Section 10: Reports and interpretation

62 General

High quality records and data should be generated, collated and passed on, as these form a fundamental part of the geotechnical design.

NOTE 1 Ground investigation works can be undertaken in a number of phases and the precise details of the development might not be fully defined in early phases.

The data generated from the ground investigation should be put into a format which allows data communication between all parties and data manipulation at various stages throughout the life of the works (see BS 8574 for guidance).

NOTE 2 A suitable protocol for management and transfer of digital data is provided by the ACS and is known as "ACS format".15)

All reports should be prepared in accordance with the requirements of BS EN 1997-1 and BS EN 1997-2 and the related test standards under which the work is carried out. Any additional reporting requirements should be identified in the contract specification. In accordance with BS EN 1997-1 and BS EN 1997-2, two separate reports should be prepared — a Ground Investigation Report (GIR) and a Geotechnical Design Report (GDR).

The GIR should present the factual information and assess and interpret the available information; this might include derivation of parameters from the test results.

The GDR should present the characteristic and design values, the calculations to verify the safety and serviceability of the geotechnical structure together with identification of the items to be checked during construction, and the supervision, monitoring and maintenance requirements.

NOTE 3 BS EN 1997 does not specify who is required to produce either these reports or their constituent parts. Although a number of parties are likely to prepare separate parts, a party or parties need to be identified and appointed to collate the whole report. For example, a ground investigation contractor might be commissioned to undertake and produce a factual report on intrusive works (i.e. exploratory holes), monitoring and laboratory testing, but not to carry out or report on the desk study or field reconnaissance which are constituents of the GIR. There is no reason why the responsibility for compiling the GIR and GDR cannot be carried out by different parties.

The GIR and GDR should remain as live documents throughout the investigation process; this includes the incorporation of the results of investigations both during construction and after construction is complete and the structure is in operation. The party responsible for this on-going compilation should be identified in the relevant contract documents.

Reports on integrated investigations (i.e. those in which geotechnical investigation is carried out in parallel with those into other aspects of the site — see 17.8) should conform to the guidance presented here and any authoritative guidance covering the other aspect(s). In particular, reports on the contamination aspect of a site should be in accordance with BS 10175 and those referring to ground gas should be in accordance with BS 8576. Information may be provided in a combined report(s) or in separate reports.

NOTE 4 Planning conditions often require that investigations and reporting are carried out in accordance with BS 10175. Failure to comply with the requirements in BS 10175 and BS 8576 regarding reporting might, therefore, cause delays In the consideration of a planning application or possibly rejection of a report.

All reports should meet the requirements of BS EN 1997-1 and BS EN 1997-2. The report and data should be passed on to the construction team and sub-contractors as required.

NOTE 5 The reporting requirements of BS EN 1997 are summarized in Table 43 where they are separated into general items that are required in all reports and then the field and laboratory reports and the GIR and the GDR respectively.

