Quality control and assurance of Rocks Grading for Coastal Protection Works

The qualities of rock materials for the hydraulic construction to be generally comply with the requirements of CIRIA Rock manual. All the tests except grading and mass distributions are straight forward and laboratory related testing. Following are the step by step approach to achieve required grading of rocks carried out at site.

Identify the suitable grading curves based on quarry yield OR adopt the ideal grading curve complying CIRIA manual. Extract percentage of different sub-classes of materials form the adopted grading curve.

Prepare a quality control plan , Use number of stones in each sub classes OR use % of each sub classes more precisely.( 1 to 2 tone rocks considered for illustration purpose)

Stack 3000-4000 tonnes of armour rocks by strictly following the above quality control plan. Sample material for testing from the stack consists of minimum 90 pieces and weigh individually. Sampling procedure shall be as per CIRIA guidelines.

Plot the actual test values besides the theoretical CIRIA grading curve used for quality control in the beginning and compare the differences

Finally adjust the CIRIA grading curve (by changing NLL between 5 to 10% and NUL 70-97%) and compare the differences with the test curve. If the allowable tolerance in CIRIA is not enough to match with the test curve, materials in the stack to be further re-sized/adjusted.