Background of the Invention

Soil stabilization is the process for improving the engineering properties of the soil and increasing the stability of the soil. The engineering properties of soils such as mechanical strength, permeability, compressibility, durability and plasticity have a great importance especially when the soil undergoes high loads, for example in construction of buildings and roads.

An important aspect in construction is to provide structured layers, which are capable of carrying certain loads. In case of an unstable base or a layer, the foundation deforms, as a result, the upper layers of the construction erode.

Among different soil stabilization techniques, one of the most commonly implemented technique, especially in construction, is chemical stabilization by means of calcium oxide, commonly known as quicklime or burnt lime. Soils with high clay content have a tendency to swell when moisture content increases. When additives, such as calcium oxide, are exposed to the mineral present in the soil or water, they react and form composite materials. As a result, the soil's expansive properties are reduced. This indicates that lime stabilization reduces the plasticity, i.e. , the swell potential.

Furthermore, friability of the soil and the bearing capacity are increased by the lime stabilization technique.

Despite the advantages of chemical soil stabilization, in practise it may be expensive as prior art chemical stabilization techniques are very time-dependent and can continue over a long period. These techniques comprise several process steps such as spreading the additive, mixing, compacting and so on. This implies high costs, high consumption of energy, high labour and machinery demand.

Another disadvantage of conventional chemical soil stabilization practises is that the additives are spread and mixed directly on the surface of the soil, complicating the control of the process. Specifically for construction of buildings, deep construction pits are needed. A large amount of soil is excavated and the excavation is either removed or stored temporarily for a later backfilling, which entails difficulties in handling. Furthermore, stabilization of the soil in a deep construction pit requires a variety of tools, machines and apparatus increasing the overall cost. Thus, there is a great demand in a compact and efficient soil stabilization system, which offers a controlled way of stabilizing soil using additives.

Summary of the invention

Unlike traditional methods, wherein the spreading and mixing of the soil stabilizer take place on the ground, the present disclosure relates to spreading a soil stabilizer on soil and mixing the soil stabilizer with the soil in a mobile soil mixing system. The present inventors have realized that by making use of a system resembling a box feeder, the process efficiency can be enhanced significantly.

In a first aspect, the present disclosure relates to a soil stabilization system, comprising:

- at least one container for receiving and containing soil,

- at least a first conveyor unit located in the container and configured for moving the soil towards an outlet end of the container, the conveyor unit defining a direction of rotation,

- at least one feeder unit for containing a soil stabilizer located towards the outlet end of the container and configured for controllably feeding the soil stabilizer to soil on the conveyor unit, and

- a rotatable mixer unit located at the outlet end of the container and configured for mixing the soil with the soil stabilizer to provide a mixture of the soil and the soil stabilizer, wherein the soil stabilization system is configured such that a direction of rotation of the rotatable mixer unit corresponds to the direction of rotation defined by the conveyor unit.

Commonly, in a construction site the excavated soil or soil of another source is towed away on trucks and replaced with dry gravel, or stored temporarily around the construction site or at a dedicated area for later backfilling. A disadvantage of this practise is that a huge amount of energy and man power is used for transportation and temporary storage demands a large space. Another disadvantage of existing soil stabilization techniques is that the clumped soil is only insufficiently mixed with the soil stabilizer. Advantageously, the presently disclosed approach is capable of receiving the soil, optionally storing the soil and feeding back stabilized soil to the construction site. An improved consolidation of the soil avoids the use of a special replacement soil completely or at least reduce to a considerable level. Furthermore, such an approach is particularly space-saving and provides an efficient solution for mixing the soil with the soil stabilizer.

Another advantage of the presently disclosed approach is that the soil stabilizer is provided to the soil by means of a controllable feeder unit. Furthermore, the blend of the soil and soil stabilizer takes place under a predefined mixing speed and direction. Specifications of the feeder unit such as dosing as well as mixing specifications can be altered depending on the specific project, soil or additive type, introducing a great flexibility to the system.

