JP2003074045A - Ground examining method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground examining method and device capable of obtaining the accurate data of the ground. SOLUTION: This ground examining device 1 is formed to continuously measure a rotary load and a tip depth when pressing a rod provided with excavating blades at a tip thereof into the ground with rotation, and the rotary load can be continuously and accurately measured. This ground examining method can accurately detect a thin soft layer to realize the excellent design of steel pipe piles and execution that boring is stopped at the upper part of a thick support layer under the soft layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a ground survey method and a ground survey apparatus.

[0002]

2. Description of the Related Art In the prior art, a method called "standard penetration test" is generally used as a method for investigating the formation of the ground before driving a pile. The pile is designed based on the N value obtained by this "standard penetration test" and a construction plan is made. What is the N value? A hammer with a mass of 63.5 kg is allowed to fall freely from a height of 75 cm, and a sampler attached to the rod tip with a pile diameter of about 100 mm is grounded to 30
cm It is the number of drops required to make a penetration. N
The measurement of the value is usually performed at intervals of 1 m in the depth direction. That is, it measures 30 cm and penetrates 70 cm without measuring.

As another investigation method, there is a cone penetration test. The cone penetration test is a method in which a vertical force is applied from the top of the rod to press it into the ground, and the load of press fitting is measured to check the ground strength.

[0004]

The data obtained by the above-mentioned prior art investigation method has the following drawbacks. Since the "standard penetration test" is fragmented data without continuity, which is obtained by dropping or hitting, there is a large variation in information and the accuracy is poor. Therefore, when the work content is the rotary press-fit type steel pipe pile, the ground survey data is the data information by the drop penetration method, so the construction method and the survey data do not always match, and the design of the rotary press-fit pile (pile There was a problem that the length, the thickness of the steel pipe, the thickness, the excavation blade, the construction method of the open end pile, the closed end pile, etc., the presence or absence of consolidation, etc., could not be made accurate and highly accurate to the ground. . In addition, when performing a standard penetration test, a hole is dug by boring and N is drilled at a predetermined depth.
Measure the value. In other words, the work of digging the boring hole and the work of measuring the N value cannot be performed at the same time. The work of once digging the hole to a predetermined depth, pulling up the rod for digging, and then performing the standard penetration test is repeated every 1 m. Was there. Therefore, the deeper the boring hole, the longer the time required to measure the N value, and the deeper the hole, the more time it takes for the rod to be pulled up and re-penetrated.

The "cone penetration test" is different from the standard penetration test and can continuously check the ground strength. However, the testable depth is relatively shallow, and it cannot be applied when the depth of the test ground becomes large. That is, there is a problem that the required pushing force becomes large at a large depth, the machine becomes large, and when a large pushing force is applied, the rod bends or buckles.

When the soft layer and the intermediate layer are multi-layered, the variation of the N value is especially large, and troubles occur during the construction of the rotary press-fitting steel pipe pile based only on the measured data. Had the potential. In addition, when there is an unexpected formation in the part where N value is not measured, stable construction may not be realized. For example, as shown in FIG. 1, when there is a thin soft layer in the middle of the reached support layer and the thin soft layer is within 70 cm where the N value is not measured, the existence information of the thin soft layer is displayed. This means that the hard layer above the soft layer is set (determined) at the pile stopping portion (the assumed support layer based on the N value) and the pile is designed and piled. That is, the constructed pile foundation becomes unstable with a soft layer below, and it may not be possible to obtain the bearing capacity expected in the design. In addition, if the presence of a thin soft layer is found during construction, it will be necessary to suspend construction and change the pile length, which will cause new problems such as extension of construction period and cost increase. .

That is, in such a conventional technique,
The precise determination of the support layer is difficult. Normally, the standard penetration test (measurement of N value) is carried out at only a few places on the site of one building. Then, the measurement results (N
The supporting layer level (depth) is determined from the value), and the supporting layer level of the entire site is assumed by connecting each depth smoothly. However, according to the construction of the rotary press-fit steel pipe piles that the inventors have carried out so far, there is often a difference between the support layer level assumed from the N value and the support layer level determined from the pile construction torque. I know. Moreover, it has been found that there is a difference of ± 5 m in some cases. This means that there are some uncertainties in the support layer level on the premises that cannot be determined by standard penetration tests at several locations, and a precise support layer level cannot be assumed simply by connecting the support layer levels based on N values smoothly. ing. During construction, if it is found that there is a difference between the expected support layer level and the actual support layer level, it is necessary to change the pile length at that point, which leads to an extension of the construction period and an increase in cost. In order to accurately determine the level of the support layer, it is necessary to increase the number of positions where the standard penetration test is performed, but as described above, since boring and N value measurement are performed individually, it takes a lot of time for the standard penetration test. Therefore, the cost and time loss will increase.

The present invention has been made in view of the problems of the prior art as described above, and its object is to obtain accurate continuous property data of the ground even at a large depth in a shorter investigation time. It is to provide a ground survey method and a ground survey apparatus that can be obtained.

[0009]

The present invention has the following features to attain the object mentioned above. <Invention of Ground Survey Method According to Claim 1> When a rod having an excavation blade at the tip is rotationally press-fitted into the ground, the rotational load and the tip depth of the rod are continuously measured. Characterize. The "rotational load" is measured by the rotational load means, when the rod rotation drive means is an electric motor, the change in the current value or voltage value that changes depending on the load, and when it is a hydraulic motor, the change in the hydraulic pressure value is measured. It can be obtained by converting. However, the measurement items are not limited to these.

<Invention of Ground Survey Method According to Claim 2>
The invention according to claim 1 is characterized in that a large diameter portion is formed on the outer periphery of the rod.

<Invention of Ground Survey Method According to Claim 3>
In the invention according to claim 1 or 2, the rotational load is
Load measuring means provided on the rotating means side for rotating the rod,
Or by the load measuring means installed inside the rod tip side,
It is characterized by being measured.

<Invention of Ground Survey Method According to Claim 4>
In the invention according to any one of claims 1 to 3, the rotation acting on the rod shaft portion is measured by measuring the rotation load at the time of press fitting with the rod head and measuring the rotation load at the time of reverse rotation and pulling out. It is characterized in that the load is separated and only the rotational load acting on the rod tip portion is calculated.

