JP2015113562A - Hole drilling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hole drilling method capable of determining whether or not to reach a target layer, even in the drilling in which a rod is vertically moved at a comparatively short hole drilling depth and with a small resistance value of an electric motor with respect to the drilled ground, when drilling a boring hole.SOLUTION: The hole is drilled in the ground by vertically moving the hole drilling rod, and effective use electric power is arithmetically operated from an electric current supplied to the electric motor for rotating the hole drilling rod and a hole drilling time, and when the effective use electric power becomes a threshold value or more, it is determined as reaching up to a layer capable of becoming as a support layer, and the effective use electric power is a numeric value obtained by multiplying the electric current by the time of drilling the hole in the ground, and the time of drilling the hole in the ground is the time required for drilling the hole in the undrilled ground, and does not include the time for vertically moving in an already drilled area.

Description

  The present invention relates to a technique for drilling a ground where a ground improvement method is applied, for example. More specifically, for example, the present invention relates to a technique for determining whether or not a drilled borehole has reached a formation that can serve as a support layer when drilling a borehole to construct a ground improvement method.

When improving composite ground (for example, ground consisting of clay, sand, and mudstone layers), drill holes to the layer that can be a support layer (for example, mudstone layer, but not limited to rock). Make a hole. Then, after drilling, insert the solidifying material injection device into the borehole, rotate while injecting the solidifying material from the solidifying material injection device, pull up to the ground side, drill the ground to be improved, solidify The ground consolidated piles are created in the region above the layer that can be mixed with the material and become the support layer.
Here, if the lower end portion of the underground consolidated pile does not reach a layer that can serve as a support layer, the underground consolidated pile will not be stable. Therefore, in drilling a boring hole, it is necessary to drill so as to reach a layer that can be a support layer.

In the prior art, a large machine is used to perform drilling using a long drilling rod without additional rods. Alternatively, holes are drilled by rotating blades (drilling bits) having a large diameter relative to the diameter of the rod.
When the target layer (layer that can be a support layer: a hard layer) is reached, the change in the resistance value or current value of the motor of the construction machine during drilling becomes large. Was determined to have reached.
However, when a hole is drilled while adding a rod without using a large machine and the bit diameter is slightly larger than the rod diameter, the resistance value (current value) of the electric motor of the construction machine is small. Therefore, there is a problem that it cannot be determined whether or not the target layer has been reached based on the current value.

Further, in the above-described prior art, since the diameter of the drill bit is larger than the diameter of the rod, the mud can be easily discharged to the ground side through an annular gap formed around the rod.
However, when the bit diameter is slightly increased compared to the rod diameter, it is difficult to discharge the mud from the annular gap around the rod to the ground side. Therefore, the rod must be moved up and down with a relatively short drilling depth to promote mud discharge. Here, when the rod is moved up and down for each relatively short drilling depth during drilling, in order to determine whether or not the target layer has been reached, the undrilled ground is drilled. It must also be determined whether or not the area already drilled is moved up and down.
In the prior art, it is difficult to make such a determination. Therefore, when the rod is moved up and down for each relatively short drilling depth, it is determined whether or not the target layer has been reached. It was difficult to do.

As another conventional technique, for example, a technique for performing bottoming determination using load current and load torque based on boring data has been proposed (see Patent Document 1).
However. Since the related art is a construction method that uses a large machine and can easily discharge the sludge to the ground side, the resistance value (current value) of the motor due to the ground that is drilled is small and the drilling is relatively short. It is difficult to apply a drilling hole that moves the rod up and down at each depth.

Japanese Patent No. 3156050

  The present invention has been proposed in view of the above-described problems of the prior art, and when drilling a boring hole, the resistance value (current value of the electric motor) due to the ground which is drilled is small and relatively short. An object of the present invention is to provide a drilling method capable of determining whether or not a target layer has been reached even when drilling is performed by moving the rod up and down at a drilling depth.