Table 43 Summary of reporting requirements (1 of 5)
Report Section Descriptive items to be included
All reports General information • Name of owner/client of the site and the proposed structure
• Names of all consultants, contractors and sub-contractors
• Location of site referenced to a national or site grid reference
• Proposed works/development
• Geotechnical category of the proposed structure
• Purpose and scope of the geotechnical investigation
• Title of the investigation and report number
Ground Investigation Report (GIR) [BS EN 1997-1:2004+A1:2013, 3.4; BS EN 1997-2:2007, Clause 6] Desk study report • Description of site history
• Collation and interpretation of previous ground investigations
• Expected geology of the site including faulting
• Expected hydrogeology and hydrology of the site
• Available survey information
• Information from aerial photographs and other sources of remote sensing
• Local experience of the area
• Topography/geomorphology
• Potential for mining and natural cavities
• Potential presence of hazards such as UXOs or contamination
• Information about the seismicity
• The current ground model
Field reconnaissance report • Description of site, its topography and surroundings
• Evidence of surface water and groundwater
• Presence of structures on the site and in the neighbouring area and their condition
• Exposures in the vicinity including natural exposures, quarries, cuttings and borrow areas
• Areas of stability or instability
• Photographs of the site and surrounding areas
• The current ground model
• Presence of existing piezometers or wells and any measurements taken
• Presence of trees and their type and other vegetation
Table 43 Summary of reporting requirements (2 of 5)
Report Section Descriptive items to be included
  Field reports including investigation holes, sampling and groundwater measurements [See also BS EN ISO 22475-1:2006, Section 12] • Summary logs of all exploratory holes including, as appropriate, drilling records, sampling records, soil and rock identification, backfilling records, installation records and groundwater measurements
• Numbering of the investigation points including boreholes, trial pits, sampling and measurement positions
• Location of investigation holes related to national or site grid
• Ground levels at all investigation positions related to national, project or site datum
• The orientation of all investigation holes
• Observations on the weather conditions during the fieldwork period
• Difficulties during excavation or construction of investigation holes including progress, stability
• Types and sizes (diameters and changes in diameter) of field equipment used to form investigation holes
• Compiled record logs of all borehole and trial excavation holes based on field descriptions including depths to the top of each stratum and its thickness
• Core recoveries (total) for all core runs and fracture state (solid core recovery, rock quality designation and fracture index in rock); identification of all zones of core loss
• Details of all samples or cores taken including type, depth and method of insertion
• Procedures used for sampling, transport and storage of samples
• Details of all tests carried out including type, depth and results
• Calibration certificates and reference numbers for test equipment in use
• Data on water strikes, levels at each sample and test and overnight, and any fluctuations of water level during the field work period
• Details of any water or other fluid added to the investigation hole to aid boring or as flush, including colour and proportion of returns
• Observations on surface and ground water
• Details of backfilling of investigation holes and of instruments installed (type and depths of the construction, confirmation of correct functioning)
• Readings from instrumentation during the field work period
• Tabulation of quantities of field work
• Presentation of field observations made by field personnel during the investigation activities
• Photographs of samples, cores, faces and spoil as appropriate
• Plans with survey data showing the structure and location of all investigation and sampling points
• Name and signature of the Responsible Expert
Table 43 Summary of reporting requirements (3 of 5)
Report Section Descriptive items to be included
  Field test report • Results of all field tests presented and reported according to the requirements defined in the EN or BS standards applied
• Certification and calibration documentation
• Tabulation of quantities of field work
• Name and signature of the Responsible Expert
Laboratory test reports • Results of all laboratory tests presented and reported according to the requirements defined in the EN or BS standards applied and other standards or methods as applicable
• Certification and calibration documentation
• Tabulation of quantities of laboratory work
Other reports • Any other reports not included above such as:
• Reconnaissance geophysical surveys
• Probe records such as DP (dynamic probe) or CPT
• Specialist testing reports such as plate load tests
• Geophysical testing reports, from the surface or using boreholes for access below the surface
• Specialist sampling such as block samples
• Contamination surveys and chemical testing
• Gas monitoring reports
Factual report • Account of all field and laboratory work
• Photographs of the field and laboratory work
• Documentation of the methods used to carry out the field investigations and laboratory testing
• Dates between which field and laboratory work was carried out
Table 43 Summary of reporting requirements (4 of 5)
Report Section Descriptive items to be included
  Parameter evaluation and derivation • Tabulation and review of the results of the field and laboratory work and evaluation according to BS EN 1997-2
• Identification of any limitations in the data including defective, irrelevant, insufficient or inaccurate readings
• Data on frost susceptibility of soils
• Interpretation of the results taking account of the drilling and sampling methods used, the sample storage and transport and the specimen preparation
• Consideration of any extreme (adverse or beneficial) results as to whether they are misleading or real and so require consideration in the design
• Review of the derived values of all geotechnical parameters including consideration of any correlations used and their applicability
• Histograms or other plots to illustrate the range of values of relevant parameters
• Description of the evolution of and changes in the ground model from initial studies through the phases of investigation
• Profiles or cross-sections showing the geometry of and differentiation between the various formations
• Position of the ground water table and its seasonal fluctuations
• Detailed description of all the formations including the range and distribution of physical properties including their strength and deformation characteristics
• Comment on any irregularities such as pockets, cavities or discontinuities
• Proposals for any necessary further field or laboratory work including justification through the specific questions that have to be answered
Geotechnical Design Report (GDR) Design report • Description of the site and surroundings
• Description of the ground conditions
[BS EN 1997-1:2004+A1:2013, 2.8] • Presentation of site ground model
• Proposed structure including actions
• Characteristic and design values of soil and rock properties, including justification as appropriate
• Standards applied
• Suitability of the site with respect to the proposed construction and level of acceptable risks
• Assumptions, data, methods of calculation and results of the verification of safety and serviceability
• Geotechnical design calculations and drawings
• Foundation design recommendations
Geotechnical Baseline Report (GBR) [see 63.5] • Anticipated geology, soil and rock profiles
• Anticipated groundwater conditions
• All information relevant to establishment of baseline conditions
Table 43 Summary of reporting requirements (5 of 5)
Report Section Descriptive items to be included
Geotechnical Design Report (GDR) [BS EN 1997-1:2004+A1:2013, 2.8] Supervision, monitoring and maintenance report • Note of items to be checked during construction, requiring maintenance or monitoring
• The purpose of each set of observations or measurements
• The parts of the earthwork, ground and/or structure to be monitored
• The locations at which observations are to be made
• The frequency of observations or measurements
• Ways in which the observations or measurements are to be evaluated
• The range of values within which the results are to be expected
• Period of time for which monitoring is to continue after construction is complete
• The parties responsible for making observations or measurement, for interpreting the results and for maintaining the instruments
• Extract of all above items as appropriate to be handed to the owner/client

BS 5930:2015 Code of practice for ground investigations