Clay box feeders used for example in brickyards for feeding clay into the oven, also typically comprise a conveyor and a rotatable mixer unit at the outlet, however the rotatable mixer unit is configured to turn slowly with a frequency of less than 400 RPM and with a direction of rotation which is opposite the direction of rotation defined by the conveyor, i.e. such that the angular momentum of the rotatable mixer unit points right relative to the movement of the soil towards the rotatable mixer unit. A great advantage of the presently disclosed approach is that the rotation direction of the mixer and the conveyor unit is chosen such that the system can handle relatively big rock fragments while delivering a homogeneous mixture. This is provided by having a higher rotation frequency and with a direction of rotation, which is opposite the direction of rotation defined by the conveyor, i.e. such that the angular momentum of the rotatable mixer unit points left relative to the movement of the soil towards the rotatable mixer unit The system is advantageously configured such that first the soil stabilizer is provided on the soil; then, the rotatable mixer blends the soil and the soil stabilizer. Thus, at least a first chemical reaction takes place when the soil stabilizer is spread on the soil, and the chemical reaction continues when the mixture blends by means of the rotatable mixer unit. A further advantage of having a series of chemical reaction may be a distributed steam output.

Additionally, an arrangement of the presently disclosed system enables an easy access to the rotatable mixer unit from both sides. As a result, any stones that may be stuck in the rotatable mixer unit can be removed, thus the risk of an equipment damage and prolonged downtime are reduced.

Furthermore, as the rotational mixer unit rotates around a same rotational direction as the conveyor unit, the mixture follows a longer path around a rotary axle of the rotatable mixer. Hence, the mixture can interact with the air longer; this may further improve the stabilization of the soil.

Additionally, the presently disclosed approach offers a possibility of providing the mixture of the soil and the soil stabilizer to deep excavated pits. The mixture can be fed back to a construction pit through a conveyor belt, placed after the rotatable mixture unit. This feature enhances the efficiency of the soil stabilization process in construction sites while decreasing the cost considerably.

A further advantage of the presently disclosed system is that the system can comprise at least one measuring unit configured for measuring the weight of soil on the first conveyor unit. Consequently, the weight percent of the soil stabilizer mixed into the soil can be calculated and controlled, resulting in an improved automation and efficiency during soil stabilization.

The present disclosure further relates to a soil stabilization method, comprising the steps of:

- receiving and containing excavated soil in at least one container,

- moving the soil towards an outlet end of the container by means of a conveyor unit,

- feeding a soil stabilizer controllably from a feeding unit to the soil on the conveyor unit, at the outlet end of the container,

- mixing the soil and the soil stabilizer with a rotatable mixer unit located in the conveying direction and after the feeding unit, such that a direction of rotation of the rotatable mixer unit corresponds to a direction of rotation defined by the conveyor unit. Consequently, the presently disclosed approach promises a decreased process time, resulting in a positive influence on the environment due to fewer emissions and lower costs by saving energy, materials, and equipment.

Description of the drawings

The present disclosure will in the following be described in greater detail with reference to the accompanying drawings:

Fig. 1 shows one embodiment of the presently disclosed soil stabilization system.

Fig. 2 is one embodiment of a back view of the presently disclosed soil stabilization system.

Fig. 3 is one embodiment of a front view of the presently disclosed soil stabilization system.

Fig. 4 is one embodiment of the first conveyor unit and the rotatable mixer.

Fig. 5 shows one embodiment of the first conveyor unit and the feeder unit.

Fig. 6 shows one embodiment of the soil and the soil stabilizer before entering to the rotatable mixer unit.

Fig. 7 shows one embodiment of the rotatable mixer unit mixing the soil and the soil stabilizer.

Fig. 8 shows one embodiment of a conveyor unit for feeding the mixture to a construction pit.

Figs. 9-10 shows one embodiment of the presently disclosed soil stabilization system with a panel mounted above the mixer unit for monitoring the mixer unit and controlling the feeding of soil stabilization.

Detailed description

The presently disclosed system is intended for, but not exclusive to, soil stabilization. The system comprises at least one container configured to receive and store soil. The soil may for example be an excavated soil, excavated during construction of buildings. Alternatively, the soil may be provided from another source. The system further comprises at least a first conveyor unit located in the container. The first conveyor unit defines a direction of rotation wherein the first conveyor unit carries the soil and moves the soil towards an outlet located at one end of the container. The system further comprises at least one feeder unit for containing a soil stabilizer. The feeder unit is preferably located above the first conveyor unit such that the soil stabilizer can spread controllably on top of the soil at the outlet end of the container.

The soil stabilization system further comprises a rotatable mixer unit located at the outlet end of the container, preferably after the feeder unit, and can be configured for mixing the soil with the soil stabilizer to provide a mixture of the soil and the soil stabilizer.

