geological investigation & land slides(1)

Observations and precautions During Drilling-

                                                                                                         To drilling data not misinterpreted and are not lost certain precautions to be taken

                                                                                                        Drilling data cannot be interpreted without knowledge of local geology

                                                                                                      Location, depth, spacing of drill   hole  depend on local , surface survey.

                                                                                                      Chas Kaman dam in pune district  depth of drill hole not decided and below which jointed compact basalt found.

                                                                                                           As soon as core removed from core barrel pieces must numbered  serially  their depth  painted on them, kept in serially order, length of all core must recorded.

                                                                                                      Core must be kept in standard core box .

                                                                                                      Core box should be mark project name, chainage ,drill hole no, RL of drill hole ,. location .

                                                                                                            Ease or difficulty of drilling and speed of drilling of different depth must be carefully noted.

                                                                                                            The returning drill water must also kept constant under observation and all changes in its nature noted (turbidity, clear)

If water is turbidity then it collect and send for laboratory for testing.

                                                                                                          Turbidity of returning drill water indicate that drill in passing through material which will not give core.

                                                                                                            It is also necessary record it any drill water loss it indicate leaky pervious zone

                                                                                                        Obtaining  core by drilling is first stage in the investigation second stage is keeping the core in proper order and carefully recorded in log book third stages  is interpretation carefully by geologist or engineer.

                                                                                                  Preservation of core rock that disintegrate on Exposure to atmosphere

                                                                                                             Rock such as shale chlorophaeite basalt , red tachylytic basalt,  and volcanic breccias with lava  matrix  of these type disintegrate on exposed to atmosphere. But as they are sound when   occurring below the cover of rock i.e. confined condition. They therefore give a good core which however when left in the core box for some time the core disintegrate into loose material is called Red Bole. This create wrong impression that it is necessary to preserve the core in sound condition for this to prevent its contact with atmosphere, as soon as core of such rock type obtained it should be immediately cover with wax. this will prevent contact with atmosphere and preserve  it as sound rock.