<Invention of Ground Survey Method According to Claim 5>
In the invention described in claim 4, the following mathematical expression is used when only the rotational load acting on the rod tip portion is calculated. Tt = Tb + Tf (1) Tt: Rotational load of rod head during rotational press-fitting Tb: Rotational load of rod tip Tf: Rotational load due to friction of rod shaft Tt '= Tb' + Tf '= αTb + βTf (2) Tt ': Rotational load when pulling out by reverse rotation Tb': Rotational load of rod pile tip that acts when pulling out by reverse rotation Tf ': When pulling out by reverse rotation Rotational load due to friction of rod shaft acting α = Tb '/ Tb β = Tf' / Tf (This α and β are obtained by stacking experiments.) From (1) and (2), Tb = (Tt ' -ΒTt) / (α-β)

<Invention of Ground Survey Method According to Claim 6>
In the invention according to any one of claims 1 to 5, a rod with a blade is rotationally press-fitted into various experimental grounds of known properties (including artificially created model grounds of known properties). It is characterized in that various experiments are performed and the ground strength and the bearing capacity of the pile are estimated from the rotational load value (Tb) of the rod tip portion based on various data obtained by the experiments. If the rotational load Tb of the tip blade portion can be obtained, the N value of the ground can be estimated from the value and the bearing capacity can be calculated. Alternatively, the value of Tb can be used as the strength of the ground, and the supporting force can be estimated from Tb.

<Invention of Ground Survey Method According to Claim 7>
In the invention according to any one of claims 1 to 6, the rod is hollowed open, the rod is rotationally press-fitted into the ground to stop the rotational press-fitting of the rod at the soil sampling position, and the soil sampling jig is inserted into the rod. It is characterized in that tip soil that has entered the hollow portion of the rod or soil below the tip of the rod is sampled by the soil sampling tool. "The rod has a hollow open end" is for inserting the soil sampling jig into the rod. At the time of rotary press-fitting, cover the tip of the rod, stop rotary press-fitting at the tip soil sampling position, remove the tip lid, insert a jig for soil sampling, and insert the tip into the hollow part of the rod. Take a sample of soil. After that, the lid is attached to the tip again, and rotation press fitting, stop, lid removal, soil sampling, and lid attachment are repeated.

<Invention of Ground Survey Method According to Claim 8>
The invention according to any one of claims 1 to 7 is characterized in that, simultaneously with the automatic measurement of the rotational load of the rod, the vertical force acting on the rod is also automatically measured.

A vertical force may be applied to the tip of the rod depending on the condition of the ground and the condition of construction. In such a case, the vertical force can be measured and recorded, and the ground strength can be converted in consideration of the influence of the vertical force to enable more accurate ground investigation. Regarding the influence of the vertical force on the load, a prior application by the inventors of the present application (Japanese Patent Laid-Open No. 2000-8
0650, JP 2000-80649).

<Invention of Ground Survey Method According to Claim 9>
Measured by the ground survey method according to claim 8,
The rotational load and vertical force of the rod are used to convert the rotational load into torque, and then the N of the surveyed ground is calculated by the following equation (3).
A ground survey method characterized by estimating a value. N = (T + b · L · Dp) / (a · Dp m) ······ (3) ( where, N: N value of the ground, Dp: pile diameter, T: Torque (converted from the rotational load) , L: vertical force, a, b, m: coefficient and index)

<Invention of Ground Surveying Apparatus According to Claim 10> A rod having an excavating blade at its tip, and a rod which is internally provided at an appropriate portion of the rod or on a rotating means side for rotating the rod. And a load measuring means for measuring a rotational load, wherein the rotational load when the rod is rotationally press-fitted into the ground is continuously measured by the load measuring means. . In “providing the rotational load measuring means on the rod rotating means side”, it is possible to obtain by detecting a change in load (such as an increase in hydraulic pressure value or current value) of the rod rotating means corresponding to the height of the load. Things are also within the technical scope. There are various types of "excavation blades" such as a single blade, a plurality of blades, a spiral blade, and a flat plate attached obliquely.

<Invention of Ground Investigation Apparatus According to Claim 11> In the invention according to Claim 10, a large diameter portion is formed on the outer circumference of the rod.

<Invention of Ground Survey Device According to Claim 12> In the invention according to claim 10 or 11, load measuring means for measuring a rotational load acting on a rod tip portion is internally provided near the rod tip. It is characterized by
The “load measuring means” is composed of a load meter installed near the tip of the rod and a load measuring means having a transmitting means for transmitting measured measurement data.

<Invention of Ground Investigation Device According to Claim 13> In the invention according to any one of claims 10 to 12,
The rod has a hollow open end and is equipped with a soil sampling jig, and at the soil sampling position of the ground press-fitted, the tip soil that has entered the hollow portion of the rod or the soil below the rod tip, the soil sampling jig from the upper end of the hollow portion. It is characterized by being inserted and collected.

<Invention of Ground Investigation Device According to Claim 14> In the invention according to any one of claims 10 to 13,
It is characterized in that the excavation blade portion at the tip of the rod is replaceable.

<Invention of Ground Investigation Apparatus According to Claim 15> In the invention according to Claim 14, the excavation blade portion of the rod tip is made replaceable, and the short tip portion of the rod attached to the excavation blade. Has a larger diameter than the upper rod.

<Invention of Ground Surveying Apparatus According to Claim 16> In the structure of the invention according to claim 15, the excavation blade portion at the tip of the rod is made replaceable, and the short rod attached to the excavation blade. The tip portion has a diameter larger than that of the upper rod, and the rod tip portion to which the short rod attached to the excavation blade is connected has the same diameter as the diameter of the short rod.

<Invention of the ground survey device according to claim 17> In the invention according to any one of claims 10 to 16,
It is characterized in that a detachable connecting portion for connecting the rods is provided at an end portion of each rod.

<Invention of the ground survey device according to claim 18> In the invention according to any one of claims 10 to 17,
Simultaneously with the measurement of the rod rotation load, depth measuring means for measuring the depth of the rod tip and vertical force measuring means for measuring the vertical force acting on the rod are provided.

<Invention of Ground Investigation Device According to Claim 19> In the invention according to any one of claims 11 to 18,
The large diameter portion is formed by welding a steel ring to the outer circumference of the rod.

<Invention of the ground survey device according to claim 20> In the invention according to any one of claims 11 to 18,
A large diameter portion is formed by making the connecting portion of the rod larger in diameter than other portions.

