Technical field

The present disclosure relates to a method for installing a ground anchor comprising an expandable part, and to a device for installing such a ground anchor.

Background

Ground anchors with underground expandable parts are commonly used today for supporting and reinforcing structures and buildings and other structures, such as fences, aerials, monuments, etc.

A ground anchor with expandable part is for example shown in

EP0820550B1 , the entire content of which is incorporated herein by reference, as is a method of its expansion.

Installation of ground anchors by means of a hydraulic pump is associated with relatively high forces and pressures. Such high forces and pressures are associated with wear on the tools used for installation.

There is a need for reducing wear on the tools, as this would lead to increase uptime of the equipment and thus a more efficient installation process.

Summary

It is an object of the present disclosure to provide a method of installing a ground anchor comprising an expandable part and to provide a system comprising such a ground anchor, which reduces the wear on the tooling.

The invention is defined by the appended independent claims.

Embodiments are set forth in the dependent claims, in the attached drawings and in the following description.

According to a first aspect, there is provided a method of installing a ground anchor comprising an expandable part. The method comprises the steps of driving the ground anchor into the ground, providing an expansion tool having an expansion member, which is operable by pressurization of a fluid, feeding fluid to the expansion tool (such that the expansion member causes the expandable part to expand. During the feeding, the method comprises measuring a flow of the fluid and/or amount of fluid fed, and increasing a feeding pressure of the fluid in response to a measured reduction of the flow.

The fluid may be a gas, such as pressurized air, or a liquid, such as hydraulic fluid.

It is understood that a the flow is the derivative with respect to time of the amount fed.

By starting out at a lower pressure and increasing the pressure during the installation, it is possible to utilize a lower pressure during most of the installation and thus only subject the expansion tool to a higher pressure if and when this is necessary. Hence, wear of tool parts, in particular seals, may be decreased, as may energy consumption.

The method may further comprise measuring a pressure of the fluid during said feeding,

A first phase of the feeding may be performed at a predetermined first pressure.

Such predetermined pressure may be received as a user input, from a data memory as a universal default value or from a data memory in response to an input or selection of ground anchor type and/or ground type.

A second phase of the feeding may be performed at a second pressure, which is higher than the first pressure.

The second pressure may be a predetermined second pressure. In the alternative, the second pressure may be determined as a function of the first pressure and/or as a function of a flow rate.

The pressure may be increased such that the flow is substantially maintained.

Hence, the second pressure may be dependent on the flow. That is, the second pressure may be provided as a function of the measured flow. The method may further comprise interrupting the feeding once a

predetermined amount of fluid has been fed. According to a second aspect, there is provided a device for installing a ground anchor comprising an expandable part. The device comprises an operable expansion member, which is operable by pressurization of a fluid, a feeding device for feeding fluid to the expansion member, a flow meter for measuring the flow of fluid fed to the expansion member and/or a volume meter for measuring an amount of fluid fed, and a pressure regulating device for regulating pressure of the fluid fed to the expansion member, and a control device, adapted to receive a flow signal from the flow meter and/or a volume signal from the volume meter, and to provide a control signal to the pressure regulating device based on the flow signal and/or volume signal, such that the pressure regulating device controls a pressure of the fluid fed to the expansion member based on the flow of the fluid fed to the expansion member and/or based on the amount of fluid fed.

A "signal" may be any type of signal, whether provided electronically (analog or digital), optically, mechanically, acoustically or through a fluid.

Thus, a "flow signal" is a signal indicating a measured flow and a "control signal" is a signal used to control the operation of the pressure regulating device.

The device may further comprise a pressure meter for measuring a pressure between the feeding device and the expansion member, wherein the control device may be adapted to receive a pressure signal from the pressure meter.

The control device may be adapted to control the pressure regulating device also based on the pressure of the fluid fed to the expansion member.

According to a third aspect, there is provided a method of installing a ground anchor comprising an expandable part. The method comprises the steps of driving the ground anchor into the ground, providing an expansion tool having an expansion member, which is operable by pressurization of a fluid, feeding fluid to the expansion tool such that the expansion member causes the expandable part to expand, during said feeding, measuring a flow of the fluid and/or an amount of fluid fed, during said feeding, measuring a pressure of the fluid, and determining, based on the measured flow and/or amount of fluid and on the pressure, whether the installation meets a predetermined strength requirement or not.

Hence, it is possible to provide, in real time, an indication to the effect that the installation was successful or not. The determination may be based on empirical data for different types of installation environments.

The method may further comprise interrupting said feeding when a predetermined pressure has been attained and/or when a predetermined amount of fluid has been fed.

