JP6532111B2 - Drilling method - Google Patents

Description

  The present invention relates to, for example, a technique for drilling a ground on which a ground improvement method is to be applied. More specifically, the present invention relates to a technique for determining whether or not a drilled boring hole has reached a formation capable of serving as a support layer, for example, when drilling a boring hole to construct a ground improvement method.

In the case of improving a composite ground (for example, a ground composed of a clay layer, a sand layer, and a mudstone layer), the borehole is drilled to a layer (for example, a mudstone layer but not limited to a bedrock) which can be a support layer (support base). Pierce. Then, after drilling, the solidified material injection device is inserted into the borehole, and while rotating while injecting the solidified material from the solidified material injection device, the ground is pulled up to the ground side, and the ground to be improved is formed by drilling. A ground consolidated pile is created in the area above the layer that can be mixed with the timber and can be the support layer.
Here, if the lower end portion of the underground consolidated pile does not reach a layer that can be a support layer, the underground consolidated pile becomes unstable. Therefore, when drilling a borehole, it is necessary to drill so as to reach a layer that can be a support layer.

In the prior art, drilling is performed using a large machine and a long drilling rod without rod joining. Alternatively, drilling is performed by rotating a blade (drilling bit) having a large diameter with respect to the diameter of the rod.
When reaching the target layer (layer that can be a support layer: hard layer), the change in resistance value or current value of the motor of the construction machine at the time of drilling becomes large. It was determined that it had arrived.
However, without using a large machine, drilling is performed while adding rods, and when the bit diameter is slightly larger than the rod diameter, the resistance value (current value) of the motor of the construction machine is small. Therefore, there is a problem that it can not be determined whether the target layer has been reached by 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 from the annular gap formed around the rod.
However, when the increase in bit diameter is small compared to the rod diameter, it is difficult to discharge the sludge to the ground side from the annular gap around the rod. Therefore, the rod must be moved up and down at a relatively short drilling depth to promote drainage. Here, when moving the rod up and down at relatively short drilling depths at the time of drilling, in order to determine whether or not the target layer has been reached, the non-pierced ground is drilled. It must also be determined if it is moving up or down in the area already drilled.
In the prior art, it is difficult to make such a determination, and therefore, when moving the rod up and down at relatively short drilling depths when drilling, it is determined whether or not the target layer has been reached. It was difficult to do.

As another prior art, for example, there is proposed a technique of making a landing determination using a load current and a load torque based on boring data (see Patent Document 1).
However, since the prior 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 being drilled is small and relatively short. It is difficult to apply to the drilling which moves the rod up and down at each drilling depth.

Patent No. 3156050

  The present invention has been proposed in view of the problems of the prior art described above, and when drilling a borehole, the resistance value (electric current value of the motor) by the ground being drilled is small and is 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 in which the rod is moved up and down at a drilling depth.

As a result of various researches, the inventor has reached the target layer by using the effective working current, which is a value obtained by multiplying the current by the time of drilling the ground (the time of actually drilling). It has been found that it can be judged whether or not.
The drilling method of the present invention is created based on such knowledge, and in the drilling of the borehole (H) for drilling the ground (G) with the drilling rod (11),
Drilling an unpierced area (e.g., the areas α, ε2 in FIG. 2) ;
Already drilled region to promote waste sludge (e.g., the region of FIG. 2 gamma, .epsilon.1) and a step of vertically moving the,
The effective working current is calculated from the current supplied to the motor (150) rotating the drilling rod (11) and the drilling time, and if the effective working current becomes equal to or more than the threshold value, the support layer It is judged that the layer that can be (GB) has been reached,
The effective working current is the time during which the ground (G) is being drilled in the current (the current supplied to the motor 150 for rotating the drilling rod 11) (the time when the actual drilling is carried out: un-punched ground Time to drill holes) (effective working current = current × "time to drill ungrounded ground"),
In order to prevent misjudging that the support layer (GB) is reached (when, for example, the resistance of the excavation temporarily increases and the current value increases as in the case where the weir partially exists) The time it takes to drill the ground is the time it takes to drill the unpierced ground (areas that have not been drilled so far: eg the regions α, ε2 in Figure 2) , It is characterized in that it does not include the time for moving up and down the area (area γ, ε1 in FIG. 2) already drilled to promote .
Here, the threshold value of the effective working current is determined on a case-by-case basis depending on the condition of the construction site (ground to be drilled), the equipment used, and other conditions.

In the present invention, when cutting the drilling rod (11), the position immediately before the drilling rod (11) is cut (the position where the tip of the drilling rod 11 lands on the bottom of the boring hole H) It is preferable to raise by a predetermined amount rather than.
When the water in the drilling rod (11) flows out from the tip of the drilling rod (11) at the time of cutting and connecting, the predetermined amount is a boring hole drilled by the flowed out water (H It is preferable to set the numerical value so as not to adversely affect the ground in the vicinity of the bottom of. The area raised by the predetermined amount is regarded as the area already drilled, and the time for moving the area up and down is not included in the time actually drilled.

  In the present invention, there is a step of calculating the drilling speed and comparing the calculated drilling speed with a threshold, and the calculated drilling speed is equal to or less than the threshold (whether the same speed as the threshold or not It is also possible to calculate the effective working current and compare it to the threshold of the effective working current if it is a slower speed).

In the practice of the present invention, the support layer (GB) is not limited to rock layers such as mudstone layers. For example, in the case of a multi-layered ground consisting 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 a support layer.
As the “layer that can be a support layer (GB)”, a layer having a high N value, for example, a layer having an N value of 50 or more corresponds. Alternatively, a layer having a layer thickness of 3 m or more and having a larger N value than the upper layer may be a support layer.

  As described above, if the effective working current is used as a parameter, it can be determined whether or not the target layer is reached. According to the present invention having the above configuration, the effective working current is calculated and the effective working current is calculated. Since it is judged that the layer which can become the support layer has reached when the threshold value becomes equal to or more than the threshold, the increase in bit diameter is small compared to the rod diameter, and the resistance value (current value of the motor of the construction machine Even in the case where the value of d) is small, it can be determined whether or not the target layer (the layer capable of becoming a support layer) has been reached.

Here, the effective working current is a value obtained by multiplying the current supplied to the motor (150) for rotating the drilling rod (11) by the time for drilling the ground (time for actually drilling) The effective working current = current × “time for drilling the ground” does not include the time for moving the already drilled area (area γ, ε1 in FIG. 2).
Therefore, when it is necessary to move the drilling rod (11) up and down with a relatively short drilling depth to promote drainage, it is necessary to drill the hole when calculating the effective working current. It is possible to calculate the effective working current by using only the time of actual drilling as a parameter without accumulating the time for moving the above area (area γ, ε1 in FIG. 2) downward.
In other words, even if it is necessary to move the drilling rod (11) up and down with a relatively short drilling depth to promote drainage, even if it is necessary to drill the ground, the support layer (GB) It can be determined whether or not the potential layer (target layer) has been reached.

  In the present invention, when cutting the drilling rod (11), from the position immediately before cutting the drilling rod (11) (the position where the tip of the drilling rod 11 lands on the bottom of the boring hole H) If the process of raising the amount by a predetermined amount is included, the water in the drilling rod (11) at the time of cutting (the amount of water accumulated above the groundwater level) the tip of the drilling rod (11) However, since the outflowing water collides with the bottom of the borehole (H), the adverse effect such as loosening the ground near the bottom is reduced.

In the present invention, there is a step of calculating the drilling speed and comparing the calculated drilling speed with a threshold, and the calculated drilling speed is equal to or less than the threshold (whether the same speed as the threshold or not In the case of slower speed), the effective working current is calculated and compared with the threshold of the effective working current, drilling is performed using two parameters of the drilling speed and the effective working current It can be comprehensively judged whether or not the borehole (H) has reached a layer (GB) which can be a support layer.
In addition, since the calculation of the effective working current only needs to be performed in the control cycle in which the drilling speed is equal to or less than the threshold, the load on the control unit (control unit 50) in automatic control is lightened.

BRIEF DESCRIPTION OF THE DRAWINGS 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 an explanatory view showing an outline of an embodiment of the present invention. It is a block diagram of a construction machine which enforces an embodiment of the present invention. It is a characteristic view showing the construction data at the time of drilling by the drilling method concerning an embodiment. It is a flow chart which shows control of an embodiment of the present invention. It is a flowchart which shows control which calculates | requires effective working current in embodiment. It is a flowchart which shows the modification of embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows an outline of a construction site to which the embodiment of the present invention is applied at the time of ground improvement work.
In FIG. 1, in a drilling method according to an embodiment of the present invention, a construction machine 100 having a drilling rod drive unit 10, a drilling rod 11, a pump 20, a soil reclamation tank 30, and a mud screen 40. The construction is carried out using a sludge pump 25. Here, a water swivel 12 is attached to the head of the drilling rod 11.

