An Impact Compactor, Compaction System and a Method of Obtaining Soil Strength

Abstract

The invention relates to an impact compactor (10) and to a method and system of obtaining an indication of the soil strength of soil (100) by using an impact compactor (10). The impact compactor (10) includes a chassis 5 structure (12), at least one wheel (14) supportively mounted on the chassis structure (12), and at least one impact drum (16) which is displaceable relative to the chassis structure (12). The method includes travelling with the impact compactor (10) over a soil surface (100) while the drum (16) is in a raised position in which it is spaced from the soil surface (100) and 10 measuring, by using a measuring arrangement (20) which is connected to or forms part of the impact compactor (10), a rut depth (54) of a rut in the soil surface (100) which is formed by the wheel (14) as the impact compactor (10) travels over the soil surface (100).

Claims

1-45. (canceled)

46. A method of obtaining an indication of the soil strength of soil by using an impact compactor, wherein the impact compactor includes a chassis structure, at least one wheel supportively mounted on the chassis structure, and at least one impact drum which is displaceable relative to the chassis structure, the method including: travelling with the impact compactor over a soil surface while the drum is in a raised position in which it is spaced from the soil surface; and measuring, by using a measuring arrangement which is connected to or forms part of the impact compactor, a rut depth of a rut in the soil surface which is formed by the wheel as the impact compactor travels over the soil surface.

47. The method of claim 46, which includes measuring the rut depth by determining the distance between a specific position on the impact compactor and a target point on the soil surface, by using the measuring arrangement.

48. The method of claim 47, wherein the specific position is on the chassis structure.

49. The method of claim 47, wherein the specific position is on a structure which is fixed/secured to the chassis structure.

50. The method of claim 47, wherein the target point is located outside the rut.

51. The method of claim 50, wherein the target point is located in front of the wheel.

52. The method of claim 50, wherein the impact compactor includes a pair of wheels and wherein the target point is located between the pair of wheels of the impact compactor.

53. The method of claim 47, wherein the measuring of the rut depth by the measuring arrangement is conducted on a continuous/continual basis as the impact compactor travels over the soil surface.

54. The method of claim 47, which includes determining a geographic position of the impact compactor for a measured rut depth.

55. The method of claim 54, wherein the method further includes storing the measured rut depth and its corresponding geographic position on a database.

56. The method of claim 47, wherein the measuring arrangement may include at least one distance measuring device.

57. The method of claim 56, wherein the distance measuring device is a non-contact distance measuring device which is mounted on the impact compactor and which is configured to measure the distance to the target point, without needing to make physical contact with the soil surface.

58. The method of claim 57, wherein the distance measuring device is a distance measuring sensor.

59. An impact compactor which includes: a chassis structure; at least one pair of wheels which is supportively mounted on the chassis structure; at least one impact drum which is rotatably mounted to the chassis structure by means of a drum mounting arrangement, wherein the drum mounting arrangement is configured to allow displacement of the drum relative to the chassis structure such that the drum can be displaced upwardly and downwardly relative to the chassis structure; and a measuring arrangement which is operatively connected to the chassis structure or another structure/member which forms part of the impact compactor, and which is configured, when the drum is in a raised position in which it is spaced from the soil surface, to measure a rut depth of a rut formed in a soil surface by at least one of the wheels, as the impact compactor travels over the soil surface.

60. The impact compactor of claim 59, wherein the measuring arrangement includes a distance measuring device/apparatus which is configured to determine the distance between a specific position on the impact compactor and the soil surface.

61. The impact compactor of claim 60, wherein the distance measuring device/apparatus is configured to determine the distance between the specific position on the impact compactor and a target point on the soil surface.

62. The impact compactor of claim 61, wherein the measuring arrangement includes two or more distance measuring devices/apparatuses.

63. The impact compactor of claim 61 wherein the distance measuring device is a distance measuring sensor.

64. The impact compactor of claim 63, wherein the sensor is directed towards the soil surface, when in use.

65. A compaction system which includes: an impact compactor as claimed in claim 59; and a processor which is communicatively connected to the distance measuring arrangement of the impact compactor in order to allow distance measurement information to be sent from the distance measuring arrangement to the processor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings. In the drawings:

[0057] FIGS. 1a-c each show an example of a type of impact compactor;

[0058] FIG. 2 shows a schematic illustration of how an impact drum of an impact compactor in accordance with the invention rolls and impacts a soils surface during operation;

[0059] FIG. 3a shows an end view of an impact compactor in accordance with the invention, when a pair of impact drums thereof is in a raised/inoperative position;

[0060] FIG. 3b shows a side view of the impact compactor in FIG. 3a;

[0061] FIG. 3c shows a side view of an impact compactor, with one of the impact drums removed;

[0062] FIG. 4a shows a bottom view of part of a single axle impact compactor, which indicates various possible mounting positions for a distance measuring sensor;

[0063] FIG. 4b shows a bottom view of part of a double axle impact compactor, which indicates various possible mounting positions for a distance measuring sensor;

[0064] FIG. 5a shows an end view of an example of an impact compactor in accordance with the invention, where two non-contact distance measuring sensors are used;

[0065] FIG. 5b shows a side view of the impact compactor of FIG. 5a;

[0066] FIG. 5c shows a schematic illustration of how rut depth is determined by using one of the sensors of the impact compactor of FIG. 5a;

[0067] FIG. 5d shows a trigonometric layout of the relative angles and distances applicable when calculating the rut depth by using the other sensor of the impact compactor of FIG. 5a;

[0068] FIG. 6a shows an end view of another example of an impact compactor in accordance with the invention, where two non-contact distance measuring sensors are used;

[0069] FIG. 6b shows a side view of the impact compactor of FIG. 6a;

[0070] FIG. 6c shows a trigonometric layout of the relative angle and distance applicable when calculating the rut depth by using one of the sensors of the impact compactor of FIG. 6a;

[0071] FIG. 7 shows a schematic illustration of how a wheel of an impact compactor, in accordance with the invention, penetrates into a soil surface, when travelling there over;

[0072] FIG. 8a shows an end view of another example of an impact compactor in accordance with the invention, where two non-contact distance measuring sensors are used;

[0073] FIG. 8b shows a side view of the impact compactor of FIG. 8a;

[0074] FIG. 8c shows a trigonometric layout of the relative angles and distances applicable when calculating the rut depth by using the sensors of the impact compactor of FIG. 8a, and also illustrates the difference between plastic and elastic deformation;

[0075] FIG. 9a shows a side view of a distance measuring contact arrangement of an impact compactor in accordance with the invention;

[0076] FIG. 9b shows a side view of a variation of the distance measuring contact arrangement of FIG. 9a;

[0077] FIG. 10a shows a side view part of an impact compactor in accordance with the invention, where the distance measuring contact arrangement of FIG. 9a is used, where there is no penetration into a soil surface over which the impact compactor is travelling;

[0078] FIG. 10b shows an end view part of the impact compactor of FIG. 10a, where the wheels penetrate into the soil surface;

[0079] FIG. 10c shows a side view of the impact compactor of FIG. 10b;

[0080] FIG. 10d shows a trigonometric layout of the relative angles and distances applicable when calculating the rut depth of a rut formed as a result of the penetration of the wheels of the impact compactor shown in FIG. 10b;

[0081] FIG. 11a shows a side view of part of an impact compactor in accordance with the invention, where the distance measuring contact arrangement of FIG. 9b is used, and where the wheels penetrate into a soil surface over which the impact compactor is travelling;

[0082] FIG. 11b shows an end view of the impact compactor of FIG. 11a;

[0083] FIG. 11c shows a trigonometric layout of the relative angle and distances applicable when calculating the rut depth of a rut formed as a result of the penetration of the wheels shown in FIG. 11a;

[0084] FIG. 12a shows a side view of part of an impact compactor in accordance with the invention, where the distance measuring contact arrangements shown in FIGS. 9a&b are both used and where the wheels penetrate into a soil surface over which the impact compactor is travelling;

[0085] FIG. 12b shows an end view of the impact compactor of FIG. 12a;

[0086] FIG. 12c shows a trigonometric layout of the relative angles and distances applicable when calculating the rut depth of a rut formed as a result of the penetration of the wheels shown in FIG. 12a;

[0087] FIG. 13a shows an end view of an impact compactor in accordance with the invention, which is positioned on a sloping soil surface, thereby resulting in roll.

[0088] FIG. 13b shows a side view of the impact compactor of FIG. 13a, which is subjected to a pitch;

[0089] FIG. 13c shows a trigonometric layout of the relative angles and distances applicable when calculating the rut depth of a rut formed as a result of the penetration of the wheels shown in FIG. 13b;

[0090] FIG. 14 shows side view of an impact compactor in accordance with the invention which includes a scraper;

[0091] FIG. 15 illustrates an example of how soil strength can be determined/estimated by using a database of stored test results for different types of soils; and

[0092] FIG. 16 shows a simplified, schematic layout of a compaction system in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0093] The invention relates to a compaction system which uses an impact compactor to obtain an indication of the soil strength of soil.

[0094] Reference is now specifically made to FIGS. 3a-c. The impact compactor 10 includes a chassis structure 12; one/two pairs of wheels 14 on which the chassis structure 12 is supportively mounted; a drum mounting arrangement 18 on which a pair of non-round impact drums 16 are rotatably mounted, and a lifting arrangement 19 (see specifically FIG. 3c) which is configured to displace the drums 16 upwardly from an operative, lowered condition (see the drum 17 shown in broken lines in FIG. 3c) in which it is positioned on the ground (e.g. on a soil surface) towards a raised position in which the drums are raised off the ground. The drum mounting arrangement 18 includes an L-shaped drag link 31. One end 33 of the drag link 31 is pivotally mounted to the chassis structure 12, and an axle assembly 35 is mounted to an opposite end 37 thereof. The lifting arrangement 19 includes a lifting arm 21 which, at one end, is pivotally mounted to a central portion of the drag link 31, and, at an opposite end, engages the end 37 of the drag link 31. The lifting arrangement 19 further includes a lifting cylinder 27 which is mounted between the chassis structure 12 and the lifting arm 21 in order to lift the drums 16 towards the raised position as shown in FIG. 3a. The operation of the lifting arrangement is well known and will therefore not be described in further detail.

[0095] When the impact compactor 10 is in a neutral orientation, the chassis structure 12 extends along a substantially horizontal plane. A neutral orientation is when the impact compactor 10 is positioned on a flat, horizontal surface and is driven/pulled horizontally along the flat surface (i.e. parallel to a horizontal plane).

[0096] If the tyres 14 of the impact compactor 10 penetrate into a soil surface 100 when the drums 16 are in their inoperative condition, as a result of the weight, the distance between an underside of the chassis structure 12 and the soil surface 100 beneath the trolley will decrease. The difference in distance from the underside of the chassis structure 12 to the soil surface 100 when there is zero penetration of the tyres 14 into the soil surface (e.g. when standing on concrete) and when there is penetration of the tyres 14 into the soil surface 100, is equal to the depth of penetration of the tyres into the soil surface 100.

[0097] In order to measure the penetration depth, a measurement/measuring arrangement (generally indicated by reference numeral 20) can be used (see FIGS. 4a&b and 5a&b). The measurement arrangement 20 can be mounted either on the chassis structure 12 or another structure 32.1-32.4 which is secured thereto, and extends from, the chassis structure 12 (see specifically FIGS. 4a&b). The structures 32.1-32-4 may, for example, be steel beams.

[0098] In one example, the measurement arrangement may include one or more distance measuring sensors 30. The sensors 30 may be positioned at various locations on the chassis structure 12 or on one of the other structures 32.1-32.4 and be directed generally downwardly towards the soil surface 100 (see FIGS. 5a&b). The sensors 30 may, for example, be laser, infrared and/or ultrasonic distance measuring sensors or any other non-contact distance measuring sensors.

[0099] FIGS. 5a and 5b show an example of two sensors 30.1, 30.2 which are mounted to an underside of the chassis structure 12. The one sensor 30.1 is located between the pair of wheels 14, while the other is located behind the wheels 14, and in-line with the sensor 30.1, when seen in end view (see FIG. 5a). The sensor 30.1 is directed downwardly away from the chassis structure 12, at an angle perpendicular to a plane in which the chassis structure 12 extends, towards a target point 40 on the soil surface 100. Therefore, when the chassis structure 12 is in a neutral orientation, the sensor 30.1 can determine the vertical distance between the underside of the chassis 12 and the soil surface 100. The sensor 30.2 is also directed downwardly away from the chassis structure 12, but extends at an acute angle away from the said plane towards the target point 40.

[0100] In FIGS. 5a and 5b, y.sub.0 refers to the vertical distance between the sensor 30.1 and the bottom of the tyre 14, which is a known distance. The vertical distance between the sensor 30.1 and the soil surface is y.sub.1, which is measured by the sensor 30.1. The difference between y.sub.0 and y.sub.1 is equal to the rut depth/penetration depth. In this regard, reference is also made to FIG. 5c (the arrow indicated by reference numeral 714 refers to the penetration depth). Reference numeral 710 refers to the initial ground level, while reference numeral 712 refers to the penetrated ground level (i.e. as a result of the wheels 14).

[0101] With regards to sensor 30.2 shown in FIGS. 5a and 5b, the distance L.sub.0 (see FIG. 5d) is known (i.e. it is measured beforehand), whereas L.sub.1 refers to the measured distance to the target point 40. Referring now also to FIG. 5d, the distance L.sub.1 is the distance measured between the sensor 30.2 and the target point 40. The angle θ refers to the known angle between a measurement direction of the sensor 30.2 towards the target point 40 and an axis which extends perpendicular to the plane in which the chassis structure 12 extends. The rut depth/penetration depth can be calculated as follows:

L=L.sub.0−L.sub.1(see FIG. 5d)

Rut depth/penetration depth=L cos(θ)

[0102] FIGS. 6a-c illustrate another example of using distance measuring sensors 30.3, 30.4, wherein the one sensor 30.3 is located on a structure 28 (see also FIG. 4b) in front of one of the front wheels 14.1 of a double axle impact compactor 10, while the other sensor 30.4 is at a similar position to that of sensor 30.2 shown in FIGS. 5a&b. The sensor 30.3 is directed vertically downwardly (similar to sensor 30.1) in order to measure the distance to the soil surface 100 directly in front of the wheel 14.1.

