1. PURPOSE
1.1 This specification defines the minimum requirements for carrying out subsoil surveys, making laboratory tests on soil samples, site testing, and preparing a report on ground conditions.
2. scope
2.1 This specification applies to subsoil investigations for all proposed Air Products sites in Europe.
3. related documents
3.1 The following standards shall apply, except as indicated below:
3.2 British Standards Institute (BSI)
BS 410 Test Sieves – Technical Requirements and Testing
BS 1377 Methods of Test for Soils for Civil Engineering Purposes
BS EN 1997 Eurocode 7 – Geotechnical Design, Ground Investigation and Testing
BS 10175 Investigation of Potentially Contaminated Sites
3.3 Department for Environment, Food and Rural Affairs (DEFRA) Contaminated Land Reports (CLR)
CLR 2, Volume 1 Guidance on Preliminary Site Inspections of Contaminated Land
CLR 11 Model Procedures for the Management of Land Contamination
Environmental Protection Act (EPA)
CLR 4, Volume 1 Sampling Strategies for Contaminated Land
Note: For subsoil investigations performed in countries other than the United Kingdom, the applicable codes and standards are the corresponding ones of the country in which the investigation takes place.
- INTRODUCTION
4.1 The work consists of subsoil surveying, laboratory testing, site testing, and reporting. The area to be surveyed is shown on drawings accompanying this specification. The drawings also show the location of trial pits, boreholes, and cone penetration tests included in the scope of the work. Should the contractor believe that additional pits, boreholes, or cone tests are required to provide the information requested in the report, he shall advise Air Products of this with his tender.
- ACCESS
5.1 If the survey area is within an existing Air Products plant, access to the site shall be by agreement with the plant manager. Otherwise, access to the site shall be by agreement with the landowner and Air Products.
5.2 The contractor shall visit the site to familiarise himself with any access restrictions before submitting a quotation.
- SITE RULES AND REGULATIONS
6.1 When the survey is within an existing plant, the contractor shall acquaint himself with all site rules and regulations and shall comply with them and enforce them without any reservation.
6.2 In particular, the contractor shall be required to obtain “Safe to Work” permits from the plant manager before start of the survey work.
- FIELD WORK
7.1 Supervision: The soil survey shall be performed under the direction of an engineer qualified and experienced in site investigation and testing techniques. The contractor shall employ, full time on the site, a foreman skilled in boring, sampling, and the recognition of strata, and also competent to record accurately the nature of the strata encountered.
7.2 Work Off Site: The contractor shall contact local authorities, inspect relevant geological maps, study local topography, and assemble all available information regarding the geology and development of the site, and surrounding areas both above and below ground. Information shall be sought regarding the susceptibility of the site to flooding and ground movements from any cause, and also any other conditions that would affect the stability and suitability of the site for development purposes. The contractor shall assess whether the site may have been exposed to any form of contamination during past usage of the site, and whether testing for contaminants shall be performed. This assessment shall be performed according to BS 10175. The contractor shall include the necessary testing and sampling in their bid. The bid shall also include details of their proposal for sampling and testing.
7.3 Work On Site
7.3.1 General: Sufficient samples and tests shall be taken and be made on site to determine the information required for the report.
7.3.2 Location and Depth of Cone Penetration Tests (CPTs), Boreholes, and Trial Pits
7.3.2.1 CPTs, boreholes, and trial pits shall terminate at such depths as will provide adequate information for the preparation of the report.
7.3.2.2 They may be repositioned locally to avoid obstructions if prior approval has been given by Air Products.
7.3.2.3 Northings and Eastings shall be given to locate the CPTs, boreholes and trial pits together with the ground level at each location.
7.3.3 Site Records
7.3.3.1 The contractor shall maintain on site a complete record of all the various operations that form the Works, and shall provide every facility to Air Products for the inspection of the records, samples, cores, or other evidence of geological strata encountered.
7.3.4 Boreholes
7.3.4.1 Boring in Overburden
Boring in overburden shall be of sufficient size to permit 100 mm diameter undisturbed samples of overburden to be obtained and also to allow cores from rock beneath the overburden to be obtained. The method of boring shall be such as to allow a continuous record of all strata to be obtained.
The method of boring in cohesive soil shall permit the taking of disturbed and undisturbed samples with their original moisture content unaltered. In cohesionless strata, the method of boring shall be as such to prevent boiling of soil penetrated, and also to permit performance of standard penetration tests.
While the work is in progress, the thickness and depth of each stratum penetrated shall be recorded, and also the depth at which water is first encountered. Thereafter, the water level in the borehole below ground level shall be measured before start and at the end of each day’s work. A tabulated summary of the daily water level observations indicating the time and depth at each observation shall be provided in the borehole log, together with any relevant comments relating to boring that might cause fluctuation in the water levels.
