Method and device for mechanically compacting clay-containing earth material

Abstract

In a method for the mechanical compaction of clayey soil material using a vibratory plate, in which the vibratory plate is guided as an end effector on a three-axis positioning system (9, 10) over the soil material to be compacted and the pressure force applied to the soil material is adjusted by controlling the positioning system (9, 10) to move it perpendicular to the plane of the vibratory plate, the degree of compaction of the soil material is measured during compaction and the pressure force, the duration of the vibratory plate remaining in the same place, the frequency of the vibration movement and / or the amplitude of the vibration movement are controlled depending on the measured degree of compaction.

Description

[0001] The invention relates to a method and a device for mechanically compacting clay-containing soil material using a vibrating plate, in particular for producing rammed earth.

[0002] The compaction of rammed earth is typically done manually with hand-held pneumatic rammers or motor-driven construction machines such as vibratory plates, also known as vibratory plates or surface vibrators.

[0003] Rammed earth is a building material with a centuries-old tradition and has experienced a renaissance in recent decades due to its sustainability and durability. Rammed earth is used in a wide variety of building applications, particularly in residential construction. Its natural thermal properties can be utilized for the production of walls and floors in buildings, as it contributes to temperature regulation, thereby improving comfort and reducing energy consumption. In particular, the use of rammed earth in the production of prefabricated ceiling elements has also been proposed. A corresponding clay-wood composite element is described, for example, in EP 4015730 A1.

[0004] Conventional vibratory plate compactors are suitable for producing rammed earth, but are primarily designed for soil compaction. These compactors operate via at least one unbalanced shaft driven by a motor. The vibration, transmitted to a base plate, generates centrifugal forces that produce the compaction effect and often propel the plate forward.

[0005] The vibration sets the soil particles in motion and simultaneously compresses them more firmly through pressure. The maximum achievable compaction pressure and depth depend largely on the weight of the vibratory plate compactor itself, i.e., the weight of the base plate plus the weight of the top / superstructure mass. High compaction performance can therefore only be achieved with very heavy machines, which are correspondingly difficult to handle.

[0006] The degree of compaction achieved depends on the operator's experience and cannot be directly determined. Some newer machines are equipped with vibration sensors on the base plate, which use frequency band analysis to correlate the soil stiffness and can indicate differences in the degree of compaction to the operator via visual signals.

[0007] Lightweight vibratory plates generate a centrifugal force of 10 kN with a weight of 40 kg. Heavy machines reach up to 130 kN with a weight of 1,200 kg.

[0008] For the production of rammed earth, where relatively small areas are treated compared to soil compaction, e.g., within a formwork or mold, pneumatic rammers or lightweight vibratory plates are primarily used due to accessibility. This results in a compaction depth of only about 8 cm. Therefore, thicker structures must be built up in several individually compacted layers.

[0009] Whether sufficient compressive strength has been achieved in the rammed earth can only be determined indirectly, not directly on the actual component. For this purpose, test cubes with 20 cm edges are created and tested. The production of these test cubes is rarely identical to the manufacturing process of the actual rammed earth component and is therefore only of limited significance. This is because the degree of compaction depends heavily on the properties of the specific material mixture used, meaning that such a test cube is more suitable for testing the material mixture itself than the compaction process.

[0010] The present invention therefore aims to provide a method and a device for the automated compaction of rammed earth, with which a very high compaction pressure (> 30 kN) can be achieved and the attainment of a predetermined compaction pressure can be indicated. At the same time, rammed earth components should also be able to be efficiently compacted even at great layer depths. Furthermore, controlled, measurable, and repeatable compaction performance should be ensured across different material compositions.

[0011] To solve this problem, the invention, according to a first aspect, provides a method for the mechanical compaction of clay-containing soil material using a vibratory plate, in which the vibratory plate is guided as an end effector on a three-axis positioning system over the soil material to be compacted and the pressure force applied to the soil material is adjusted by controlling the positioning system to move it perpendicular to the plane of the vibratory plate, wherein the degree of compaction of the soil material is measured during compaction and the pressure force, the duration of the vibratory plate remaining in the same position, the frequency of the vibration movement and / or the amplitude of the vibration movement are controlled as a function of the measured degree of compaction.

[0012] By combining a vibratory plate compactor with a three-axis positioning system, the invention enables precise control of the pressure exerted on the soil. This allows for the adjustment and adaptation of the compaction degree independent of the weight of the vibratory plate compactor. With conventional methods, the compaction degree was often determined or limited by the weight of the vibratory plate compactor or pneumatic rammer, resulting in less precise control over the compaction process.

[0013] The three-axis positioning system serves two purposes: firstly, to guide the attached vibratory plate compactor in two spatial dimensions over the material to be compacted; and secondly, to adjust the pressure exerted by the vibratory plate compactor on the material by controlling the movement in the third spatial dimension. Suitable positioning systems can be combined with sensors and control systems to precisely control the position and movement of the vibratory plate compactor.

[0014] Any device capable of moving the vibratory plate as the end effector in three spatial directions and applying pressure across the material surface via the vibratory plate is suitable as a positioning system. For example, the positioning system could include a robot arm that can move the vibratory plate with high precision and control along three axes. Alternatively, linear guide systems, such as linear robots or gantry robots, with three-axis adjustability can be used.

[0015] By measuring the degree of compaction of the soil material during compaction, the system can provide feedback that can be used to immediately adjust parameters such as pressure force, dwell time, frequency, and / or amplitude of the vibration motion. The degree of compaction can be measured continuously or at specific time intervals. In the case of continuous measurement, real-time monitoring and corresponding real-time adjustment of the compaction parameters can be achieved.

[0016] Depending on the compaction degree measurement, one or more of the following compaction parameters can be adjusted. The pressure exerted by the vibratory plate on the soil is one of the main factors influencing the degree of compaction. Higher pressure generally leads to a higher degree of compaction because the soil is compressed more. By using the three-axis positioning system in this invention, the pressure can be precisely controlled independently of the weight of the vibratory plate, thus enabling more accurate control of the compaction degree.

[0017] The length of time the vibratory plate remains in a particular position also influences the degree of compaction. A longer dwell time generally results in a higher degree of compaction, as the soil material is compressed for a longer period. The lower the feed rate of the vibratory plate for the same amplitude, the greater the amount of energy input into the compaction process.

[0018] The frequency at which the vibratory plate compactor vibrates is another factor influencing the degree of compaction. A lower frequency can result in soil material being compacted to a greater depth. A high frequency (e.g., above 50 Hz) combined with a small amplitude of the vibration movement usually has only a shallow compaction depth.

[0019] The amplitude of the vibration motion, i.e., the maximum vertical displacement of the vibratory plate, also influences the degree of compaction. Larger amplitudes can result in more intensive compaction of the soil material, with the compaction exhibiting a greater compaction depth, particularly when a larger amplitude is combined with a low frequency.

[0020] Since the invention can provide the required pressing force independently of the weight of the vibratory plate compactor due to the action of the positioning system, vibratory plates of varying weights can be used. According to a first embodiment of the invention, a relatively light (< 100 kg) vibratory plate compactor can be used and a high pressing force still be achieved by generating an additional contact force via the positioning system. In other words, the pressing force can be generated by applying a contact force from the positioning system that acts in the same direction as the force of gravity on the vibratory plate compactor. The advantage of this embodiment lies in its simpler handling. Lighter vibratory plates are generally easier to handle and move, which can improve work efficiency. They also require less energy to be positioned and moved, which can improve the overall energy efficiency of the system.If the positioning system provides a large portion of the compaction force, the actual compaction force can be easily varied by adjusting the force exerted by the positioning system. This offers greater flexibility in adapting the compaction force to the specific requirements of the soil material being compacted.

[0021] According to a second embodiment of the invention, a relatively heavy (> 1,000 kg) vibratory plate compactor can be used, and the pressure force can be adjusted by applying a lifting force via the positioning system. In other words, the pressure force can be adjusted by changing the lifting force of the positioning system, which acts against the force of gravity on the vibratory plate compactor. The advantage of this embodiment lies in the possibility of using heavy vibratory plate compactors with a small footprint, which can exert higher pressure on the soil material, resulting in more effective compaction. Heavy vibratory plate compactors can be difficult to handle manually, especially when they need to be lifted into specific areas, such as formwork. By using a positioning system, the tool can be precisely positioned and guided, which facilitates handling and improves safety.By raising the tool, the weight acting on the surface can be reduced in a controlled manner. This offers additional flexibility in adjusting the pressure force to the specific requirements of the soil material being compacted and allows for finer control of the compaction process.

[0022] The degree of compaction of the soil material can preferably be determined by evaluating vibration measurement data from the vibratory plate compactor. A method for determining soil stiffness values ​​is disclosed, for example, in WO 2005 / 028755 A1. In particular, at least one vibration sensor can measure the vibration behavior of the base plate, with this data being processed on a separate computing unit or directly in the control system of the positioning system. This allows real-time control of the compaction process by adjusting the travel speed and / or the contact pressure of the positioning system. The control preferably operates in a feedback loop until the desired degree of compaction is achieved. Optionally, the power of the vibratory motor can also be adjusted via the control algorithm.

[0023] The actual value of the pressure force exerted by the positioning system on the vibratory plate can also be incorporated into the control of the compaction process. In this context, a preferred embodiment of the invention provides that the pressure force is measured with a load cell, which measures the force acting on the positioning system from the vibratory plate.

[0024] Regarding the control of the compaction parameters depending on the determined degree of compaction, a preferred embodiment of the invention provides that the pressure force is increased incrementally while the vibratory plate remains in the same position, as long as a target value for the degree of compaction has not been reached. The primary control variable is thus the pressure force, while the other parameters of the compaction process remain unchanged. This means that the pressure force is increased while the vibratory plate remains in the same position and the frequency and amplitude of the vibration motion remain constant. Preferably, the pressure force is not adjusted continuously, but rather at predetermined time intervals.

[0025] The frequency and / or amplitude of the vibration motion can be used as a secondary control variable. This is preferably the case when increasing the pressure force is insufficient to achieve the desired degree of compaction. The preferred approach is to specify a maximum pressure force and increase it incrementally until the maximum value is reached, then to increase the degree of compaction by changing the frequency and / or amplitude of the vibration motion. Preferably, the vibrating plate remains in the same position during this secondary control process.

[0026] The vibrating plate is only moved once the desired degree of compaction has been achieved.

[0027] Preferably, decoupling the vibrating plate from the positioning system prevents the transmission of vibrations to the positioning system, such as the robot arm. Rubber-metal buffers, whose effective range is matched to the frequency band of the vibrations occurring, are preferably used as damping elements.

[0028] In summary, the invention allows for the cost-effective production of rammed earth elements, as large construction heights (>8 cm), which usually require compaction in several layers and work steps, can be processed in a single operation. Furthermore, the control of compaction quality ensures that only the necessary amount of process time is used.

[0029] According to a second aspect of the invention, the compaction method according to the invention is used to produce a clay-wood composite element. The clay-wood composite element is a wall or ceiling element of a building, wherein the composite element comprises a plurality of elongated wooden beams, between each of which a space is formed, clay being introduced into the spaces and compacted in each space by means of the compaction method according to the first aspect of the invention. The clay-wood composite element is, for example, a composite element according to EP 4015730 A1.

[0030] According to a third aspect of the invention, a device for the mechanical compaction of clay-containing soil material is provided, which is particularly suitable for carrying out a method according to the first aspect of the invention, comprising a vibratory plate, a three-axis positioning system on which the vibratory plate is arranged, such that the vibratory plate can be guided as an end effector over the soil material to be compacted and the compressive force applied to the soil material can be adjusted by moving the positioning system perpendicular to the plane of the vibratory plate, wherein at least one sensor is provided for determining the degree of compaction of the soil material during compaction, the measured values ​​of which are supplied to a control unit configured to control the compressive force, the duration of the vibratory plate remaining in the same position, the frequency of the vibration movement and / or the amplitude of the vibration movement as a function of the measured degree of compaction.

