Intro

Question 1

What knoweledge is needed before site investigation can be carried out?

Answer 1

For each of the principal strata:
The engineering description & classification in terms of the nature (grading/plasticity) and state (stress, void ratio or OCR)

Positions of the boundaries between the strata
Geological environment when soil was deposited & history of subsequent deposition, erosion, weathering and ageing

Descriptions of visible features of structure & fabric (e.g. layering, fissuring and jointing)

Representative values for geotechnical parameters for strength, stiffness and permeability relevant to the design and construction of the works

Question 2

Objectives

Answer 2

a) Suitability: To assess general suitability of site and environs for proposed works including effects of previous use and contamination.
(b) Design: To enable adequate and economic design to be prepared, including design of temporary works.
(c) Construction: To plan best method of construction, to foresee and provide against difficulties during construction due to ground and other local conditions. To select sites for waste disposal.
(d) Effects of Change: To determine the changes that may arise in the ground and environmental conditions, either naturally or as a result of works
(e) Site Choice: Where alternatives exist, to advise on the relative suitability of different sites or different parts of the same site.
(f) Existing works: necessary when reporting on safety of existing works, planned alterations, when investigating failures and when looking for sources of construction materials.

Question 3

Stages of investigation

Answer 3

Stage 1, Desk Study & Site reconnaissance (walkover)

Stage 2, Detailed investigation for design including ground investigation, topographic and hydrographic surveying and special studies

Stage 3, Construction review, including any follow-up investigations during construction, and the appraisal of performances

Question 4

types of investigations

Answer 4

topography, geological, historical maps; mine workings, archaeological site, previous site investigations or existing borehole data logs (desk studies)

Walk over surveys

Question 5

Successfully managing an investigation

Answer 5

Creation of a relationship between structure, Borehole layout and depth.

Sampling appropriate quality and quantity related to required parameters and soil types.

site supervision.

Sample descriptions and careful preparation and monitoring of borehole so work can be modified as construction continues

Question 6

why use trial pits, boring and drilling methods?

Answer 6

Carried out to:

(a) Establish general nature of strata below site;
(b) Establish vertical and lateral variability of soil;
(c) Verify interpretation of geophysical surveys;
(d) Obtain samples for lab tests;
(e) Allow in situ tests to be conducted;
(f) Install instrumentation.

Question 7

Factors affecting frequency of boreholes

Answer 7

Controlled by structure and geological complexity

May need to change as work proceeds

Should allow cross section to be drawn and be able to pick out geological succession

Question 8

sampling, lab testing and in situ testing should aim to?

Answer 8

(a) Provide sufficient samples to classify soil into broad soil groups on basis of particle size and composition;
(b) Assessing the variability of the soil;
(c) Providing specimens of suitable quality for strength and compression testing;
(d) Provide specimens of soil and groundwater for chemical testing.

Question 9

what is important for in situ testing?

Answer 9

) Good quality sampling is impossible;

(b) Parameter cannot be obtained from lab tests;
(c) When in situ tests are relatively cheap compared to sampling and lab testing;
(d) For profiling and classification of soil.

Question 10

Soil classification types

Answer 10

Sample description

Particle size

distribution

Plasticity

Compaction

Specific gravity