geological investigation & land slides

 Preliminary Geological investigation

To find out geological   conditions at foundation before design a structure if it is neglect then increase the cost of project.

In many cases in which geological condition has given rise to all sorts of difficulties and has lead to delay and increase in costs of project

At  warasgav dam near pune by 13m raise the foundation reducing cost of dam by crore of rupees because of proper geol investigation.

The aim of preliminary Geological investigation to find out nature and structure of rock at site to obtain correct information                                                                                                                               

a)      Surface Survey

1)      Literature survey ,General geological survey- In this work is to establish general geological structure.

2)       To establish the Regional geological  structures.

3)      Local geological survey

4 )  Geological mapping, drawing  section

 5)  Type a rocks,  physical properties  ,Engg properties

 6)  Structure features like, strike, dip joint Fracture , fault bedding planes dykes fold .

       It is tendency to neglect surface work however surface and subsurface exploration          are complimentary to each other, neither alone can give all the information with necessary accuracy . Location and  depth of drilling on the basis of surface work. Therefore proper procedure is to carried out surface work first and then undertaken drilling.

b)     Subsurface survey

Two methods

i)                    Excavation

Excavation will be more reliable data but practical ,  economical  limitation up to depth  of 10m.  Excavation by  Test pits, trenches, adits , drifts ,pilot cuts, shafts etc. they provide very accurate information as rocks and their structure.

2) Core Drilling

It is process of drilling by which specimens of rock from drill core depths be brought to the surface  intact in  form of  solid cylinder. Information from deeper level is obtained more conveniently  by drilling.

Core drilling – Two methods.

a)      Diamond drilling    b) calyx or shot drilling

Diamond  drilling more efficient process than shot drilling .diamond drilling cannot be used for more  than 100mm diameter. For  lifting  of core core barrel are used . Single double triple also.

b)      Bit- cutting tool-metal alloy (beryllium copper studded with diamond inside and outside and at bottom. Bit is rotated by rotary drill machine.  The core can be periodically raised to the ground for examination.