How to select polymer mud?

Firstly, we should know there are 2 pile types: Precast pile and bored pile. Generally the polymer mud is only used in bores piles.

What is bored pile? Drill first, then pour concrete. Bored piles are divided into rotary drilling and impact drilling according to different drilling methods. The polymer mud is used in rotary drilling bored piles. When encountering loose soil and sand underground during the drilling process, the middle will be hollowed out and the hole wall will collapse, resulting in failure to drill the hole smoothly. The wall protection is needed to drill the hole smoothly.

For protecting the wall, there are mainly 4 kinds of construction technologies: Dry drilling (solid geology, preferably without groundwater), mud wall, casing and concrete wall.

Mud wall protection mainly involves two products: bentonite and polymer mud.

Bentonite itself is a kind of earth mineral, and its mineral grade varies. After being processed by the bentonite plant, bentonite of different grades is formed, which is suitable for different engineering fields and different geological conditions.

Bentonite is high-density, high-specific-gravity mud.

Working principle:

1. Generate sufficient lateral pressure on the hole wall; at the same time, form a mud skin on the hole wall to achieve a wall protection effect.

2. Suspend the remaining drill cuttings so that there is no sediment at the bottom of the hole.

Advantages:

1. Applicable to a wider range of geology than polymer

2. Wall protection effect lasts longer

Disadvantages:

1. Large amount of usage

2. High transportation cost

3. Difficult to handle the mud after using

Polymer mud is pure chemical product, belonging to organic polymer material. Non-toxic and harmless.

After dissolving, it is a polymer chain structure with high viscosity.

Working principle:

1. Chain-shaped high-viscosity mud penetrates into the hole wall to achieve the wall protection effect

2. Accelerate the sedimentation of residual drill cuttings at the bottom, and use the drill bit to salvage them so that there is no sediment at the bottom of the hole.

Advantages:

1. Easy to use and economical

2. Easy to transport

Disadvantage:

The range of application is not as wide as bentonite.

Before using the polymer mud, we need to judge whether the actual situation is suitable for using polymer mud. Generally, the judgment is based on two key points——Geological hardness and mud level.

- Geological hardness: Generally, when the water level meets the requirements and the foundation bearing capacity is >160KPa, polymer is more likely to be used successfully.

When there is no foundation bearing capacity data, the standard penetration number (N value) can be used as a reference.

- Mud level height: The mud level must be at least 3 meters higher than the groundwater level to generate a normal pressure difference and allow the mud to penetrate into the hole wall.

If the groundwater level is low enough, nothing needs to be done.

If the groundwater level is not low enough, it is necessary to raise the construction surface or add a cofferdam at the orifice to artificially increase the pressure difference.

After confirming that the actual situation is suitable for the use of polymer mud, we need to confirm which type of polymer mud to use.

Our current types of polymer mud include GQ , HQ and A610

- GQ:

Advantages: powder, fast dissolution; low price; viscosity value is at a medium level compared with competing products; can be used for slurry pool and orifice slurry.

Disadvantages: short viscosity duration; viscosity value is the lowest.

- HQ:

Advantages: powder, fast dissolution; moderate price; viscosity value is at a higher level than competing products; can be used for slurry pool and orifice slurry.

Disadvantages: short duration of viscosity.

- A610:

Advantages: Viscosity lasts for a long time; Viscosity value is significantly higher than most competing products.

Disadvantages: Granular, slow dissolution; The price is the highest among the three types; Only slurry can be made in mud pools.

If the strata is very simple, relatively stable, good density, and has a high foundation bearing capacity, GQ is enough. HQ is a cost-effective choice for general situations. The A610 is the industry's top performer for demanding, high-budget projects. In most cases, different models can be mixed and used universally.

Water quality

The water used for pulping has an impact on the effect of the polymer mud, which is reflected in the viscosity value and dosage in the actual application of the polymer mud.

Ideal water is pure water used in the laboratory. Seawater is the representative of dirty water. Dirty does not refer to the color, taste, or visible debris of the water, but to the invisible trace elements. The trace elements in seawater are often more than most land freshwater, but some polluted groundwater is actually very poor. And there are also impurities in ordinary construction water.

Therefore, the concept of salt resistance is introduced, and the ability of materials to adapt to trace elements is generally expressed by salt resistance.

At present, considering the salt resistance of materials alone, HQ is the best.

However, in actual use, the dosage and viscosity effect are not simply considered in terms of salt resistance. For example, GQ is not as salt resistant as HQ, and its viscosity value is also lower, but by increasing the dosage of GQ, the same effect can be achieved, and the final material cost is not much different.

Tips: Adding alkali can improve water quality.

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