The feeding may be interrupted automatically, on reaching the predetermined amount of fluid and/or the predetermined pressure. In the alternative, an indication may be provided when the amount of fluid or pressure has been attained, whereby the user may, in response, interrupt the feeding.

By such interruption, it is possible to reduce the risk of the tools overrunning. It is also possible to automate the installation process.

The method may further comprise recording said measured flow and/or amount of fluid fed and pressure in a data memory.

By recording such measured flow and/or pressure in a data memory, it is possible to derive an indication of the installation quality, i.e. it is possible to learn whether a particular ground anchor has been properly installed. If, e.g. the amount of fluid indicates complete expansion, and the greatest measured pressure is too low, this would indicate that the ground anchor has not reached its maximum strength, e.g. as a result of the expansion having been made in a region where the density of the ground is too low. If, on the other hand, less than 100 % expansion is indicated by the amount of fluid, while the maximum pressure has been reached, this may indicate that the ground anchor has been expanded in a region where the density is very high, e.g. in the presence of rocks.

At least one of the measured flow and/or the amount of fluid fed, and the pressure may be recorded as a data series comprising a plurality of values taken at different points in time during the feeding. This would then enable detailed analysis of the expansion process. The method may further comprise deriving an amount of expansion based on the amount of fluid that has been fed.

The method may further comprise providing a user indication based on the measured pressure and/or flow and/or amount of fluid fed. Such a user indication may be an indication that the expansion process resulted in an acceptable anchoring or not, e.g. merely by a green or red lamp. As further options, the user indication may provide more details on e.g. what pressure was reached and how much fluid was fed or how much expansion was attained.

Brief Description of the Drawings

Fig. 1 is a schematic view of a ground anchor system comprising a ground anchor with an expandable part, in a non-expanded state.

Fig. 2 is a schematic perspective view of a ground anchor in an expanded state.

Detailed Description

In Fig. 1 , there is provided a schematic view of a ground anchor system, comprising a ground anchor 1 having one or more expandable parts 3. Such a ground anchor 1 is shown in perspective view in fig. 2.

The ground anchor 1 may be driven into the ground 0 for example by screwing or by hammering (not shown), both of which are per se known methods. A separate tool may be used for this driving process. For example, the ground anchor 1 may be driven into the soil by means of a pike which is disposed in the tube, and which, after the tube has been driven in, is removed there from. In more dense soils, a pilot hole may initially be drilled into the earth before the ground anchor is inserted into the ground 0. As another example, the ground anchor may be driven into the ground by simply hammering on an uppermost portion thereof.

The expandable part 3 of the ground anchor may be made of a plastically deformable material, for example a steel tube with at least one axial slot 2 extending over part of the length of the steel tube, where the slotted region is to be driven into the soil 0. Expansion of the expandable part

3 of the ground anchor 1 may be achieved by means of an expansion tool 10 which is inserted into the ground anchor 1 after the ground anchor has been driven into the ground 0.

In Fig. 1 , there is illustrated a system for expanding an expandable part

3 of the ground anchor disclosed in Fig. 1 .

The system comprises a pump 20 with a supply of hydraulic fluid, such as hydraulic oil, at least one expansion member 1 1 a, 1 1 b, such as a hydraulic piston, a pressure meter 23 for measuring pressure in the hydraulic fluid supplied to the expansion member and a flow meter 22 for measuring the flow of hydraulic fluid supplied to the expansion member 1 1 a, 1 1 b.

The system further comprises a pressure regulating device 21 . Such a device 21 may be implemented as an integral part of the pump 20, i.e. a feed rate or a displacement of a pump 20 may be controlled.

As an alternative, or supplement, the pressure in the hydraulic fluid fed to the expansion member may be controlled, e.g. by a throttle valve or a variable bypass valve, which may form part of the pressure regulating device

21 .

The system further comprises a controller 24, which is connected to the pressure meter 23, the flow meter 22, and the pressure regulating device 21 .

The controller 24 may be provided with a plurality of functions for collection of data related to the expansion of the expandable part 3.

For the present disclosure, the controller 24 may capable of receiving a flow signal from the flow meter 22 and a pressure signal from the pressure meter 21 . Moreover, the controller 24 may be capable of providing a control signal to the pressure regulator 21 .

Moreover, the controller 24 may be capable of receiving control parameters, e.g. as a result of a user input, received from a database based on e.g. a type of installation to be made, or received or derived based data contained in an identifier provided on the product, e.g. in the form of a barcode or an RFID device. The control parameters may comprise base pressure and flow values for the supply of hydraulic fluid to the expansion member 1 1 a, 1 1 b.