As a result of various studies, the inventors have found that it is possible to determine whether or not the target layer has been reached if the effective power consumption is used as a parameter.
The drilling method of the present invention was created based on such knowledge. The drilling rod (11) is moved up and down (with a relatively short drilling depth) to drill the ground (G), The effective power consumption is calculated from the current supplied to the electric motor (150) rotating the hole rod (11) and the drilling time. If the effective power consumption exceeds the threshold value, the support layer (GB ) And the effective power consumption is the time during which the ground (G) is drilled in the current (current supplied to the motor 150 that rotates the drilling rod 11) (Time to drill: time to drill uncut ground)) (effective power consumption = current x "time to drill uncut ground") Is the time when the uncut ground (the areas that have not been drilled so far: for example, the areas α and ε2 in FIG. 2) is ground. The time required for already drilled region (region in FIG. 2 gamma, .epsilon.1) characterized in that it does not include the time to move up and down the.
Here, the threshold value of the effective power consumption is determined on a case-by-case basis according to the situation of the construction site (the ground to be drilled), the equipment used, and other conditions.

In the present invention, when the drilling rod (11) is cut, the position immediately before the drilling rod (11) is cut (the position where the tip of the drilling rod 11 is attached to the bottom of the boring hole H). ) Is preferably increased by a predetermined amount.
When the water in the hole-drilling rod (11) flows out from the tip of the hole-drilling rod (11) during the cut-off, the predetermined amount is determined by the bored hole (H ) Is preferably set to a value that does not adversely affect the ground near the bottom. The region raised by this predetermined amount is regarded as the already drilled region, and the time for moving up and down this region is not included in the actual drilling time.

  In the present invention, there is a step of calculating a drilling speed and comparing the calculated drilling speed with a threshold value. It is preferable that the effective power consumption is calculated and compared with a threshold value of the effective power consumption.

In carrying out the present invention, the support layer (GB) is not limited to a bedrock layer such as a mudstone layer. For example, in the case of a multi-layered ground composed of a clay layer and a sand layer, the sand layer may be used as a support layer. Alternatively, a hard clay layer may be used as the support layer.
The “layer (GB) that can be a support layer” corresponds to a layer having a high N value, for example, a layer having an N value of 50 or more. Alternatively, a layer having a layer thickness of 3 m or more and a higher N value than the upper layer can be a support layer.

  As described above, if the effective power consumption is used as a parameter, it can be determined whether or not the target layer has been reached. Therefore, according to the present invention having the above configuration, the effective power consumption is calculated and the effective power consumption is calculated. If it exceeds the threshold value, it is judged that the layer that can serve as a support layer has been reached, so the bit diameter increases slightly compared to the rod diameter, and the resistance value (current value) of the motor of the construction machine ) Is small, it can be determined whether or not a target layer (a layer that can be a support layer) has been reached.

Here, the effective power consumption is a numerical value obtained by multiplying the current supplied to the electric motor (150) for rotating the drilling rod (11) by the time during which the ground is drilled (the actual drilling time). Effective use current = current × “time for drilling in the ground”), and does not include the time for moving the already drilled regions (regions γ, ε1 in FIG. 2).
Therefore, when it is necessary to drill the ground by moving the drilling rod (11) up and down at a relatively short drilling depth in order to promote drainage, the drilling has already been performed when calculating the effective current. The time required to move downward in the regions (regions γ, ε1 in FIG. 2) is not accumulated, and the effective current can be calculated using only the actual drilling time as a parameter.
In other words, even if it is necessary to move the drilling rod (11) up and down at a relatively short drilling depth to drill the ground in order to promote mud drainage, the support layer (GB) It is possible to determine whether or not a potential layer (target layer) has been reached.

  In the present invention, when the drilling rod (11) is cut, the position immediately before the drilling rod (11) is cut (from the position where the tip of the drilling rod 11 is settled to the bottom of the boring hole H). If the step of raising the amount by a predetermined amount is included, the water in the hole-drilling rod (11) at the time of severing (by the amount of water accumulated above the groundwater level) is the tip of the hole-drilling rod (11) However, since it has risen by a predetermined amount, the speed at which the outflowed water collides with the bottom of the borehole (H) is reduced, and adverse effects such as loosening the ground near the bottom are reduced.