7.3.4.2 Boring in Bedrock by Diamond Drilling
Boring in rock shall be executed by rotary diamond drilling with thin wall, double core barrel for the extraction of continuous cores of the rock strata.
Boreholes in rock shall be cased when necessary to prevent the sides caving in.
While boring in rock is in progress, the following observations shall be made and recorded in the borehole logs:
- Nature, depth, and thickness of strata and detail of discontinuities.
- Behaviour of drills, ease of drilling, and time taken for each cut.
- Behaviour of drilling water return of each cut giving an indication of any loss.
- Depth at which total loss of drilling water occurs.
- Water level observations before start and at end of each day’s work.
7.3.4.3 Rock Cores
On being brought to the surface, the nature of the rock or rocks forming the core and the position of any joints, rock faults, shear, or bedding planes shall be identified and recorded.
The length of core recovered from each cut shall be measured, recorded, and given in the borehole log. The percentage recovery shall also be stated.
7.3.4.4 Backfilling Boreholes: On completion of the field work, the contractor shall backfill all borings to the satisfaction of the engineer.
7.3.5 Trial Pits
7.3.5.1 Trial Pits (Hand Dug): Trial pits shall have a minimum plan size measured inside poling boards of 1800 mm by 1800 mm. The sides shall be securely supported to ensure that no slips or cracks occur in the adjacent ground. All boards shall be fixed vertically with wedges so that they may be withdrawn one at a time for inspection.
7.3.5.2 Trial Pits (Machine Dug): Trial pits may be machine dug when practicable to depths not exceeding 4.5 m. The widths of pit at the surface shall not be less than 750 mm and not greater than 1200 mm. The sides of trial pits shall be temporarily shored when necessary, by removable timber of adequate size placed vertically and pinned by horizontal timbers at suitable levels to permit inspection of the pit and sides.
7.3.5.3 Trial Pit Inspection: The engineer shall be notified at least three days before the trial pit is to be dug so that the pit can be inspected by the engineer and the contractor within 12 hours of being completed.
7.3.5.4 Trial Pit Records: A descriptive record shall be made of the following:
All sub-strata encountered.
The depth of strata changes.
Details of any water or moisture encountered.
When cohesive soils are encountered, penetrometer readings shall be taken for comparison of soil stiffness only.
Full details of the pit bottom.
A brief description of the general weather conditions for the previous month likely to have affected the records.
7.3.5.5 Trial Pit Covers
At all times, the pit shall be adequately protected from the weather, particularly sun and rain, to allow as little change in the exposed soil as possible.
The contractor shall ensure that at all times, the pit does not constitute any kind of hazard to person or livestock.
7.3.5.6 Refilling Trial Pits: On receipt of instructions from the engineer, trial pits shall be refilled with the original excavated soil in 300 mm thick layers; each layer being thoroughly compacted before the next layer is placed, to a density equal to the original density.
7.3.6 Cone Penetration Tests
7.3.6.1 Tests shall be performed using an electric cone penetrometer.
7.3.6.2 One third of the tests shall be performed with friction measurement.
7.3.6.3 Results of each test shall be presented in graphical form with cone resistance and sleeve friction plotted against depth.
7.4 Samples
7.4.1 Disturbed Samples
7.4.1.1 Each sample must be truly representative of the composition of the in-situ soil and contain sufficient material to carry out its identification and mechanical analysis.
7.4.1.2 The soil in the cutting shoe shall be examined, and a disturbed sample of this material shall be taken and placed in an airtight container clearly marked as “sample from cutting shoe.”
7.4.1.3 When required, samples of sand and other suitable materials from below the water table shall be obtained using a compressed air sampler with a thin-walled tube.
7.4.1.4 All disturbed samples shall be clearly referenced in the borehole logs and shall be preserved when possible until disposal is agreed with the engineer.
7.4.2 Undisturbed Samples
7.4.2.1 Standard undisturbed samples shall be 100 mm diameter and not less than 450 mm long in cohesive soils. When possible, undisturbed samples shall be taken at 1500 mm intervals of depth and at a change in strata.
7.4.2.2 All undisturbed samples shall be clearly referenced in the borehole logs; the reference mark shall also appear on the sampling tube. All undisturbed samples shall be carefully preserved in the sampling tubes until the contractor is required to either perform testing or dispose of the samples according to instructions from the engineer.
7.4.3 Water Samples: Representative samples of ground water shall be taken at suitable levels and placed in clean containers for laboratory testing for chemical impurities.
