Class B – Ground Investigation

BE2S85David Harper

Ground investigation covered by Class B of the CESMM includes:

1. Trial pits and trenches; 2. Light cable percussion boreholes; 3. Rotary drilled boreholes; 4. Samples (from the surface or form trial pits and trenches as well as from boreholes); 5. Site tests and observations; 6. Instrumental observations;7. Laboratory tests; and 8. Professional services in connection with ground investigation.

Ground investigation covered by Class B of the CESMM excludes:• Excavation which is not carried out for the purpose of ground

investigation is excluded from Class B and is measured under Class E; and

• Boring for piling is also excluded and is measured under Classes P and Q.

Common theme to all CESMM 3 Classes

Note as with all Classes there is:• First Division description column; • Second division column; • Third division column; • Additional measurement rules column (M); • Definition rules (D); • Coverage rules (C); and • Additional description rules (A).

C1 and C2 page 21 CESMM 3

• The preparation and submission of records and results is deemed to be included in items for ground investigation as is the disposal of excavated material and removal of dead services.

• There is no specific provision for the packing, transporting and disposing of samples and test specimens. Whilst the specification should provide details of these, it is prudent to include preamble clauses stating that items for samples and tests in ground investigation are deemed to include packing, transporting and disposing of samples, cores and test specimens as required by the specification.

The following extract from a Bill of Quantities would be based on a site plan indicating the location of the exploratory holes and a schedule setting out the probable depths of the holes. This information would be included with the tender documents which accompany the BoQ

Trial Pits and Trenches

• A1 Item descriptions for the number and depth of trial pits and trenches shall state the minimum plan area at the bottom of the pit or trench or, where the work is undertaken to locate services, the maximum length of the trench (see examples on previous slide).

• A2 Item descriptions for the number and depth of trial pits and trenches shall identify those which are expressly required to be excavated by hand (see example on previous slide i.e. B114).

• The items measured for trial holes include items for the number of holes and items, in linear metres, for their depths. In both cases the items state whether they are in materials other then rock or in material which includes rock.

Trial Pits and Trenches (cont.)

• The numbered items state also the maximum depth of the holes in ranges measured from the commencing surface (see example two slides previous).

• Holes otherwise similar but of different depths are grouped in separate items for each standard depth range.

Above - Light cable percussion borehole equipment

Above – Rotary drilled borehole equipment

Boreholes – 2 types: 1) Light cable percussion boreholes; and2) Rotary drilled boreholes

Boreholes (Cont.)• Each of the two types of boreholes, for which classifications

are given in Class B, requires that items are measured for the collected number and the collected depths, in linear metres, for each group of similar boreholes.

• Holes are grouped by diameter for each type.• The diameters given in the items for light cable percussion

boreholes are the diameters at the base of the holes. • For rotary drilled boreholes the core diameters are given.• Depth items for each type of borehole state the maximum

depth range (or depth where exceeding 40m), as given in the third division features, of the deepest borehole of those grouped in an item.

Boreholes (Cont.)• When measuring rotary drilled boreholes, items for depth

without core recovery are given separately from those for depth with core recovery.

• Where cores are recovered numbered items are given for core boxes, stating the length of cores.

• The depth of any casings required to rotary drilled boreholes is measured in linear metres.

• Casings for light cable percussion boreholes are deemed to be included in the items.

• The type of material through which boreholes are sunk does not have to be stated, but items in operational hours are given for chiselling, expressly required to prove rock or to penetrate obstructions in light cable percussion boreholes.

• Any backfilling of boreholes is measured by depth in linear metres and the items state the backfilling material.

Example BoQ for Light percussion boreholes

Example BoQ for Rotary drilled boreholes

Samples

• Samples are numbered stating size, type and class of samples in accordance with BS 5930.

• The specification will need to relate to the British Standard and item descriptions will usually refer to the appropriate clause in the specification.

• They are classified as either ‘from the surface or from trial holes and trenches’ or ‘from boreholes’. Separate items are given in the Bill of Quantities for the number of each kind of sample required.

• The Bill should make clear that the items for samples are deemed to include for all requirements as to samples and sampling as are set out in the specification

Samples (Cont.)

Site Tests, Observations and Laboratory Tests• These fall under three first division headings, namely ‘Site

tests and observations’, ‘Instrumental observations’ and ‘Laboratory tests’.

• Many tests are identified in the features by British Standard references.

• Additional detail to that contained in the BS, such as where and when tests and observations are to be carried out and other requirements the Engineer desires to impose need to be given in the Specification.

• Item descriptions may make reference to clauses in the Specification to make clear the scope of activities etc., intended to be included in the testing and observation items.

E.g. California Bearing Ration (CBR) test

The California Bearing Ratio was developed by The California State Highways Department. It is in essence a simple penetration test developed to evaluate the strength of road subgrades. It can be undertaken on site or in the laboratory. The test is fully covered in :-BS 1377 : Soils for civil engineering purposes : Part 4,Compaction related tests.

E.g. Static cone sounding (Static cone penetration test)

Static cone penetration test is internationally recognized as a standard field test to collect data about bearing capacity and frictional resistance of soil. It was initially developed in the 1950s at the Dutch Laboratory for Soil Mechanics in Delft to investigate soft soils. Based on this history it has also been called the "Dutch cone test".

The test is performed using a cylindrical penetrometer with a conical tip (cone) penetrating the ground at a constant rate. During the penetration, the forces on the cone and the friction sleeve are measured. The measurements are carried out using electronic transferand data logging, with a measurement frequency that can secure detailed information about the soil conditions.

E.g. Mackintosh probe

The Mackintosh Probe consists of a cased screwed onto the lower end of the rod. The rods are of 16mm diameter HY steel each of length 120 cm. The rods are connected to each other by 25 mm outer diameter couplings. These couplings provide the lateral support to the rods so as to prevent buckling during driving. Driving is performed with a small hammer of 5 kg in weight and falling vertically through a fixed height of 30 cm along a guide rod. The total number of blows required for the pointer to penetrate a distance of 30 cm is recorded and used as a measure of the consistency of cohesive soil and the packing of granular soil.

Site tests and Laboratory test BoQ example:

Professional Services• Any professional services required for supervising and

progressing the work are included in the Contract and items for ground investigation are deemed to include preparing and submitting records and results.

• Items for professional services as set out in Class B are measured only where it is expressly required that records and results shall be analysed. They are given in units of hours for the stated grade of personnel.

• The hours measured are working hours; hours spent travelling, taking meals etc. are not measured and are deemed to be included in the items for professional services.

Professional Services (Cont.)

Professional Services (Cont.)

• Expressly required visits and overnight stays for expressly required professional services on site are given as numbered items. The items are deemed to include travelling, meals, accommodation and other incidental expenses.