1) The lack of access is a compensation event under clause 60.1(2) and can should be assessed on its own merits. If you can mitigate any costs then you should, but equally you should not be disadvantaged for something that is not your risk under the contract - so if you have/will incur costs as a result of this delayed access then this is what this compensation event will pick up.
2) If the Employer is changing the quantity of earthworks to be moved then this will be a a compensation event - and yes this would have the capacity to reduce the total of the Prices. 63.2 says Prices cant be changed except as stated in the contract - and 63.10 is then one of these places. You would assess the cost of the reduced quantity - and if you can prove that somehow the reduced quantity will increase your cost in moving the remaining quantity then all this can be taken into account when you assess this second compensation event.
2) If the Employer is changing the quantity of earthworks to be moved then this will be a a compensation event - and yes this would have the capacity to reduce the total of the Prices. 63.2 says Prices cant be changed except as stated in the contract - and 63.10 is then one of these places. You would assess the cost of the reduced quantity - and if you can prove that somehow the reduced quantity will increase your cost in moving the remaining quantity then all this can be taken into account when you assess this second compensation event.