Geotechnical Investigation Specification

Geotechnical Investigation

Specification

1. Scope of Work

The scope of work for this contract involves broadly the following

(a) Site exploration, sampling and testing.

(b) Geotechnical engineers supervision for exploration, sampling and testing in field.

(c) Laboratory test and analysis for soils.

(d) Geotechnical engineering analysis and recommendation report.

The geotechnical engineers shall be sent by Contractor to the jobsite to supervise in-situ boring workers to perform exploration, sampling and testing work. The soil tests shall be carried out by Contractor's Laboratory.

2. Site Conditions and Geotechnical Investigation

2.1 Site Condition

Please refer to attached information.2.2 Boring, Sampling and Soil TestingThe field work of investigations include boring, sampling, and SPT. The arrangement of boreholes shall be distributed evenly and cover all area.

2.2.1 Boring, and Sampling

Boring and Sampling shall be carried out by experienced operators, under the supervision of the engineers from Contractor. Drilled by auger method shall be adopted above the ground water level, and wash boring method shall be used below the ground water level. During the period of boring, different sampling method and apparatus shall be used as follows

(1) Standard penetration test (SPT) and 2Split-Spoon sampling of soils are refer to the ASTM D 1586 standard method.

Split-Spoon sampling shall be taken in hard cohesive or in non-cohesive strata and have to be taken at least at every change in soil formation at intervals not exceeding 2 meters. The samples have to be placed in core boxes (plastic or wood) or sample jars (SPT only). All boxes have to be stored by protection from sunlight and vibration. Transportation to the Laboratory has to take place at least once a week by suitable equipment to prevent rolling, bumping and temperature extremes.

All core boxes have to be labeled properly, showing the borehole and box number on every box. The depth of where the samples have been retrieved shall be clearly shown on each side of the box.

(2) The 3Shelby tube sampling in soil is refer to ASTM D 1587 standard method.

Undisturbed samples have to be taken in cohesive strata by use of thin wall tube sampler, triple tube core barrel or Denison sampler. The Samples have to be preserved in sample tubes, coated with wax and sealed in sturdy containers to protect from changes of water content, shock and vibration. The cutting shoes shall be clean and without burred edges. Following a break in the boring work, such as an overnight stoppage, boring shall advance by 0.75 m before any undisturbed samples are taken.

The internal diameter of the boreholes has to be always adequate to receive soil samples of min.75 mm and rock samples of min. 50 mm diameter except where SPT samples will be taken only.

2.2 Laboratory Test

In this investigation work, soil samples shall be tested according to the requirements for geotechnical analysis. Laboratory test includes the following items

General physical properties of soils

Shear strength test(DS)

Unconfined compression test (UN)

Triaxial unconsolidated undrained compression test (UU)

Consolidated undrained triaxial test (CU)

One-dimensional consolidation test

Soil general physical properties shall be determined in order to classify the soil. The direct shear test is used to evaluate the shear strength behavior of cohesionless soils. The unconfined compression test, triaxial consolidated-undrained compression test and the triaxial saturated unconsolidated undrained compression test are used to evaluate the shear strength behavior of cohesive soils. One-dimensional consolidated test on undisturbed soil yields the compressibility of cohesive soils.

2.3.1 General Physical Properties of SoilsGeneral Physical Properties of Soils include natural water content, void ratio, specific gravity, grain size analysis, dry and wet densities, and Atterberg limits. These tests shall be refer to ASTM D 421, D 854, D 2216 and D 4318 standard methods. From the test results, soil samples shall be refer to the Unified Soil Classification System (USCS) ASTM D 2487,and the soil condition shall be drawn in discontinuous soil column.

2.3.2 Shear Strength Behavior of Soils

Four types of shear test, i.e., direct shear test, unconfined compression test, and the triaxial compression test (CU and UU) are conducted to evaluate the shear strength characteristics of soils.

Direct Shear TestRefer to ASTM D 3080

Unconfined compression testRefer to ASTM D 2166

Triaxial Compression TestRefer to ASTM D 2850

2.3.3 One-Dimensional Consolidation Test

Consolidation test is executed to evaluate the volume change characteristic of soil, refer to ASTM D 2435

2.4 Photographs

Colour photographs have to be taken in-situ field investigation and Laboratory test. Each photograph shall clearly show all necessary details and shall contain a graduated scale, which shall be the same in every photograph of a particular type.

Theses photograph shall be attached in the Geotechnical Investigation Report.

3. Records and Reports

3.1 Field Records

The field records taken have to include the following data

Project name

Contract number

Date and weather conditions

Location and identifying number of investigation point

Elevation of ground water table

Elevation of the top and bottom of the borehole

Diameter and description of casing (when used)

Boring and Sampling Method used.

Depth of each change of strata with brief description.

Depth or elevation of top and bottom of disturbed and undisturbed samples, with notes on any lost recovery.

Standard Penetration N value.

Results of in situ tests.

Descriptions of soil, rock and groundwater represented by the samples.

Details of any delays and other special circumstances affecting the progress of the Works.

3.2 Laboratory RecordsThe laboratory records taken have to include the following data:

Project name

Contract number

Location and identifying number of investigation point

Sample number

Descriptions of soil, rock and groundwater represented by the samples.

Specified test results

3.3 Geotechnical Investigation Report

The report has to include following data

Description of the works carried out, including reference to specifications and standards adopted and any deviations from them.

Exploration hole logs In-situ test records Laboratory test results Survey records Continuous summary of exploration logs with scale Photos of in-situ field investigation and Laboratory test6