[0103] In FIG. 6c, the vertical distance y.sub.0 between the sensor 30.3 and the bottom part of the wheel 14.1, is a known distance. The vertical distance between the sensor and the soil surface is y.sub.1. The difference between y.sub.0 and y.sub.1 is equal to the soil penetration depth/rut depth (generally indicated by the arrows 54).

[0104] In a slightly alternative arrangement, the sensor 30.3 might be angled slightly towards a front part of the wheel 14.1 in order to measure the distance to a target point 50 which is closer to the front of the wheel 14.1.

[0105] The target points 50 should however not be too close to the wheel 14.1 in order to help avoid inaccuracies as a result of possible forward upheaval of the soil in front of the wheel 14.1, generally indicated by reference numeral 52. In order to calculate y.sub.0, the distance measured (L.sub.1) and the measurement angle (θ) (relative to a vertical axis 56) are used in the following equation in order to obtain y.sub.1:

y.sub.1=L.sub.1 cos(θ)

[0106] FIG. 7 illustrates how plastic and elastic deformation occur when an impact compactor 10 travels over the soil surface 100. Reference numeral 200 indicates the direction of travel of one of the wheels 14. As the wheel 14 travels over the soil surface 100, it penetrates into the soil surface 100 to form a rut. The depth of the rut, where the wheel is positioned 14, is indicated by the arrows 42. As the wheel 14 travels onwards, the depth of the rut lessens due to elastic deformation (see reference numeral 44), thereby leaving a more permanent rut (which is due to plastic deformation) generally indicated by the arrows 46.

[0107] In another example shown in FIGS. 8a-c, a sensor 30.5 is mounted behind the rear wheel 14.1 in order to measure the distance towards the rut 102 formed by the wheels 14.1, 14.2. In FIG. 8c, the vertical distance between the sensor 30.5 and the soil surface 100 is y.sub.2, and the distance measured is L.sub.2. θ.sub.2 is the measurement angle (as described above) of the sensor 30.5. Therefore:

y.sub.2=L.sub.2 cos(θ.sub.2)

[0108] Similar to the example shown in FIGS. 6a-c, y.sub.1=L.sub.1 cos(θ.sub.1).

[0109] The difference between y.sub.0 and y.sub.2 is the amount of soil rebound/elastic recovery (SR), as a result of elastic deformation of the soil (see the arrows 60). The difference between y.sub.2 and y.sub.1 is equal to the amount of plastic deformation of the soil after the impact compactor 10 has travelled there over. The more permanent rut formed by the wheels 14.1, 14.2 is equal to the amount of plastic deformation (i.e. y.sub.2−y.sub.1). The temporary rut depth caused by the wheels 14.1, 14.2 is equal to the difference between y.sub.0 and y.sub.1. The sensor 30.5 needs to target an area far enough behind the tyres 14.1, 14.2 to ensure that the soil has fully recovered before the reading takes place. An additional sensor could be mounted which can target an area further back from the sensor 30.5, in order to check if the soil recovers any further. Another sensor 30.7 may be mounted behind the wheel 14.3, in a similar fashion to the sensor 30.5 (see FIG. 8a).

[0110] The sensors 30 may be mounted in such a way in order to help steady the sensors 30 during operation, as well as to allow for the adjustment of the position (e.g. the measurement angle) of the sensors 30. Rubber mounting pads may, for instance, be used to help damp vibrations. A pivotal mounting arrangement may be used in order to help accommodate for relative movement and positioning adjustment of the sensors 30 (relative to the chassis structure 12).

[0111] A servo system may be implemented in order to control the position of the sensor 30 by using data obtained from a dynamic sensor and an electronic control unit. The dynamic sensor takes measurements such as the angle of the sensor with respect to a vertical plane, which could be used to determine the optimum position for the distance measuring sensor in order to obtain more accurate readings. A program of the system can typically send through signals to an electronic control unit of the servo system which controls the positioning of the distance measuring sensor. The electronic control unit uses these signals to instruct the servo system to move the sensor to a new position determined by the program.

[0112] Reference is now specifically made to FIG. 9a. In this example, the measurement arrangement 20 is a distance measuring contact arrangement which makes physical contact with the soil surface 100, in order to help determine the distance from the chassis structure 12 to the soil surface 100. The arrangement 20 has a type of rigid jockey wheel contact mechanism and includes a mounting member 62 (a first member) which is secured to an underside of the chassis structure 12, and an elongate member/rod 64 (a second member) which is pivotally mounted to the mounting member 62 and extends downwardly towards the soil surface 100. A wheel 66 is rotatably mounted to a free end of the rod 64 and engages the soil surface 100.

