E.3 Test Method 2

E.3.1 Investigation Test - Loading Procedure

The anchor should be loaded to failure (R_a) or to a proof load (P_p) which should be limited to 0,80 P_tk or 0,95 P_t0,1k whichever is the lower.

The anchor should be loaded to the maximum test load in a minimum of six cycles, see Figure E2.

The load cycles and periods of observation are given in Tables E.1 and E.2.

If the cumulative load loss, at the proposed lock-off load, after 7 time periods (3 days) does not exceed the allowable and the load loss per time interval is not increasing then the test may terminate and the load cycling of the anchor be continued to P_p or, to failure. Should the allowable loss of load be exceeded and/or the load loss per time interval be increasing the observation period may be extended to the eighth period (10 days) or longer until stability is achieved. If stability is not achieved the applied load is too high for a serviceability condition but the test should be continued to determine the failure load.

E.3.2 Suitability Test - Loading Procedure

The proof load required for the working anchor should be:

P_p ≥ 1,25P₀ or P_p ≥ R_d

whichever is greater.

The load in the tendon should not exceed 0,95 P_t0,1k.

The anchor may be loaded to the maximum test load in two load cycles of approximately 10 %P_P – 25 %P_P – 50 %P_p – 75 %P_P – 100 %P_p – 75 %P_p – 50 %P_p – 10 %P_p and then to the lock-off load P₀.

Periods of observation for are given in Table E.2.

The load loss (k_l) at the lock-off load P₀ should not exceed the limits specified in Table E.2 over seven time periods (3 days).

E.3.3 Acceptance Test - Loading Procedure

The anchor should be loaded to proof load (P_p) by a minimum of three equal increments. The anchor should then be unloaded to a datum load P_a and again reloaded to lock-off load (P₀). The proof load should be a minimum of 1,25 P₀ but should be no greater than 0,9 P_t0,1k.

NOTE The load-extension curves may provide additional information about the ground and behaviour of the anchor components in the ground.

Behaviour under lock-off load should be observed over 3 time periods (50 min) and the load loss should not exceed the cumulative figure shown in Table E.2. If the loss is greater than the limit the test should be extended until stability is achieved and an acceptable load loss is measured.

If the monitoring system accuracy does not comply with 9.2 in terms of load loss tests but does comply with clause 9.2 using lift-off tests then acceptance may be established by lift-off after 6 time periods (1 day) showing cumulative load loss k_l less than 6 %.

The following limit should apply at the lock-off load:

a) the load loss k_l should not exceed 3 % P₀ in 50 min; or

b) the load loss k_l should not exceed 6 % P₀ in 24 h.

E.3.4 Measurement of Load Loss Characteristics

At lock-off load the anchor head displacement relative to the structure should be held constant and the load should be monitored. The anchor head should be fixed against a load cell or an inactive jack and the load loss should be monitored at the end of each time interval for up to ten days to determine k_l, the percentage load loss.

The load loss limit is the maximum cumulative load loss recommended at the specified load level at the end of a number of time periods.

Measurement of load loss as required in E.3.4 should be made at times shown in Table E.2. The minimum duration of observation is as follows:

• investigation Test - 7 periods (3 days);
• suitability Test - 7 periods (3 days);
• acceptance Test - 3 periods (50 min).

Load loss characteristics are representative of true load loss as applied to the structure via the anchor head. If used to interpret actual creep displacement of the fixed anchor then allowance must be made for the influence of the anchor free length, i.e. the longer the free length the smaller the load loss effect from the same absolute creep displacement of the fixed anchor.

Key

• 1 Applied load in %P_P
• 2 Datum load P_a
• 3 Anchor displacement