(a) Field and in-situ testing components and methods for soils
In-situ soil testing exists because sampling and transporting soil to a laboratory disturbs its structure and stress state — especially for sensitive clay, loose sand, or soil where in-place stress and pore pressure are the property of interest — so field methods measure the soil where it lies. The core components of the field program are the exploratory borehole/test pit network (location, spacing and depth set by the desk study and project footprint), the sampling and logging carried out as each hole advances, and a suite of in-situ tests run either within or alongside the boreholes:
Standard Penetration Test (SPT, ASTM D1586) — a split-spoon sampler driven by a standard hammer/drop; the blow count N is an empirical index of relative density/consistency, correlated to friction angle, undrained shear strength, liquefaction susceptibility, and allowable bearing pressure; simple and low-cost, but the disturbed sample and hammer-energy variability limit precision.
Cone Penetration Test (CPT/CPTu, ASTM D5778) — a instrumented cone pushed continuously, recording tip resistance, sleeve friction and (in the piezocone, CPTu) pore pressure; produces a continuous, highly repeatable stratigraphic and strength profile with no sample recovered, and directly measures pore pressure response useful for consolidation and liquefaction assessment.
Field vane test (VST, ASTM D2573) — a four-bladed vane rotated in-place in soft-to-firm clay to measure in-situ undrained shear strength (peak and, after remoulding, residual, giving sensitivity) with minimal disturbance, the standard method for soft clay strength.
Pressuremeter test (ASTM D4719) — a cylindrical probe expanded radially against the borehole wall, giving an in-situ stress-strain curve from which shear modulus, undrained shear strength and in-situ horizontal stress can be derived; particularly valuable where undisturbed sampling is difficult (stiff fissured clay, weak rock, coarse gravel).
Plate load test (ASTM D1194) — a rigid plate loaded at or near the proposed founding level to measure a direct load-settlement response, used to derive a subgrade reaction modulus or verify a design bearing pressure at full scale (subject to the well-known limitation that its influence depth is small relative to the plate size).
Dynamic/static cone penetrometer (DCP) — a lightweight, low-cost penetration index test widely used for pavement subgrade/shallow characterization.
Permeability/groundwater testing (falling/rising head tests, slug tests, pumping tests) — in-situ hydraulic conductivity, essential for dewatering, seepage and consolidation-rate assessment.
Geophysical methods (seismic refraction/MASW, electrical resistivity) — non-intrusive, spatially continuous coverage between and beyond borehole locations, used to interpolate stratigraphy or bedrock depth economically over a large footprint.
Sample recovery (disturbed via split-spoon, or relatively undisturbed via thin-wall Shelby tube, ASTM D1587/D6519) runs alongside these in-situ tests to supply material for laboratory index and strength testing, so the field program is understood as combining continuous/point in-situ measurement with discrete physical sampling, not one or the other alone.
(b) Field and in-situ testing components and methods for rocks
Rock characterization in the field centres on core drilling and its logging, supplemented by in-situ tests that address properties (mass strength, deformability, permeability, in-situ stress) that a small intact core specimen cannot represent on its own:
Diamond core drilling and logging — continuous rock core (typically NQ/HQ size) recovered for direct examination; core recovery, RQD (Rock Quality Designation, the percentage of core in pieces ≥100 mm), fracture frequency/spacing, and joint condition are logged and feed directly into rock mass classification systems (RMR, Q-system, GSI).
Point load index test (ASTM D5731) — a portable field test on core or irregular lumps giving an index strength (Is(50)) correlated to unconfined compressive strength, allowing rapid strength screening along the whole core run rather than only at the few points where lab UCS specimens can be prepared.
Packer (Lugeon) permeability test (ASTM D4630) — an isolated borehole interval pressurized between inflatable packers; the water take rate (in Lugeons) characterizes rock mass permeability, dominated by joint/fracture connectivity rather than the intact rock matrix, and is a standard input for grouting/seepage assessment (dams, tunnels).
Borehole geophysical logging (acoustic/optical televiewer, natural gamma, caliper) — images the borehole wall to log fracture orientation and frequency directly (avoiding core-rotation ambiguity), and characterizes rock quality/lithology continuously between core runs.
In-situ stress measurement (overcoring, e.g. CSIRO/USBM cells; or hydraulic fracturing) — determines the pre-existing rock stress magnitude and orientation, essential for underground excavation and tunnel design where stress-induced failure (spalling, rockburst) governs.
Plate load / flat-jack testing — in-situ deformability of the rock mass (as opposed to intact-specimen modulus), accounting for the softening effect of joints that a small lab specimen does not capture.
Discontinuity (joint) survey — scanline or window mapping of joint orientation, spacing, persistence, roughness and infill, either on exposed outcrop or via oriented core, feeding kinematic stability analysis (wedge/planar/toppling) for slopes and underground openings.
Because rock mass behaviour is governed as much by its discontinuities as by the intact material, the field program deliberately targets both scales — intact-rock index strength (point load) and mass-scale properties (RQD, permeability, deformability, stress, joint geometry) — rather than relying on core strength testing alone.
Item
Answer
2(a)
Borehole/test-pit network with SPT, CPT/CPTu, field vane, pressuremeter, plate load, DCP, permeability tests and geophysics, plus disturbed/undisturbed sampling for lab testing
