Perspective Chapter: Ways to Improve the Ecological State of Abandoned Quarries in Countries with Mountainous Terrain

Abstract

The wall stone of a correct form is one of the main construction materials used in Armenia and other countries with mountainous terrain. The current technology of stone cutting using rail-mounted machines is ineffective due to various reasons. These include excessive cutting forces, vibrations, formation of chips and cracks, incomplete cutting of benches resulting in remnants left at the quarry bottoms, and significant accumulation of waste. These problems have severe environmental consequences. In countries with mountainous regions and limited quarry lengths, the problem of inefficient stone cutting is even more pronounced. Over the past few decades, and particularly after the devastating earthquake of 1988, stone quarries have been operated without considering environmental regulations. Many quarries have been abandoned as well. The author proposes two approaches to improve the mountain ecosystem: the conversion of abandoned quarries into a connected network of small reservoirs and the development of new trackless stone-mining machines equipped with wheels instead of rails. These innovations enable the extraction of the wall stones minimizing waste and reducing harm to the ecosystem. The addition of forest zones around the reservoirs can further mitigate the environmental impact of quarries by reducing stone dust release into the atmosphere.

1. Introduction

The wall stone of a correct form is one of the main construction materials used in Armenia and other countries with mountainous terrain.

For decades in the Countries of the Independent States (CIS) of the former Soviet Union and neighboring countries, the extraction of wall stone of the correct form with cross dimensions of 200 × 300 mm was carried out by rail machines CMP-026/1.

1.1 Problems

The efficiency of these machines is quite low because their design, tooling and technology of stone extraction have exhausted all their technical possibilities for improvement. High cutting forces during the extraction of rocks with a strength of up to 40 MPa, lead to vibrations in the multi-ton machines, causing formation of chips and cracks and large mining waste causing significant environmental damage. Quarry saws emit clouds of stone dust into the air, especially in quarries located in windy areas, posing severe natural hazards for nearby settlements. The installation of rails at different heights creates underused stepped sections within the quarry. The saw blades of the machine have insufficient durability due to the increased strength of the lower layers of the quarry.

These issues are particularly challenging for countries with mountainous landscapes, where quarry lengths are relatively small. Therefore, improving the efficiency of stone extraction becomes a complex and demanding task. Figure 1 provides a typical illustration of the stone extraction process using a CMP-026/1 rail machine.

Figure 1.

View of machine and quarry when extracting a stone of the correct form.

Figure 2 depicts an abandoned quarry, which highlights the issue of accumulated waste mountains resulting from stone extraction. These waste piles, along with the abandoned quarries, pose a significant environmental threat and the risk of a potential catastrophe for future generations. Therefore, it is crucial to address and resolve the challenges related to the protection, utilization, and restoration of mountain ecosystems. Immediate solutions are needed to tackle these pressing issues.

Figure 2.

Landscape view of an abandoned quarry in a country with mountainous terrain.

Given the small land area of the Republic of Armenia and other comparable countries, it is essential to formulate a well-defined strategy for the development of the stone industry. This strategy should be built upon the utilization of modern scientific and engineering advancements that prioritize minimizing environmental harm.

2. Solution

The author proposes two approaches to address the conservation, exploitation, and restoration of ecosystems in countries with mountainous terrain:

1. The conversion of abandoned quarries into a connected network of small reservoirs, supplied by a central dam located at a higher geographical level than the quarries. This project can be realistically implemented over an area of 3–4 thousand square kilometers in mountainous countries. The implementation of a such project requires thorough study of the physical properties of the quarry rocks, utilization/disposal of stone mining waste both in the quarry and in its surrounding areas, as well as the establishment of forest zones covering the perimeter of the quarry.

2. The development of new trackless stone-mining machines and technologies that are equipped with wheels instead of rails. These innovative machines would enable the extraction of the wall stones of the correct form with minimal waste and without causing harm to the ecosystem. Furthermore, they would allow for the utilization of abandoned quarries by extracting the remaining hard and unexploited layers of rock located at lower levels.

2.1 Transformation of abandoned quarries

Research and development efforts have been undertaken in the first approach, focusing on the Shirak region of Armenia. The following steps have been taken:

1. Identification of a feeding dam with the highest geographical location to serve as the water source for a network of small reservoirs-quarries. In this case, the newly constructed Caps reservoir is considered. It has a water volume of 61 million cubic meters and is situated at an altitude of 1730 meters above sea level. The dam is being built on the Akhuryan River, which originates from Lake Arpi at an elevation of 2017 meters and flows into the Araks River at an elevation of 905 meters.

