Laboratory Testing of Intact Rocks: Laboratory Testing of Intact Rocks Chapter 8 Lesson 12


Why Test Rock?: Why Test Rock?


Objectives: Lab Testing of Rock: Objectives: Lab Testing of Rock Recognize why and when to test intact rock Locate andamp; review standard lab testing procedures for indexing parameters of strength, stiffness, and durability. Select representative specimens for testing Recognize importance of QA/QC for mitigating common errors during lab testing of intact rock.


Laboratory Testing of Rocks: Laboratory Testing of Rocks Index testing of intact rock materials for identification andamp; classification. Strength and stiffness characteristics Degradation potential; Durability Used in assessing the overall Rock Mass Purposes of Construction: rockfill, cuts, slopes, foundations, tunnels


Rock Core Specimens: Rock Core Specimens FIG.8-0


Index Testing of Intact Rocks: Index Testing of Intact Rocks Unit weight, gR = Weight/Volume Ultrasonics Velocities Strength Point Load Index Swiss Hammer (Schmidt Hammer) Uniaxial Compressive Strength


Ultrasonics Testing: Ultrasonics Testing Determine compression (P-wave) and shear (S-wave) velocities of rock core Nondestructive measurements Fast and inexpensive Evaluation of small-strain elastic stiffness (strains andlt; 10-6 mm/mm) May be used to evaluate anisotropy FIG.8-7


Lab Ultrasonics Testing of Rocks: Lab Ultrasonics Testing of Rocks Vp Vs FIG.8-7


Uniaxial Compression Test: Uniaxial Compression Test GCTS Device ARA Setup at Tyndall AFB, Florida Page 8-4


Uniaxial Compression Test: Uniaxial Compression Test Fig.8-2


Uniaxial Compressive Strength: Uniaxial Compressive Strength Standard index property (qu = su = sc) Analogous tests in concrete and soil (unconfined compression test). ASTM 4543 procuredures. Planar ends on NQ size core (d = 47.6 mm) Length-to-width ratio: 2 andlt; H/d andlt; 2.5 Axial loading of cylindrical core specimen su = Max. Force/(pd2/4) Page 8-4


Swiss Hammer (Schmidt Hammer): Swiss Hammer (Schmidt Hammer)


Point Load Index: Point Load Index Quick evaluation for uniaxial strength (field or lab setup) ASTM D 5731 procedures Little sample preparation (cores, pieces) Measure force (P) to crunch intact rock specimen Point Load Index: Is = P/de2 where de = equivalent core diameter Fig.8-1


Point Load Index: Point Load Index GCTS Device Roctest Equipment Fig.8-1


Slide15:


Triaxial Compression (ASTM D 2664): Triaxial Compression (ASTM D 2664) Computerized Compression Frame Rock Triaxial Cell


Deformation Parameters of Intact Rocks: Deformation Parameters of Intact Rocks Elastic Modulus from Uniaxial and/or Triaxial Compression Fig. 8-6


Tensile Strength (T0) of Rocks: Tensile Strength (T0) of Rocks Direct tensile strength (ASTM D 2936) is difficult because of end effects. Generally replaced by indirect (Brazilian) split-tension test (ASTM D 3967). Length-to-diameter ratios: 2 andlt; H/d andlt; 2.5 Diametrical compression of rock core specimens across Page. 8-5


Brazilian Split-Tension Test on Rock: Brazilian Split-Tension Test on Rock Fig. 8-3


Direct Shear Testing of Rock Specimens(ASTM D 5607): Direct Shear Testing of Rock Specimens (ASTM D 5607) Fig. 8-4


Direct Shear Testing of Rock Specimens(ASTM D 5607): Direct Shear Testing of Rock Specimens (ASTM D 5607) Roctest Equipment, Montreal


Durability of Rock Materials: Durability of Rock Materials Longevity of the materials for use in construction (fill, backfill, rockfill) Will the rock deterioriate when exposed to the elements, time, freeze-thaw, wet-dry cycles, temperatures, chemicals. Tests used to accelerate exposure (slake durability, LA abrasion, freeze-thaw). Section 8.2.2.


Slake Durability Test of Rocks: Slake Durability Test of Rocks Evaluate shales and weak rocks that may degrade in service environment. Rock fragments of known weight placed in rotating drum apparatus (ASTM D 4644). Materials are circulated through wet andamp; dry cycles. Reweigh rock fragments to determine the Slake Durability Index (SDI). Fig. 8-5.


Slake Durability Test: Slake Durability Test Fig. 8-5


Common Sense Lab Testing of Rocks: Common Sense Lab Testing of Rocks Clear identification of samples andamp; specimens Avoid moisture loss Prevent physical damage to samples Consult field records during specimen selection Maintain equipment in good working order Photo documentation of test specimens Careful alignment of axes for measurement by dial gages, load cells, and displacement transducers Save remnant pieces of rock after testing. Table 8-2


Objectives: Lab Testing of Rock: Objectives: Lab Testing of Rock Recognize why and when to test intact rock Locate andamp; review standard lab testing procedures for indexing parameters of strength, stiffness, and durability. Select representative specimens for testing Recognize importance of QA/QC for mitigating common errors during lab testing of intact rock.