An advantageous aspect of the presently disclosed approach is that the soil stabilization system can be configured such that a direction of rotation of the rotatable mixer unit corresponds to the direction of rotation defined by the conveyor unit. Preferably, the rotatable mixer unit can rotate around the same direction as the conveyor unit. As a result, the system can accommodate large rock fragments.

In an advantageous embodiment, the presently disclosed system is configured such that the direction of rotation of the rotatable mixer unit is reversible. The system may comprise a control unit such as a PLC control unit for controlling the direction of rotation. Furthermore, the soil stabilization system can be configured to monitor a rotation speed of the rotatable mixer. Consequently, the system can be configured to reverse the rotation direction of the rotatable mixer based on the speed of the rotatable mixer. For example, when an obstacle such as a fragment of a rock squeezes between the first conveyor and the rotatable mixer, the control unit can monitor and identify that the rotatable mixer cannot rotate and reverse the rotation direction of the rotatable mixer. After a few revolution, the rotation direction of the mixer can be re-reversed to the direction of rotation defined by the conveyor unit. If the obstacle is not loosened, the system can be configured to reverse and re-reverse the direction of the rotation of the mixer multiple times. The system can be further configured such that the system shuts off after a predefined consecutive change in the direction of rotation.

Advantageously, the soil stabilization system can run safely and smoothly. Thus, in an alternative embodiment, the presently disclosed system is configured such that the direction of rotation of the first conveyor unit and/or the rotatable mixer unit is reversible.

In an embodiment, the system is configured to handle soil, comprising rock fragments of up to 25 cm in diameter. In a preferred embodiment, rock fragments are up to 30 cm in diameter, more preferably up to 35 cm in diameter. While the physical characterization of soil may alter in different location or in different construction sites, the proposed system can minimize a need for fine screening for rock fragments.

Another important aspect of the presently disclosed approach is that the carrying capacity of the container and the conveyor belt can be improved. In an embodiment, the conveyor unit comprises chain plates such that said conveyor unit is configured to withstand a load of at least 40 tons of soil. The conveyor unit may preferably be a conveyor belt made of lamellar steel chain plates. Advantageously, the system may be suitable for deeper construction pits as the conveyor unit can allocate 40 tons of soil.

The presently disclosed soil stabilization system is particularly suitable for excavated soil, such as clay and/or moler. The strength gain of stabilized soil is influenced by the water content needed to maintain the chemical reaction. In an embodiment, the soil has a water content of up to 20 %, more preferably up to 25 % weight percent by weight of soil.

However, a high water content of soil may result in an unfavourable interactions and poor engineering properties, such as swelling and high plasticity of the soil. Advantageously, chemical soil stabilizers interact between water and soil by chemical reactions and alter the behaviour of the soil. When supplying the soil stabilizer, it may be preferred that the soil stabilizer is provided per unit area of the soil in a controlled manner. Specifically, for the stabilizers that are in powder form, a uniform distribution of the stabilizer can be challenging. In an embodiment, the feeder unit comprises at least a second conveyor unit for providing the soil stabilizer. Advantageously, the second conveyor unit has a predefined speed and it is located above the first conveyor unit such that the soil stabilizer is provided to the soil on the first conveyor unit homogeneously. Thus, the proposed system can provide a uniform distribution of the stabilizer on per unit area of the soil.

In addition to the spreading technique of the soil stabilizer, dosing may be another important aspect. In an embodiment, the feeder unit is configured for controllably adding the soil stabilizer to the soil before the rotatable mixer unit mixes the soil with the soil stabilizer. This foresees that the feeding unit can comprise a metering device or a measuring sensor or mechanical means such that the soil stabilizer can be provided with a predefined amount. In an embodiment, a feed rate of the soil stabilizer is controlled by adjusting the speed of the second conveyor unit.

Furthermore, spreading the stabilizer on the soil before the rotatable mixer mixes them, has an advantage, because when burnt lime (calcium oxide) dissolves in water, it is converted through an exothermic reaction to calcium hydroxide (hydrated lime). Thus, this reaction develops heat and produces steam. By spreading the stabilizer on the soil before mixing results in a first reaction, which develops a first steam wave. Up on arrival of the mixture to the rotatable mixer unit a further reaction takes place, which develops a second steam wave. This stepwise procedure leads to a more complete chemical reaction enhancing the properties of the stabilized soil.