<Invention of Ground Survey Device According to Claim 21> In the invention according to any one of claims 10 to 20,
By covering the rod shaft part with a sheath tube and separating the peripheral frictional resistance received when the rod penetrates with the sheath tube, and measuring the load of rotation applied to the rod head on the rotating means side, the rod tip It is characterized by being able to measure the rotational load of. The rod body and the sheath tube are joined and fixed at appropriate portions by joining and fixing means such as bolts.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. <Embodiment 1> FIG. 1 is a comparative view of a ground measuring method according to a conventional technique and a ground measuring method according to the present invention, and FIG. 2 is an example of an overall schematic view of a ground surveying device according to a first embodiment of the present invention. In FIG. 1, according to the ground investigation method of the present invention, since the rotational load value at the time of rotationally press-fitting the rod with blades at the tip is measured, the rotational load can be continuously measured as shown in the figure. It will be possible. At this time, it is desirable to automatically record the rod tip depth at the same time, but the length of the press-fitted rod may be manually recorded on the ground and collated with the load data.

For example, in the prior art N value measurement of FIG. 1, when a thin soft layer existing in an N value unmeasured portion (70 cm) is between the hard layer and the support layer, this thin soft layer is detected. I can't. Therefore, in this case, in the conventional technique, the upper part of the hard layer is used as an assumed supporting layer based on the N value, the length of the steel pipe pile is designed, and the assumed supporting layer based on the N value is used as the supporting layer. . The hard layer shown in Fig. 1 corresponds to the assumed support layer depending on the N value, but if a pile is constructed using this layer as a support layer, a weak layer exists under the pile tip, so it may not be possible to exhibit the supporting force required for the design. There is a nature. On the other hand, in the ground measuring method of the present invention, since a thin flexible layer can be detected with high accuracy, the upper portion of the thick support layer at the lower portion of the flexible layer is set as the stop position, and the steel pipe pile is designed and constructed. become. Of course, more accurate information can be obtained for the construction of other construction method piles such as cast-in-place concrete piles and PHC piles by investigating according to the present invention. Further, according to the present invention, since penetration and load measurement are performed at the same time, measurement (ground investigation) can be performed in a short time, and more investigations can be performed at low cost. In the ground where the level difference of the support layer is large, it is possible to conduct an investigation for all pile positions.

In the ground survey in the present invention, it is necessary to reduce the total rotational load when the rod is press-fitted.
Accurate increase or decrease of the rotational load detected according to the property of the corresponding ground is important for ensuring the reliability of the survey data. Fig. 2 shows the change in the rotational load (rotational load is measured from the change in the hydraulic pressure on the rotating means side) when using a rod equipped with excavation blades at the tip of the rod for ground investigation. The change in rotational load when using a ground excavation blade with a large diameter portion formed at regular intervals on the outer circumference of the rod is ○, the tip of the rod is larger than the upper rod portion, The change in the rotational load is shown as x when the drilling blade is provided at the tip of the large diameter rod and the large diameter portion is formed on the outer circumference of the rod when it is used for the ground survey.

As shown in FIG. 2, when the large diameter portion is formed on the outer periphery of the rod, the former is more rotationally press-fit than the latter when compared with the case where the large diameter portion is not formed on the outer periphery of the rod. It can be understood that the rotational load at time decreases and the detected rotational load increases / decreases accurately in accordance with the known ground property. Further, by forming a large diameter portion on the outer circumference of the rod and by making the tip end portion of the rod to which the excavating blade is attached have a larger diameter than the upper rod portion, the rotational load at the time of rotational press fitting is further reduced. This result is because the large diameter portion of the rod and the large diameter portion of the rod tip portion reduce the circumferential surface friction of the rod. As one of the means for forming the large diameter portion on the outer circumference of the rod, there is a method in which a steel member such as a reinforcing bar is formed into a ring shape and fixed to the outer circumference of the rod by welding. Further, in order to detect the resistance at the tip of the rod more accurately, load measuring means may be internally provided at the tip of the rod.

Ground survey apparatus 1 according to the first embodiment of the present invention
As shown in FIG. 3, the excavation blade 9 is attached to the rod 2 or the tip portion having a rod diameter of about 50 mm with the spiral excavation blade 9 attached to the tip portion, and the large diameter portion 100 is formed on the outer periphery thereof. A rod 2 having a diameter of about 50 mm, a rod rotating means 3 including a rotary press-fitting device for rotationally press-fitting the rod 2, and a load acting on the rod is detected from a hydraulic pressure and a voltage value of the rotary press-fitting device. It is composed of a load measuring device 4. As described above, in the first embodiment that adopts the method of measuring the load acting on the rod 2 by the output of the rotary press-fitting device, since the small diameter rod is used, the rotary press-fitting device may use a small leader type or a crane. Since it is many, small and more compact, it is effective in terms of work efficiency and cost. In the following description of the embodiments, the same configurations as the configurations of the above-described embodiments are designated by the same reference numerals and the description thereof will be omitted.

<Second Embodiment> FIG. 4 is an overall schematic view of a ground investigation device according to a second embodiment of the present invention. The ground survey device 1 has a rod diameter of 100 m with the excavation blade 9 attached to the tip.
The rod 2 having a thickness of about m or a blade 2 is attached to the tip portion, and a large diameter portion 100 is formed on the outer periphery at regular intervals, and the rod 2 having a thickness of about 100 mm and the rod 2 are rotationally press-fitted. Rod rotating means 3 comprising a rotary press-fitting device
And a load measuring unit 4 having a load meter for rotation and vertical force provided near the tip of the rod 2 and a transmitting unit for transmitting measured measurement data, and a process of receiving measurement data from the load measuring unit 4. The load data reception processing device 5 (stores / outputs). The rotational load changes depending on the ground strength as described above, but the vertical force may remain constant depending on the penetration state of the rod, or the pushing force or the pulling force may be applied. It is desirable to measure rotational load, vertical force and depth simultaneously.
The rod 2 has a tip portion 6 having an excavation blade 9, and a load measuring rod member 8 having a hollow portion 7 for transmitting a radio wave, in which a load measuring means 4 is detachably attached to the tip portion, the load measuring means 4 being provided therein. A connecting rod member 10 having a hollow portion 7 that is detachably connected to the load measuring rod member 8. FIG. 10 shows the large diameter portion 100 formed of a steel ring, but depending on the ground conditions, the large diameter portion 100 may be attached only to the tip portion 6. Also,
The large diameter portion 100 of the rod may not be needed.

