Step 01
Receive and schedule
Samples are logged, checked against the borehole record and scheduled so classification runs before the strength testing that depends on it.
Soil & Rock Testing
The laboratory is where samples become design parameters. Classification, strength, compressibility and swelling, each run to a stated method with the instrument calibration on record.
Soil & Rock Testing: what it actually tells you
Classification comes first, because it decides what else is worth running. Particle size distribution by sieve and hydrometer, Atterberg limits, moisture content and specific gravity place the soil in the USCS system, and that classification is what tells you whether to expect settlement, swelling or liquefaction.
Strength testing is selected to match the design case. Direct shear for a quick friction angle in granular soil, unconsolidated undrained triaxial for short term stability in clay, and consolidated undrained triaxial with pore pressure measurement where effective stress parameters are needed. Consolidation testing gives compression index, preconsolidation pressure and the coefficient of consolidation for settlement and its timing.
Rock is tested for unconfined compressive strength, point load index as a rapid field correlated screen, and slake durability where the rock is at risk of breaking down on wetting and drying. Karachi and much of Sindh sit on weak sedimentary rock where that last point is not academic.
At a glance
- TurnaroundClassification 3 to 5 days, consolidation 2 to 3 weeks
- Sample typeDisturbed, undisturbed tube and rock core
- ReportingMethod reference and calibration status on every result
- ScopeClassification, strength, compressibility, rock
How we run it
The sequence we follow on site and in the laboratory, and the point of each stage.
Step 02
Classify
Grading by sieve and hydrometer, Atterberg limits, natural moisture content and specific gravity, giving the USCS group symbol.
Step 03
Compaction and CBR
Standard or modified Proctor to establish maximum dry density and optimum moisture, with CBR at the specified compaction for pavement design.
Step 04
Strength and compressibility
Direct shear, unconfined compression, UU and CU triaxial with pore pressure, and oedometer consolidation including swell pressure where clay is expansive.
Step 05
Rock testing
Unconfined compressive strength, point load index, slake durability and specific gravity with water absorption on core specimens.
What you receive
- USCS classification with grading curve and Atterberg limits
- Shear strength parameters, cohesion and friction angle, total and effective
- Consolidation parameters for settlement magnitude and rate
- Swell potential and swell pressure for expansive clay
- CBR and compaction curve for pavement and fill design
- Rock strength, point load index and durability
When this test is the right one
- Every soil investigation, following the boreholes
- Foundation settlement and bearing capacity analysis
- Slope stability and retaining wall design
- Pavement subgrade and fill acceptance
- Expansive soil assessment before slab on grade construction
Methods and standards
Every result is reported with its method reference and the calibration status of the instrument used.
ASTM D422 and D6913 particle size analysisASTM D4318 liquid limit, plastic limit and plasticity indexASTM D2216 moisture contentASTM D698 and D1557 Proctor compactionASTM D1883 CBRASTM D3080 direct shearASTM D2850 and D4767 triaxial compressionASTM D2435 one dimensional consolidationASTM D7012 rock compressive strengthASTM D5731 point load strength index
Common questions
What engineers most often ask us about soil and rock testing.
It depends on the drainage condition that governs. Short term stability in clay is an undrained problem, so UU triaxial or unconfined compression applies. Long term stability and granular soil are effective stress problems, so CU triaxial with pore pressure measurement or direct shear applies.
Each load increment has to be held until primary consolidation is complete, which in a low permeability clay is 24 hours per stage. A full curve with loading and unloading is therefore two to three weeks. It cannot be rushed without invalidating the result.
Undisturbed samples are sealed at the borehole and transported upright with the ends waxed. On receipt the tube is checked for disturbance and the specimen is examined when extruded. If a sample is compromised we say so rather than testing it anyway.
Often ordered alongside
Most investigations combine several of these. We scope them together so you are not paying to mobilise twice.
Need soil and rock testing on your project?
Send us the location, the structure and your programme. You get a scoped quotation with the standard, the number of tests and the turnaround written into it.