[0031] Preferred embodiments of the device according to the invention relate to design and control engineering aspects, the technical effects and advantages of which have already been explained above in connection with the method according to the invention.

[0032] Preferably, the control unit is designed to gradually increase the pressure force while the vibratory plate remains in the same position, as long as a target value for the degree of compaction has not been reached.

[0033] Preferably, the control unit is designed to carry out the stepwise increase of the pressure force at predetermined, equal time intervals.

[0034] Preferably, the control unit is designed to gradually increase the pressure force at a constant frequency and amplitude of the vibration movement, as long as a target value for the degree of compaction has not been reached.

[0035] Preferably, the control unit is designed to increase the pressure force in stages until a predetermined maximum pressure force value is reached, and the degree of compaction is then increased by changing the frequency and / or amplitude of the vibration movement.

[0036] Preferably, a force transducer is provided which measures the force acting on the positioning system from the vibrating plate.

[0037] Preferably, the compressive force is increased by increasing the contact force of the positioning system, acting in the same direction as the force of gravity on the vibratory plate. Alternatively, the compressive force is increased by reducing the lifting force of the positioning system, acting against the force of gravity on the vibratory plate.

[0038] Preferably, the sensor is designed to determine vibration measurement data of the vibrating plate.

[0039] The invention is explained in more detail below with reference to exemplary embodiments schematically illustrated in the drawing. In this drawing, Fig. 1 an isometric view of the compaction tool, Fig. 2 an exploded view of the compaction tool, Fig. 3 a side view of a compaction tool on a robot arm, Fig. 4 a side view of a compaction tool on a portal axis and Fig. 5 a flow diagram of a control of the compaction process.

[0040] The compression device according to the invention comprises, according to Fig. 1 and 2A vibratory plate compactor with a rigid steel base plate 3, which is optionally designed as a cast element or as a welded construction. A vibration motor 8 is mounted on the base plate 3 to directly set it into vibration. Optionally, a frequency converter connected to the vibration motor 8 allows the vibration frequency and force to be controlled. A metal plate 6 is connected to the base plate 8 via rubber-metal buffers 1. Another rubber-metal buffer 2 sits on the metal plate 6 and is connected to a load cell 4. Finally, an adapter plate 7 sits on this, which provides a positive connection to a robot arm 9 ( Fig. 3 ) or a mechanically guided portal axis 10 ( Fig. 4 ) is permitted. Additionally, a vibration sensor 5 can be attached to the base plate 3.

[0041] The vibration sensor 5, the force transducer 4, the vibration motor 8, and a frequency converter are connected to a robot controller. A control system on the robot controller evaluates the data from the force transducer 4 and the vibration sensor 5 and adjusts the movements of the robot arm 9 accordingly, or controls the frequency converter and vibration motor 8.

[0042] The regulatory process in is Fig. 5As shown, at the beginning of the compaction process, the vibratory plate is inserted perpendicular to the plate plane into the material to be compacted, thereby exerting a compressive force on the material. A force transducer 4 is used to check whether a predetermined target compressive force has been reached. If not, the control system returns to the previous step and causes the vibratory plate to be inserted further. This cycle is repeated until the predetermined target compressive force is reached. The degree of compaction is then measured, and it is checked whether the target degree of compaction has been achieved. If not, the vibratory plate remains in the same position, and the check for the degree of compaction is repeated. If the target degree of compaction has still not been reached after a predetermined time limit, it is checked whether a predetermined maximum compressive force has been applied.If this is not the case, the target pressure is adjusted and the control process returns to the first step. If, however, the specified maximum pressure has already been reached, the amplitude and / or frequency of the vibration is adjusted instead of increasing the pressure. The verification of whether the target compaction level has been achieved is then carried out with the new setting of the amplitude and / or frequency of the vibration, and the compaction process is carried out as described above until the target compaction level is reached.

Claims

1. A method for mechanically compacting clayey earth material by means of a vibrating plate, in which the vibrating plate is guided as an end effector on a three-axis positioning system (9, 10) over the earth material to be compacted and the compressive force applied to the earth material is adjusted by controlling the positioning system (9, 10) for displacement perpendicular to the plate plane of the vibrating plate, wherein the degree of compaction of the earth material is measured during compaction and the compressive force, the duration of the vibrating plate remaining in the same place, the frequency of the vibrating movement and / or the amplitude of the vibrating movement are controlled as a function of the measured degree of compaction.

2. Method according to claim 1, characterized in that the pressure force is gradually increased while the vibrating plate remains in the same position as long as a target value for the degree of compaction is not reached.

3. Method according to claim 2, characterized in thatthe gradual increase in pressure force occurs at predetermined, equal time intervals.

4. Method according to claim 2 or 3, characterized in that the pressure force is gradually increased while maintaining the same frequency and amplitude of the vibration movement until a target value for the degree of compaction is reached.

5. Method according to one of claims 1 to 4, characterized in that the compressive force is gradually increased until a predetermined maximum value of the compressive force is reached, and the degree of compaction is then increased by changing the frequency and / or amplitude of the vibrating movement.

6. Method according to one of claims 1 to 5, characterized in that the compressive force is measured with a load cell (4) which measures the force acting from the vibrating plate on the positioning system (9,10).

7. Method according to one of claims 2 to 6, characterized in thatthe pressure force is increased by increasing the contact force of the positioning system (9,10) acting in the same direction in addition to the gravity of the vibrating plate.

8. Method according to one of claims 2 to 6, characterized in that the pressure force is increased by reducing a lifting force of the positioning system (9,10) acting against the gravity of the vibrating plate.

9. Method according to one of claims 1 to 8, characterized in that the degree of compaction is determined by evaluating vibration measurement data from the vibrating plate.

10. A method for producing a clay-wood composite element as a wall or ceiling element of a building, wherein the composite element comprises a plurality of elongated wooden beams, between each of which an intermediate space is formed, characterized in that Clay is introduced into the spaces and the clay in the spaces is compacted by means of a method according to one of claims 1 to 9.

11. Device for the mechanical compaction of clayey earth material, in particular for carrying out a method according to one of claims 1 to 9, comprising a vibrating plate, a three-axis positioning system (9, 10) on which the vibrating plate is arranged, so that the vibrating plate can be guided as an end effector over the earth material to be compacted and the compressive force applied to the earth material can be adjusted by displacing the positioning system (9, 10) perpendicular to the plate plane of the vibrating plate, wherein at least one sensor (5) is provided for determining the degree of compaction of the earth material during compaction, the measured values of which are fed to a control unit which is designed to control the compressive force, the duration of the vibrating plate remaining at the same location, the frequency of the vibrating movement and / or the amplitude of the vibrating movement as a function of the measured degree of compaction.

12. Device according to claim 11, characterized in thatthe control unit is designed to gradually increase the pressure force while the vibrating plate remains at the same location as long as a target value of the degree of compaction is not reached.

13. Device according to claim 12, characterized in that the control unit is designed to carry out the gradual increase of the pressure force at predetermined, equal time intervals.

14. Device according to claim 12 or 13, characterized in that the control unit is designed to gradually increase the pressure force while maintaining a constant frequency and amplitude of the vibration movement as long as a target value for the degree of compaction is not reached.

15. Device according to one of claims 11 to 14, characterized in that the control unit is designed to increase the compressive force gradually until a predetermined maximum value of the compressive force is reached, and the degree of compaction is then increased by changing the frequency and / or amplitude of the vibrating movement.

16. Device according to one of claims 11 to 15, characterized in that a load cell is provided which measures the force acting from the vibrating plate on the positioning system (9,10).

17. Device according to one of claims 11 to 16, characterized in that the pressure force is increased by increasing the contact force of the positioning system (9,10) acting in the same direction in addition to the gravity of the vibrating plate.

18. Device according to one of claims 11 to 16, characterized in that the pressure force is increased by reducing a lifting force of the positioning system (9,10) acting against the gravity of the vibrating plate.

19. Device according to one of claims 11 to 18, characterized in that the sensor (5) is designed to determine vibration measurement data of the vibrating plate.

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