The pump 20 is a water pump for pumping high pressure water for drilling, and the sludge pump 25 is a slurry pump for sucking the sludge generated by drilling to the ground side. In addition to the two pumps 20, 25, an air compressor (not shown) for pumping high pressure air can also be provided.
The pump 20 and the water swivel 12 are connected by a high pressure hose 22.
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 by high pressure water jetted from a nozzle (not shown) Do.
The drilling rod 11 is, for example, a double tube (or a single tube or a triple tube), and high pressure water for drilling is supplied via the inner tube (or tube), and the sludge generated by drilling Is sucked by the ground-side mud pump 25 via an annular gap between the outer tube of the double tube and the bored inner wall of the bored hole H.

The sludge pump 25 sucks in the sludge generated at the time of drilling and projects it to the sludge line 27. The sludge discharged by the sludge pump 25 is collected by the mud screen 40 (sieve) installed above the soil tank 30. The mud screen 40 accommodates the small particle size sludge in the residual soil tank 30, and discharges the large particle size sludge out of the residual soil tank 30.
The code | symbol G in FIG. 1 shows the ground of a construction area | region, and the code | symbol GB has shown the "layer which can become a support layer" which is the drilling target of the borehole H, for example, a rock bed layer.

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

As apparent from FIG. 2, in the illustrated embodiment, the drilling rod 11 drilling the ground does not advance only downward at the time of drilling. When the drilling rod 11 drills a relatively short distance, for example, the region indicated by the symbol α in FIG. 2 (when drilling is performed to the location indicated by the symbol β), the drilling rod 11 is located above (symbol γ To the area shown by) (up to the point shown by the symbol δ)). Thereafter, the drilling rod 11 is lowered and drilled to a position (E) below the portion 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 moved down (boring) and rising (moving up and down) at a relatively short distance. This is to promote the drainage of the bored hole H that has been drilled.
Here, since the drilling speed is faster as the softer formation is used, the amount of sludge is increased, and the number of repetitions of the vertical movement is increased to promote the drainage. On the other hand, in the case of a hard stratum or rock, since the drilling speed is low and the amount of mud discharge is small, the number of repetitions of vertical movement for promoting mud drainage may be small.

In the illustrated embodiment, it is determined whether or not the drilled hole H has reached the formation GB which can be a support layer, using the effective use current as a determination parameter.
In FIG. 2, the effective use current in the shaded area (area where many short horizontal lines are attached: the length of the hollow arrow along the vertical axis is equal to the depth direction) is the determination parameter in the illustrated embodiment. It has become.
The effective working current is defined as the working current per unit depth (for example, per 0.5 m depth). The working current is given by the following equation.
Working current = current x time
Effective working current = current × "time for drilling the ground (time for actual drilling)"
Here, "time for drilling the ground (time for actually drilling)" refers to drilling of the ground which has not been drilled so far, as in the region α and the region ε2 in FIG. It does not include the time for moving the already drilled area (area γ, ε1 in FIG. 2).
In other words, in the illustrated embodiment, after drilling by the drilling rod 11, the regions (regions γ and ε1 in FIG. 2) in which the rod 11 is once raised and then drilled down It does not include in "time to drill the ground" in.
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 uneven or even as shown in FIG. It may be.

Referring to FIG. 2, the cutting of the drilling rod 11 will be outlined. When cutting the drilling rod 11, the drilling rod is used from the position EC (the position where the tip of the drilling rod 11 is bottomed at the bottom of the boring hole H) drilled by the rod 11 immediately before the drilling. 11. Move the tip 11 a little amount upward to move the tip of the rod 11 (bottom end: not shown in FIG. 2) to the position ED. As a result, at the time of cutting, the tip end ED of the drilling rod 11 is elevated above the landing position EC of the drilling rod 11 and is not bottomed at the bottom of the borehole H.
At the time of cutting, only 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, when the end (lower end) of the drilling rod 11 is bottomed (when located at the deepest position EC), the drained water collides with the ground in the vicinity of the bottom of the boring hole H, and boring occurs. An adverse effect occurs such as loosening the ground near the bottom of the hole H or the like. On the other hand, when cutting the drilling rod 11, the tip of the rod 11 and the boring hole are pulled up by pulling up the drilling rod 11 from the bottom position (the deepest position EC) slightly upward to the moving position ED. A relatively large gap is formed between the bottom of H and, at the time of cutting, the water in the drilling rod 11 flows out of the tip of the rod 11 by the amount of water accumulated above the groundwater level. However, the energy possessed by the drained water is attenuated by the relatively large gap, 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. Do.
After that, the cutting work of the drilling rod 11 may be performed according to a conventionally known procedure.