[0113] A rotational/angle measurement sensor 68, such as an inertial angle measurement device and/or an inclinometer, is operatively connected to the rod 64 in order to measure the angle of the rod 64. Alternatively, a linear or rotary encoder may be used. The measured angle can then be used in order to calculate the required vertical distance between the mounting member 62 and the soil surface 100. In this regard, reference is specifically made to FIGS. 10a-d. As the wheels 14.1, 14.2 penetrate into the soil surface 100, the angle of the rod 64 changes. By implementing a simple geometric calculation using the length (L) of the rod 64 and the angle measured by the rotational measurement sensor 68, the vertical distance between the mounting member 62 and the soil surface 100 can be calculated.

[0114] Reference is now specifically made to FIGS. 10a-d in which the measurement arrangement 20 is mounted between the wheels 14.1, 14.2, y.sub.0=L cos(θ.sub.0), wherein y.sub.0 refers to the vertical distance between the mounting member 62 and the soil surface when there is no penetration into the soil surface 100 (y.sub.0 is therefore known). Similarly, y.sub.1=L cos(θ.sub.1), wherein y.sub.1 refers to the vertical distance between the mounting member 62 and the soil surface 100 when there is penetration into the soil surface 100. The rut depth/penetration depth therefore equals y.sub.0−y.sub.1.

[0115] The arrangement 20 includes a biasing means in the form of a linear spring 70, which is mounted between the chassis structure 12 and the rod 64 in order to urge the rod 64 downwardly against the soil surface 100 (see the arrow 72). In addition, or alternatively, a torsion spring 71 may be mounted between the mounting member 62 and rod 64 in order to urge the rod 64 downwardly against the soil surface 100.

[0116] In a slightly alternative embodiment, two rods 64.1, 64.2 may be used as shown in FIG. 9b. In this example, reference numerals 68.1 and 68.2 refer to rotational measurement sensors mounted on each rod 64.1, 64.2. A linear spring 70 is mounted between the rods 64.1, 64.2 in order to urge the rods 64.1, 64.2 towards each other, which results in the wheels 66.1, 66.2 urging against the soil surface 100. In addition, or alternatively, a torsion spring 71 may be mounted between the mounting member 62 and the rods 64.1, 64.4 in a similar manner as described above.

[0117] In another example illustrated in FIGS. 11a-c, the arrangement 20 shown in FIG. 9b is mounted on a structure (see structure 26 in FIG. 4b) in front of the wheel 14.2 in order to measure the distance directly in front of the tyre 14.2. The vertical distance between the mounting member 62 and the soil is y.sub.1. y.sub.0 is the same as in the example shown in FIGS. 10a-d. The difference between y.sub.1 and y.sub.0 is equal to the rut depth/soil penetration depth of the tyre 14.2. The arrangement 20 should preferably target an area of the soil surface 100 close to the tyre 14, but not too close in order to avoid inaccuracies due to the forward upheaval of the soil (see reference numeral 72) in front of the tyre 14.2.

[0118] In a further example shown in FIGS. 12a-c, an arrangement 20.1 as shown in FIG. 9a is mounted on a structure (see the structure 26 in FIG. 4b) in front of the wheel 14.2, and an arrangement 20.2, as shown in FIG. 9b, is mounted on a structure 29 (which is secured to the chassis structure 12) behind the wheel 14.2. These arrangements 20.1 and 20.2 are then used to calculate the same distances as the example shown in FIGS. 8a-c. The vertical distance between the mounting member 62 and the soil surface 100 is y.sub.2. y.sub.1 and y.sub.0 are the same as the example shown in FIGS. 11a-c. The difference between y.sub.2 and y.sub.0 is the amount of soil rebound/elastic recovery (SR). The difference between y.sub.1 and y.sub.2 is equal to the amount of plastic deformation of the soil surface 100 left by the wheel 14.2. As show, in FIG. 12c, y.sub.2=L cos(θ).

[0119] As mentioned previously, the arrangement 20.2 should preferably be mounted far enough behind the wheel 14.2 in order to target an area of the soil surface 100 which has recovered (preferably fully recovered) before the distance measurement takes place. An additional arrangement 20 could be mounted which can target an area further back from the arrangement 20.2, in order to determine whether the soil surface 100 has recovered any further.

[0120] The soil penetration is calculated using distance readings from measurement arrangements 20 illustrated in FIGS. 5a-6c and 8a-12c. Filters and/or other techniques can be implemented to reduce the signal noise of the readings in order to get more accurate readings. Additional sensors can be used to target similar areas in order to check the readings of other sensors or to calculate an average reading from the combination of sensors. The deflection of the tyres of the wheels may not remain constant under all soil conditions. Since the deflection of the tyres might affect the calculated values, this deflection can also be taken into consideration. The tyre type and pressure of the tyre will affect the amount of deflection the tyre will experience. The tyres of an impact compactor 10 are usually pneumatic, pneumatic with tyre fill or solid tyres. The properties of the chosen tyres and the tyre pressure will be generally known. A pressure sensor can also be used to measure the pressure inside the tyres. These values can be inserted into equations that calculate the amount the tyres deflect. The amount of soil penetration can then be calculated taking into consideration the amount of tyre deflection.