In the present invention, there is a step of calculating a drilling speed and comparing the calculated drilling speed with a threshold value. If the effective power consumption is calculated and compared with the threshold value of the effective power consumption, drilling is performed using two types of parameters: excavation speed and effective power consumption. It is possible to comprehensively determine whether or not the boring hole (H) has reached the layer (GB) that can be the support layer.
In addition, the calculation of the effective power consumption may be performed only in the control cycle in which the excavation speed is equal to or less than the threshold value, so that the burden on the control device (control unit 50) in the automatic control is reduced accordingly.

It is explanatory drawing which shows the outline | summary of the construction site which applied embodiment of this invention to the ground improvement construction method. It is explanatory drawing which shows the outline | summary of embodiment of this invention. It is a block diagram of the construction machine which implements embodiment of this invention. It is a characteristic view which shows the construction data at the time of drilling with the cutting method which concerns on embodiment. It is a flowchart which shows control of embodiment of this invention. It is a flowchart which shows the control which calculates | requires effective electric power used in embodiment. It is a flowchart which shows the modification of embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows an outline of a construction site to which an embodiment of the present invention is applied in ground improvement work.
In FIG. 1, in the drilling method according to the embodiment of the present invention, a construction machine 100 having a drilling rod driving unit 10, a drilling rod 11, a pump 20, a residual soil tank 30, and a mud screen 40. The construction is done using the drainage pump 25. Here, a water swivel 12 is attached to the head of the drilling rod 11.

The pump 20 is a water pump that pumps high-pressure water for drilling, and the mud pump 25 is a slurry pump that sucks the mud generated by drilling to the ground side. In addition to the two pumps 20 and 25, an air compressor (not shown) that pumps high-pressure air may be provided.
A high pressure hose 22 is connected between the pump 20 and the water swivel 12.
For example, a bit (not shown) is disposed at the tip of the drilling rod 11, and the boring hole H is drilled in the construction area by the bit or high pressure water sprayed from a nozzle (not shown). To do.
The drilling rod 11 is, for example, a double pipe (or a single pipe or a triple pipe), and is supplied with high-pressure water for drilling via the inner pipe (or inside the pipe), and the waste mud generated by drilling. Is sucked into the ground-side mud pump 25 through an annular gap between the outer pipe of the double pipe and the bored borehole H inner wall.

The mud pump 25 sucks the mud generated at the time of drilling and protrudes to the mud line 27. The mud discharged from the mud pump 25 is collected on a mud screen 40 (screen) installed above the remaining soil tank 30. The mud screen 40 stores the waste mud having a small particle size in the residual soil tank 30 and discharges the waste mud having a large particle size outside the residual soil tank 30.
In FIG. 1, the symbol G indicates the ground in the construction area, and the symbol GB indicates a “layer that can be a support layer”, for example, a rock layer, which is a drilling target of the borehole H.

Next, the outline of the drilling method according to the embodiment of the present invention will be described with reference to FIG.
In FIG. 2, the vertical axis indicates the position (depth direction position) of the rod tip that drills the ground, and the horizontal axis indicates time. The white arrow shown along the vertical axis indicates the drilling process of the uncut ground.

As apparent from FIG. 2, in the illustrated embodiment, the drilling rod 11 for drilling the ground does not advance only downward when drilling. If the drilling rod 11 is drilled in a relatively short distance, for example, the region indicated by symbol α in FIG. 2 (if the region indicated by symbol β is drilled), the drilling rod 11 is moved upward (reference symbol γ). To the area indicated by the symbol δ). Thereafter, the drilling rod 11 is lowered and drilled to a position (E) below the location indicated by the symbol β (the regions indicated by the symbols ε1 and ε2 are drilled).
That is, as shown in FIG. 2, in the illustrated embodiment, the drilling rod 11 is repeatedly lowered (drilled) and raised (moved up and down) at a relatively short distance. This is to promote drainage of the drilled bore hole H.
Here, the softer the formation, the faster the drilling speed, the greater the amount of mud, and the greater the number of repetitions of vertical movement for promoting mud drainage. On the other hand, in the case of a hard formation or bedrock, the drilling speed is slow and the amount of mud is small, so the number of times of vertical movement for promoting mud is small.

