Thank you ITACET Foundation

My thanks are due to ITACET Foundation and International Tunnelling Association for finding me suitable for the ITACET scholarship and supporting me to pursue 2nd Level Specializing Masters in Tunnelling and Tunnel Boring Machines for the session Jan '14 to Jan '15 in Politecnico di Torino. In the spirit of ITACET foundation's scholarship awarding criteria, I have decided to blog my experiences during my course work in Turin so as to create higher benefit/investment ratio for the ITACET foundation.

Following blogs will document my experiences, learning and details of the course. I hope this information will be useful for all the future aspiring students of this course and as well as the practicing Geotech/Tunnelling engineers.

For those who have landed here to seek details about the ITACET Scholarship, details can be found here.

Book Review: Soil Improvement - PVD Technique

Book Review: Soil Improvement - Prefabricated Vertical Drain Techniques by M.W.Bo, J.Chu, B.K. Low and Choa. V, Thomson Publishers 2003.

I had become Dr. B.K.Low's fan immediately after reading his papers on Geotechnical reliability analysis and probabilistic approach to geotechnical problems. I liked the way he solves a complicated problem with an easy-to-understand numerical model in the form of spreadsheet. So when I came across this book, I was really curious to go through it. 

This handy book, entitled Soil Improvement, gives the reader an account of case studies of projects where PVDs are installed for ground improvement, along with the theoretical background behind it. Authors present a spreadsheet template for computation of degree of consolidation using the implicit finite difference solution. The computed settlements are then compared with field measurements from case studies. Case studies presented are Changi Airport, Changi East Reclamation Project, Chep Lap Kok Airport, Tianjin East Pier Project & Oil Storage Station Project.

What is particularly interesting in this book is that it discusses, in-detail practical aspects of installation, quality control, field instrumentation and assessment procedures. In absence of any International code for implementing Ground improvement using PVDs, this book proves to be a treasure of knowledge for practicing geotechnical engineers. Every engineering firm involved in PVD design/installation should have at least one copy.

Preliminary Design of Earth Retaining Walls

The enclosed spreadsheet is set for a quick design check of Mechanically Stabilized Earth (MSE) wall using the method given in US Federal Highway Authority (FHWA) manual FHWA-NHI-00-043. The sheet summarises the procedure outlined in the foresaid manual and works for simple vertical MSE wall without any sloping surcharge. The sheet performs, sliding check, eccentricity check, bearing check, tensile resistance (in geotextiles) check for static and dynamic condition. Mononobe Okabe formulation is used for dynamic earth pressure.

The sheet has many limitations. It does not check for global stability, etc

Reference for FHWA manual

Download mse_fhwa_v0 spreadsheet here.

SMEC's Quarterly Magazine - Geotech & Tunnelling

SME SMEC Geotech & Tunnels

This quarter, SMEC has featured Geotech and Tunneling group highlighting some of the key projects delivered by SMEC. It also features a Q&A with SMEC's Geotech Chief Technical Principal, Dr. Jeff Hsi.

Click here to view: Flash Version | PDF Version

Brom's Method for Short Pile

Following the the Brinch Hansen's Method, I share similar spreadsheet using Brom's method. Major disadvantage of this method is, it can not handle c-phi soil.

This spreadsheet is set to calculate lateral pile capacity using Brom's method for short piles. The procedure for calculation is straight forward and is explained in detailed manner in "Pile foundations in engineering practice" book by Shamsher Prakash. Brom's method is also available for long pile and will share it in a later post.

This method is applicable to either purely cohesive soils or purely cohesionless soils and hence soil properties to be entered accordingly.

Download broms_shortpile
[Update: The link was broken, it has been updated]

Brinch Hansen - Lateral Resistance of Soils - Free Head

The Brinch Hansen spreadsheet is set up to calculate lateral resistance of short rigid piles, for free head condition. The method is based on earth pressure thory for c-phi soils. It consists of determining the centre of rotation by taking moment of all forces about the point of load application and equating it to zero.

The spreadsheet uses Brinch Hansen's coefficients Kq and Kc to calculate the capacity. For intermediate values of Phi and z/B values, the spreadsheet does a two dimensional interpolation to calculate Kq and Kc values.

"Notes" worksheet covers the assumptions and limitations of the spreadsheet. The spreadsheet also calculates the maximum deflection of pile under maximum lateral load. This sheet can be used as a quick check for lateral resistance and ofcourse, almost in all cases pile design is governed by pile deflection.

The spreadsheet uses MS Excel Add-In "Solver" to calculate the location of virtual point of rotation (instead of using trial and error method).s

Click here to Download

[Update: The link was broken, I updated it]

Bearing Capacity (Single Layer)

The SBC-Single Layered spreadsheet is set up to calculate Bearing pressure of single layered soil. Although this is an idealized case and is seldom a practical soil stratification, this sheet can be used to compare bearing capacity values computed by following methods:

• Mayerhof (1963)
• Terzaghi (1943)
  
• Hansen (1970)
• Vesic (1975)
• Mayerhof (1956, 1974) - Correlated from SPT
• Schmertmann (1978) - Correlated from CPT

Download here.

SBC from SPT

Here is a small User Defined Function (UDF) to quicly calculate safe bearing capacity from SPT Value. 

Download SPTSBC UDF

Formula used: Bowles Book (5th Edition) - Section 4-10

UDFs have no tooltips but there is a workaround to display tooltip-like hints while using the formula.

• First import the sbtsbc.bas (In VBA window, CTRL+M to import .bas file)
  
• Start typing the UDF: =sbtsbc(then press CTRL+SHIFT+A)  and your function parameter will be displayed

Parameters for input are:

Er - Energy efficiency of the SPT Hammer (55% or 70%)

B - Width of the footing (m)

N - Fild SPT N value (blows per 300mm)

D - Depth of footing (m)