TECHNICAL FIELD

The present invention relates to construction industry, in particular to underground construction.

BACKGROUND

On construction sites, it is often necessary to transport construction aggregate material such as gravel over a longer distance to a specific location. The transport can be time-consuming and costly and in some cases can adversely affect the area of the construction site. The present invention is aimed at transporting construction aggregate material such as gravel to a specific location effectively and inexpensively, while reducing or avoiding damage to the area of the construction site.

OVERVIEW

A first aspect relates to a double lock aggregate mixer that includes: an upper tank including an inlet opening for receiving a construction aggregate; a lower tank arranged below the upper tank and including an inlet port for receiving a fluid (i.e. a liquid, e.g. water, or a gas, e.g. air) and an outlet port for releasing a mixture of the construction aggregate and the fluid; an upper lock configured to open and close the inlet opening of the upper tank; and a lower lock arranged between the upper tank and the lower tank and configured to open and close a passage between the upper tank and the lower tank.

A second aspect relates to an aggregate transport system that includes a double lock aggregate mixer according to the first aspect, and a fluid pump coupled to the inlet port of the lower tank. The fluid pump (e.g. a fluid pump or a gas pump; the latter may also be referred to as “compressor”) is configured to pump a fluid via the inlet port of the lower tank into the lower tank. A third aspect relates to a method for operating a double lock aggregate mixer according to the first aspect. The method includes: continuously pumping a fluid via the inlet port of the lower tank into the lower tank; cyclically opening and closing the upper lock and the lower lock such that each time the upper lock is open, a construction aggregate enters the upper tank via the open upper lock and the inlet opening of the upper tank; each time the lower lock is open, at least a part of the construction aggregate contained in the upper tank enters the lower tank via the open lower lock and mixes with the fluid in the lower tank such that an aggregate-fluid-mixture is formed; wherein the aggregate-fluid-mixture formed in the lower tank is pressed out of the lower tank through the outlet port due to a pressure generated in the lower tank by the fluid pumped by the fluid pump fluid into the lower tank.

A fourth aspect relates to a method for operating an aggregate transport system according to the second aspect. The method includes: providing an aggregate transport system according to the second aspect and operating the double lock aggregate mixer according to the method of the third aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments described below can be better understood with reference to the following drawings and descriptions. The components in the figures are not necessarily to scale; instead emphasis is placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts. In the drawings:

FIG. 1 schematically illustrates a construction site with a plant for the production of stone columns.

FIG. 2A schematically illustrates a cross-sectional view of a first embodiment of a double lock aggregate mixer that may be used in the plant for the production of stone columns shown in FIG. 1, with two locks of the double lock aggregate mixer being in a first state. FIG. 2B schematically illustrates a cross-sectional view of the double lock aggregate mixer of FIG. 2A with the two locks being in a second state different from the first state.

FIG. 3 schematically illustrates a cross-sectional view of a second embodiment of a double lock aggregate mixer that may be used in the plant for the production of stone columns shown in FIG. 1.

FIG. 4 schematically illustrates a cross-sectional view of a third embodiment of a double lock aggregate mixer that may be used in the plant for the production of stone columns shown in FIG. 1.

FIG. 4 schematically illustrates a cross-sectional view of a fourth embodiment of a double lock aggregate mixer that may be used in the plant for the production of stone columns shown in FIG. 1.

FIG. 6A schematically illustrates a cross-sectional view of a section of a rig used in the plant for the production of stone columns shown in FIG. 1.

FIG. 6B schematically illustrates a more detailed cross-sectional view of a hopper shown in FIG. 6A.

FIG. 7 schematically illustrates a two-stage system for conveying a construction aggregate.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings. The drawings form a part of the description and, for the purpose of illustration, show examples of how the invention can be used and implemented. It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically noted otherwise. Further, although the examples described herein are directed to a plant for the production of stone columns, the invention is not limited to the production of stone columns or to construction plants.