2. Compilation and collection of maps of both active and abandoned quarries in the region. The selection of quarries to be included in the network of small reservoirs is based on several parameters, including their location, altitude, contour, dimensions, depth, type of stone, composition, and physical and mechanical properties.

3. Preliminary assessment of waste utilization possibilities for each selected quarry and its surroundings. Suitable crushing, screening, and dispersion techniques are employed to process the waste into crushed stone, sand, and powders. The potential uses of stone powders are determined, such as their application as lightweight and active fillers in concrete, fillers in the production of plastic and rubber, heat-insulating materials, acid-resistant products, soil fertilizers due to their filtration properties, and for polishing materials with dimensions of 0.05 mm or smaller.

4. A network of water supply channels to individual reservoirs-quarries is being developed in advance.

The map of the Shirak region shows the places of stone quarries (Figure 3).

Figure 3.

Map of stone quarries in the Shirak region: Δ – quarries included in the zone of the network of reservoirs; Δ – quarries of high mountain zones.

There are two designated zones. The first zone covers the quarries located below the level of the Caps reservoir. Total area of those quarries, along with the surrounding forest zones covers about a third of the area of the region.

Out of the quarries assessed, approximately 50% are currently in operation. A network of small reservoirs has been established, incorporating 17 abandoned quarries. The central water supply channel, represented by a dotted line, is still undergoing refinements as the project continues to develop.

The second area focuses on the quarries located in highland regions. Efforts to preserve, utilize, and restore highland ecosystems are partially being addressed through the pilot grant program called “Waste Management of Closed Stone Quarries and Flooding of the City of Artik.” This program is initiated by the Ministry of the Environment and funded by the United Nations Adaptation Fund. As part of this initiative, forest parks and recreational areas are being established on closed quarries, and efforts are being made to restore cultivated lands.

The overall outcome of the aforementioned initiatives will involve conducting research and assessing the environmental impact of the entire network of reservoirs once the project is completed. It is anticipated that the system of small reservoirs will have a substantial positive influence on improving the regional environment. The emission of stone dust into the atmosphere will notably decrease, the climate will become milder, the water basin of the Akhuryan River will improve, and there will be an expansion of recreational areas for the local population, among other benefits. These effects will be examined and evaluated as part of the post-project assessment.

2.2 Replacement of the machinery

The author sees the second approach for the cardinal improvement of the ecosystems of mountainous regions, which involves moving away from the utilization of rail-based stone mining machines in the extraction wall and facing stones. Presently, various countries, including Armenia, Russia, China, and Italy, produce and employ different rail-mounted stone mining machines. However, these machines suffer from similar drawbacks as mentioned earlier.

The solution of this problem is in the development of the new wheeled trackless stone mining machines and technologies that ensure the extraction of wall stone of the correct form with minimal waste, without harming the ecosystem. Patent solutions to these problems and preliminary results of engineering developments and tests confirm the correctness of the chosen direction [1, 2, 3, 4, 5].

Analysis of the dimensions of stones of the correct form showed that currently, the stones are predominantly mined with cross dimensions of H × B generally not exceeding 200(250) × 250(300) mm, with the lengths ranging from10 to 400 mm. Moreover, the purpose of the wall stone also has changed. They are now primarily utilized for decorative exterior cladding with beautiful “rock” relief rather than serving as load-bearing elements.

To extract stones with the aforementioned parameters, a special wheeled machine has been developed. This machine aims to significantly reduce cutting forces, minimize vibrations, eliminate the formation of chips and cracks, and enable operation at higher cutting speeds and feeds. These improvements are achieved through the optimization of operational parameters and instrumental characteristics of the machine.

Transitioning from the conventional rail-based machine design to a wheeled and highly maneuverable design opens up opportunities for applying new and more efficient technological processes. The development of new stone cutting machines offers significant prospects for incorporating modern hydraulic units of the latest generation. These hydraulic units can be utilized not only in the drives of the stone-cutting heads but also in the hydrostatic transmissions of the machine for feed motion.

The new machine features saw blades positioned at the edges of the machine, with their cutting surfaces covering the transverse width L_m of the machine. In this prototype machine, the distance l_p between adjacent saws is set to be twice the length L of the stone being cut, taking into account the width b_p of the cut, i.e. l_p = 2(L + b_p). This configuration is preferable since lp is a multiple of the L_m width of the machine. As a result, the machine undergoes a periodic displacement/offset by the length of the stone before each new transverse passage.