In an embodiment, the rotatable mixer unit has a rotation frequency of at least 350 rpm, more preferably at least 400 rpm, even more preferably at least 500 rpm, most preferably at least 600 rpm during mixing. While the rotational speed may need to be adjusted depending on the soil content and the stabilizer type, an advantage of the disclosed approach is that the rotatable mixer unit can rotate at the same direction of rotation as the first conveyor unit on which the soil and the spread of stabilizer situate. As a result, the mixture can be displaced and circulated more and the chemical reaction continues. An enhanced interaction of the mixture in the air may enhance the stability of the soil. Additionally, a high rotational speed improves the productivity of the system.

In an embodiment, the rotatable mixer unit comprises a rotary axle and a plurality of paddles located along the rotary axle and extending radially from the rotary axle. In a further embodiment, the paddles comprise an L-shaped or T-shaped end formed from blade-like or shovel-like rigid elements for engagement with the soil on the conveyor. I.e. , during soil mixing the paddles engage with soil and soil stabilizer on the conveyor such that the soil splits apart while mixing with the soil stabilizer. In a further preferred embodiment, the paddles extend from the rotary axle with various orientations such that the soil can be split and mixed efficiently. An advantage of this embodiment is that the paddles with smaller edge radius or T-shape paddles can reduce the amount of energy that needs to be used for mixing the soil to a similar stabilization degree, compared to paddles with larger edge radius or blunt end. In a preferred embodiment a single rotatable mixer is used, however, in an alternative embodiment, two or more rotatable mixer rotating with an opposite direction of rotation is used. This implies that at least one of the rotatable mixer can rotate with the same rotational direction as the first conveyor unit on which the soil and spread of soil stabilizer is provided.

Depending on the nature and water content of the soil and the stabilizer, the final properties of the stabilized soil may differ. In an embodiment, the soil stabilizer is calcium oxide. Furthermore, it is preferred that the feed rate of the soil or the soil stabilizer can be adjusted such that at a constant mixing ratio, a desirable degree of mixing can be achieved. Hence, in a further embodiment, the amount of the soil stabilizer is at least 2 weight percent, more preferably at least 3 weight percent, most preferably at least 4 weight percent by weight of soil. An advantage of using calcium oxide (burnt lime) for soil stabilization, i.e. , lime stabilization, is that the soil improved with burnt lime leads to an immediate reduction in water content.

In a further embodiment, the stabilized soil has a water content of less than 10 %, more preferably less than 8 % after the excavated soil is mixed with the soil stabilizer. An advantage of this embodiment is that decreased water content by means of lime stabilization increases load-bearing capacity and reduces plasticity. As a result, the stabilized soil can carry ordinary soil materials and it can be compacted in satisfactory layers. This foresees that due to the increased load-bearing capacity, a significant reduction in the thickness of the bottom protection layer can be expected, thereby saving from expensive raw materials of sand and gravel.

In an embodiment, the soil stabilization system comprises at least one measuring unit for measuring the weight of soil on the first conveyor. The measuring unit may be a sensor for measuring the force exerted on the first conveyor unit. The measuring unit may be located in accordance with the first conveyor at the outlet end of the container, such that the measuring unit measures the weight of the mixture of the soil and the soil stabilizer on the first conveyor. Thus, in a preferred embodiment, the system can be configured to measure the weight of soil and the soil stabilizer on the first conveyor.

In an embodiment, the soil stabilization system comprises at least a second measuring unit for measuring the amount of soil stabilizer provided to the soil. The second measuring unit may for example be a laser scanner for measuring the soil stabilizer amount provided to the soil. Consequently, the soil stabilizer added to the soil can be controlled in relation to the weight of the soil and soil stabilizer mixture. Thus, a desirable degree of mixing can be achieved.

In an advantageous embodiment, the soil stabilization system further comprises a regulator unit, for adjusting a feed rate of the soil stabilizer. Preferably, the regulator unit regulates the rotation speed of the second conveyor. Thus, amount of soil stabilizer provided to the soil can be increased and/or decreased by means of the regulator unit resulting in a flexible soil stabilization system.