In the illustrated embodiment, it is determined whether or not the drilled borehole H has reached the formation GB that can serve as a support layer using the effective power consumption as a determination parameter.
In FIG. 2, the effective power consumption is shown in the shaded area (the area where a number of short horizontal lines are attached: the white arrow along the vertical axis is equal in length in the depth direction). It is a judgment parameter in the form.
Effective power consumption is defined as power consumption per unit depth (for example, per 0.5 m depth). The power used is given by the following equation.
Power used = current x time
Effective power consumption = Current x "Time for drilling the ground (actual drilling time)"
Here, “the time when the ground is drilled (the time when the drilling is actually performed)” refers to the drilling of the ground that has not been drilled so far, such as the region α and the region ε2 in FIG. The time for moving the already drilled regions (regions γ, ε1 in FIG. 2) is not included.
In other words, in the illustrated embodiment, after drilling with the drilling rod 11, the regions (the regions γ and ε1 in FIG. 2) that are once lifted and then lowered to the drilled holes are “effective power consumption”. "" Is not included in the "time to drill holes in the ground".
In addition, the depth (the length of the white arrow on the vertical axis in FIG. 2) for drilling “the ground that has not been drilled so far” may be non-uniform as shown in FIG. There may be.

With reference to FIG. 2, an outline of the cut-and-join of the drilling rod 11 will be described. In the case where the drilling rod 11 is cut, the drilling rod starts from the position EC (the position where the tip of the drilling rod 11 reaches the bottom of the boring hole H) immediately before the cutting. 11 is moved upward by a slight amount, and the tip (lower end: not shown in FIG. 2) of the rod 11 is moved to the position ED. As a result, the tip ED of the hole drilling rod 11 is raised from the bottom position EC of the hole drilling rod 11 at the time of cutting, and is not bottomed at the bottom of the boring hole H.
At the time of severing, the amount of water at a position higher than the groundwater level in the drilling rod 11 flows out from the tip of the drilling rod 11. At that time, if the tip (lower end) of the drilling rod 11 is bottomed (when it is located at the deepest position EC), the outflowed water collides with the ground near the bottom of the borehole H, and the boring Adverse effects such as loosening the ground near the bottom of the hole H occur. On the other hand, when cutting the rod 11 for drilling, when the rod 11 for drilling is pulled up from the bottom position (the deepest position EC) to the position ED for moving slightly upward, the tip of the rod 11 and the borehole A relatively large gap is formed between the bottom of H, and the water in the drilling rod 11 flows out from the tip of the rod 11 by the amount of water accumulated above the groundwater level at the time of cutting. Even so, the energy held by the water flowing out by the relatively large gap is attenuated, the speed of collision with the bottom of the borehole H is reduced, and adverse effects such as loosening the ground near the bottom are reduced. To do.
Thereafter, the drilling rod 11 may be connected according to a conventionally known procedure.

The drilling rod handling unit 10 of the construction machine 100 that performs drilling as described in FIG. 2 is shown in FIG. 3.
In FIG. 3, the drilling rod handling unit 10 includes a plurality of chucks 110, a plurality of holders 120, a plurality of rod moving cylinder mechanisms 130, a measuring scale 140, and a drilling rod rotation driving electric motor. (Hereinafter referred to as “electric motor”) 150.
The chuck 110 is a member that holds the drilling rod 11 when the drilling rod 11 is moved up and down. On the other hand, the holder 120 is a member for gripping (holding) the drilling rod 11 when the chuck 110 releases the gripping of the drilling rod 11.

In FIG. 3, reference numeral 160 denotes a base member fixed (directly or indirectly) to the ground surface Gf.
In the vicinity of the cylinder mechanism 130, a measurement scale (hereinafter referred to as “scale”) 140 is arranged in parallel with the cylinder mechanism 130. The scale 140 is configured to measure the expansion / contraction amount (or chuck movement amount) of the piston rod 133 of the cylinder mechanism 130.
A scale pointer 134 is attached to the piston rod 133 of the cylinder mechanism 130, and the scale pointer 134 indicates the scale of the scale 140. The scale pointer 134 has a function of converting the indicated scale (read scale) into an electrical signal and outputting it to the effective power calculation block 51 (see FIG. 3) of the control unit 50 via the line Li2. doing.

In FIG. 3, electric power is supplied to the electric motor 150 from an AC power supply via a power supply line LE.
The power meter EM of the switchboard of the AC power supply has a function of outputting information (current value) regarding the power consumption of the electric motor 150 to the effective power calculation block 51 of the control unit 50 via the line Li1.

The control unit 50 that is a control means includes an effective power calculation block 51, a storage device 52, a comparison block 53, and a timer 54 that is a time measuring means.
The effective power consumption calculation block 51 determines the “time spent for effective drilling” determined from the information (current value) regarding the power consumption obtained from the power meter EM, the information from the scale pointer 134 and the time data of the timer 54. ”And multiplying the current value by“ time spent in effective drilling ”to calculate“ effective power consumption ”.
The storage device 52 stores “the threshold value of the effective power consumption when reaching the target ground” obtained in a past demonstration experiment or the like. Here, “the threshold value of the effective power consumption when reaching the target ground” is determined on a case-by-case basis, depending on the construction site (ground to be drilled), equipment used, and other conditions. To be determined.

The comparison block 53 compares the “threshold value of the effective power consumption when reaching the target ground” stored in the storage device 52 and the “effective power consumption” calculated by the effective power calculation block 51. It has a function to do. When the “effective power consumption” calculated by the effective power consumption calculation block 51 is equal to or greater than the “threshold value of the effective power consumption when reaching the target ground”, the “boring hole H becomes the target value”. It has a function to judge that it has reached.
The comparison block 53 is connected to an external monitor 60 via a line Lo, and is configured to display the comparison result and determination contents in the comparison block 53 on the monitor screen.
Although not explicitly shown in FIG. 3, the control unit 50 calculates the drilling speed from the “time spent for effective drilling” determined from the information from the scale pointer 134 and the timing data of the timer 54. It has a function to do.

FIG. 4 shows the current value, drilling speed, and effective power used when drilling a composite ground composed of a clay layer, a sand layer, and a mudstone layer until the construction machine 100 shown in FIG. 3 reaches the mudstone layer. ing.
In FIG. 4, the horizontal axis indicates the depth, the symbol H1 indicates a clay layer, the symbol H2 indicates a sand layer, and the symbol H3 indicates a mudstone layer.
The vertical axis on the left side of FIG. 4 shows the current value (solid line LA in FIG. 4) and the effective power consumption (the dashed line LB in FIG. 4), and the vertical axis on the right side shows the drilling speed (dotted line LC in FIG. 4). Show. Here, the effective power consumption in FIG. 4 is the effective power consumption per 0.5 m depth.

In the mudstone layer H3 of FIG. 4, the current value is not significantly different from the current values in the clay layer H1 and the sand layer H2, but the value of the effective power consumption is much larger.
The drilling speed in the mudstone layer H3 is slower than the drilling speed of the clay layer and sand layer, but the value of the effective power consumption increases because the drilling speed is slow in the mudstone layer H3. Due to the long time. That is, “effective power consumption = current × time”, and even if there is no difference in the current value, the drilling time becomes long and the effective power consumption increases in the case of uncut ground, etc. (the value of the effective power consumption increases) Therefore, the effective power consumption in the mudstone layer H3 increases.
Here, when the current value determines whether or not the mudstone layer H3 has been reached, for example, if gravel is present in the sand layer H2, the resistance of the drilling hole increases for a moment, and the current value increases. Nevertheless, there is a possibility of misjudging that the mudstone layer H3 has been reached. If effective power is used as a parameter, even if gravel is present in the sand layer H2, the effective power does not increase, so that it reaches a hard enough layer to become a support layer without making the above-mentioned misjudgment. It can be determined whether or not.

As is clear from FIG. 4, the effective power consumption in the mudstone layer H3 is much larger than the effective power consumption of the clay layer H1 and the sand layer H2.
Therefore, when the mudstone layer H3 is selected as the formation that can be the support layer, it is possible to determine whether or not the formation has been drilled to the formation that can be the support layer by monitoring the effective power consumption.

