suppose I am using very good earths ( let 2 numbers) at my home to avoid the risk of failure of neutral of electric company. Then should I common my earth with neutral? But if this is done the in case of failure of neutral, other consumers may load my earth, leading to over heating. So can I rely completely on my good quality earths and break the neutral of electricity company?
How you should connect your earth and neutral will be dictated by your local wiring codes. Your supplier may be unhappy if you don't follow them. The same goes for anybody you manage to electrocute.
That said, unless you have gone to a lot of trouble to achieve a very low earth impedance, the chances are that the worry about other people's supplies through your earth is less of a problem than you think it is.
A simple earth rod may only achieve impedances in the tens to hundreds of ohms. If that's the case, then even a dead short between supply and earth will only allow a few ones or tens of amps to flow. Using appropriate gauge wire between your main earth terminal and the earth rod will keep that safe. This limit will apply no matter how many other consumers' supplies are attempting to use your earth connection.
Singe wire earth return supplies - ones with no neutral connection - only really work at high voltages. At normal domestic voltages, the voltage lost at the earth rods soon becomes excessive. You don't say what your supply is, so let's assume 30A at 230V. Let's assume that you have somehow managed to get down to 1 ohm on your earth connection (perhaps the foundations of your building are reinforced conductive concrete), and the suppliers have done the same at their transformer. That's 2 ohms total. If you now try to pass 30 amps through this, you'll drop 60 volts just in the earth connections, and your supply will be down to 170 volts.