__SLOPE STABILITY ANALYSIS OF EARTHDAM:__

Earth Dams are usually constructed using the locally
available soil. The soil properties used for construction of earth dam are
important in design of slopes. Civil engineers involved in design and
construction of earth dams know the difficulty of design of slopes for
stability of earth dams. I worked as Assistant Engineer in Design Circle in 1999 in Tamilnadu Public
Works Department. At that time I saw many engineers involved in design of earth
dams working on A0-size graph sheets drawing the cross section and draw a slip
circle. Then they will create many vertical slices of Earth dam portion and
calculate the area of slices below MWL/FRL/DDL of SPZ/IPZ and take the moments
of weight of slices and resisting forces and put them in tabular form in the
graph sheet itself to find the factor of safety as per IS Code(Indian Standard
code). The area is calculated by counting the number of squares manually from
the graph sheet. The notations above are

MWL- Maximum water level

FRL - Full Reservoir
Level

DDL – Draw Down Level

SPZ - Semi Permeable
Zone( Outer Zone of earth dam)

IPZ - ImPermeable
Zone(Inner Zone of earth dam)

spzblk- Bulk Density of Semi Pervious Zone soil

ipzblk- Bulk Density of Im Pervious Zone soil

spzsub- Submerged Density of Semipervious zone

ipzsub- Submerged Density of Impervious zone

spzsat- Saturated Density of Semipervious zone

ipzsat- Saturated Density of Impervious zone

usually 6 trials for upstream and 6 trials for downstream
are done for arriving at the minimum factor of safety against failure. Roughly
one month will be taken to do the 12 no of trials and factor of safety for the
worst condition is found out. After seeing the laborious work involved in that
process, I develop a program in AutoLisp to work in Autocad with one input
table in Visual Basic for AutoCAD. This program made the design of slope
stability in one minute in Autocad.

You can download that STABILITY.RAR file from the following
link.

http://www.nirt.in/software/stability.rar
The manual for this software is avalable in the following link

http://archive.org/details/SLOPESTABILITYOFEARTHDAM