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# For Peck’s pressure envelope for braced excavation, should total weight or effective weight be used in rectangular and trapezoidal envelope?

The use of active and at-rest theory is not applicable in braced excavation. In essence, upper struts tend to be more heavily loaded while lower struts appear to be less loaded when compared with active pressure theory.

Peck then measured the bracing loads which were converted back to soil pressures. For example, the pressure envelope for non-cohesive soils is 0.65rHKa
where
r=soil density
H=height of excavation
Ka=active pressure coefficient

Some engineers consider r as total soil weight without applying any water pressure. However, Peck has said “the earth pressures are essentially effective active pressures multiplied by a factor and redistributed as a
rectangle or a trapezoid.” Hence, effective weight of soils should be used for r with water pressures added separately.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

### Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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## One comment on "For Peck’s pressure envelope for braced excavation, should total weight or effective weight be used in rectangular and trapezoidal envelope?"

Parthasarathy.p says:

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