FIG. 1 schematically illustrates a construction site with a plant for the production of construction aggregate columns 13 like stone columns made from a suitable construction aggregate using a construction aggregate column rig 16. In the sense of the present invention, the term “construction aggregate” refers to any or any combination of medium- to coarse-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. In the following, the construction aggregate is briefly also referred to as “aggregate”. When aggregate columns 13 are built in an area where there is a risk that slope failures 14 can be triggered by the installation process of the aggregate columns 13, it is not advisable to provide the aggregate to the aggregate column rig 16 using a wheel loader driving within the range of the possible slope failure 14 since the use of the wheel loader can adversely affect the mechanical stability of the soil, so that the probability of occurrence of landslides can be additionally increased.

The plant further includes a crane 1 located at a safe distance from of the reach of the possible slope failure 14, and the rig 16 is suspended from the crane 1 in a region of an aggregate column 13 to be produced. In order to avoid the necessity of a wheel loader driving within the range of the possible slope failure 14, the aggregate is delivered to the rig 16 using a fluid pump 3 in combination with a double lock aggregate mixer (in the following simply referred to as “aggregate mixer”) 2 and an aggregate-fluid-mixture transport hose 5 that bridges the area of the possible slope failure 14. The aggregate mixer 2 is placed at a safe distance from the area of the possible slope failure 14.

The (high-volume) fluid pump 3 is, via a fluid supply hose 4, in fluid connection with the aggregate mixer 2 and pumps a fluid, e.g. water, through the fluid supply hose 4 into the aggregate mixer 2. Within the aggregate mixer 2, the fluid is mixed with aggregate and flows, mixed with the aggregate, via the aggregate-fluid-mixture transport hose 5 to a hopper 6 of the rig 16. In the hopper 6, the aggregate and the fluid are separated from one another. If the fluid is a liquid the majority of the liquid that was needed to pump the aggregate from the aggregate mixer 2 to the hopper 6 is now discharged from the hopper 6 through a feedback hose 15 back to the fluid pump 3 which in this case is a liquid pump, so that the liquid can be used again to transport a further amount of aggregate from the aggregate mixer 2 to the rig 16. In other words, instead of just letting the liquid run onto the ground at the rig 16, the majority of the liquid may be recycled. On the one hand, this saves costs, and on the other hand, the soil is softened less, thus avoiding an increase in the risk of landslides occurring. Instead of one feedback hose 15 only, two or more feedback hoses 15 connected in parallel may also be used.

Optionally, the feedback hose(s) 15 may enter into a buffer tank (here not shown) before the liquid is fed back into the pumping cycle to the liquid pump 3. Such buffer tank may also have the purpose of separating the returning water from any sand and mud that could harm the liquid pump 3. In the present embodiment, the feedback hose 15 is shown as in part hanging from the crane boom. However, this is not required. Alternatively, the feedback hose(s) 15 may also just lay on the ground.

FIG. 2A schematically illustrates a cross-sectional view of a first one of several embodiments of a double lock aggregate mixer 2 that may be used as the double lock aggregate mixer 2 shown in FIG. 1. Compared to conventional (non-double-lock)-aggregate mixers, the double lock aggregate mixers described herein have the advantage that the aggregate mixing can be continuous and does not have to be interrupted to refill aggregate. Not interrupting such aggregate flow means a huge time saving of almost 50% of the process time required in connection with conventional aggregate mixers.

As illustrated in FIG. 2A, the aggregate mixer 2 may include an optional hopper 28, an upper lock 26, an upper tank 23, a lower lock 27, a lower tank 22 and an optional throughput adjusting means 25. The hopper 28 is arranged above the upper tank 23 and the upper tank 23 is arranged above the lower tank 22. The upper lock 26 is configured to open and close an inlet opening 230 of the upper tank 23 and the lower lock 27 is configured to open and close a passage between the upper tank 23 and the lower tank 22. The inlet opening 230 may be arranged at the top side of the upper tank 23. In case the hopper 28 is present, the upper lock 26 is also configured to open and close a passage between the hopper 28 and the upper tank 23. The inlet opening 230 of the upper tank 23 serves to receive the aggregate 29, so that the upper container 23 is filled with the aggregate 29 provided that the upper lock 26 is open. In the illustrated embodiment, the aggregate 29 is supplied to the inlet opening 230 via the hopper 28, which, optionally, may be part of the aggregate mixer 2. From time to time, the hopper 28 may be refilled with aggregate by a wheel loader so that, in ideal circumstances, there is always aggregate in the hopper 28.