FIG. 5 is a perspective view showing the structure of the rod and the tip of the ground survey device according to the second embodiment of the present invention. Grooves 13, 13 facing the protrusions 11, 11 facing each other at the upper ends of the tip 6, the rod 8 with a load meter, and the connecting rod 10.
And a pin hole 16 into which a connecting fixing pin 15 (not shown, including a bolt) formed in the protrusions 11 and 11 is inserted, a connecting portion 17 is provided, and the rod 8 with a load meter and the connecting rod 10 are provided. The lower end is provided with a connecting portion that has the same structure as the connecting portion 17 and that has the same configuration (the orientation is reversed). Each rod member can be easily connected and disconnected.

The diameter of the rod is arbitrary, but if the diameter is too large, the required construction equipment will be large and it will be too large for ground surveys, so a diameter of about 100 mm or less is desirable. With such a diameter, the rotational load required for ground penetration is often about 2 to 3 tm or less,
Construction equipment is also small. In order to directly measure the tip load, it is preferable to install a load meter on the tip blade portion or the shaft portion near the tip blade portion. Also, in this example,
The excavation blade at the tip of the rod has a spiral shape whose diameter is about twice the diameter of the rod.

From the load measuring means 4, the measurement data is transmitted by radio waves to the receiving antenna 20 through the hollow portion 7. In addition to this, the method of transmitting the measurement data to the load data reception processing device 5 is by an electric wire, by an ultrasonic wave or a laser beam, by flowing an electric signal to the rod and detecting it from the rod, There are various methods such as detecting what has flowed underground. The load sensing unit (not shown) of the load measuring unit 4 has a method of detecting a change in voltage or current due to pressure by sandwiching a pressure sensor between the engaging protrusions 11, 11 or twisting the rod. There is a method such as by sensing.

As described above, the load measuring means is based on detecting a change in the voltage value or the current value which changes depending on the load of the rod rotating means of the first embodiment. It is not limited to the one provided with, but there are various ones such as one in which a load meter is attached to the rod rotating means. Further, there are various methods for the rod rotating means, such as a rotating means supported and guided by a column so that it can be moved up and down, and a tubing device.

Further, the rod tip portion 6'shown in FIG. 6 is a case where the diameter of the tip end portion of the rod to which the excavation blade 9'is attached is made larger than the diameter of the upper rod. With such a configuration, a thick hole can be formed at the tip, so that the effect of friction between the peripheral side surface of the upper rod and the ground is reduced, and the effect of improving the rotational load measurement accuracy of the tip is obtained. . When the influence of friction can be sufficiently reduced by making the tip diameter larger than the rod diameter, the large diameter portion 100 of the rod may be unnecessary. Even in such a configuration, it is possible to easily replace a portion of the excavation blade where the tip of the rod is heavily worn with a new one and use it. Regarding the connection structure, even if the rod diameter is thick,
It is similar to the case of the same thickness.

The rod 21 shown in FIG. 7 has a large diameter connecting female portion 23 formed at one end and a connecting male portion 22 fitted to the connecting female portion 23 at the other end. By connecting the plurality of rods, the connecting portion of the rod has a larger diameter than the other rod portions, and large diameter portions are formed on the outer circumference of the rod at regular intervals. With this configuration, the strength of the connecting portion is increased, the large diameter portion formed on the outer periphery of the rod reduces the influence of friction with the ground around the rod, reduces the rotational load, and reduces the rotational load. The effect of improving the measurement accuracy can be obtained.

In FIG. 8, the excavation blade portion at the tip of the rod is made replaceable, and the short rod tip portion 6'attached to the excavation blade 9 has a diameter larger than that of the upper rod. By making the distal end portion 23 'of the rod 21' to which the short rod 6'attached to 9 has the same diameter as that of the short rod 6 ', it is possible to make a thick hole at the distal end and to surround the upper rod. The effect of the friction between the side surface and the ground is reduced, the accuracy of measuring the rotational load at the tip is improved, and the strength of the rod tip portion can be increased.

<Third Embodiment> FIG. 9 is a perspective view showing a connecting structure of rods of a ground investigation device according to a third embodiment of the present invention. One of the rods 24 is formed with a connecting male portion 22 composed of a hexagonal protrusion on one end, and the other rod 2
At the end of 5, the connecting female portion 23 into which the connecting male portion 22 fits
To form. Reference numerals 16 and 26 are a pin hole and a pin fitting groove into which the connection fixing pin 15 fits.

<Fourth Embodiment> FIG. 10 is a perspective view showing a structure for connecting piles to each other in a ground survey device according to a fourth embodiment of the present invention. The connecting rod 27 has a connecting male portion 28 formed of a cylindrical protrusion at the end of one rod 30, and a connecting female portion at the end of the other rod 31 to which the connecting male portion fits. Two inverted T-shaped grooves 32 are provided in the connecting male portion 28 at opposite positions, and the connecting female portion 29 is fitted into the groove 32 from above and is a protrusion 33 that moves laterally and does not come off.
Is provided.

<Fifth Embodiment> FIG. 11 is a structural diagram of a ground investigation device according to a fifth embodiment of the present invention. Ground investigation device 5
7 accommodates a survey rod 42 having an excavation blade 41 at the tip in a sheath tube 44, and a flat base 45 is provided above the excavation blade 41.
Is provided so that the flat base 45 and the tip of the sheath tube 44 do not come into contact with each other to form a slight gap, and an O-ring or a bearing 43 is appropriately provided between the sheath tube and the rod.
Mutual position is maintained without any force transmission between the rod and the sheath tube.

FIG. 12 is a perspective view showing the connecting portion of the sheath tube. The sheath pipe 44 has a connecting portion 48 for connecting the sheath pipes at substantially the same site as the pile connecting portion 22 of the survey rod 42. The connecting portion 48 is a mesh-type connecting member having concave and convex ends, is provided with protrusion rings 49, 49 on the outer side, and is a joint structure having two ring fitting grooves 50 into which the protrusion rings 49 fit. The cover 52 and the bolt 46 are connected and fixed. An adapter 53 is attached to the upper portion of the flat base 45 to prevent the sheath tube 44 from blurring and to prevent the entry of dirt and sand. By adopting the sheath tube type, the rotational resistance (load) of the tip (blade) can be measured by measuring the load on the rod head or the rotating means of the rod without providing the rotational load measuring means at the tip. It will be measured.