The drilling rod handling unit 10 of the construction machine 100 for drilling as described in FIG. 2 is shown in FIG.
In FIG. 3, the hole processing rod handling unit 10 includes a plurality of chucks 110, a plurality of holders 120, a plurality of cylinder mechanisms 130 for moving the rods, a measurement scale 140, and an electric motor for driving the rotation of the rods for drilling. (Hereinafter referred to as "electric motor") 150 is provided.
The chuck 110 is a member that holds the drilling rod 11 when moving the drilling rod 11 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 is 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 disposed in parallel with the cylinder mechanism 130. The scale 140 is configured to measure the amount of expansion and contraction (or the amount of movement of the chuck) 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 points to the scale of the scale 140. The scale pointer 134 has a function of converting the information of the indicated scale (read scale) into an electrical signal and outputting it to the effective working current calculation block 51 (see FIG. 3) of the control unit 50 through the line Li2. doing.

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

The control unit 50 which is a control means includes an effective use current calculation block 51, a storage device 52, a comparison block 53, and a timer 54 which is a clocking means.
The effective working current calculation block 51 determines the “time spent in valid drilling determined from information (current value) on consumption current obtained from the current meter EM, information from the scale pointer 134, and time data of the timer 54. It has a function to calculate “effective working current” by determining “the current value and time spent for effective drilling”.
The storage device 52 stores “the threshold value of the effective use current value when the target ground is reached” obtained in the past demonstration experiments and the like. Here, “the threshold value of the effective working current value when reaching the target ground” is a case-by-case according to the condition of the construction site (ground to be drilled), the equipment used, and other conditions. To be determined.

The comparison block 53 compares the “threshold value of the effective working current value when reaching the target ground” stored in the storage device 52 with the “effective working current” calculated by the effective working current calculation block 51. Have a function to Then, if the “effective working current” calculated by the effective working current calculation block 51 is “the threshold value of the effective working current value when reaching the target ground”, “boring hole H becomes the target value It has a function to judge that it has
The comparison block 53 is connected to the external monitor 60 by a line Lo, and is configured to display the comparison result and the determination content in the comparison block 53 on the monitor screen.
Although not clearly shown in FIG. 3, the control unit 50 calculates the drilling speed from the “time spent for valid drilling” determined from the information from the scale pointer 134 and the time data of the timer 54. Have a function to

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

In the mudstone layer H3 of FIG. 4, the current value is not significantly different from the current value in the clay layer H1 and the sand layer H2, but the value of the effective working current is much larger.
The drilling speed in the mudstone layer H3 is slower than the drilling speed in the clay layer and sand layer, but the value of the effective working current is increasing because the drilling speed is slow in the mudstone layer H3 Because it is long. That is, “effective working current = current × time”, and even if there is no difference in the current value, the drilling time becomes longer in the unpierced ground etc., and the effective working current becomes larger (the value of the effective working current rises ), The effective working current in the mudstone layer H3 increases.
Here, if it is judged by the current value whether or not the mudstone layer H3 is reached, for example, if there is a weir in the sand layer H2, the resistance of the drilling increases for a moment and the current value becomes large, and in the sand layer H2. Despite this, there is a possibility that the mudstone layer H3 has been reached and misjudged. If the effective working current is judged as a parameter, the effective working current does not increase even when there is a wrinkle in the sand layer H2, so that a hard layer sufficient to become a support layer is reached without making the above erroneous judgment. It can be determined whether or not it has.

As described above, as apparent from FIG. 4, the effective use current in the mudstone layer H3 is much larger than the effective use current of the clay layer H1 and the effective use current of the sand layer H2.
Therefore, when the mudstone layer H3 is selected as the layer capable of becoming the support layer, it is possible to determine whether or not the layer capable of becoming the support layer has been drilled by monitoring the effective use current.

In FIG. 4, the effective use current of the sand layer H2 is significantly larger than the effective use current of the clay layer H1.
From this, even in the case where the sand layer H2 is selected as a layer capable of becoming a support layer in the multi-layered ground composed of the clay layer H1 and the sand layer H2, drilling to a layer capable of becoming a support layer by monitoring the effective use current It can be judged whether or not it has been done.

