Soil development methods

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

In the course of construction and mining operations, excavation is traditionally carried out in one of three ways: cutting, hydromechanical fracturing, and blasting.

The engineer makes a choice in favor of a particular method based on the amount of work to be done, the nature of the ground soils, the technical means of development available, etc.

If a small excavator can easily cope with digging a foundation pit for the construction of a country house, then when mining, it is necessary to use a whole range of machines and mechanisms. Moreover, most of these means of production will not be directly involved in the development of the soil. Their purpose is to serve the production process and ensure the continuity of operations.

Characteristics of soils

Soil is the top layer of the earth's crust formed by weathered rocks. Depending on the density and origin, soils can be classified into:

• Rocky (such soil is resistant to moisture, tensile strength is more than 5MPa). This category includes granite, limestone, sandstone.
• Semi-rocky (tensile strength up to 5 MPa). For example: clay, gypsum, marl.
• Coarse clastic - non-cemented fragments of semi-rock and hard rocks.
• Sandy (they are dispersed (up to 2 millimeters in diameter) particles of rocks).
• Clay (fine (0.005 millimeters in diameter) rock particles).

Developing soil manually in trenches is a rather laborious process. In principle, it cannot be carried out when mining rocks.

The composition of soils includes solid parts, water, and various gases (accumulate in the pores). Soil moisture is a value that characterizes the ratio of the mass of liquid to the mass of solids per unit volume. It can vary over a wide range and can take a value from one (sand) to two hundred percent (silt at the bottom of reservoirs).

Ground in the development process increases in volume. This is due to the formation of pores and cavities. The magnitude of the volume change is characterized by the loosening coefficient (the ratio of the volume occupied by the soil before work to the volume that the soil occupies after development). Over time, the density of the loosened soil decreases (natural compaction). It is also possible to implement forced soil compaction using heavy construction equipment. The density of such soil approaches the original, although somewhat less. This difference can be neglected, especially sinceover time, and it will disappear, and the soil itself will completely restore its properties (get old).

Mechanical properties of soils (primarily strength and ability to deform) depend on the composition and nature of the bond between the particles. During development, connections are destroyed, during compaction they are restored.

Cutting development

Earth-transport and earth-moving machines are used to develop the soil in this way.

During operation, the cutting tool experiences very significant frictional and mechanical loads. Under such conditions, conventional structural hoist will not last long. Therefore, the cutting edge of the working body is reinforced with cermet elements or special steels. Composite ceramic-metal plates are the most efficient in operation. But their cost is quite high. Therefore, most often buckets are reinforced with brazed electrodes made of wear-resistant alloys. Among other things, such a bucket has the effect of self-sharpening during operation due to more accelerated wear of the ordinary steel part of the bucket.

Such machines cut a certain layer of soil. The cut mass is transported by a special conveyor to a dump or is immediately poured into a dump truck for transport to a quarry or other construction sites. Excavation with an excavator falls under this category.

Types of excavators

Depending on the design and parameters of the bucket, excavators are divided into the following types:

• single-bucket;
• rotary and chain (multi-bucket);
• milling.

The most common is the single-bucket type of excavator. This type of machine is versatile and has very good maneuverability. The optimal useful volume of the bucket is from 0.15 to 2 cubic meters. Excavation by an excavator (single-bucket) with a more massive and capacious bucket is not economically feasible, since the hydraulics and mechanical parts of the equipment often fail due to heavy loads.

Also, depending on the drive mechanism, earth-moving machines are divided into tracked and automobile. There are also so-called walking excavators, as well as pneumatic wheeled excavators. However, in practice, such machines are extremely rare, if ever caught in the eye. Even experienced builders, and even then not all of them can boast that they have ever worked at the same facility with this type of machine.

Shovel excavator operation

This type of excavator can excavate both lateral and straight walkways. In the first case, the excavator performs work along the axis of movement. At the same time, the soil falls into the back of a truck that drives up from the other side.

In the second case, work is carried out in front of the excavator, and vehicles for loading are fed from behind.

If you need to get a significant excavation to a great depth, then there is no alternative to mechanized excavation. All work is carried out through the development of severalstages (tiers). The tier does not exceed the technological capabilities of a particular excavator model in terms of excavation depth.

Bucket-bucket operation

This type of machine is a prime example of a continuous action mechanism. Therefore, of course, the performance of such an excavator is an order of magnitude higher than the performance of conventional single-bucket machines. But it should be said that such equipment is used only in the construction of large-scale facilities. This type of equipment is absolutely unsuitable for excavation in a small trench: very expensive maintenance, very high fuel consumption.

Working buckets can be fixed on the chain or on the rotor. Hence the name of the excavators: chain and rotary.

This type of excavator can be used in the development of group 2 soil. Although in practice there are cases when such machines easily coped with soils of 1 … 3 groups. The soil should be relatively clean, without large stones and powerful stumps.

Earthmoving machine development

One machine in one working cycle carries out the extraction of rock, its movement over short distances. These machines include scrapers, graders, and bulldozers.