In FIG. 4, the effective power consumption of the sand layer H2 is significantly larger than the effective power consumption of the clay layer H1.
Therefore, even if the sand layer H2 is selected as the base layer that can be the support layer in the multi-layered ground composed of the clay layer H1 and the sand layer H2, if the effective power consumption is monitored, the formation of the base layer that can be the support layer is drilled. It can be judged whether or not.

  Although not shown in the figure, in the multi-layered ground composed of the clay layer H1 and the sand layer H2, when the sand layer H2 is selected as the ground layer that can be the support layer, by observing the current value instead of the effective power consumption, It is possible to judge whether or not a formation that can be a support layer has been drilled.

Next, mainly referring to FIG. 5, the control when drilling to the formation GB (see FIG. 1) that can be the support layer will be described with reference to FIG. 3.
In FIG. 5, in step S1, the effective power consumption is calculated by the effective power consumption calculation block 51 of the control unit 50, and the process proceeds to step S2.
In step S2, the comparison unit 53 of the control unit 50 compares the effective power used calculated in step S1 with the threshold value stored in the storage device 52 (effective power threshold value). As described above, the threshold value of the effective power consumption is determined on a case-by-case basis according to the situation of the construction site (the ground to be drilled), the equipment used, and other conditions.
If the effective power calculated in step S1 is greater than or equal to the threshold (step S2 is YES), the process proceeds to step S3, and if less than the threshold (step S2 is NO), the process proceeds to step S4.

In step S3 (when the effective power calculated in step S1 is greater than or equal to the threshold value), the comparison block 53 determines that the tip of the drilling rod 11 has reached the layer GB that can be the support base. . And control is complete | finished.
On the other hand, in step S4 (when the effective power consumed calculated in step S1 is less than the threshold value), it is determined that the drilling rod 11 has not yet reached the layer GB that can be the support base, Return to step S1 to continue drilling. Then, step S1 and subsequent steps are repeated.

Here, details of the “calculation of effective power consumption” in step S1 in FIG. 5 will be described mainly with reference to FIG. 6 and also with reference to FIGS.
In FIG. 6, in step S <b> 11, the power consumption data (data related to the current value) from the power meter EM and the data from the scale 140 (scale data: the uncut ground as in the region α and the region ε2 in FIG. 2). Data necessary for determining the time for drilling) is read and input to the effective power calculation block 51 of the control unit 50. Then, the process proceeds to step S12.
In step S12, based on the data from the scale 140 (scale data) and the time measurement result of the timer 54, “time for drilling the uncut ground” (“time spent for effective drilling”: for example, FIG. 2) (time for drilling the region α2 and the region ε2).

As described above with reference to FIG. 2, the “time for drilling the uncut ground” used in the calculation of the effective power consumption is the uncut area (the area in the ground that has not been drilled so far: For example, it is the time for drilling the regions α, ε2) in FIG. 2, and does not include the time for moving up and down the already drilled regions (regions γ, ε1 in FIG. 2).
To determine whether a non-drilled region (for example, regions α and ε2 in FIG. 2) has been drilled or a region that has already been drilled (region ε1 in FIG. 2) is moved up and down The scale 140 shown in FIG. 3 is used.
In step S12, “time for drilling the uncut hole ground” (“time spent for effective drilling”: for example, time for drilling the region α, region ε2, etc. in FIG. 2: a short horizontal line in FIG. The mode of determining the time spent for drilling a large number of regions will be described in more detail.