Instead of being supplied through a hopper 28, the aggregate 29 may be supplied to the inlet opening 230, and, therefore, to the upper tank 23 in any other manner. For instance, the aggregate 29 may be stored in a large storage tank (not illustrated) arranged above the inlet opening 230 and be released from the large storage tank into the upper tank 23 via the inlet opening 230. The volume of the large tank may be a multiple of the volume of the upper tank 23. Alternatively, it is also possible to supply the aggregate to the inlet opening 230, and, therefore, to the upper tank 23 via a hose coupled to the inlet opening 230.

As illustrated in FIG. 2A, the hopper 28 may be filled with aggregate 29. By opening the upper lock 26, aggregate 29 can fall from the hopper 28 into the upper tank 23, and by opening the lower lock 27, aggregate 29 can get from the upper tank 23 into the lower tank 22. In FIG. 2A, the lower lock 27 is closed. The aggregate 29 in the lower tank 22 mixes with the fluid, e.g. water or air, flowing into the lower tank 22 from the fluid supply hose 4 and, together with the fluid, is introduced through the aggregate-fluid-mixture transport hose 5 into a hopper 6 located at the rig 16 (FIG. 1). During the time the lower lock 27 is closed, the upper tank 23 may be refilled with aggregate 29 falling down from the hopper 28 through the upper lock 26, if the upper lock 26 is open.

Compared to FIG. 2A, in FIG. 2B the locks 26, 27 are in the opposite positions, i.e., the upper lock 26 is closed and the lower lock 27 is open. Since the lower lock 27 is open, aggregate 29 can get from the upper tank 23 into the lower tank 22. Also in this state, the aggregate 29 in the lower tank 22 mixes with the fluid flowing into the lower tank 22 from the fluid supply hose 4 and, together with the fluid, is introduced through the aggregate- fluid-mixture transport hose 5 into the hopper 6 (FIG. 1). Since the upper lock 26 is closed, also in this state there is pressure in the lower tank 22 sufficient to convey the aggregate-fluid-mixture contained in the lower tank 22 through the aggregate-fluid-mixture transport hose 5 to the hopper 6.

By controlling the locks 26, 27 during the conveying of aggregate in such a way that at any time at least one of the locks 26, 27 is closed, there is always a pressure in the lower tank 22 which is sufficient to convey the aggregate-fluid-mixture in the lower tank 22 through the aggregate-fluid- mixture transport hose 5 to the hopper 6 without a need to interrupt this flow when the lower tank 22 is filled with additional aggregate. Such interruption would be necessary, if there would not exist the two locks as per this invention. In case of such interruption the aggregate- fluid-mixture transport hose 5 would need to always be emptied of all aggregate before the flow may stop and the lower tank 22 refilled. Not obeying this would lead to clogging of such aggregate-fluid- mixture transport hose 5 after a restart of the flow as any remaining aggregate would form plugs in the aggregate-fluid-mixture transport hose 5 once the flow is interrupted. This prevention of clogging and saving the time to fully empty the aggregate-fluid-mixture transport hose 5 after each blow cycle from all aggregates is a major advantage of this invention. The plant may be configured such that when at least one of the upper lock 26 and the lower lock 27 is closed, a fluid supplied to the lower tank 22 via the inlet port 221 may cause a pressure to build up in the lower tank 22 which at any time during operation of the plant may be, without being restricted to, at least 3 bar, e.g. in a range from 3 bar to 6 bar.

Since the lower tank 22 and hence also the fluid supply hose 4 and the aggregate-fluid-mixture transport hose 5 may stay permanently under pressure provided by the fluid pump 3, the flow of the aggregate- fluid-mixture in the aggregate-fluid-mixture transport hose 5 can be maintained uninterrupted. Operating the upper lock 26 and the lower lock 27 in the described manner may take place using a controller 7 that is electrically coupled to both the upper lock 26 and the lower lock 27. The controller 7 may be part of the aggregate mixer 2 or be separate therefrom.