Scrapers are used for large-scale work. These machines are very productive, they can be used in soil conditions of 1 … 4 types. However, despite the incredible power, the scraper cannot handle dense soils. Therefore, such soils must first be loosened. In one pass, this machine can removea layer of soil up to 320 millimeters thick. The specific value depends on the power, bucket shape and scraper model.

The bottom of the scraper bucket is equipped with a blade. This is not the knife that most people use to cut food in the kitchen. In this case, a strip of abrasion-resistant and self-reinforcing Hadfield steel was welded on.

Bulldozers are used to work at shallow depths and over long distances. Also, this type of machine is used for cleaning and leveling the bottom of pits, the development of which was carried out by large excavators.

To the depth the bulldozer moves through the tiers. The depth of the tier is equal to the size of the layer that the machine can remove in one pass. It is very important that the working movement of the bulldozer is carried out on a slope. This will allow some unloading of the power units and minimize the likelihood of equipment failure.

Graders have low power and potential. They are mainly used for decorative work: embankments and slopes, planning work.

Description and scope of hydromechanical development

In this case, the development of soils manually is out of the question. However, as with the use of earthmoving machines. The scope is very extensive: from the creation of artificial reservoirs to the construction of roads. The technology also allows the reclamation of areas for residential and industrial development in swampy and coastal areas prone to floods. All processes are mechanized. This method of excavation requirescreating a special infrastructure, which makes it advisable to use it only with very large upcoming volumes of work.

Hydromechanical development using hydromonitors

The essence of this method of development is as follows: the soil is washed out with a jet of water under high pressure (about 15 MPa). The resulting mud mass (in the slang of professionals - pulp) initially accumulates in intermediate tanks, and from there it is pumped through the pipeline to the right place.

Over time, the moisture completely evaporates, and a dense layer of soil is formed. If it is compacted with a roller, then such soil becomes quite suitable for the construction of communication lines (roads and railways).

The great technological advantage of this method is the ability to develop soils of almost any category of complexity.

Hydromechanical development using suction dredgers

When carrying out work on the bottom of reservoirs, manual excavation, as well as using traditional earthmoving machines, is excluded. Special vessels needed.

A dredging projectile is a floating craft equipped with special equipment. A powerful pump pumps the eroded soil from the bottom of the reservoir and transports it through a pipeline either into the hold of the vessel, or to an auxiliary transport vessel, or throws it away with a powerful jet far from the excavation site.

Similar suction dredgers have found application in deepening and clearing the fairways of ships in shallow water conditions, deepening rivers in order to provideuninterrupted navigation, as well as in the extraction of diamonds from the shelf of the oceans.

The soil mass is sucked through the pipe. For suction of silt and soft soil, the pipe is not equipped with an additional ripper. The presence of the latter is necessary when developing dense soils. According to the complexity of development, this method is in the lead. Operation and maintenance of special transport, its parking in port waters is very expensive. There are high requirements for the qualification of service personnel.

Development of frozen soils

For development in permafrost conditions, as well as for the development of rocky rocks, powerful directed explosions are used. TNT, ammonite and toll can be used as explosives.

Explosive projectiles can be placed both on the surface and deep into pre-drilled holes or in natural cavities.

The so-called borehole charges are used in the development of a large area of the pool, as well as for dumping soil. Explosive projectiles are installed in pre-drilled wells. The minimum borehole diameter is 200 mm. To increase the destructive power of the charges, the holes are covered from the outside with sand or fine rock (formed when drilling wells).

Shpurovye charges are used when it is necessary to excavate a small amount of soil. It is possible to carry out both in open mining and in underground mining. Holes are a kind of shells. Have a diameter of 25up to 75 millimeters. They are filled with explosives by a maximum of two-thirds. The remaining space is filled with rock (in order to receive a directed blast wave and achieve the greatest beneficial effect).

Chamber charges. This type of charge is used when it is necessary to excavate significant volumes of soil by implementing a directed release. The essence of the method is as follows. In the working area, vertical wells or horizontal tunnels are equipped, in the walls of which blind holes are drilled for laying charges. After laying the explosives, adits and wells are covered with soil (this allows you to increase the power of the explosion). The direction of the ejection is provided by the uneven laying of the explosive. So, on one side there can be several times more drilling holes for charges. Also for this purpose mismatch of explosions can be used.

The so-called slotted charge is used mainly in the development of soil in permafrost conditions. It is hardly possible to carry out a directed release of such a rock. But to loosen it so that in the future it can be removed with a bulldozer or excavator is quite realistic. For this, a tool is used that, according to the principle of operation and in appearance, resembles a disk cutter for metal. Only, of course, such a tool is much larger. Such a cutter cuts peculiar grooves in the ground at a distance of up to 2.5 meters from each other. The explosive is not placed in every groove, but through one - the hollow unfilled space acts as a compensator. blast wavecrushes the soil, and it shifts towards the cavity. Such works require careful preparation and detailed study of the project.