  Although not shown, in the case where sand layer H2 is selected as a layer capable of becoming a support layer in a multi-layered ground consisting of clay layer H1 and sand layer H2, by observing the current value instead of the effective use current, It is possible to judge whether or not the formation that can be a support layer has been drilled.

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

In step S3 (when the effective operating current calculated in step S1 is equal to or higher than the threshold value), the comparison block 53 determines that the tip of the drilling rod 11 has reached the layer GB which can be a support base. . And control is ended.
On the other hand, in step S4 (when the effective working current 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 which can be a support base, It returns to step S1 to continue drilling. And step S1 or subsequent ones are repeated.

Here, the details of “calculation of the effective working current” in step S1 in FIG. 5 will be described mainly with reference to FIG. 6 and also with reference to FIG. 2 and FIG.
In FIG. 6, in step S11, the data on the current value from the current meter EM and the data from the scale 140 (scale data: time for drilling the uncut ground as in the region α and the region ε2 in FIG. 2) (Data necessary to determine) is input to the effective working current calculation block 51 of the control unit 50. Then, the process proceeds to step S12.
In step S12, based on the data (scale data) from the scale 140 and the time measurement result of the timer 54, "time to drill the uncut ground"("time spent on effective drilling: for example, The time to drill the area α and the area ε2 of 2) is determined.

As described above with reference to FIG. 2, the “time to drill the uncut ground” used in the calculation of the effective working current is the uncut area (the area in the ground which has not been drilled so far: For example, it is time to drill the area α, ε2) in FIG. 2 and does not include the time to move up and down the already drilled area (area γ, ε1 in FIG. 2).
To determine whether you are drilling a non-drilling area (for example, areas α and ε2 in FIG. 2) or move up and down a previously drilled area (area ε1 in FIG. 2) , Scale 140 shown in FIG.
In step S12, "time to drill the unpierced ground"("time spent for effective drilling: for example, time to drill the region α and the region ε2 etc. in Fig. 2: a short horizontal line in Fig. 2 The aspect of determining the time spent for drilling a large number of areas will be described in more detail.

In FIG. 2, in one cycle in which the drilling rod 11 and the pistons of the cylinder mechanism 130 move downward and rise, 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 lowermost position in the one cycle, and the position is measured by the scale 140 (FIG. 3). Let the position of the piston of the cylinder mechanism 130 be “PS1 (not shown)”.
In the next cycle (the cycle of lowering / rising the piston of the cylinder mechanism 130) in the descending (area between position δ and position E in FIG. 2), the previously drilled area (area 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 at a position above the position PS1, "unground ground in the effective use current" is ground It does not include in the time of drilling (the time of actually drilling).
If the position of the piston of the cylinder mechanism 130 measured by the scale 140 is less than or equal to the position PS1 (the same depth as the position PS1 or a position deeper than that), “the uncut area in the ground is being drilled (It is the area ε2 in FIG. 2), and it is counted as “the time for drilling the unpierced ground” in the “effective use current”.
In this manner, in the step S12 of FIG. 6, "time spent for effective drilling" or "time for drilling ungrounded 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 unpierced ground is being drilled) to obtain an effective current value for use (= current value x " Calculate the time it takes to drill the unpierced ground.
If the effective working current value is calculated in step S13, the process proceeds to step S2 in FIG. 5, and control for drilling to a formation GB (see FIG. 1) that can be a support layer (a formation GB that can be a support layer has been reached or not Control to determine the

  When drilling in the illustrated embodiment, if the position of the piston of the cylinder mechanism 130 reaches the cylinder bottom dead center, it is not possible to lower the drilling rod 11 as it is. It must return to the vicinity of the top dead center of the cylinder. The procedure for returning the piston of the cylinder mechanism 130 to near the cylinder top dead center 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 drilling 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, since it is determined that the effective working current is calculated and the layer GB which can become a support layer is reached when the effective working current becomes equal to or more than the threshold value, Whether or not the diameter of the bit (not shown) increases slightly compared to the diameter and the target layer GB is reached even when the resistance value (current value) of the electric motor 150 of the construction machine 100 is small Can be judged.
Also, for example, when mudstone layer H3 is a layer that can be a support layer, effective current does not increase significantly even if there is a weir in sand layer H2, so the part where weir is present in sand layer H2 is mudstone layer H3 Therefore, it is possible to determine whether or not the mudstone layer H3 serving as the support layer has been reached without making a misjudging determination.

