the blows fro two last increments are counted. Why the blows for first 150mm increment are not counted for SPT-value?

How to use SPT resistance to determine the density of sand and the consistency of clay?

Example of SPT: a spt yieded the following results: 5/6/7, what should be N value? If soil is a sand, what would be te state?

What is RQD? How can RQD be determined?

What should be noted when determining RQD? is the fracture caused by drilling process counted? is the highly weathered piece measured?

The different between two type of stresses, i.e. increased stress and

What items of information are expressed in borehole log?

Find the example of borehoe log to see.

to be continued.....

Technical terms

read the text book

Extra Readings

read the text book carefully

Examples of borehole logs

Practical problems

A borehole log that lack of some information is give. Students are required to filled the missing information in the borehole log.

Data of SPT results are given, students are required to determine the SPT-values, classify the state of soil (relative density of cohesionless soil and consistency of cohesive soil).

A sketch or picture of rockcore and data of rock core are given. Student determine rock core recovery ratio (RR) and rock quality designation (RQD), classify the rock mass quality based on RQD value.