Geotechnical Soil & Rock Testing

lab_piOur in-house laboratories are equipped to provide comprehensive geotechnical soil, rock and groundwater testing services which meet the appropriate British and European Standards.

Soil and groundwater testing more commonly undertaken by Southern Testings geotechnical testing laboratories is used for classification of materials. These tests include Moisture Content, Atterberg Limits (PI’s), Bulk Density, Dry Density, Particle Size Distribution (PSD or Grading Analysis), Particle Density (Small Pyknometer and Gas Jar), as well as Sulphate Content and Triaxial Tests, but wide range of geotechnical soil testing is available.

Classification Testing

Natural Moisture Content; MC BS1377-2:3 & BS EN ISO 17892-1 The mechanical properties of a soil often depend on their moisture content and the test is used in assessment of soil profiles, strength, desiccation etc
Plasticity Index (Atterberg Limit Test); PL, LL & PI BS1377-2:4 – 5 & & BS EN ISO 17892-12 The properties of cohesive soils are strongly influenced by the mineralogy of the clays. These tests along with moisture content are used for classification and to assess mechanical properties and are used for Earthworks Materials, NHBC Volume Change potential, desiccation etc.
Particle Density; PD or Specific Gravity; SG BS1377-2:8 && BS EN ISO 17892-3 Used for the determination of porosity and voids ratio. Frequently used in road construction in the determination of the state of compaction of fill materials.
Bulk & Dry Density; BD & DD BS1377-2:7 & BS EN ISO 17892-2 The density of soils depends on the density of the solid particles, on the porosity and the moisture content. The dry density is used in the evaluation of porosity and voids ratio. It is frequently used in road construction for the determination of the state of compaction of fill material.
Saturation Moisture Content of Chalk; SMC BS1377-2:3.3 & BS EN ISO 17892-2 Establishes the state of saturation of a soil to determine the extent the pores are filled with water. The presence of free air or gases in a soil influences the mechanical properties of the soil. It is most commonly used for chalk materials.
PSD Grading by Wet & Dry Sieve Methods BS1377-2:9.2 & 9.3 & BS EN ISO 17892-4 Particle size expresses the size of the particles comprising a soil in terms of percentages by weight of individual sizes. This analysis is used for classification of sands and gravels and coarser particles. This can be related to the mechanical properties of the material e.g. suitability as a fill material, permeability etc.
PSD by Pipette Method (sedimentation) BS1377-2:9.2 & 9.3 & BS EN ISO 17892-4 Used in conjunction with a sieve analysis to determine the silt and clay content of a soil. Used in the classification of soil and assessment of their mechanical properties.

Chemical Testing

pH value BS1377-3:9.5 A measure of the acidity/alkalinity of soil and groundwater. Concrete that is subject to highly mobile acid (low pH) water can deteriorate rapidly. This is assessed for concrete design.
Sulphate Content BS1377-3:5 A measure of the sulphate content of soil and groundwater. These sulphates can attack concrete leading to its deterioration. This is assessed for concrete design.
Organic Content BS1377-3:3 & 4 Derived from the decomposition of plant, animal and bacterial life. The organic material shows high water absorption and strongly influence mechanical properties especially strength and settlement behaviour.
Chloride Content BS1377-3:7 & BRE CP 2/79 This test measures chloride content of soil and water. Only very high concentrations affect unreinforced concrete but could attack steel at lower concentrations.
BRE SD1 Suite BRE SD1 2005 This suite is used to determine the risks of sulphate attack when other ions, particularly carbonates are present. This is used in concrete design.

Performance Testing

Dry Density Moisture Content Relationship (Compaction); DD/MC, OMC & MDD BS1377-4:3 This test measures the dry density of the compacted soil in relationship to moisture content depending on the manner of the compaction effort. Compaction influences the shear strength and compressibility of the soil and is frequently used in earthworks and road construction.
Moisture Condition Value; MCV BS1377-4:5 Primarily used as a rapid test to determine the moisture suitability of earthwork materials at the construction phase. Calibration lines are usually determined through a range of moisture contents in the laboratory. The MCV is used to quantify the compactive effort to produce near full compaction and can be correlated with shear strength and CBR value.
Laboratory Californian Bearing Ratio; CBR BS1377-4:7 Used for the evaluation of sub-grade strength in road design. The test measures the load required to cause a plunger to penetrate a specimen of soil. Although an arbitrary test it is an indirect measure of strength. Not suitable for materials with more than 25% of particles larger than 20mm).

Consolidation Testing

One Dimensional Consolidation (Oedometer) BS1377-5:3 & BS EN ISO 17892-5 The rate and degree of settlement from a proposed structure is estimated from this small scale laboratory test for soil investigation. A soil sample is compressed within a metal mould sandwiched between porous plates. A change in thickness is measured at different loads.
Swelling Pressure BS1377-5:4 & BS EN ISO 17892-5 In the oedometer swelling potential can be assessed

Shear Testing

Immediate Undrained Shearbox BS1377-7:4 & BS EN ISO 17892-10 Undrained estimates of the shear strength of soils can be measured under different normal stresses. In the shear box failure is caused in a predetermined plane of the soil. True immediate tests cannot be made in material not fully saturated or in more permeable soils.
Consolidated Drained Shearbox BS1377-7:4 & BS EN ISO 17892-10 The soils in the shear box are allowed to consolidate under a vertical load and then sheared slowly. The results are usually used in assessment of slope stability and retaining wall design.
Laboratory Vane BS1377-7:3 The torque required to cause shearing of soil from twin blades fixed at right angles. The test allows the measurement of shear strength for foundation design and road pavements. They can assist in stability of earthworks.

Triaxial Testing

Quick Undrained Triaxial BS1377-7:8 A soil sample is subjected to three stresses at right angles with the vertical stress increased until the specimen fails. The test results are used for the design of conventional and piled foundations but can also be used in short term stability of slopes and underground openings.

Effective Stress Testing

Isotropically Consolidated Undrained Test BS1377-8:7 An effective strength test where the sample is consolidated to a mean effective stress and the undrained strength and pore water pressure is measure. In an undrained test the volume remains constant. Stability of slopes and design of retaining structures.
Isotropically Consolidated Drained Test BS1377-8:8 This test is for the long term condition of the above test. This is usually carried out in sands and free draining materials. In the drained test the pore pressure remains constant but the volume may change. Stability of slopes and design of retaining structures.

Permeability Testing

Direct Measurement of Permeability under Constant Head BS1377-5 & 6 Measures the coefficient of permeability usually in cohesive soils in the Triaxial apparatus. This is frequently used in the assessment of permeability in compacted soils in landfill and road construction.

Rock Testing

Measurement of Uniaxial Compressive Strength; UCS ISRM Part 1 2007  The rock/soil strength is determined from a uniaxial compressive strength on a cylindrical specimen. Often used to assess the strength of rock for foundation design. The strength can also be used on the stability of rock slopes and underground openings. It should be noted that this strength only refers to the solid parts of a rock mass.
Point Load; PL ISRM 2007 Where uniaxial strengths cannot be directly measured the point load tests offers a possible alternative method of assessment.

The above tables do not list all available tests.

Want to find out more about our geotechnical soil testing services? Please contact our laboratory manager to discuss your site investigation testing requirements.

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