A further advantage of the present disclosure is to provide an efficient and safe soil stabilization system. The proposed system offers such an efficient soil stabilization system that the amount of the soil stabilizer used for stabilizing the soil can be decreased significantly. In an embodiment, the system is configured such that the amount of soil stabilizer added during operation is less than 4 weight percent, more preferably less than 2 weight percent, more preferably less than 0.5 weight percent by weight of soil. As explained above this can for example be controlled by knowing the weight of the soil going in to the system and by knowing the weight of soil stabilizer added during operation. The presently disclosed system has surprisingly been found to be very efficient in mixing soil and soil stabilizer such that the soil stabilizing effect of the soil stabilizer can be optimized. In the hitherto known method of soil stabilization an amount of approx. 2 weight percent of soil stabilizer is spread on the ground surface of the soil before being mixed into the soil by for example tractors with mixing units.

However, with the presently disclosed system the amount of soil stabilizer used can be much reduced, for example below 1 weight percent or even below 0.6 or 0.5 weight percent, because the mixing is more efficient, in particular when using calcium oxide as the soil stabilizer. This is important for both economic and environmental reasons. For example, it requires a lot of energy, typically fossil energy, to produce calcium oxide and the presently disclosed approach therefore provides a solution that can stabilize soil with much lower CO2 emission.

In an embodiment, the system comprises at least a third conveyor unit configured to receive the mixture of the soil and the soil stabilizer. In a further advantageous embodiment of the present disclosure, the third conveyor unit is configured to move the mixture of the soil and the soil stabilizer to a predefined location.

Preferably, the presently disclosed system is mobile, e.g. movable on a truck, such that the stabilized soil can be provided to construction pits, which are at different locations.

The present disclosure further relates to a soil stabilization method, comprising the steps of receiving and containing excavated soil in at least one container, moving the soil towards an outlet end of the container by means of a conveyor unit, feeding a soil stabilizer controllably from a feeding unit to the soil on the conveyor unit, at the outlet end of the container, mixing the soil and the soil stabilizer with a rotatable mixer unit located in the conveying direction and after the feeding unit, such that a direction of rotation of the rotatable mixer unit corresponds to a direction of rotation defined by the conveyor unit. An aspect of the presently disclosed method is that the amount of the soil stabilizer added to the soil can be less than 1 weight percent relative to the amount of soil. In a preferred embodiment, the soil stabilizer added to the soil can be less than or equal to 0.5 weight percent relative to the amount of soil. This foresees that, in an embodiment the weight percent of a soil stabilizer is continuously calculated by weight of soil.

In an embodiment of the present disclosure, the weight of soil on the first conveyor unit is measured. In a further embodiment, the amount of soil stabilizer provided to the soil is measured. Preferably, the weight of soil and the soil stabilizer on the first conveyor can be measured. In an advantageous embodiment, a feed rate of the soil stabilizer is adjusted. This can for example be performed by adjusting the speed of the second conveyor feeding the soil stabilizer such that a feed rate of the soil stabilizer is controlled. Consequently, the presently disclosed method can control the amount of soil stabilizer provided to the soil such that the amount of the soil stabilizer added during operation can be at least 2 weight percent, more preferably at least 4 weight percent by weight of soil. In another embodiment, the method can comprise controlling the amount of soil stabilizer provided to the soil such that the amount of the soil stabilizer added during operation is less than 2 weight percent, preferably less than 1 weight percent by weight of soil, more preferably less than 0.8 weight percent by weight of soil, even more preferably less than 0.6 weight percent by weight of soil, most preferably less than 0.5 weight percent by weight of soil. Furthermore, the soil and the soil stabilizer can be mixed by means of a rotatable mixer unit having a rotation frequency of at least 350 rpm, more preferably at least 500 rpm, most preferably at least 600 rpm during mixing. In an embodiment, the speed of the rotatable mixer is monitored such that the direction of rotation of the rotatable mixer unit can be reversed when the speed of the rotatable mixer is under a predefined speed value. In a further embodiment, the direction of rotation of the rotatable mixer unit can be reversed for a predefined number of rotation.

