530 Ground investigations, contracts and pile testing
intersect (Figure 11.14b). The inverse slope of the line gives the ultimate load in each case.
Chin describes how a broken pile is detected by a curved plot (Figure 11.14c).
11.4.3 Uplift tests
Uplift or tension tests on piles can be made at a continuous rate of uplift (CRU), or an
incremental loading basis (ML). Where uplift loads are intermittent or cyclic in character,
as in wave loading on a marine structure, it is good practice to adopt repetitive loading on
Figure 11.13Typical load/settlement curves for compressive load tests (a) Friction pile in
soft-firm clay or loose sand (b) Friction pile in stiff clay (c) Pile bearing on weak
porous rock (d) Pile lifted off seating on hard rock due to soil heave and pushed
down by test load to new bearing on rock (e) Gap in pile shaft closed up by test
load (f) Weak concrete in pile shaft sheared completely through by test load.Load LoadLoadBreakdown
of rock structure
below pile toeGeneral shear
failure of rock massLoadLoadNormal
curve Normal
curveLoadSettlement SettlementSettlement SettlementSettlement Settlement(a) (b)(c) (d)(e) (f)