Performance of piles and limit state design

Question

Explain the performance of piles and limit state design. Also explains its three Geo technical categories?

Answer 1

Performance of piles and limit state design:

Traditionally, design resistance of foundations has been evaluated on an allowable stress basis that piles were designed with ultimate axial capacity between 2 and 3 times than working load. However structural design is now using a limit state design (LSD) bases whereby partial factors are applied to various elements of the design according to the reliability with which the parameters are known or can be calculated. The base of all Euro codes including those which are used in the designing of the foundation is LSD approach. It is considered that this approach can be economical for the pilling process.

Geo constructions can be divided in to three categories on the basis of investigation, design and implementation using Euro code.

Geotechnical category, GC 1:

All the small and simple structures come under this category. Those constructions in which it is somewhat becomes difficult to ensure, with the basis of experience and also by using geotechnical designs, that the fundamental requirements will be satisfied use this code. In this the risk of life and property is also negligible.

Geotechnical Category 1 procedures will be only be sufficient in ground conditions which are known from comparable experience to be sufficiently straight-forward that routine methods may be used for foundation design and construction. Qualitative geotechnical investigations

Geotechnical Category, GC 2:

Those foundations and structures in which there is minimum risk, or any kind of abnormal ground and loading conditions fall under this category. In order to ensure the satisfaction of the fundamental rights, requirement of quantitative geotechnical data and analysis needs to done in this category. Also for laboratory and fields testing, designing and execution the routine methods can be used. A qualified engineer having sufficient knowledge in this field can be involved in carrying out the whole work. Some of the structures which come under this category are:

• Spread foundations
• Piled foundations
• Raft foundations
• Excavations
• Embankments and earthworks
• Bridge piers and abutments
• Ground anchors and some other tie-back systems
• Walls and some other structures which are formed to retain the support for soil or water
• tunnels in hard, non-fractured rock and not subjected to special water tightness or other requirement

Geotechnical Category, GC 3:

There are some conditions which are favorable and some which are unfavorable for the construction in this category.