In an advantageous embodiment, the soil stabilization system and/or the method of the present disclosure can handle obstacles and large rock fragments in the soil by monitoring the rotatable mixer unit and at least short-term, e.g. on the order of below 1 minute, or 30 seconds, maybe just a few seconds, reversing the direction of rotation of the rotatable mixer unit when the rotational speed of rotatable mixer drops below a predefined threshold, e.g. below 90% or below 80% or below 70% of the current rotational speed. Thereby the passage can be cleared. This process can be repeated a few times if it does not work. Ultimately the system can be configured to stop if the mixer unit cannot function properly. Thus, the present disclosure offers an efficient approach for mixing the soil and the soil stabilizer with an optimized weight ratio while providing handling of rock fragments of different sizes continuously.

Detailed description of the drawings

The present disclosure will now be described more fully hereinafter with reference to the accompanying exemplary embodiments shown in the drawings when applicable. However, it is to be noted that the invention may be embodied in various forms. The hereby provided embodiments are to guide a thorough and complete disclosure. Hence, embodiments set forth herein should not be interpreted as limiting but be construed as a tool for delivering the scope of the invention to those who are skilled in the art. Same reference numbers refers to the same element throughout the document.

Fig. 1 shows one embodiment of the presently disclosed soil stabilization system. The system comprises a container 1 for receiving a substance, such as soil and a first conveyor unit 12 located at the bottom of the container 1. In this specific embodiment, the container is part of a box feeder, which can receive and store a content up to 150 m ³ . The conveyor unit 12 is configured for moving the soil in the container 1 towards an outlet 20 at one end of the container 1. At the outlet 20, there is a rotatable mixer unit 2, with a rotation axis parallel to a rotation axis of a conveyor belt 14 of the conveyor unit 12. As shown in Fig. 2, conveyor belt 14 is at the bottom of the container 1 , such that when the soil is provided to the container 1, the soil sits on the bottom of the container 1 on a top surface 14’ of the conveyor belt 14. The soil can be provided from an upper opening 10 at the upper side of the container 1. Furthermore, smaller amount of the same or another substance can be provided through a middle opening 9, located at a lower level than the upper opening 10 at the back side of the container 1 , as exemplified in Fig. 2.

Fig. 3 shows one embodiment of the front view of the presently disclosed soil stabilization system. The first conveyor unit 12 is configured for moving the soil towards the outlet 20 of the container. The rotatable mixer unit 2, located at the outlet 20 of the container 1 and configured for mixing the soil with the soil stabilizer to provide a mixture of the soil and the soil stabilizer. The mixer unit 2 comprises a rotary axle 6 and paddles 5 extending from the rotary axle 6. Each paddle 5 is positioned along the rotary axle 6 and has an extension length, extending from the centre of the rotary axle 6. The extended end of the paddles are T-shaped (5”). Furthermore, the extension length and the orientation of each paddle 5 may be different. In this preferred embodiment, the extended edges of the paddles are blade-like or knife-like or shovel like, which enhances the quality of the mixture and the soil stabilization process such that soil can be mixed sufficiently, homogeneously and efficiently.

Fig. 4 is one embodiment of the conveyor belt 14 and the rotatable mixer unit 2, seen from the inside 30 of the container 1. Conveyor belt 14, has a lamellar structure and made of steel such that it can withstand a high weight of soil up to 40 tons. The design of the steel plate contributes to a high efficiency and provides a good distribution of the load to the underlying construction. Additionally, Fig. 4 shows one embodiment of the paddles, wherein paddles have a blunt tip (5’).

The system comprises at least one feeder unit for containing and feeding a soil stabilizer to the soil. Fig. 5 shows one embodiment the feeder unit 4. Said feeder unit 4 stores a soil stabilizer 22, such as calcium oxide, also known as burnt lime, and comprises a second conveyor belt 15. Furthermore, the feeder unit 4 has a dosing mechanism, such that a predefined amount of burnt lime 22 is provided on the second conveyor belt 15. The second conveyor belt 15 rotates with a predefined speed and has direction of rotation same as the direction of rotation of the first conveyor belt 14. Thus, upon further rotation of the second conveyor belt 15, which is located above the first conveyor belt 14, burnt lime 22 is distributed on the soil conveyed on the first conveyor belt 14, homogeneously. The spreading of the burnt lime 22 on the soil results in a first chemical reaction and a mixture 3 of the soil and the soil stabilizer. The mixture 3 is conveyed on the first conveyor belt 14 further, until the mixture 3 reaches to the rotatable mixer unit 2 as shown in Fig. 6. This arrangement of longitudinal space behind the rotatable mixer unit 2 permits an easy maintenance of the rotatable mixer unit 2. Because the paddles 5 can be reached easily for any adjustments in operative conditions, for example in case of production stop due to large rock fragments, the maintenance and service of the paddles 5 and the rotatable mixer unit 2 can be carried out efficiently and smoothly.