Optionally, the flow of aggregate from the upper tank 23 to the lower tank 22 and thereby the ratio of water to aggregate in the aggregate-fluid-mixture transport hose 5 may be controlled (e.g. limited) by adjusting a throughput adjusting means 25 configured to adjust the throughput rate of aggregate 29 getting from the upper tank 23 down to the lower tank 22. According to one embodiment, the throughput adjusting means 25 may include a screw conveyor 251 and a variable speed motor 252 coupled to the screw conveyor 251 and configured to rotate the screw conveyor 251 at a desired, adjustable rotational speed such that aggregate 29 is conveyed from the upper tank 23 via the rotating screw conveyor 251 into the lower tank 23 at an adjustable rate that depends on the rotational speed of the screw conveyor 251. It is to be noted that such throughput adjusting means 25 is not a necessary component of the double lock aggregate mixer 2 and, therefore, may be omitted. However, it may be advantageous to prevent clogging of the aggregate-fluid-mixture transport hose 5.

FIG. 3 schematically illustrates a cross-sectional view of a second embodiment of a double lock aggregate mixer 2 that may be used as the double lock aggregate mixer 2 shown in FIG. 1. Compared to the first embodiment illustrated in FIGS. 2A and 2B, the upper tank 23 is formed like a pressurized channel, and the screw conveyor 251 is much longer and/or much larger in diameter. Due to the channel-shape of the upper tank 23, the mixer can be manufactured more easily. The operating principle of the aggregate mixer 2 may be the same as described with reference to FIGS. 2 A and 2B.

FIG. 4 schematically illustrates a cross-sectional view of a third embodiment of a double lock aggregate mixer 2 that may be used in lieu of the double lock aggregate mixer 2 shown in FIG. 1. According to this embodiment, the throughput adjusting means 25 may include a cone valve 32 or any other flow restrictor that can be more or less closed depending on the desired throughput rate of aggregate 29 from the upper tank 23 to the lower tank 22. The shape of the upper tank 23 can be freely selected. For example, the upper tank 23 can have a bulbous shape, as shown in FIGS. 2 A and 2B, or a channel shape, as shown in FIG. 3. The operating principle of the aggregate mixer 2 may be the same as described with reference to FIGS. 2A and 2B.

FIG. 5 schematically illustrates a cross-sectional view of a fourth embodiment of a double lock aggregate mixer 2 that may be used in lieu of the double lock aggregate mixer 2 shown in FIG. 1. According to this embodiment, the throughput is not limited by reducing the downward flow by means as per FIGS. 3 and 4 but in this fourth embodiment a piston 301 controlled by a stick 300 may be pressed with force downward in the upper tank 23 (which in the present embodiment, without being restricted to, is cylindrically shaped) to force more of the aggregate downward into the lower tank 22 as otherwise would flow down by gravity alone. This can be useful if the (specific) weight of the aggregates is lighter than that of concrete or gravel or if a violent hydraulic flow regime in the lower tank 22 would not allow enough aggregate to enter the aggregate-fluid-mixture transport hose 5. The piston 301 may have small holes in driving direction of the piston 301 to let fluid pass through but no aggregate.

Referring now to FIGS. 6A and 6B, the principle of separating liquid used as the fluid from the aggregate-fluid-mixture (which in this case is an aggregate-liquid-mixture) at the rig 16 and feeding back the separated fluid to the fluid pump 3 (which in this case is a liquid pump) will be explained in more detail. FIG. 6A shows an upper section of the rig 16 illustrated in FIG. 1, and FIG. 6B shows the hopper 6 in more detail.

The aggregate-liquid-mixture flowing through the aggregate-liquid-mixture transport hose 5 is fed into the hopper 6 through the inlet opening 63 (FIG. 6B) of the hopper 6. In principle, one could just let the liquid contained in the aggregate-liquid-mixture flow over the top of the hopper 6 and onto the ground floor. This is however not a viable option for many reasons:

1) Waste of expensive water

2) Water entering the ground via the ground surface in large quantities (typically several hundred m ³ per hour) would cause erosion and be environmentally of concern in many jurisdictions.

3) Most importantly, in projects with a potential for landslides triggered by the aggregate column installation, the adding of liquid in the area of the rig 16 would create a destabilizing flow gradient that could very well trigger a landslide that otherwise would not happen, since the liquid flow would be in direction of the landslide and thereby could generate large additional horizontal (driving downhill) forces.

