The consequences of excessive sand content, viscosity and specific gravity of the wall protection mu

The purpose of sediment content control in slurry is to control the amount of sediment.

In the construction of bored pile, the thickness of sediment can not exceed 5cm, if it exceeds 5cm, it will affect the end bearing effect of cast-in-place pile.

However, the sediment of the mud is a time-dependent quantity, and if it does not exceed 5cm within 2 hours from the final hole to the perfusion stage, it can be poured without affecting the construction quality.

The larger the sand content, the easier it is to sediment, so it is necessary to control the amount to be less than 1% during construction. However, if the one-sided pursuit of the sand content is less than 1%, it will affect the specific gravity of the mud, which involves the concept of viscosity and specific gravity.

The greater the specific gravity of the slurry, the safer the hole wall. If the specific gravity of the mud is less than 1, close to 1, the hole at this time is very dangerous, and the hole will collapse at any time, and the consequences are very serious.

The greater the viscosity and specific gravity to a certain extent, the more conducive to the safety of the hole wall, the stronger its suspension capacity and slag discharge capacity, but the larger the amount, the higher the construction cost and the higher the energy consumption. Because the mixing mud is diatomaceous earth or laterite, the mud is generally recycled several times, and if the formation with large sand content is encountered, the quality of the mud will be seriously polluted, and the final hole acceptance will also be affected.

Drilling is sometimes done with in-situ clay to mix the mud, which is also possible if there is no problem in practice.

In addition, although the sediment of 5cm seems to be very small, it can be detected when the pile is high and low, and it will also bring uncertainties to the settlement of the pile.

I don't know if you understand, if you have the chance, you can chat privately, hehe.

Reduced adhesion is in trouble.

The borehole wall protection only has requirements for the index of mud, and there is no requirement for the classification of soil layer.

In general, when drilling, due to the loose structure of the geological layer, the specific gravity of the mud is required to be around, which is also:

In order to increase the positive pressure in the hole (that is, when the water level in the hole is the same as the water level outside the hole, the pressure in the hole is formed from inside the hole to the outside due to the large proportion of mud) to prevent the hole wall from collapsing;

Better suspension of drill slag (when circulating);

It can take away the heat of the drill bit faster;

It can play a role in reverse osmosis (that is, due to the high pressure in the hole, the material in the hole has a tendency to penetrate into the hole wall, and has the effect of reinforcing the hole wall).

In addition, there are several indicators for the mud when drilling, namely: pH, colloidal rate, and sand content to be controlled.

The pH is greater than 7, which can produce negative ions in the mud, so that the cement of the mud can be tightly attached to the hole wall and protect the hole wall; The colloidal rate is greater than 18, which enhances the viscosity of the mud and is also beneficial to the hole wall; The sand content is less than 3%, which is a requirement before pouring concrete.

Because the specific gravity of the mud is around the time of drilling, it is beneficial to the slag in the hole, but it is not good for pouring concrete, so before pouring concrete, try to produce more slag (sand removal), and at the same time reduce the mud concentration as much as possible, and finally control the specific gravity of the mud is not greater than, and the sand content is less than 3% After the concrete can be poured.