[0121] In certain cases, it may be useful to increase the load applied by the impact compactor 10 onto the soil surface 100 in order to help obtain more accurate/meaningful soil strength readings. In order to do so, additional weight can be added temporarily to/onto the impact compactor 10. This can be done by attaching or securing weighted object(s) to the impact compactor 10. The term “weighted object(s)” refers to one or more objects which adds/collectively add a significant amount of weight to the impact compactor 10 in order to increase the load onto the soil surface 100 by a significant amount. Alternatively, or in addition, material (e.g. liquid such as water)) can be pumped/introduced into an inner cavity of each of the drums 16 in order to increase the weight of the impact drums 16, such that the load applied to the soil surface 100 increases as a result of the additional weight. Stated slightly differently, the weight of the drums 16 may be increased by effectively ballasting the impact drums 16 with material. Afterwards, the material may again be discharged from the cavities.

[0122] During operation, the impact compactor 10 will not always be 100% level all the time. In order to obtain more accurate readings, the orientation of the impact compactor 10 needs to be taken into account. This includes measuring the pitch and the roll of the impact compactor 10 relative to a level horizontal plane (see FIGS. 13a&b). Sensors, such as inertial angle measurement devices, inclinometers, rotary encoders, linear encoders and other similar devices, can be mounted on the impact compactor 10 in order to measure the changes in the angle/orientation of the impact compactor 10. The angular measurements can be used in combination with the distance measurements in order to calculate more accurate rut depth/soil penetration and plastic deformation values.

[0123] For example, if the impact compactor 10 (which in this example includes a trolley that needs to be pulled) is mounted to a tractor such that the impact compactor 10 is not 100% parallel to a horizontal plane (see FIG. 13b), even if it is a relatively small angle, it can make a large difference to the distance measurement, due to the long length of the impact compactor 10. Referring specifically to FIGS. 13b&c, the angle of the impact compactor 10 relative to the horizontal is called the pitch angle (φ). The trolley rotates about an axle (P1) on which the wheels 14.1, 14.2 are mounted. A line (L.sub.o) can be drawn from the distance measuring sensor 30.2 (P2) to this point of rotation (P1). The distance measured by the sensor 30.2 is L.sub.m. These variables can then be used in an equation in order to calculate what the measured distance would be if the trolley was horizontally level (i.e. the adjusted measured distance L.sub.A). The equation and calculations are set out in FIG. 13c. More specifically, φ=8 if the sensor 30.2 (P2) is pointing perpendicular to the chassis structure 12, and θ=0 if the sensor 30.2 (P2) is pointing vertically down. L.sub.A can be determined by using the following equation:

L.sub.A=L.sub.m cos(θ)−L.sub.o sin(θ)

[0124] The distance measuring sensors 30 can be mounted to the impact compactor 10 in a manner which allows them to move in order to change their targeted area (i.e. the measurement direction). The sensors can be mechanically locked into a certain position and changed manually, if need be, or the movement can be controlled electronically using a servo system. The servo system can use dynamic measurements, such as acceleration and angular velocity, in order to determine the positioning of the distance measuring sensors 30 in order to either stabilize the sensors 30 or adjust their targeted area so as to improve the accuracy of the measurements.

[0125] The soil surface 100 may be uneven and/or contain objects, such as rocks, which would affect the penetration measurements significantly. A mechanical device 80 can be installed on the impact compactor 10 which clears the path of unwanted objects and/or makes the soil surface 100 more level in front of the targeted areas of the measurement arrangements 20. Any mechanical device that performs either one or both of these actions could be used.

[0126] In one example shown in FIG. 14, a scraper 82 can be pivotally mounted to the impact compactor 10, in front of the targeted areas of the distance measuring sensors 30. The scraper 82 could be biased slightly against or into the soil by using a biasing means which biases the scraper 82 downwardly and urges it against the soil surface 100. The biasing means may, for example, be a torsion spring 84 or a hydraulic cylinder. The scraper 82 will typically help push aside objects, such as rocks, and help to level the soil surface 100.

[0127] The pivotal mounting of the scraper 82 helps to prevent damage to the scraper 82 and the rest of the impact compactor 10 since it will generally pivot upwardly when it strikes an object/obstacle too hard to be moved. The biasing means 84 may be configured to allow the blade 82 to pivot upwardly only once the force applied thereto by an object exceeds a certain amount. The biasing means 84 may also be designed so that the force amount can be adjusted in order to accommodate different soil conditions.

