Explain pressure balance method and compressed air method, Civil Engineering

Assignment Help:

Pressure balance method vs. compressed air method in pipe jacking

Pressure balance method generally requires the use of mechanically operated tunnel-boring machine at its cutting head in pipe jacking. Slurry or steel bulkhead is usually adopted to provide the balance of earth pressure and groundwater in front of boring machine. Slurry used in balancing earth pressure and ground water pressure is constantly supplied to the face of cutting wheel through slurry pipes. Excavated materials drop into a crusher for reduction in material size. Afterwards the debris and spoils would enter the spoil removal chamber near the invert of shield and would be transported to ground level via slurry discharge pipes. This method of construction is generally adopted in gravel andsand.  Though, it suffers from the disadvantage that it is quite tough to remove large rock boulders at the time of advancement of the machine. It is quite time-consuming for workers to go inside the comparatively small airlock chamber and remove large bounders by hand tools. 

The other kind of pressure balance technique is known as earth pressure balance method that is commonly used in clay and silty soils. It makes use of principle of sustaining the pressure of excavation chamber the same as the pressure in ground. Excavated materials are transported through screw conveyor to jacking pit. 

Compressed air method in pipe jacking is generally adopted in locations where groundwater table is high. An air pressure of less than 1 bar is normally sustained to provide the face support and to avoid water ingress. Depressurization and Pressurization has to be conducted for workers leaving and entering the pipe-jacked tunnels. In the case of porous ground, certain ground treatment such as grouting has to be carried out. Removal of boulders by this method is convenient however it hasthe demerits of slow progress and significant noise problem produced by generators and compressors.


Related Discussions:- Explain pressure balance method and compressed air method

REQUIREMENT OF GOOD BUILDING STONE, HOW TO MAKE A GOOD BUILDING .? TELL ABO...

HOW TO MAKE A GOOD BUILDING .? TELL ABOUT SOME TIPS OF REQUIREMENT OF GOOD BUILDING STONE? AND SAY ABOUT CEMENT?

Write a short note on economic span of a bridge, Q. Write a short note on E...

Q. Write a short note on Economic Span of a Bridge? The span for which the total cost of bridge will be minimum is known as the economic span. The ratio of Cost of super str

Convert the azimuth reading of 273.34 to a land bearing, Convert the azimut...

Convert the azimuth reading of 273.34º to a land bearing:  Solution: Convert 273.34º to degrees minutes and seconds = 273º 20' 24" Next, convert the angle to orient to IV

Concrete pavement - thickness, Concrete Pavement: Thickness T...

Concrete Pavement: Thickness The thickness of concrete pavements is determined from the stresses induced due to loads and temperature. The thickness adopted is genera

Statics - SFD & BMD Calculations, Could someone please help me with the cal...

Could someone please help me with the calculations of determining the sfd & bmd for cantilevers with udl''s, lvl''s and point loads? Also could I please have the same for ssb with

One-way pre stressing vs two-way pre stressing, Q. One-way pre stressing vs...

Q. One-way pre stressing vs two-way pre stressing? At the time of pre-stressing operation at one end, frictional losses will take place and the prestressing force decreases alo

Define sulphate attack - underwater inspection of bridge, Define Sulphate A...

Define Sulphate Attack - underwater inspection of bridge? Cement contains a proportion of tricalcium aluminates, which takes part in the hydration process. These can react with

Rcc flooting, Explain the simple square footing, simple squral footing an...

Explain the simple square footing, simple squral footing and slop footing with the help of drawing

Som, derive the expression for stress in arbitrary plane in a body subjecte...

derive the expression for stress in arbitrary plane in a body subjected to bi axial stress condition

Flow, what is maximum flood level

what is maximum flood level

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd