Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Terzaghi, Theoretical Soil Mechanics, Article 70 question

Terzaghi, Theoretical Soil Mechanics, Article 70 question

Terzaghi, Theoretical Soil Mechanics, Article 70 question

I read Article 70 this morning, and an equation is presented for the pressure on a tunnel crown "at a great depth below the surface."

σv = [(γ*B1)/(Ktanф)] * [1-e^(-Ktanф(D1/B1))] + [γ*D2] * e^(-Ktanф(D1/B1))

In the paragraph below, Terzaghi writes "As soon as the height D1 becomes equal to about 20 per cent of the total depth D1+D2 the second term on the right-hand side of the preceeding equation becomes negligible."

This second term would be: [γ*D2] * e^(-Ktanф(D1/B1))

I'm not able to make the term become negligible at this 20% point. An example I am running right now has the following parameters:

Tunnel dimensions = 20'x20', therefore B1=21.55' based upon Terzaghi equation 70.1
total height above tunnel = 50', check with D1=1', 2', 3', etc. and the corresponding D2=49', 48', 47', etc.

At 20%, D1=10' & D2=40', I have the first term coming out to 1096.56 and the second term coming out to 3630.67, which is not negligible.

Am I missing something? Would appreciate any insight. Thanks in advance, and my apologies if this a silly math error I'm overlooking.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


eBook - 10 Reasons to Choose CATIA on the Cloud
To compete in today’s fast-paced and competitive market, smaller and newer firms need a powerful platform that will enable them to compete with bigger players, without the heavy investments needed in computer hardware, software and personnel. Download Now
White Paper - Smart Manufacturing for Electronics
This white paper describes a transformative approach to electronics manufacturing made possible by the addition of Mentor Graphics to the Siemens family. It describes a completely digitalized strategy that supports both printed circuit board (PCB) and mechanical design and manufacturing, uniting the entire product lifecycle – from idea and production to customers and back. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close