The survey rod 42 is rotationally press-fitted by the rotational press-fitting means 59 which is connected to the rotational load measuring means (not shown) for continuously measuring the rotational load value, and the sheath tube 44 is rotationally press-fitted by the rotational press-fitting means 60. To be done. Both rotation press-fitting means 5
9 and 60 are set so as to rotate synchronously, and the rod 42 and the sheath tube 44 are rotationally press-fitted together without being displaced.

<Seventh Embodiment> FIG. 13 is a construction procedure diagram showing a ground investigation method according to a sixth embodiment of the present invention. (A) Survey rod rotation press-fitting rotational load measuring step The survey rod 65, which is an open-ended hollow steel tube having the excavation blade 64 at the rod tip, and the tip closing member 6 at the tip of the operation rod 66.
The open end opening / closing means 68 provided with 7 is inserted from the upper part of the survey rod 65, and the open end is closed and rotationally press-fitted to the soil sampling site. The rotational load value of the investigation rod 65 is continuously measured by the rotational load measuring means ((not shown)) during rotational press-fitting. (B) Opening end opening / closing means take-out process When the tip of the pile reaches the soil sampling location, rotation press fitting is stopped,
The open end opening / closing means 68 is taken out to bring the survey rod 65 into the open end state.

(C) Soil sampling process A pipe-shaped soil sampling pipe 69 is inserted into the survey rod 65 from above, and the soil 70 that has entered the rod from the ground at the tip of the survey rod 65 is taken into the soil sampling pipe 69. . After the required amount of soil 70 is taken in, the soil sampling pipe 69 is pulled up to the ground to collect the soil 70. (D) Re-examination rod rotation press-fitting rotary load measuring step The open end opening / closing means 68 is inserted into the soil sampling pipe 69, and while pressing the open end, the rotary press-fitting to the next soil sampling site and the measurement of the rotary load value are performed. The steps (a) to (d) are repeated to collect a predetermined soil 70n.

<Seventh Embodiment> FIG. 14 is a conceptual diagram showing a ground survey method according to a seventh embodiment of the present invention. The inspection rod 65 is stopped while reaching the support layer, and the inspection rod 6
A weight 75 of which the weight is known is placed on the upper part of 5, and a load test is performed. Although there are various loading test methods, in the illustrated one, a load 75 is applied on the survey rod 65, and the sinking of the survey rod 65 is read by the indicating needle member 73 and the scale 74 to estimate the actual bearing force. To do. Based on the data obtained in this way, it can be reflected in the construction plan of the main pile.

In the conventional ground survey, only a part of the burying place of the main pile is surveyed because it takes time and cost for the survey. Therefore, at the actual construction stage, it was not uncommon to find that the bearing capacity of the piles varied and that the structure was adversely affected.
In this respect, the present invention is quick in investigation, and it is easy to perform the soil sampling according to the sixth embodiment, the loading test according to the seventh embodiment, and the like at almost all the sites where the main piles are to be buried. It enables high-grade ground investigation.

<Embodiment 8> Embodiment 8 uses a numerical value obtained by measuring the rotational load at the rod head and measuring the rotational load when the rod is reversely rotated to pull out the rod by a mathematical expression. The rotational load acting on the shaft portion is separated, and only the rotational load acting on the rod tip portion is calculated. Let Tt be the rotational load of the rod head during rotational press-fitting: Tt = Tb + Tf (1) Tt: Rotating load of the rod head during rotational press-fitting Tb: Rotating load of the rod tip Tf: Rod shaft Rotational load due to friction of the part If the rotational load when reversely rotating and pulling out is Tt ', Tt' = Tb '+ Tf' = αTb + βTf (2) Tt ': Rotating load when reversely pulling out Tb ': Rotational load of rod tip (vane part) that acts when pulling out by reverse rotation Tf': Rotational load due to friction of rod shaft that acts when pulling out by reverse rotation α = Tb ′ / Tb β = Tf '/ Tf (This α and β are determined by stacking experiments.) From (1) and (2), Tb = (Tt'-βTt) / (α-β) Rotating load (Tb) of the rod tip Can be asked.

The inventor of the present application has already filed an application (Japanese Patent Application No. 20
00-272639) is also a patent application, and in the construction method of a rotary press-fitted steel pipe pile that is equipped with a spiral blade at the tip and is rotationally press-fitted into the ground, it is necessary from the ground strength (N value) obtained by the ground survey when construction is required. The method of constructing a rotary press-fitted steel pipe pile is clarified, which is characterized by calculating the torque value by the following formula. ^{Tt = a · N · Dp m} -b · Lt · Dp ······ (4) ( where, Tt: Torque, Dp: pile diameter, Lt: overburden load, N: N value, a, b, m: coefficient and index) In the detailed description of the above-mentioned applied patent application, m = 2 to 3, a = α / X1, b = Y1 / X1 α: coefficient of friction between ground and blade (steel plate) X1 = 2π・ Atr / {(2/3 + i) α ・ π + g} ... (5) Y1 = atr (i ・ α ・ π + g) / {(2/3 + i) α ・ π + g} ・ ・ (6) atr: Transmission rate i = {2 (h ³ -1)} / {3 (h ² -1)} of the torque Tt and the load Lt to the lower end of the pile (h: blade diameter ratio (= Dw / Dp), Dp: pile Diameter, Dw:
Blade diameter, g: Ratio of pitch of spiral blade to pile diameter (= P
/ Dp), P: difference between the start end and the end of the spiral blade) The formula (4) is modified into the form of N = to obtain the formula (3). Since the formula (4) is for managing the construction of the pile, it is considered standard to use the measured value at the pile head position for the torque and the overlaid load (vertical load in the present invention). However, the present invention includes both the case where the rotational load (torque) and the vertical force are measured near the rod head and the case where the vertical load is directly measured at the rod tip. When the torque and the vertical force are measured in the vicinity of the rod head, the coefficients in the equation (3) may be obtained from the equations (5) and (6). When the torque and the vertical force are measured at the tip of the rod, the term of the transmissibility is not necessary, and the equations (5) and (6) may be replaced by the following equations (7) and (8). X1 = 2π / {(2/3 + i) α ・ π + g} ... (7) Y1 = (i ・ α ・ π + g) / {(2/3 + i) α ・ π + g} ・ ・ ・ ・ ・ ・ ( 8) Further, when the influence of the vertical force is comparatively small, it may be calculated as “L = 0” or “L = fixed load on the rod such as motor mounted on the upper portion of the rod”.