As illustrated in the enlarged view of the hopper 6 in FIG. 6B, the hopper 6 may have a double wall 61, 62 formed from an outer wall 61 and an inner wall 62. The inner wall 62 is formed as a screen 31 with screen openings 30. The openings 30 of the screen 31 are shaped so that the aggregate 29 contained in the aggregate-liquid mixture does not substantially pass through the openings 30, but is retained by the screen 31 and exits through the outlet opening 64 of the hopper 6 so that it may be used in the further construction process like, but without being restricted to, the production of aggregate columns 13.

In contrast, a substantial portion of the liquid contained in the aggregate-liquid mixture passes through the screen openings 30 into a gap 60 formed between the outer wall 61 and the inner wall 62, from which it flows into the feedback hose(s) 15 and is returned to the liquid pump 3 through the feedback hose(s) 15, as described above with reference to FIG. 1, and recycled. Each feedback hose 15 may be in fluid connection with both the gap 60 and, directly or (e.g. via a buffer tank as described with reference to FIG. 1) indirectly, the liquid pump 3.

The design of the screen 31 is basically arbitrary. For example, it can be formed as a mesh 31 known from sieves (e.g. woven wires, woven metal stripes, etc.), or just metal plates with holes drilled or stamped into it which have a size smaller than the aggregate to be retained by the screen 31.

It is to be noted that such a hopper 6 configured to separate a liquid contained in a mixture of construction aggregate and a liquid from the construction aggregate contained in the mixture is not restricted to the production of construction aggregate columns but may be used in any other construction technique. Particularly, there is no requirement to operate such a hopper 6 in connection with a double lock aggregate mixer.

In some construction projects, it may be desirable to convey the aggregate-fluid-mixture to great heights, such as in the manufacture of deep aggregate columns 13, which requires the hopper 6 to be at a great height above the ground level 100. If the great height exceeds the height achievable with commercially viable fluid pumps or exceeds the height for the capacity of a conventional aggregate-fluid-mixture transport hose (it is sensible to limit the aggregate-fluid-mixture transport hose pressure to some value around a maximum of 8 bar), then a further double action aggregate mixer, possibly together with a further fluid pump, may be suspended, e.g. approximately half way up the crane boom, e.g. from a second crane wire rope. An example for such an installation will be explained with reference to FIG. 7. In order to simplify the drawing, only the most essential elements are shown. Other elements, such as the crane, the fastening ropes for the pumps and aggregate mixers, etc., are omitted.

The plant illustrated in FIG. 7 includes a first conveying stage and a second conveying stage which is, relative to the first conveying stage, placed at an elevated position. The first conveying stage conveys a construction aggregate to the second conveying stage which is, relative to the first conveying stage, located at an elevated position. The second conveying stage conveys the construction aggregate to an elevated position (in the present example, but without being restricted to, a hopper 6) relative to the second conveying stage.

The first conveying stage includes a (first) fluid pump 3, a (first) aggregate mixer 2, a (first) fluid supply hose 4, and at least one (first) feedback hose 15, and the second conveying stage includes a further (second) fluid pump 3’, a further (second) aggregate mixer 2’, a further (second) fluid supply hose 4’, and at least one further (second) feedback hose 15’. The (first) aggregate mixer 2 includes a (first) upper tank 23, a (first) lower tank 22, a (first) upper lock 26, a (first) lower lock 27 and a (first) hopper 28. The further (second) aggregate mixer 2’ includes a further (second) upper tank 23’, a further (second) lower tank 22’, a further (second) upper lock 26’, a further (second) lower lock 27’ and a further (second) hopper 28’.

The components of the first conveying stage may operate in the same way as the corresponding elements described with reference to the previous figures. However, the aggregate-fluid-mixture generated in the first aggregate mixer 2 is conveyed through the first aggregate- fluid mixture transport hose 5 into the second hopper 28’. In case the fluid is a liquid, the second hopper 28’ may be designed according to the principle described with reference to the hopper 6 illustrated in FIGS. 1, 6A and 6B, so that the majority of the liquid contained in the aggregate-liquid mixture can be separated from the aggregate contained in the aggregate-liquid mixture and fed back to the first pump 3 via the at least one first feedback hose 15. The second conveying stage may operate in the same way as the corresponding elements described with reference to the previous figures with the difference that the second conveying stage is at an elevated position and, if the fluid is a liquid, that the aggregate received by the second hopper 28’ may include some liquid. The elements of the second conveying stage are designated by the same reference numerals but with an added single prime (‘).

