Point Load Lump Strength Index(IS 8764:1998 — Irregular Lump Method)
Point load strength index on irregular rock lumps per IS 8764 — strength estimation where no drilled core exists, from quarry blocks, boulders and excavated fragments.
What is the Point Load Lump Strength Index Test?
Not every project has drilled core to test. Quarry acceptance, boulder foundations, rubble sources and excavated rock often present only irregular lumps — and IS 8764:1998 provides the irregular-lump procedure exactly for this: lumps within the standard size and shape ratios are loaded between conical platens, and the index is size-corrected to Is(50) just as for cores.
Global Lab screens lumps for the standard dimension ratios, tests the prescribed minimum number per sample (results on irregular lumps scatter more than cores, so the standard requires a larger population and median-based reporting), and reports Is(50) with estimated UCS correlation — giving usable strength numbers from material every other test would reject.
How the Point Load Lump Strength Index is Conducted
- 1
Lump Screening
Lumps are measured and screened for the IS 8764 size and shape ratio requirements; the standard minimum population is assembled. - 2
Platen Loading
Each lump is loaded between conical platens through its smallest dimension until failure; load and dimensions are recorded. - 3
Validity Screening
Failure surfaces are checked against the standard criteria; invalid breaks are rejected and replaced. - 4
Size Correction & Statistics
Indices are corrected to Is(50) and the population median computed per the irregular-lump procedure. - 5
Reporting
Median Is(50), estimated UCS correlation and individual results are issued via Autovity QLMS.
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| IS 8764:1998 | Method for Determination of Point Load Strength Index of Rocks (Reaffirmed) | Irregular Lump Method | Indian Standard |
| ISRM SM | ISRM Suggested Method for Determining Point Load Strength | Supplementary Practice | International |