Further, in this embodiment, various kinds of experiments are performed by rotationally press-fitting the experimental piles into various experimental grounds of known properties (including artificially created model grounds of known properties). Various experiments are conducted to collect and analyze various data, and based on the results, the ground strength and pile bearing capacity are estimated from the rotational load value (Tb) at the tip. (1) If the rotational load Tb of the tip blade portion can be obtained, the N value of the ground is estimated from the value and the bearing capacity is calculated. Conventionally, the Tb value in the ground where the N value is measured is measured, and the correlation between the N value and Tb is obtained. However, it has already been pointed out by many researchers that the N value itself is data with a large variation.

(2) The value of Tb is taken as the strength of the ground, and Tb
The bearing capacity is estimated from. Tb itself is more reliable as ground resistance, and by accumulating data, the correlation with bearing capacity can be clarified. Since Tb is static data and continuous data, the ground strength can be measured more accurately than the N value. As described above, the relationship between Tb and bearing capacity is obtained by collecting data through experiments using model ground (artificially created ground whose properties are known). According to this method, it is not necessary to provide a special measuring mechanism on the survey rod, and it is possible to obtain highly accurate data by a simple method of continuously measuring the rotational load of the rotary press-fitting means. Ground strength and pile bearing capacity can be estimated from the estimated rotational load of the tip blades.

[0057]

Since the present invention is constructed as described above, it has the following effects. <Effects of the first invention (ground survey method)> The rotational load and the tip depth of the rod are continuously measured when the rod having the excavation blade on the rod tip side is rotationally pressed into the ground. Therefore, there is an effect that it is possible to continuously and precisely measure the change in the rotational load and obtain highly accurate ground information. In particular, since the survey method is the same as the method for constructing the rotary press-fit type steel pipe pile, the design and construction of the rotary press-fit type steel pipe pile will be realized with high accuracy and high accuracy. For example,
Even if there is a thin soft layer between the hard layer and the support layer as shown in FIG. 1, the presence and thickness of the thin soft layer can be grasped with high accuracy. Even in the existing ground, it is possible to grasp the thickness and properties of those strata with high accuracy and take appropriate measures, and to eliminate the defects of the prior art.

Further, since there is no operation of pulling up and re-penetration of the rod and the penetration by the pile with the excavation blade has better penetration than the hole excavation in the standard penetration test, the same ground depends on the ground conditions. At the depth of 50 m, the standard penetration test required 3 days, but according to the present invention, it can be completed in 2 to 3 hours. Has the effect of doing. In addition, since the blades exert propulsive force by the tip blades, the blades have the effect of pulling the shaft portion, and since the penetration is not made only by the pushing force from the pile head, the pushing force (compression) acting on the rod is the cone. It is smaller than the penetration test. As a result, there is an effect that the rod does not buckle even at a large depth, and the large depth survey can be performed efficiently and safely.

<Effect of the Second Invention (Ground Surveying Method)> A drilling blade is provided on the rod tip side, and one or a plurality of stages of ring-shaped projections are formed on the outer circumference to rotationally press fit the survey rod into the ground. As it continuously measures the rotating load and the depth of the rod tip when moving, it reduces the rotating load when press-fitting the rotation and accurately matches the changes in the detected ground load with the corresponding ground properties. By doing so, it is possible to continuously and precisely measure, and it is possible to obtain highly accurate ground information.

<Effect of the third invention (ground survey method)> In addition to the effect of the first invention, when the rotational load is measured by the load measuring means provided on the rod rotating means side for rotating the rod, The device can be made simple and inexpensive. In addition, the load acting on the rod tip is not directly measured, but converted from the hydraulic pressure or current that rotates the auger into a load. However, according to the experimental results of the inventors of the present application, the load due to friction generated during construction is relatively small, and depending on the soil condition, the load is 80% at the rod tip even if the rod length is about 60 m. The above was transmitted. Therefore, the strength of the rod tip ground can be sufficiently sensed even with the load measured by the load measuring means provided on the rod rotating means side. However, depending on the ground conditions (such as when there is an intermediate layer in the middle), the effect of friction cannot be ignored. In such a case, the influence of friction can be reduced by forming a large diameter portion on the rod shaft portion.

Alternatively, when the rotational load is measured by the load measuring means internally provided on the rod tip side, there is an effect that the rotational load acting on the rod tip (excavation blade) can be measured more accurately. That is, there is an effect that it is possible to measure only the characteristics of the ground without being affected by the friction between the rod shaft portion and the ground. It means grasping the accurate information of the ground layer.

<Effects of the Fourth, Fifth and Sixth Inventions (Ground Surveying Method)> The forward rotation load value at the time of positive rotation press-fitting of the rod (during excavation rotation) and the reverse rotation of the rod (during extraction rotation). It is possible to obtain the forward rotation load value of the excavation blade by measuring the reverse rotation load value of and the coefficient obtained in advance by various experimental grounds whose properties are known. It is possible to perform measurement only by itself, does not require a complicated device, can grasp ground data in a short time, and has an effect of reducing cost. In addition, the positive rotation load value,
In order to obtain the rotational load Tb acting on the rod tip (excavation blade) from the reverse rotation load value and the coefficients α and β, the forward rotation load value Tb of the excavation blade, which is possible by the above formula, is obtained. Estimate the ground N value from that value,
The bearing capacity can be calculated. Alternatively, the value of Tb can be used as the strength of the ground, and the supporting force can be estimated from Tb. Tb itself is more reliable as the load on the ground, and by accumulating data, the correlation with bearing capacity can be clarified. Since Tb is static data and continuous data, Tb has an effect that the ground strength can be measured more accurately than the N value.

Since the mechanism of the small diameter rod for ground investigation is the same as that of the large diameter rotary press-fit steel pipe pile, the "survey data" according to the invention of this claim for the small diameter rod is replaced with "geological data" described later. , By using it as comprehensive data combined with "load test data", it can be used as important data for guaranteeing bearing capacity of large-diameter main piles or for making construction plans, and construction loss can be prevented in advance. It has a great effect.

<Effect of seventh invention (ground survey method)> Since characteristic data of the stratum can be obtained from the soil collected at each depth of the stratum, the effect that the construction of the main pile can be made more accurate Play.