7.4.4 Samples from Trial Pits: When directed by the engineer, representative samples weighing not less than 1 kg shall be taken from each separately distinguishable strata at 750 mm intervals for strata over 1500 mm thick, and placed in airtight bottles or other approved containers. Representative bulk samples of at least 50 kg shall be excavated from any part of the trial pit as directed by the engineer, and placed in approved containers.
7.5 Other On Site Tests
7.5.1 Standard Penetration Test
7.5.1.1 Standard penetration testing shall be performed in cohesionless soils when encountered and repeated at approximately 1500 mm intervals of depth in the same stratum.
7.5.1.2 The number of blows for the initial penetration of 150 mm and the number of test blows for 300 mm penetration shall be given in the borehole logs at the appropriate depths.
7.5.1.3 Boring and cleaning operations in cohesionless strata shall be performed under an induced head above the water table to prevent boiling of the cleared hole before performing standard penetration tests.
7.5.2 C B R Tests: California Bearing Ratio (C B R) tests shall be made on freshly exposed soil at a minimum of 1 metre below the surface. The CBR Tests shall also be used to assess the suitability of the existing top strata to act as a subgrade for road pavement design and piling mat.
7.5.3 Soil Resistivity Tests: Resistivity shall be measured in ohm meters at depths of 3, 6, and 9 metres across the survey area.
7.5.4 Soil and Ground Water Contamination Tests: The contractor shall obtain soil and ground water samples for the testing of contaminants, according to the proposals put forward in their bid or subsequent proposals agreed with Air Products, and as detailed below:
Sampling shall be undertaken according to the Department for Environment, Food and Rural Affairs (DEFRA) Contaminated Land Report CLR No. 4 1994 “Sampling Strategies for Contaminated Land.”
Samples shall be obtained from any obvious potential contaminated location, such as sites of chemical tanks.
- LABORATORY TESTS
8.1 Generally, tests shall be undertaken to determine the information specified for the report. Generally, laboratory tests shall be performed on undisturbed samples as follows:
One undrained triaxial compression test, at varying pressures, to be taken on each undisturbed sample of cohesive strata in each bore hole.
Two consolidation tests to be taken from each cohesive strata encountered.
Determine the sulphate content and acidity of soil and ground water in each bore hole.
Determine the particle distribution analysis for each strata encountered through mechanical and wet methods.
Determine the nature and level of any contaminants within the soil and ground water.
- ENGINEERING REPORT
9.1 A report shall be submitted in three parts. The first part shall include:
All data obtained from field work and laboratory work.
A drawing showing the location and ground level of each CPT, borehole, and trial pit relative to an established datum. Also included in the report shall be a profile of the subsoil and water levels.
9.2 The second part shall include soil properties ascertained from the field and laboratory work as follows:
9.2.1 To classify and identify the soils for each strata:
Geological formation.
Particle size distribution.
Natural moisture content and void ratios.
Natural soil density.
Consistency limits (plasticity index, liquid limit, plastic and shrinkage limits).
9.2.2 To determine the engineering properties of each strata:
Coefficients of consolidation and compressibility.
Sheer strengths drained and undrained including cohesion and internal friction values, degree of sensitivity of remoulded clay.
Coefficients of permeability for permeable soils, data from standard penetration tests.
9.2.3 For road construction and earthwork:
Optimum moisture contents and maximum densities.
California Bearing Ratio of subgrade material.
9.2.4 The depth of frost penetration for the locality, used for the design of roads, foundations, and underground pipes.
9.2.5 When pore water pressures are found to be different from that of natural water head, these shall be given.
9.2.6 The Barkan coefficients for compression and shear (both uniform and nonuniform).
9.2.7 The soil resistivity results in tabular or graphical format.
9.2.8 The soil and ground water contamination levels against published trigger levels in tabular format. Also shall advise the necessary requirements to protect buried civil works against such contaminates and any required certification for disposal of excavated material off site.
9.3 The third part shall include an interpretation of the first two parts as follows:
Acceptable bearing capacities and instantaneous settlements at ground level for crane outriggers during erection of equipment. Although loads from outriggers can be spread over large areas, it shall be assumed that the outrigger size will be 3 m by 2.5 m.
The report shall provide safe bearing capacities for suitable footings and foundations at various depths, estimates of probable settlements and their relation to time, recommendations as to the type, length, and size of pile when required, and the advisability of using sulphate-resisting cement or other precautions that might be necessary to protect underground civil works. To assist with this section, typical information on equipment and structures likely to be built on the site accompanies this specification.
Recommendations for dealing with any contamination encountered and the restrictions on the use and/or disposal of any contaminated land.
A summary of the information gathered regarding the topography and geology of the areas surrounding the site, and comment on the possible effects on the proposed works.
9.4 The Report shall be in English. One hardcopy shall be submitted with one electronic copy formatted in Microsoft Word version 2007.