[0128] The impact compactor 10 forms part of a compaction system 111 shown in FIG. 16. The data obtained from the rut depth/penetration depth measurements can be used by a processor 200 with appropriate software (e.g. a computer program), in combination with other variables, in equations, to determine/estimate actual soil strength values. More specifically, the processor 200 can use the data to correlate it to soil strength measurements, by using a database which contains information on soil strength values for different soil types and for a range of soil penetration depth values (i.e. rut depth values) that can be used to correlate measured soil penetration/rut depth values with soil strength values from the database (see FIG. 15) In FIG. 16, reference numerals 730 and 732 refer generally to a number of distance measurement sensors and angle measurement sensors (as described above) which can be installed in the impact compactor 10.

[0129] A number of different soil strength measurements could be determined by the processor 200 by using: [0130] measured values from the distance measuring sensors 30 (and values from dynamic sensors, such as tyre pressure sensors and inertial angle measurement devices); [0131] assumptions and approximations of certain unknown variables and properties based on experience, lab experiments and/or on site experiments; [0132] formulae that are self-developed and/or found in textbooks, journals or similar sources; [0133] databases of stored information which contains soil strength values for different soil types and for a range of soil penetration values (again see FIG. 15); and [0134] data obtained from performing on-site tests with conventional soil strength measurement methods at locations with known soil penetration values and then extrapolating values for the entire site.

[0135] Dynamic sensors such as inertial angle measurement devices, and tyre pressure sensors may be used to get more accurate soil penetration values. The tyre penetration depth is required in calculations and correlations to soil strength. The tyre pressure can be used in determining the contact area of each tyre with the soil surface, where the contact area can be used in calculating the applied pressure.

[0136] FIG. 15 shows an example of a database where test results are stored. The actual field test values of displacement (i.e. rut depth) will then use the database in order to correlate the measured rut depth to a K-Value. In this regard, an interpolation can be performed to estimate a K-value for a specific rut depth value.

[0137] In one example the impact compactor can be used to determine the soil bearing capacity of the soil surface 100 or the amount of pressure the soil can support. The bearing capacity refers to the amount of pressure the soil can take without shear failure or excessive settlement occurring. The mass of the impact compactor 10 and the number of wheels 14 is known, and the soil penetration depth can be calculated as mentioned above. The tyre pressure and penetration depth can be used in determining the contact area between the tyre and the soil surface. The processor 200 can then calculate the applied pressure by using these values as follows:

[00001]$\mathrm{load}.Math..Math.\mathrm{per}.Math..Math.\mathrm{tyre}=\frac{\mathrm{mass}.Math..Math.\mathrm{of}.Math..Math.\mathrm{impact}.Math..Math.\mathrm{compactor}.Math..Math.\mathrm{in}.Math..Math.\mathrm{kg}*9.81.Math..Math.m.Math.\text{/}.Math.s^2\left(N\right)}{\mathrm{number}.Math..Math.\mathrm{of}.Math..Math.\mathrm{tyres}}$$\mathrm{Applied}.Math..Math.\mathrm{Pressure}=\frac{\mathrm{load}.Math..Math.\mathrm{per}.Math..Math.\mathrm{tyre}.Math..Math.\left(N\right)}{\mathrm{contact}.Math..Math.\mathrm{area}.Math..Math.\mathrm{between}.Math..Math.\mathrm{tyre}.Math..Math.\mathrm{and}.Math..Math.\mathrm{soil}.Math..Math.\mathrm{surface}.Math..Math.\left(m^2\right)}$

[0138] A pass/failure criteria dependant on penetration depth measured can be determined for the applied pressure. Using correlations to standard plate load tests, the penetration depth pass/failure criteria can be calculated by the processor 200. The processor 200 can use this criteria in order to determine whether each measured soil penetration depth value passes or fails the required criteria. This information can then be provided to interested parties, such as the site engineer, in order to see whether any sections of the site require further compaction. For example, if it is determined that the soil should have a bearing capacity of 200 kPa, with settlement required to be under 15 mm, as measured by the standard plate load test and the processor 200 determines that the applied pressure between the impact compactor's tyres and the soil surface is 40 kPa, the processor 200 can calculate a pass/failure criteria using this information. The result could be, for example, that all penetration depths measured under 5 mm passes the required criteria and satisfies the required bearing capacity. The processor 200 can show where on the site the required criteria has not been met, and hence which areas on the site require further compaction in order to satisfy the requirements of the soil if measured using standard plate load tests.

[0139] In order to improve the validity/accuracy of the soil strength values, the soil moisture content can be taken into account. A device can be included within the system 111 that will perform a spectroscopic measurement of soil moisture content. Any device capable of measuring soil moisture content may be used. The soil moisture content may provide more details on the soil being measured to ensure that certain soil strength measurements are valid and/or accurate.