The primary data used for designing the new machine were as follows:

1. The strength of the stone being cut was up to 40 MPa.

2. Circular saws with diameters of 800 and 630 mm, and a width of 12 mm, equipped with cutters featuring hard alloy or diamond polycrystal plates, capable of achieving a cutting depth of up to 250 mm.

3. The calculated power and torque values for one saw were 10 kW and 1200 Nm, respectively.

4. The maximum cutting speed and feed were set at 6 m/s and 5 m/min, respectively.

5. Solid tires were used instead of tubes in the machine’s construction.

The project was conducted collaboratively between the Gyumri branch of the National Polytechnic University of Armenia and the Open Joint Stock Company “Karatmekena”. Their efforts led to the development of a completely innovative machine capable of performing both transverse and longitudinal technological operations, as well as their combinations. The hydraulic units utilized in the machines were sourced from Poclain Hydraulics. A prototype of the new machine, featuring combined operations, was created using the forklift model 4014 from the Lvov plant “Avtopogruzchik,” which has a load capacity of 5 tons. The selection of hydraulic units was made in consultation with a representative from Poclain Hydraulics.

Figure 4 showcases the newly developed combined machine designed specifically for extracting a stone block of the correct form with cross dimensions of 200 × 300 mm. The machine follows a sequence of operations that involve:

1. Cross passages when the horizontal cutting head is raised upwards.

2. Longitudinal passages when the transverse saw blades are removed and only one is left at the left cutting head. This is the stage when the separation of stone from the massif occurs.

Figure 4.

Combined machine for the extraction of regular shape rock-stone.

An important aspect of the new wheeled machine is its ability to maintain straight-line movement, despite potential deviations caused by solid inclusions in the rock or external factors. To address this, the machine is equipped with an electronic control system comprising a three-axis gyroscopic servo system, a servo amplifier, an electromagnetic hydraulic distributor, and a parallel-connected reverse portioner to the power steering mechanism. This system, along with an external device responsible for adjusting straight-line movement, continuously monitors the machine’s motion and intervenes promptly in case of any deviations.

The flexibility offered by this machine in performing various technological operations presents a wide range of opportunities for repurposing abandoned quarries. Such machines will prove highly efficient for the secondary utilization of these quarries, which are numerous and have been environmentally harmful. The elimination of such residues will significantly contribute to the improvement of mountainous ecosystems.

The technology of stone extraction by the new machine addresses an important issue in quarrying: the formation of residual stepped protrusions. By utilizing edge saw blades covering the transverse width of the machine, it is able to create smooth, vertical walls without protrusions as it moves along in successive longitudinal passes.

Figure 5 depicts the cross-sectional profile of an abandoned quarry formed after the extraction of stone by the CMP-026/1 rail machine. This profile exhibits a stepped formation along the quarry’s perimeter, extending down to the lower layers. The steps have dimensions of 420 × 1000 mm. Approximately 30–40% of the original stone volume remains in the quarry. The image showcases the profile of the quarry after mining several layers using the new machine, resulting in a vertical wall with no remaining residues. The stone extraction process follows the same technology described earlier.

Figure 5.

Cross profile of an abandoned quarry and a usage scheme.

The comparison between the productivity of the new machine and the CMP-026/1 machine for extracting wall stone of the correct form has been conducted. The calculation has resulted in a relationship that determines the actual productivity of the new machine, which features four vertical saws and one horizontal saw. It has been determined that the actual productivity of the new machine will range from 2.2 to 3 cubic meters per hour. On average, this is 1.2 to 1.8 times higher than the productivity of the CMP-026/1 machine. The increased productivity is achieved through the optimization of stone cutting modes, a higher percentage of usable output, enhanced machine utilization over time, and reduced time spent on auxiliary operations.

3. Conclusion

1. Creating a network of small reservoirs on abandoned stone quarries, surrounded by forest zones, is a viable approach to improving the condition of mountain ecosystems in countries with mountainous terrain.

2. The utilization of new wheel-based stone-mining machines instead of rail-based machines shows promise as it minimizes waste generation. The flexibility of maneuvering these machines in the quarry allows for the extraction of stone from untouched lower layers, enabling the secondary use of abandoned quarries.