<Effects of the eighth and ninth inventions (ground survey method)> Since the depth data and vertical force data of the rod tip can be obtained, the relationship between the forward rotation load value and the depth can be accurately measured. . This makes it possible to clearly show the relationship between depth and ground strength. In addition, by measuring and recording the vertical force, it is possible to convert it into the ground strength in consideration of the influence of the vertical force and to perform a more accurate ground survey. Further, in this ground survey method, as shown in the seventh embodiment, it is possible to obtain subsidence data of the rod due to loading on the rod. Therefore, it is possible to accurately predict the subsidence possibility of the main pile. Therefore, it is possible to form a highly reliable support pile group having a stable supporting force by the construction with less loss suitable for each ground. Since the mechanism of the small diameter rod for ground investigation is similar to the large diameter rotary press-fit steel pipe pile,
The load test / construction data for small diameter rods can be used as important data for guaranteeing the bearing capacity of large diameter piles or for making construction plans. Until now, since there were only boring data and soil test data before construction, it was not possible to understand the unevenness of the support layer level and the change in workability due to formations not expressed in N values. Although the length is adjusted and the workability is unexpectedly changed, the present invention solves these problems.

<Effect of Tenth Invention (Ground Survey Device)>
A ground survey device comprising a rod having a digging blade at its tip and load measuring means for measuring a rotational load, which is internally provided at an appropriate portion of the rod or provided on a rotating means side for rotating the rod. Therefore, it is possible to continuously measure the rotational load when the rod is rotationally press-fitted into the ground by the load measuring means, and it is possible to obtain precise ground survey data.

<Effect of Eleventh Invention (Ground Survey Device)>
Load for measuring rotational load, which is equipped with a drilling blade at the tip and has a large diameter portion on the outer circumference, and which is internally provided at an appropriate portion of the rod or provided on the rotating means side for rotating the rod. It is a ground investigation device comprising a measuring means, the rotational load when the rod is rotationally press-fitted into the ground, it is possible to continuously measure by the load measuring means, the rotational press-fitting by the large diameter portion of the rod outer periphery. The rotating load at the time is reduced, and the detected rotating load changes accurately according to the property of the ground, and accurate ground survey data can be obtained.

<Effect of twelfth invention (ground survey device)>
Since load measuring means for measuring the rotational load acting on the rod tip is installed near the rod tip (tip vane or shaft near the tip vane), load due to friction on the rod peripheral surface is eliminated. Then, the tip load can be directly and accurately measured.

<Effect of thirteenth invention (ground survey device)>
Since the ground investigation device has a hollow open-ended rod and is equipped with a soil sampling jig, it is possible to obtain characteristic data of the stratum from soil collected at each depth of the stratum.

<Effect of Fourteenth Invention (Ground Survey Device)>
Since the tip of the rod is replaceable, it is possible to replace the part of the excavating blade that is heavily worn with a new one and use it, and it is possible to constantly obtain accurate survey data with the same survey rod. Play.

<Effect of Fifteenth Invention (Ground Survey Device)>
By making the diameter of the rod large only at the tip, it is possible to make a hole larger than the upper rod in the ground, so the influence of friction around the rod can be reduced and the tip load can be measured more accurately. Become.

<Effect of Sixteenth Invention (Ground Survey Device)>
By making the short rod attached to the excavation blade and the rod tip to which the short rod is connected larger than the upper rod part, it is possible to make a hole larger than the upper rod in the ground, so the effect of friction around the rod is affected. Can be reduced and the tip load can be measured more accurately,
Further, the effect of increasing the strength of the connecting portion is exerted.

<Effect of 17th Invention (Ground Survey Device)>
Since this is a ground surveying device with removable connecting parts for connecting the rods at the end of each rod, it is possible to easily connect the rods, eliminating on-site welding work, and connecting work time The effect is that the workability is shortened and the workability is greatly improved.

<Effect of the eighteenth invention (ground survey device)>
Simultaneously with the measurement of the rod rotation load, the ground survey device is equipped with depth measuring means for measuring the depth of the rod tip and vertical force measuring means for measuring the vertical force acting on the rod. Play.

<Effects of the 19th invention (ground survey device)>
By forming a large-diameter portion by welding a steel ring with a reinforcing rod or the like in a ring shape on the outer circumference of the rod, the large-diameter portion on the outer circumference of the rod reduces the rotational load at the time of rotational press fitting,
The detected rotational load changes accurately according to the properties of the ground, and the effect is obtained that precise ground survey data can be obtained.

<Effects of the twentieth invention (ground survey device)>
By making the connecting part of the rod larger in diameter than other parts, a large diameter part is formed on the outer circumference of the rod, and the large diameter part of the rod outer circumference reduces the rotational load at the time of rotational press fitting, and the detected rotational load is the ground. It has the effect of accurately changing according to the property of the ground, precise ground survey data can be obtained, and the strength of the connecting portion can be increased.

<Effect of 21st Invention (Ground Survey Device)>
Since the rod shaft is covered with a sheath pipe so that the rod shaft is not affected by the ground, the ground load is a ground surveying device that can measure the rotational load value of the excavation blade at the rod tip. This has the effect that the properties can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a comparison diagram of a ground measuring method of a conventional technique and a ground measuring method of the present invention.

FIG. 2 is a comparative diagram of the ground measuring method when the rod shape of the present invention is changed.

FIG. 3 is an overall schematic diagram of the ground survey device according to the first embodiment of the present invention.

FIG. 4 is an overall schematic diagram of a ground survey device according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing a structure of a rod and a rod tip portion of the ground investigation device according to the second embodiment of the present invention.

FIG. 6 is a perspective view showing the structure of the second embodiment of the present invention in which the diameter of the rod tip portion is increased.

FIG. 7 is a diagram showing a structure in which a connecting portion of a rod, which is one embodiment of the present invention, has a larger diameter than other portions.

FIG. 8 is a diagram showing a structure in which the connecting portion at the tip of the rod has a large diameter, which is one embodiment of the present invention.

FIG. 9 is a perspective view showing a connecting structure of piles of the ground survey device according to the third embodiment of the present invention.

FIG. 10 is a perspective view showing a connecting structure of piles of the ground survey device according to the fourth embodiment of the present invention.

FIG. 11 is a structural diagram of a ground survey device according to a fifth embodiment of the present invention.

FIG. 12 is a perspective view showing a connecting portion of the sheath tube according to the fifth embodiment of the present invention.

FIG. 13 is a construction procedure diagram showing a ground survey method according to a sixth embodiment of the present invention.

FIG. 14 is a conceptual diagram showing a ground survey method according to a seventh embodiment of the present invention.

