What is meant by "LD clause"?

The loss or Clim for Loss caused due to delay / failure in Competion of the work as per agreed Contract Conditions imposed by the Employer/ Client can be defined as LD ( Liquidated Damages)

LD is already explained. It is a clause that take care of to avoid time overrun of projects and is normally limited to a maximum of5% of contract value.

 

LD Clause meant damages of liquidated.
In projects damages that are sufficiently uncertain may be referred to as unliquidated damages

LD clause essentially refers to "liquidity damage clause" The clause title itself indicates that it's related to liquidity i.e.
Revenues.
This is a essential part of any contract because contract is an agreement between the parties with consideration and obligations at either or both end.
Now if these consideration or obligation is not met then the party who has defaulted on obligations shall be liable to pay damage to the other parties.

 clause is included in a Contract to protect the Company against genuine losses due to the Contractor's inability to meet the delivery schedules.
Under this clause, the Contractor shall pay the Company a sum of money as liquidated damages as per the percentage specified under the clause.

LD means liquidated damage and this clause is refferred to the contract as per the agreement.
If any party  failed to meet the contractual oblgations it will pay the amount(loss) to the other party. 

LD clause is a pre-agreed contractual clause which entitles one of the contracting/agreement parties to retain/claim/deduct a pre-determined amount of money as compensation related to a failure to comply with condition and terms of contract/agreement.

Concept and mechanism of liquidated damages is widely recognized in common law countries, but in Middle-East area where is a civil law system, claimant for liquidated damages can face serious difficulties because under civil law rules enforceability of the LD clause is not certain. It depends a lot on the wording of the contract/agreement and the governing law of the contract/agreement, but in the court of law at civil law system a LD clause will be seen as ancillary contractual obligation related to the primary/main obligation. If the primary/main obligation is terminated, so the LD clause will be.

Going further with your secondary question, there are plenty of project management and legal strategies to overcome LD clauses to be enforceable.  In few words, the defendant shall prove: is not liable for the breach of contract, like there was a concurrent action from the other contracting/agreement party which prevented the defendant to fulfill his obligation, that claimant has not sustained any damages as a result of the breach, that there is no legal connection between defendant fault and claimant damage.

Keep in mind that contract/agreement wording is playing a high role and also project daily correspondence can and shall be used as a proof in the court of law.

Usually before the moment when a contracting party invokes or put in effect a LD clause, there was daily project correspondence where the future claimant alleged the breach of contract and damages. Never confirm such allegations in your correspondence and try to comply with the contractual obligation before the case will reach to court of law.

When a contractor fail to hand over the works or part of the works to the owner to use the owner will be intitled of any loss and damages he suffered from this failuir and the contractor will pay this loss or damages.