Here, the effective use current is a value (effective use) obtained by multiplying the current supplied to the electric motor 150 for rotating the drilling rod 11 by the time for drilling the ground (time for actually drilling). Current = current × “time for drilling the ground”), and does not include the time for moving the already drilled region (region γ, ε1 in FIG. 2).
Therefore, in the illustrated embodiment, in the case of drilling the ground by moving the drilling rod 11 up and down with a relatively short drilling depth in order to promote drainage, drilling is already performed when calculating the effective working current. Since the time for moving the perforated area (area ε1 in FIG. 2) downward is not integrated, the effective working current can be calculated using only the time for actual drilling as a parameter. It can be determined whether it has reached the formation GB which can be a layer.

  In the illustrated embodiment, including the step of raising the drilling rod 11 by a predetermined amount from the position immediately before the drilling connection when cutting the drilling rod 11, the tip of the rod 11 and the bottom of the boring hole H Even if the 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 has flowed out by the relatively large clearance is sufficient. It attenuates and the speed of collision with the bottom of the borehole H is reduced. Therefore, adverse effects such as loosening the ground near the bottom portion are reduced.

In the illustrated embodiment, although the effective use current is used as a parameter, it is possible to make a comprehensive determination as to whether or not a layer that can be the support layer GB has been reached using other parameters.
FIG. 7 shows such a modification (modification of the embodiment). The configuration of the modified example 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 according to a modification will be described mainly with reference to FIG. 7 and also with reference to FIG.

In FIG. 7, first, the drilling speed is calculated by the control unit 50 (FIG. 3) from the "time spent for valid drilling" determined from the information from the scale pointer 134 and the time data of the timer 54. (Step S11).
“Effective working current = current × time for drilling ungrounded ground” If the drilling time is long, the effective working current becomes large. And if drilling time is long, drilling speed will become slow. Therefore, in the modification shown in FIG. 7, the drilling speed is used as a parameter first, and then the effective working current is used as a parameter. Therefore, after calculating the drilling speed (step S11), in step S12, it is determined whether the calculated drilling speed is equal to or less than the threshold of the drilling speed.
Here, the threshold value of the drilling speed is also determined on a case-by-case basis according to the condition of the construction site (ground to be drilled), the equipment used, and other conditions.

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

If the effective working current calculated in step S13 is equal to or more 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 working current is equal to or more than the threshold , It is determined that the layer GB which can be a supporting base has been reached (step S15).
If the effective use current calculated in step S13 is less than the threshold (NO in step S14), it is determined that the layer GB which can be a support base is not reached (step S16), and the process returns to step S11 .
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 of the digging speed and the effective use current.
In addition, since the calculation of the effective working current only needs to be performed in the control cycle in which the drilling speed is equal to or less than the threshold, the load on the control unit 50 in automatic control is lightened.
The other configurations and operational effects in the modification of FIG. 7 are the same as those of the embodiment described in FIGS.

It should be noted that the illustrated embodiment is merely an example, and is not a description for the purpose of limiting the technical scope of the present invention.
For example, in the illustrated embodiment, although the effective working current is used as a parameter for determining whether or not the formation that can be the support layer has been reached, it is also possible to adopt a current value as the parameter.
Also, in the illustrated embodiment, instead of the control unit 50, the operator can perform judgments and operations.

10 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · drilling rod drive unit 11 · · · drilling rod 20 · · · mud pump 30 · residual soil tank 50 · · · · control unit 51 Storage device 53 ... Judgment block 100 ... Construction machine 110 ... Chuck 120 ... Holder 130 ... Cylinder mechanism 140 ... Measurement scale 150 ... Electric motor

Claims (1)

In the drilling of a borehole where the ground is drilled with a drilling rod,
Includes a step of boring a non-drilling region, and the step of vertically moving the already drilled region to promote waste sludge,
The effective working current was calculated from the current supplied to the motor for rotating the drilling rod and the drilling time, and when the effective working current became equal to or more than the threshold value, a layer that could become a support layer was reached. Judge,
The effective working current is a value obtained by multiplying the current by the time for drilling the ground,
In order to prevent the erroneous decision that it has reached the support layer, the time that drilling the ground is the time required for drilling the non-drilling soil, already drilled to facilitate waste sludge A drilling method characterized in that it does not include the time for moving up and down the area.

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