- Construction additives
UNIPRO EARTH STABILIZATION VISCOMUD
Unipro Viscomud is an anionic synthetic polymer characterized by a medium anionic charge and high molecular weight. It is mainly used for th preparation of stabilizing and lubricating mud in drilling , civil engineering , pipe jacking and micro tunneling application. Unipro Viscomud drilling fluid is easy to prepare and easy to dispose after usage, in fact Unipro Viscomud is fully degradable polymer , non- toxic and safe for environment and users. Its main characteristics are its stabilizing and lubricating properties and the possibility to be recycled many times also with the presence into the soil and into the water f bivalent ions and salts.
POLYMER MIX DESIGN
When the soil contains sand or gravel layers. It is possible to variable percentage of cross-linked polymer in the slurry. This is recommended by most polymer manufacturers as an adjunct for the initial “sealing” of the borehole wall in the preamble layer.
The initial mix design has been formulated for use in fine sand to yield the following properties.
|Marsh Viscosity||> 60sec|
To achieve this, the drilling fluid mix design shall initially be as follows:-
|1 kg||Unipro viscomud (powder)|
|~0.5 kg||NaOH (varies to suit ph)|
After commencement of drilling , the marsch viscosity may be increased above 60 sec to control or reduce the fluid loss and to maintain borehole stability.
Polymer mixing can be carried out without special mixing equipment by dispersing the polymer powder directly into moving water and moderately agitating the mixture. In emergency situation the polymer can be mixed in the borehole by sprinkling the powder into the recharge outlet of the fluid(or water) into the borehole.
However,in order to optimum yield from the polymer fluid, avoid to mix the powder polymer directly on the borehole.
Mix Station Preperation
Prior to mixing , equipment and materials shall be properly prepared at a mixing station.
A water tank of minimum 20 Cum capacity shall be kept at a mixing station for the purpose of having adequate quantities of mixing water.
A high speed recirculation mixer shall be used for cross linked polymer preparation.
A storage tank for the cross linked polymer premix shall also be kept at the mixing station.
Shortage tank with a combined capacity equal to the pile volume shall complete the layout of the mixing station.
All slurry storage tank shall be interconnected by a manifold system to enable the combined storage facility to be activated at any time. Each storage tank shall also be fitted with a 100mm , submersible pump to enable mix circulation within and between the tanks.
Mixing of the drilling shall be carried out in steps as follows :-
- Adjust the ph of the mixing water in the water tank by the addition of NaOH.
- Premix Unipro Viscomudpowder polymer with the mixing water (ph adjusted) at the required dosage.
- If required from the soil condition, premix the cross linked polymer with the mixing water (ph adjusted) . To minimize storage requirement, the premix can be mixed at a higher concentration and diluted to the required concentration during step 5 mixing. The cross linked polymer solution shall be discharged to cross linked polymer premix tank.
- Allow the cross linked polymer premix to hydrate.
- Using the recirculation mixer, mix the Unipro Viscomudpoymer solution, with the required quantity of Unipro Viscomudas necessary to achieve the required viscosity.
- Discharge to storage tanks.
The sequence of the bored pile construction will enable alternation between mixing of cross linked polymer premix and polymer drilling fluid.
The slurry is deleivered to the borehole via pumps and pipelines in the same manner as conventional slurries. The slurry fluid is added to the borehole before the excavation proceeds the past the toe of the temporary or permanent casing. The level of the drilling fluid is then maintained at about ground level at all the times except as following.
- During drilling the fluid level will be allowed to fluctuate by 2 mtr to the extent that when the driving tool is out of the borehole the fluid level is at or above ground level and when the drilling tool is out of the borehole(to discharge soil) the drilling fluid shall be more than 2 mtr below ground level.
- When the drilling tool is out of the borehole for protracted periods the fluid level shall be regularly “topped up” to be maintained at the ground level but at no time shall it be allowed to drop lower than 2 mtr.
- For piles and Dwalls constructed in the river the drilling fluid level shall be kept at or above water level at all times.