In FIG. 2, in one cycle in which the drilling rod 11 and the piston of the cylinder mechanism 130 descend and rise, when the drilling rod 11 reaches the deepest position (for example, the position β in FIG. 2). The piston of the cylinder mechanism 130 is also at the lowest position in the cycle, and the position is measured with the scale 140 (FIG. 3). The position of the piston of the cylinder mechanism 130 is “PS1 (not shown)”.
When descending (region between position δ and position E in FIG. 2) in the next cycle (cycle of lowering / raising the piston of cylinder mechanism 130), the already drilled region (region ε1 in FIG. 2) is lowered. During this time, the position of the piston of the cylinder mechanism 130 measured by the scale 140 is a position above the position PS1. In step S12 of FIG. 6, while the position of the piston of the cylinder mechanism 130 measured by the scale 140 is a position above the position PS1, the “effective drilling ground” is cut. It is not included in “time of drilling (time of actual drilling)”.
If the position of the piston of the cylinder mechanism 130 measured by the scale 140 is equal to or less than the position PS1 (the same depth as the position PS1 or a position deeper than that), “the uncut hole region in the ground is drilled. (It is the area | region (epsilon) 2 of FIG. 2) ", and time-measures as" the time which is drilling the uncut hole ground "in" effective power use ".
In this manner, in step S12 of FIG. 6, “time spent for effective drilling” or “time for drilling uncut ground” is determined.

In step S13, the “current value” in step S11 is multiplied by the “time” determined in step S12 (the time during which the uncut ground is drilled) to obtain an effective power consumption value (= current value × “ "Time for drilling the uncut ground" is calculated.
When the effective power consumption value is calculated in step S13, the process proceeds to step S2 in FIG. 5 and control for drilling to the formation GB that can be the support layer (see FIG. 1) (whether or not the formation GB that can be the support layer has been reached). Control to determine the above.

  In the drilling according to the illustrated embodiment, if the piston position of the cylinder mechanism 130 reaches the bottom dead center of the cylinder, the drilling rod 11 cannot be lowered as it is. It must be returned to near the top dead center of the cylinder. The procedure for returning the piston of the cylinder mechanism 130 to the vicinity of the top dead center of the cylinder is performed in the same manner as in the prior art. That is, the drilling rod 11 is held by the holder 120, the chuck 110 is separated from the drilling rod 11, and the piston of the cylinder mechanism 130 is raised to the top dead center. Then, the chucking rod 11 is gripped (checked) by the chuck 110, and the gripping of the drilling rod 11 by the holder 120 is released.

According to the illustrated embodiment, the effective power consumption is calculated, and if the effective power consumption is equal to or greater than the threshold value, it is determined that the layer GB that can be the support layer has been reached. Whether or not the target layer GB has been reached even when the diameter of the bit (not shown) increases slightly compared to the diameter and the resistance value (current value) of the electric motor 150 of the construction machine 100 is small. Can be judged.
Further, for example, when the mudstone layer H3 is a layer that can serve as a support layer, even if gravel exists in the sand layer H2, the effective power consumption does not increase significantly. It is possible to determine whether or not the mudstone layer H3 serving as the support layer has been reached without misjudging that it is.

Here, the effective power consumption is a value obtained by multiplying the current supplied to the electric motor 150 that rotates the drilling rod 11 by the time during which the ground is drilled (actual drilling time). Current = current × “time for drilling in the ground”), and does not include the time for moving the already drilled regions (regions γ, ε1 in FIG. 2).
Accordingly, in the illustrated embodiment, when the ground is drilled by moving the drilling rod 11 up and down with a relatively short drilling depth in order to promote the drainage, the effective working current is already calculated. Since the time for moving downward in the perforated region (region ε1 in FIG. 2) is not integrated, the effective power consumption can be calculated using only the actual drilling time as a parameter. The power used can be calculated, and it can be determined whether or not the formation GB that can be the support layer has been reached.

  In the illustrated embodiment, if a step of raising the drilling rod 11 by a predetermined amount from the position immediately before cutting is included when cutting the drilling rod 11, the tip of the rod 11 and the bottom of the boring hole H Even when water in the drilling rod 11 flows out from the tip of the rod 11 at the time of cutting, the energy held by the water that flows out by the relatively large gap is retained. Attenuating, and the speed of colliding with the bottom of the borehole H is reduced. Therefore, adverse effects such as loosening the ground near the bottom are reduced.

In the illustrated embodiment, effective power consumption is used as a parameter, but it is possible to comprehensively determine whether or not a layer that can be the support layer GB has been reached using other parameters.
FIG. 7 shows such a modified example (modified example of the embodiment). The configuration of this modification is the same as that described with reference to FIG.
A control or procedure for determining whether or not a layer that can become the support layer GB has been reached by a modification will be described mainly with reference to FIG. 7 and also referring to FIG.