[Explanation of symbols]

1 ... Ground investigation device 2 ... Rod 3 ... Rod rotation means 4 ... Load measuring means 5: Load data reception processing device 6 ... Rod end 6 '... with large diameter rod end 7: Hollow part 8: Rod with load meter 9 ... Excavation blade 9 '... Drilling blade with large diameter 10 ... Connecting rod material 11 ... Projection 13 ... Groove 16-pin hole 17 ... Connection part 19: Storage 20: Receiving antenna 21: Rod 22 ... Connected male part 23 ... Connection female part 24: Rod material with load meter 26-Pin fitting groove 25 ... Connecting rod material 27 ... Rod 28 ... Connected male part 29 ... Connection female part 30: Rod material with load meter 31 ... Connecting rod material 32 ... Groove 33 ... Protrusion 40 ... Ground investigation device 41-Drilling blade 42 ... Survey rod 43-O-ring or bearing 44 ... Sheath tube 45: Flat stand 47 ... Rotating press-fitting means 48 ... Connection part 49 ... Protrusion ring 50 ... Ring fitting groove 52 ... Connection cover 53 ... Adapter 54 ... Connecting pin 55 ... Screw hole 57 ... Ground investigation device 58 ... Bolt 59 ... Rotating press-fitting means 60 ... Rotary press-fitting means 61 ... Screw hole 64 ・ ・ ・ ・ ・ Excavation blade 65 ... Survey rod 66 ... Operation rod 67 ... Tip closing member 68 Opening / closing means for open end 69-Soil sampling pipe 70 ... Sat 73 ... Indicator member 74 ... Scale board 75 ... weight 100 ... Large diameter part

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Claims (21)

[Claims] 1. A ground survey method, wherein a rotational load and a depth of the tip of the rod are continuously measured when a rod having an excavation blade at its tip is press-fitted into the ground. 2. The ground survey method according to claim 1, wherein a large diameter portion is formed on the outer circumference of the rod. 3. The rotating load is measured by a load measuring means provided on a rotating means side for rotating the rod, or a load measuring means internally provided on a rod tip end side. Ground survey method described in 2. 4. The rod according to claim 1 or 2, wherein the rotational load at the time of press fitting is measured by the rod head, and the rotational load at the time of reverse rotation and pulling out is measured,
4. The ground survey method according to claim 1, wherein the rotational load acting on the rod shaft portion is separated and only the rotational load acting on the rod tip portion is calculated. 5. The ground survey method according to claim 4, wherein the following mathematical expression is used when only the rotational load acting on the rod tip portion is calculated. Tt = Tb + Tf (1) Tt: Rotational load of rod head during rotational press-fitting Tb: Rotational load of rod tip Tf: Rotational load due to friction of rod shaft Tt '= Tb' + Tf '= αTb + βTf (2) Tt ': Rotational load when pulling out by reverse rotation Tb': Rotational load of rod pile tip that acts when pulling out by reverse rotation Tf ': When pulling out by reverse rotation Rotational load due to friction of rod shaft acting α = Tb '/ Tb β = Tf' / Tf (This α and β are obtained by stacking experiments.) From (1) and (2), Tb = (Tt ' -ΒTt) / (α-β) 6. A variety of experimental grounds of known properties (including artificially created model grounds of known properties)
Various tests were carried out by rotationally press-fitting a rod with blades, and based on various data obtained by the experiments, from the rotational load value (Tb) of the rod tip portion according to claim 5,
The ground survey method according to claim 1, wherein the ground strength and the bearing capacity of the pile are estimated. 7. The hollow hollow rod, the rotary press-fitting of the rod into the ground to stop the rotary press-fitting of the rod at the soil sampling position, the soil sampling jig is inserted into the rod, and the hollow rod is hollowed by the soil sampling jig. The tip soil that has entered the part or the soil below the rod tip is collected.
The ground investigation method according to any one of to 6. 8. The ground investigation method according to claim 1, wherein the vertical force applied to the rod is automatically measured at the same time as the automatic measurement of the rotational load of the rod. 9. The N value of the surveyed ground is calculated by the following formula (1) after converting the rotational load into torque by using the rotational load and vertical force of the rod measured by the ground survey method according to claim 8. A ground survey method which is characterized by estimating N = (T + b · L · Dp) / (a · Dp m) ······ (3) ( where, N: N value of the ground, Dp: pile diameter, T: Torque (converted from the rotational load) , L: vertical force, a, b, m: coefficient and index) 10. A rod having a drilling blade at its tip,
It is composed of load measuring means for measuring a rotational load, which is internally provided at an appropriate portion of the rod or provided on a rotating means side for rotating the rod, etc., and is used when the rod is rotationally press-fitted into the ground. A ground surveying device, wherein the rotating load is continuously measured by the load measuring means. 11. The ground survey apparatus according to claim 10, wherein a large diameter portion is formed on the outer circumference of the rod. 12. The ground survey device according to claim 10, wherein load measuring means for measuring a rotational load acting on the rod tip portion is internally provided near the rod tip. 13. The soil-collecting jig is provided with a hollow hollow open end of the rod, and a soil sampling jig is provided. The ground surveying device according to any one of claims 10 to 12, wherein the jig is inserted from the upper end of the hollow portion and collected. 14. The ground investigation device according to claim 10, wherein the excavation blade portion at the tip of the rod is replaceable. 15. The excavating blade portion mounted on the tip of the rod is configured to be replaceable, and the short rod tip portion attached to the excavating blade has a diameter larger than that of the upper rod. The ground investigation device according to any one of to 14. 16. The excavating blade portion at the tip of the rod is configured to be replaceable, and the short rod tip portion attached to the excavating blade has a larger diameter than the upper rod. Ground investigation device. 17. The ground survey device according to claim 10, wherein a detachable connecting portion for connecting the rods is provided at an end portion of each rod. 18. A depth measuring means for measuring a depth of the rod tip and a vertical force measuring means for measuring a vertical force acting on the rod are provided at the same time as the measurement of the rotational load of the rod. The ground investigation device according to claim 10. 19. The large diameter portion is formed by welding a steel ring to the outer circumference of the rod.
The ground investigation device according to any one of 1 to 18. 20. The ground investigation device according to claim 11, wherein the large diameter portion is formed by making the connecting portion of the rod larger in diameter than the other portion. 21. The shaft portion is covered with a sheath pipe, and the peripheral frictional resistance received when the pile penetrates is received and separated by the sheath pipe, and the rotation load applied to the head portion of the rod on the rotating means side is measured. The ground survey device according to any one of claims 9 to 18, characterized in that the rotational load at the tip of the rod can be measured.