With this two-stage design, the first conveying stage (including the first fluid pump 3 and the first aggregate mixer 2) standing on the ground 100 may convey an aggregate-fluid mixture into the second hopper 28’ of the second aggregate mixer 2’ (being in an elevated position above the ground 100, e.g. in mid-air suspended from the boom of the crane 1 (FIG. 1)) of the second conveying stage.

With the second conveying stage, the second aggregate-fluid-mixture transport hose 5’ conveys the aggregate- fluid-mixture generated in the second aggregate mixer 2’ into the hopper 6 at the rig 16, where, if the fluid is a liquid, the majority of the liquid contained in the aggregate-liquid- mixture is separated from the aggregate contained in the aggregate-liquid-mixture and fed back to the second pump 3’ via the at least one second feedback hose 15’. The liquid fed back to the second pump 3’ may be recycled, i.e. supplied to the second aggregate mixer 2’ via the second liquid supply hose 4’.

If the fluid of the first stage is a gas, the first feedback hose(s) 15 may be omitted and if the fluid of the second stage is a gas, the second feedback hose(s) 15’ may be omitted.

Compared to a one-stage design, such a two-stage design allows to achieve approximately twice the height achievable with a single stage.

In the example of FIG. 7, the second fluid pump 3’ has been described to be located at an elevated position relative to the first conveyer. However, this is only an example. In principle, the position is arbitrary. For instance, the second fluid pump 3’ may also be placed on or close to the ground 100 since pumping just a fluid (i.e. without aggregate) to great heights is unproblematic. In the above examples, hoses are used in order to convey the fluid, the aggregate or the aggregate-fluid-mixture. However, these hoses are only an example. Instead, any suitable type of conduit such as rigid pipes or rigid pipes in combination with flexible hoses may be used.

In the following, some example embodiments of the present invention are summarized here. Other embodiments can also be understood from the entirety of the specification and the claims filed herein.

Example 1. A double lock aggregate mixer including: an upper tank including an inlet opening for receiving a construction aggregate; a lower tank arranged below the upper tank and comprising an inlet port for receiving a fluid and an outlet port for releasing a mixture of the construction aggregate and the fluid; an upper lock configured to open and close the inlet opening of the upper tank; and a lower lock arranged between the upper tank and the lower tank and configured to open and close a passage between the upper tank and the lower tank.

Example 2. The double lock aggregate mixer according to example 1 configured to operate the upper lock and the lower lock such that, at any time during the operation of the double lock aggregate mixer, at least one of the upper lock and the lower lock is closed.

Example 3. The double lock aggregate mixer according to example 2 including a controller configured to operate the upper lock and the lower lock such that, at any time during the operation of the double lock aggregate mixer, at least one of the upper lock and the lower lock is closed.

Example 4. The double lock aggregate mixer according to any one of the preceding examples including a throughput adjusting means configured to adjust a throughput rate of the construction aggregate fed from the upper tank down to the lower tank.

Example 5. The double lock aggregate mixer according to example 4, wherein the throughput adjusting means includes a screw conveyor or a cone valve. Example 6. An aggregate transport system including a double lock aggregate mixer according to any one of the preceding examples; and a fluid pump coupled to the inlet port of the lower tank and configured to pump a fluid via the inlet port of the lower tank into the lower tank.

Example 7. The aggregate transport system according to example 6, wherein the fluid pump is configured to produce in a state, in which at least one of the upper lock and the lower lock is closed, a pressure 3 bar.

Example 8. The aggregate transport system according to one of examples 7 or 8, further including: a further double lock aggregate mixer according to any one of examples 1 to 5 located in an elevated position with respect to the double lock aggregate mixer; and a further fluid pump coupled to the inlet port of the lower tank of the further double lock aggregate mixer and configured to pump a fluid via the inlet port of the lower tank of the further double lock aggregate mixer into the lower tank of the further double lock aggregate mixer.