Fig. 7 shows one embodiment of the rotatable mixer unit 2 seen from front, i.e. , from the outlet 20 side of the container 1. The rotatable mixer unit 2 mixes the soil and the soil stabilizer mixture 3. A great advantage of this system is that the direction of rotation of the rotatable mixer unit 2 corresponds to the direction of rotation of the first conveyor belt 14. This implies that the mixture 3, lying on the conveyor belt 14 is received by the rotatable mixer unit 2 such that the paddles 5 displace the mixture 3 towards an opposite direction of the mixture’s initial relative direction of movement. Thus, the mixture interacts with the paddles 5 for a longer time and a larger surface area of the mixture 3 gets in contact with air. It implicates that the chemical reaction between the soil and the stabilizer is triggered to a higher degree.

In a preferred embodiment, exemplary illustrated in fig. 8, the soil stabilization system comprises a third conveyor unit 16. The third conveyor unit 16 is mounted on the bottom of the container 1 at one end where the outlet 20 is located. The third conveyor unit 16 is located under the rotatable mixer unit 2 such that the mixture 3 is released from the rotatable mixture unit 2 and collected by and moved on a conveyor belt 17 of the third conveyor unit 16. The tip 16’ of the conveyor unit is arranged such that the mixture is fed continuously to a predefined region.

An additional preferred embodiment, exemplary illustrated from the side and behind in fig. 9 and from the side in fig. 10, also comprises the third conveyor unit 16, as used in fig. 8, but also a panel mounted above the mixer unit for monitoring the mixer unit and controlling the feeding of soil stabilization.

Items

1. A soil stabilization system, comprising: at least one container for receiving and containing soil, at least a first conveyor unit located in the container and configured for moving the soil towards an outlet end of the container, the conveyor unit defining a direction of rotation, at least one feeder unit for containing a soil stabilizer located towards the outlet end of the container and configured for controllably feeding the soil stabilizer to soil on the conveyor unit, and a rotatable mixer unit located at the outlet end of the container and configured for mixing the soil with the soil stabilizer to provide a mixture of the soil and the soil stabilizer, wherein the soil stabilization system is configured such that a direction of rotation of the rotatable mixer unit corresponds to the direction of rotation defined by the conveyor unit.

2. A soil stabilization system according to any of the preceding items, configured to handle excavated soil, such as clay and/or moler, comprising rock fragments of up to 35 cm in diameter, more preferably up to 30 cm in diameter, most preferably up to 25 cm in diameter.

3. A soil stabilization system according to any of the preceding items, wherein the soil stabilization system is configured to calculate and control the weight percent of the soil stabilizer mixed into the soil.

4. A soil stabilization system according to any of the preceding items, wherein the conveyor unit comprises chain plates such that said conveyor unit is configured to withstand a load of at least 40 tons of soil.

5. A soil stabilization system according to any of the preceding items, configured such that the feeder unit controllably adds soil stabilizer to the soil before the rotatable mixer unit mixes the soil with the soil stabilizer. 6. A soil stabilization system according to any of the preceding items, wherein the soil stabilizer is calcium oxide.

7. A soil stabilization system according to any of the preceding items, configured such that the amount of the soil stabilizer added during operation is at least 2 weight percent, more preferably at least 4 weight percent by weight of soil.

8. A soil stabilization system according to any of the preceding items, configured such that the amount of the soil stabilizer added during operation is less than 4 weight percent, preferably less than 2 weight percent, more preferably less than 1 weight percent by weight of soil, most preferably less than 0.5 weight percent by weight of soil.

9. A soil stabilization system according to any of the preceding items, wherein said rotatable mixer unit comprises a rotary axle and a plurality of paddles located along the rotary axle and extending radially from the rotary axle.

10. A soil stabilization system according to item 9, wherein the paddles comprise an L-shaped or T-shaped end formed from blade-like or shovel-like rigid element for engagement with the soil on the conveyor.

11. A soil stabilization system according to any of the preceding items, configured such that said rotatable mixer unit has a rotation frequency of at least 350 rpm, more preferably at least 500 rpm, most preferably at least 600 rpm during mixing.