The control parameters may also comprise threshold values, e.g.

pressure and/or flow threshold values, determining at what points pressure and/or flow should be modified during expansion.

The control parameters may also comprise limit values, e.g. an upper pressure limit and/or a lower flow limit both of which may indicate that expansion should be interrupted.

The system may be operated as follows when installing a ground anchor.

The ground anchor 1 may be driven into the ground in the conventional manner.

Once the ground anchor 1 has reached the desired depth, the expansion tool 10 may be inserted into the ground anchor 1 and its correct positioning, e.g. its angular position relative to the ground anchor 1 , may be verified.

Control parameters may be provided to the controller 24, e.g. by the user selecting the relevant type of ground anchor to install and the controller retrieving the control parameters from a data memory. In its simplest form, the controller 24 may simply use a preprogrammed desired pressure and/or flow value.

The pump 20 is operated to feed pressurized hydraulic fluid to the expansion member 1 1 a, 1 1 b at a first pressure. During the feeding, at least the flow, optionally also the pressure, is measured. The total amount of fluid supplied to the expansion member 1 1 a, 1 1 b may be calculated based on the flow measurement.

When the flow drops below a predetermined threshold value, thus indicating that the pressure is not sufficient to continue expansion at the same rate, and the maximum amount of fluid has not yet been supplied, the pressure may be increased by the controller 24 providing a control signal to the pressure regulator 21 to achieve a second pressure, higher than the first pressure. The pressure may be maintained at the second pressure until complete expansion has been attained, e.g. as derived based on the flow

measurement.

In the alternative, the pressure may be further increased, optionally up to an upper pressure limit, which may be provided as a control parameter or by a safety valve, until complete expansion has been attained.

For example, the pressure may be continuously increased in order to maintain a predetermined flow, until complete expansion has been attained.

The controller may be provided in the form of a programmable computer, or in the form of a dedicated circuit.

At least one of the pressure regulating device 21 , the flow meter 22, the pressure meter 23 and the controller 24 may be integrated with the pump 20, e.g. by being arranged in a common housing. As another option, at least two of the pressure regulating device 21 , the flow meter 22, the pressure meter 23 and the controller 24 may be provided in a common housing that is separate from a pump housing.

Measuring the flow and pressure provides further opportunities for reducing tool wear and quality control.

For example, by measuring pressure and flow when expanding the ground anchor, it is possible to interrupt the expansion process when a sufficient amount of expansion has been attained or when a predetermined pressure has been attained. Thus, the risk of overloading the tool and/or over expanding the ground anchor can be reduced, with further improvement of tool life as a result. Moreover, such measurement provides an opportunity for automating the installation process, that is, a single user input may be sufficient to start the expansion process, whereby the controller will interrupt the expansion process as soon as the predetermined pressure and/or expansion have been attained.

The pressure and/or flow data may be recorded in a data memory, wherein it may be saved together with information uniquely identifying the associated ground anchor. Such data may be saved either as individual values, such as maximum pressure during expansion and/or total amount of fluid provided.

As another option, the data may be recorded as data series comprising a plurality of values taken at different points in time during the expansion process. This would then enable evaluation of the process with a view to finding any abnormalities which may have occurred during the expansion process.

It is also possible to derive an amount of expansion based on the amount of fluid that has been fed. This amount of expansion may be presented as a percentage of maximum expansion, the percentage being derived based on the amount of fluid that would normally be fed to achieve

100 % expansion.

Moreover, it is possible to provide a user indication based on the measured pressure and/or flow. Such a user indication may be a real time feedback that the expansion was successful or unsuccessful. The indication may also be recorded in a data memory, such that it will be possible to later determine what the operator knew about the installation.

It is possible to empirically determine, for different types of installation environment (soil, ground type), strength properties for ground anchors as a function of amount of expansion and/or as a function of expansion pressure or maximum expansion pressure. Such empirical data may to some extent be interpolated or extrapolated to provide more general rules for what properties are achieved.

Hence, the determination on whether a measured and/or derived pressure and/or expansion amount is acceptable or not, may be made subject to ground type and strength requirement.

While the description above refers to measurement of the flow and integration of the flow to derive an amount of fluid that has been fed, it is understood that it is possible to additionally or alternatively measure the volume that has been fed, e.g. by measuring a volume at a fluid source and/or a position of the expansion member, whereby the amount of fluid that has been fed to the expansion member can be directly measured. In order to derive a flow rate, the flow rate may be derived as the derivative over time (dV/dt) of the amount of fluid fed.