Example 9. The aggregate transport system according to example 8 configured to: generate an aggregate-fluid-mixture in the lower tank of the double lock aggregate mixer and convey the aggregate-fluid-mixture via the outlet port of the lower tank of the double lock aggregate mixer to the further double lock aggregate mixer; generate an aggregate-fluid-mixture in the lower tank of the further double lock aggregate mixer using the construction aggregate contained in the aggregate-fluid-mixture received by the further double lock aggregate mixer and convey the aggregate-fluid-mixture generated in the lower tank of the further double lock aggregate mixer via the outlet port of the lower tank of the further double lock aggregate mixer to an elevated position with respect to the further double lock aggregate mixer.

Example 10. A method for operating a double lock aggregate mixer according to one of examples 1 to 5. The method includes: continuously pumping a fluid via the inlet port of the lower tank into the lower tank; cyclically opening and closing the upper lock and the lower lock such that each time the upper lock is open, a construction aggregate enters the upper tank via the open upper lock and the inlet opening of the upper tank; each time the lower lock is open, at least a part of the construction aggregate contained in the upper tank enters the lower tank via the open lower lock and mixes with the fluid in the lower tank such that an aggregate-fluid-mixture is formed; wherein the aggregate-fluid-mixture formed in the lower tank is pressed out of the lower tank through the outlet port due to a pressure generated in the lower tank by the fluid pumped by the fluid pump into the lower tank.

Example 11. A method for operating an aggregate transport system. The method includes: providing an aggregate transport system according to one of examples 6 to 9; operating the double lock aggregate mixer according to the method of example 10.

Example 12. A two-stage aggregate transport system including: a first aggregate mixer configured to: receive both a fluid from a first fluid pump and a construction aggregate; and produce a first mixture containing the construction aggregate and the fluid received from the first fluid pump; a second aggregate mixer located at an elevated position with respect to the first aggregate mixer, the second aggregate mixer configured to: receive both a fluid from a second fluid pump and the first mixture; and produce a second mixture containing the construction aggregate contained in the first mixture and the fluid received from the second fluid pump; and a conduit configured to receive the second mixture from the second aggregate mixer and to release the second mixture at an elevated position with respect to the first aggregate mixer. The first aggregate mixer and/or the second aggregate mixers may be double lock aggregate mixers, but are not required to.

Example 13. A hopper including: an outer wall; an inner wall formed as a screen comprising screen openings; and a gap formed between the outer wall and the inner wall. The screen is configured to retain solid material contained in a mixture of solid material contained and a liquid. The hopper includes a first outlet coupled to the gap in order to allow for a part of the liquid entering the gap through the screen openings to exit the gap via the first outlet. The hopper further includes a second outlet configured to release the retained solid material.

Example 14. An aggregate transport system including: an aggregate mixer configured to receive both a liquid from a liquid pump and a construction aggregate and to produce an aggregate- liquid-mixture containing the construction aggregate and the liquid received from the liquid pump; and a hopper according to example 13 located at an elevated position with respect to the aggregate mixer. The aggregate transport system is configured to convey the aggregate-liquid- mixture into the hopper such that the majority of the construction aggregate contained in the aggregate-liquid-mixture is retained by the screen and that at least a part of the liquid contained in the aggregate-liquid-mixture enters the gap via the screen openings and is feedback to the liquid pump.

REFERENCE NUMERALS

1 crane

2, 2’ aggregate mixer

3, 3’ fluid pump

4, 4’ fluid supply hose

5, 5’ aggregate- fluid- mixture transport hose

6 hopper

7 controller

13 stone column

14 slope failure

15, 15’ feedback hose

16 rig

20 inlet opening of aggregate mixer

22 lower tank

23 upper tank

25 throughput adjusting means

26, 26’ upper lock

27, 27’ lower lock

28, 28’ hopper

29 aggregate

30 screen opening

31 screen

32 cone valve

60 gap

61 outer wall of hopper

62 inner wall of hopper

63 inlet opening of hopper

64 outlet opening of hopper

100 ground

221 , 221 ’ inlet port of lower tank 222, 222’ outlet port of lower tank

230 inlet opening of upper tank

251 screw conveyor

252 variable speed motor 300 stick

301 piston