In FIG. 7, first, the control unit 50 (FIG. 3) calculates the drilling speed from the “time spent for effective drilling” determined from the information from the scale pointer 134 and the timing data of the timer 54. (Step S11).
“Effective power consumption = current × time for drilling the uncut hole ground”. If the drilling time is long, the effective power consumption increases. And if a drilling time is long, a drilling speed will become slow. Therefore, in the modification shown in FIG. 7, the drilling speed is first used as a parameter, and then the effective power consumption is used as a parameter. Therefore, after calculating the drilling speed (step S11), in step S12, it is determined whether or not the calculated drilling speed is equal to or less than a threshold value of the drilling speed.
Here, the threshold value of the drilling speed is also determined on a case-by-case basis according to the situation of the construction site (the ground to be drilled), the equipment to be used, and other conditions.

If the drilling speed calculated in step S11 is less than or equal to the threshold value (YES in step S12), the process proceeds to step S13, and if faster than the threshold value (NO in step S12), the process proceeds to step S16.
In step S16 (when the drilling speed calculated in step S11 is faster than the threshold value), it is determined that the layer GB that can be the support base has not yet been reached, and the process returns to step S11.
In step S13 (when the drilling speed calculated in step S11 is equal to or less than the threshold value), the effective power consumption is calculated and compared with the threshold value (step S14).

If the effective power calculated in step S13 is equal to or greater than the threshold (YES in step S14), in other words, if the drilling speed is equal to or less than the threshold and the effective power is equal to or greater than the threshold. Then, it is determined that the layer GB that can be the support base has been reached (step S15).
If the effective power calculated in step S13 is less than the threshold (NO in step S14), it is determined that the layer GB that can be the support base has not been reached (step S16), and the process returns to step S11. .
Note that steps S13 to S16 in FIG. 7 are the same as steps S1 to S4 in FIG.

According to the second embodiment of FIG. 7, it is possible to comprehensively determine whether or not a layer that can be the support layer GB has been reached, using two types of parameters, excavation speed and effective power consumption.
In addition, the calculation of the effective power consumption needs to be performed only in the control cycle in which the excavation speed is equal to or less than the threshold value, so that the burden on the control unit 50 in the automatic control is reduced accordingly.
Other configurations and operational effects in the modification of FIG. 7 are the same as those of the embodiment described with reference to FIGS.

It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.
For example, in the illustrated embodiment, effective power is used as a parameter for determining whether or not a formation that can be a support layer has been reached, but a current value can also be used as such a parameter.
In the illustrated embodiment, instead of the control unit 50, an operator can perform determination and operation.

DESCRIPTION OF SYMBOLS 10 ... Drilling rod drive part 11 ... Drilling rod 20 ... Sludge pump 30 ... Residual soil tank 50 ... Control unit 51 ... Effective power calculation block 52 ... Storage device 53 ... Judgment block 100 ... Construction machine 110 ... Chuck 120 ... Holder 130 ... Cylinder mechanism 140 ... Measurement scale 150 ... Electric motor

Claims (3)

Move the drilling rod up and down to drill the ground, calculate the effective power consumption from the current supplied to the motor that rotates the drilling rod and the drilling time, and the effective power consumption is the threshold value. If it is above, it is judged that the layer that can be the support layer has been reached, and the effective power consumption is a value obtained by multiplying the current by the time for drilling the ground, and the time for drilling the ground, The drilling method according to claim 1, which is a time required for drilling an uncut hole ground and does not include a time for moving up and down an already drilled region.   2. The drilling method according to claim 1, wherein when the drilling rod is cut, the drilling rod is raised by a predetermined amount from a position immediately before the cut.   It has a step of calculating the drilling speed and comparing the calculated drilling speed with a threshold value. When the calculated drilling speed is less than or equal to the threshold value, the effective power consumption is calculated and the effective use is calculated. 3. The drilling method according to claim 1, wherein the drilling method is compared with a power threshold value.

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