12. A soil stabilization system according to any of the preceding items, configured to handle the soil with a water content of up to 20 %, more preferably up to 25 %.

13. A soil stabilization system according any of the preceding items, configured such that the mixture has a water content of less than 10 %, more preferably less than 8 %. 14. A soil stabilization system according to any of the preceding items, wherein the system is configured such that the direction of rotation of the rotatable mixer unit is reversible.

15. A soil stabilization system according to any of the preceding items, wherein the feeder unit comprises at least a second conveyor unit having a predefined speed and located above the first conveyor unit and configured to provide the soil stabilizer to the soil on the first conveyor unit.

16. A soil stabilization system according to item 0, configured such that a feed rate of the soil stabilizer is controlled by adjusting the speed of the second conveyor unit.

17. A soil stabilization system according to any of the preceding items, further comprising at least one measuring unit configured for measuring the weight of soil on the first conveyor.

18. A soil stabilization system according to any of the preceding items, further comprising at least a second measuring unit configured for measuring the amount of soil stabilizer provided to the soil.

19. A soil stabilization system according to item 18, wherein the system is configured to measure the weight of soil and the soil stabilizer on the first conveyor.

20. A soil stabilization system according to any of the preceding items, further comprising a regulator unit configured for adjusting a feed rate of the soil stabilizer.

21. A soil stabilization system according to any of the preceding items, wherein the system comprises at least a third conveyor unit configured to receive the mixture of the soil and the soil stabilizer.

22. A soil stabilization system according to item 21 , wherein the third conveyor unit is configured to move the mixture of the soil and the soil stabilizer to a predefined location. 23. A soil stabilization method, comprising the steps of: receiving and containing excavated soil in at least one container, moving the soil towards an outlet end of the container by means of a conveyor unit, feeding a soil stabilizer controllably from a feeding unit to the soil on the conveyor unit, at the outlet end of the container, mixing the soil and the soil stabilizer with a rotatable mixer unit located in the conveying direction and after the feeding unit, such that a direction of rotation of the rotatable mixer unit corresponds to a direction of rotation defined by the conveyor unit.

24. The soil stabilization method according to any one of items 23, wherein the method further comprises the step of measuring the weight of soil on the conveyor unit.

25. The soil stabilization method according to any one of items 23-24, wherein the method further comprises the step of measuring the amount of soil stabilizer provided to the soil.

26. The soil stabilization method according to any one of items 23-25, wherein the method further comprises the step of measuring the weight of soil and the soil stabilizer on the first conveyor.

27. The soil stabilization method according to any one of items 23-26, wherein the method further comprises the step of adjusting a feed rate of the soil stabilizer.

28. The soil stabilization method according to any one of items 23-27, wherein the method further comprises adjusting the speed of a second conveyor feeding the soil stabilizer such that a feed rate of the soil stabilizer is controlled.

29. The soil stabilization method according to any one of items 23-28, wherein the method further comprises controlling the amount of soil stabilizer provided to the soil such that the amount of the soil stabilizer added during operation is at least 2 weight percent, more preferably at least 4 weight percent by weight of soil. The soil stabilization method according to any one of items 23-28, wherein the method further comprises controlling the amount of soil stabilizer provided to the soil such that the amount of the soil stabilizer added during operation is less than 2 weight percent, preferably less than 1 weight percent by weight of soil, more preferably less than 0.8 weight percent by weight of soil, even more preferably less than 0.6 weight percent by weight of soil, most preferably less than 0.5 weight percent by weight of soil. The soil stabilization method according to any one of items 23-30, wherein the method further comprises the step of mixing the soil and the soil stabilizer by means of a rotatable mixer unit having a rotation frequency of at least 350 rpm, more preferably at least 500 rpm, most preferably at least 600 rpm during mixing. The soil stabilization method according to any one of items 23-31 , wherein the method further comprises the step of reversing the direction of rotation of the rotatable mixer unit for a predefined number of rotation. The soil stabilization method according to any one of items 23-32, wherein the method further comprises monitoring the speed of the rotatable mixer such that the direction of rotation of the rotatable mixer unit is reversed when the speed of the rotatable mixer is under a predefined speed value. The soil stabilization method according to any one of items 23-33, wherein the soil stabilization is provided by means of the soil stabilization system of any of the items 1-22.