[0140] A global positioning system (GPS), such as GNSS (Global Navigation Satellite System) or RTK GNSS (Real Time Kinetic GNSS) 90, could be used to record the geographic position of the impact compactor 10 accurately (see FIG. 16). The position data can then be used by the processor 200 to provide the soil penetration, soil recovery and/or soil strength values with reference to a specific geographic position. The processor typically forms part of a computer which has a software program that calculates all the relative values with reference to their corresponding geographic positions and then displays this information on a GUI (Graphical User Interface) 92. The GUI 92 could allow the user to choose what is displayed and in what format. The information could be sent to a GUI 94,96 which can be easily viewed on an on-site computer 94 and/or to an off-site computer 96 (or storage device 98) which could then be analysed further.

[0141] All the sensors 30 on the impact compactor 10 can typically send through their raw data to a computer, which includes the processor 200, to be analyzed and interpreted by the processor 200 and software. The processor 200, together with the software, can typically do all the necessary calculations, apply the necessary filters to the data and produce the required information. The information can be viewed on the GUI 92. The GPS 90 is configured to send through the coordinates to the computer, in order to provide geographic location coordinates for all the measurements. The data can be used by the processor 200 and software to provide automatic real-time mapping of soil penetration and soil strength values. The software may offer a number of ways to display the information to a user.

[0142] Referring specifically to FIG. 16, the GPS 90 can calculate the geographic location coordinates of the impact compactor 10 by using the satellites 300 and then send the coordinates through to the processor 200. The signals from the various sensors are also sent to the processor 200. The GUI could be located in a cabin 400 of the impact compactor 10 and/or somewhere else on site and/or somewhere off site. The data could also be sent to and stored on a storage device 98 off site.

[0143] The GUI 92, 94, 96 can include a feature which shows what areas of the work site (i.e. the soil surface 100) require further compaction. For example, this can be done by providing specific colours to different measurements. Measurements that indicate well compacted soil may be allocated a colour such as green or blue, and measurements that indicate poorly compacted soil may be allocated a colour such as red. The compaction site can also be divided into a grid of cells. Each cell would, for example, represent one square metre of land. Each cell would receive a certain colour which depends on all the soil strength and/or penetration measurement data collected/calculated within the cell. The colour of the cell would thus be representative of the soil strength and penetration measurements collected/calculated within the cell. Whilst the system 111 is in the process of determining the soil strength of the work site, the GUI's 92, 94, 96 may typically show the cells and their representative colours on a site map. This will help an operator to know where on the site further compaction is required.

[0144] The processor 200 may be configured, by way of software, to plan a prescribed route for the operator to follow, by utilising the measurements, geographic location information and a map, in order to calculate optimal routes to follow and to compact the entire site efficiently and economically. As new measurements and their relative geographic positions are added, the processor 200 can include them in the route calculation and the calculated route can therefore change, if necessary. This may help with compaction optimisation. The operator can follow the prescribed route by using information shown on the GUI 92. Alternatively, the processor can be configured to control the impact compactor 10 automatically. The optimal route plan may help to lower operating costs and reduce the cost of achieving the required degree of compaction on a construction site. The impact compacter 10 used as a soil testing device may help ensure that all areas of the site have been compacted to the required specification.

[0145] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. The invention is not restricted to the illustrated examples, but the desired features can be implemented by using a variety of alternative architectures and configurations.

[0146] Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the invention.

[0147] Over and above its function as a machine used to compact the soil surface 100, the system 111 gives an impact compactor 10 the additional ability to “proof roll” soil surfaces by providing measurements of the penetration depth formed under the wheels in order to provide an indication of the soil strength and/or level of compaction. The system 111 also gives the impact compactor the ability to measure the amount of elastic deformation of the soil under the wheel load, as well as the amount of plastic deformation of the soil under the wheel load. The system 111 also has the advantage that a single piece of construction equipment that is carrying out compaction on a construction site is also able to carry out soil testing on the same site.

[0148] The system 111 can function using either one or more wheel axles on either dual or single drum impact compactors 10. The configuration of the measurement arrangement 20 and system 111 may typically be dependent on the number of wheel axles used. The amount of penetration will depend on how well compacted the soil is. The wheels 14 will penetrate into the soil significantly more at the start of the compaction process when there is less soil strength, compared to the small amount of penetration of the wheels 14 when the ground is well compacted and the soil strength is greater. For this reason, being able to measure the penetration of the wheels 14 into the soil provides a direct measurement of the soil strength achieved.

[0149] The impact compactor 10 is unique in that it can perform a dual function of being able to both compact the ground when the compacting drums 16 are used in a compaction mode and to also measure the degree of compaction achieved by raising the drums 16 off the ground and applying the full weight of the drums 16 onto the trolley wheels 14 of the impact compactor 10, thereby transforming the compactor 10 into a soil strength testing device. The invention comprises of mechanisms and sensors that will record data signals required in order to calculate the soil penetration under the load. These measurements can then be correlated to measurements of soil strength such as bearing capacity or other standard methods of measuring soil strength.