OR/17/006 Appendix 2 - Summary geotechnical data graphs
|Monaghan, A A, Dochartaigh, B O, Fordyce, F, Loveless, S, Entwisle, D, Quinn, M, Smith, K, Ellen, R, Arkley, S, Kearsey, T, Campbell, S D G, Fellgett, M, and Mosca, I. 2017. UKGEOS - Glasgow geothermal Energy Research Field Site (GGERFS): initial summary of the geological platform. British Geological Survey Open Report, OR/17/006.|
The summary graphs of geotechnical (engineering geology) data show different data and information that can be used to indicate the ground conditions for each of the superficial and bedrock units (see section 7 above). This includes the consistency for fine soils (very soft to very stiff), density for coarse soils (very loose to very dense) and strength (very weak to extremely strong). Other graphs show field or laboratory data.
Standard penetration test (SPT) N-values are used to indicate the relative density of coarse soils and strength of fine soils. There are various correlations that are used to estimate foundation in particular for piling.
Plasticity charts are used to classify fine soils as clays (above the A-line) and silt (below the A-line) and classification of the plasticity (low to extremely high), which can be used to indicate shrink swell characteristics and likely strength as water content changes, permeability and some shear strength parameters (angle of internal friction and residual strength).
Particle size distribution is used in engineering classification particularly for coarse soils but also for use in construction. The data presented here are where there are few data as individual samples, but for those units with many data they are summarised as percentiles, the number of percentiles shown depends on the number of samples. The particle size distribution shows how variable a unit is, for instance the Wilderness Till and the Gourock formations are much more variable than the Paisley and Ross members.
The use of undrained shear strength includes the calculation of the short term strength of fine soils for foundation bearing capacity and the stability of excavations. The consistency descriptions have been used in the past to indicate the undrained shear strength classes, but this is no longer the case, although they can be used to provide an idea of this strength.
The uniaxial compressive strength of bedrock is a classification and characterisation test. It can be used to identify if certain types of drilling is suitable and, with discontinuity data, the stability of slopes, or excavations (at surface or beneath the ground) and excavatability.
This section presents the data and information in a number of different ways: as summary bar graphs of superficial and bedrock units, consistency, density or strength descriptions at depth below surface, or below the top of the unit, and field and laboratory parameters, some plotted against depth below ground level. The extended box and whisker plots present various percentiles depending on the number of values and provide a rapid assessment of the data range and allow for easy comparison between different characteristics such as lithology.
Clyde Valley Formation — Law Sand and Gravel Member
Killearn Sand and Gravel Member
Paisley Clay Member
Bridgeton Sand Member
Broomhouse Sand and Gravel Formation (including clay facies) unclassified
Ross Sand Member
Wilderness Till Formation
Bedrock summary graph
The bar charts below use the old strength classification descriptors as in the original data.
Scottish Upper Coal Measures Formation
Scottish Middle Coal Measures Formation
Scottish Lower Coal Measures Formation
Upper Limestone Formation
Intrusive Igneous Rocks (Western Midland Valley Westphalian to Early Permian Sills, WMVAS)
Limestone Coal Formation