JP2014218824A - Ground evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a ground evaluation method that an N value of ground can be accurately estimated even when a simple drilling machine is used.SOLUTION: In a ground evaluation method, a measured value obtained during drilling is used. The ground evaluation method includes a step (step S3) of measuring a penetration speed and a feeding force acting on a rod penetrating ground by a vibro-drill 1, and a step (step S4) of estimating an N value of the ground by an estimated equation in which measured values of the feeding force and the penetration speed, measured in the step, are used as variables.

Description

  The present invention relates to a ground evaluation method for performing ground determination using measured values obtained during drilling from a drilling machine.

  There is known an evaluation method for estimating the N value of the ground using various measurement values obtained while drilling the ground with a drilling machine. (Refer patent documents 1-3 etc.). Normally, ground surveys are performed separately from drilling holes, but if the ground can be evaluated using the measurement values obtained during drilling, the ground at all drilling points can be properly evaluated. become.

  For example, Patent Documents 1-3 disclose a method of using a rotary percussion drill as a drilling machine and evaluating the ground based on information obtained during drilling.

  Here, the measurement values obtained from the rotary percussion drill are of various types such as a feeding force, rotational torque, impact energy, impact number, and drilling speed. In Patent Document 1, the converted N value is calculated using all of these types of measurement values.

JP-A-8-210075 Japanese Patent Laid-Open No. 11-200355 Japanese Patent Laid-Open No. 9-242459

  However, in the method disclosed in Patent Documents 1-3, the ground cannot be evaluated unless a rotary percussion drill or a drilling machine capable of obtaining a measurement value equal to or higher than that is used. Further, when estimating the N value of the ground, it is not necessary that there are many types of input information, and it is necessary to select the input information so that the estimation can be performed with high accuracy.

  Accordingly, an object of the present invention is to provide a ground evaluation method capable of accurately estimating the N value of the ground even when a simple drilling machine is used.

  In order to achieve the above object, the ground evaluation method of the present invention is a ground evaluation method using a measurement value obtained during drilling, and acts on a penetrating body penetrated into the ground by a drilling machine. A step of measuring the feeding force and the penetration speed, and a step of estimating the N value of the ground by an estimation formula using the measurement value of the feeding force and the measurement value of the penetration speed measured in the above steps as variables. It is characterized by.

  Here, a vibro drill can be used for the hole drilling machine. Further, the N value estimation formula is (b−a × V) × where F is the measured value of the feeding force, V is the measured value of the penetration speed, and a and b are coefficients for specifying each ground. Can be represented by F.

  The ground evaluation method of the present invention configured as described above estimates the N value of the ground using measured values of the penetration force and penetration speed measured even when a simple drilling machine is used. .

  As a result, it is possible to easily estimate the N value of the ground with high accuracy. Moreover, since the penetration speed is measured and used to estimate the N value, it becomes possible to drill holes at an arbitrary penetration speed, and efficient construction can be performed.

  For example, if the hole drilling machine is a vibro drill, a smaller machine can be used as compared with a rotary percussion drill, so that it is possible to cope with a narrow construction site.

It is a flowchart explaining the flow of the ground evaluation method of embodiment of this invention. It is explanatory drawing which showed schematic structure of the drilling system for obtaining the measured value required for evaluation of a ground. It is the figure which showed the relationship between propulsion hydraulic pressure and a feed force. It is the figure which plotted the measured value of feed force and penetration speed, and the conversion N value obtained from Swedish sounding on the graph which made N value, feed force, and penetration speed the horizontal axis, and made the vertical axis the depth. It is the figure which showed the relationship between the penetration speed and the ratio of the feeding force with respect to conversion N value. A graph in which the estimated N value calculated by the ground evaluation method of the embodiment of the present invention and the converted N value obtained from Swedish sounding are plotted on a graph with the N value as the horizontal axis and the depth as the vertical axis. It is. It is the flowchart which showed the flow of the process of the ground injection construction method of an Example. It is explanatory drawing which showed the process of the ground injection construction method of an Example. It is the perspective view which showed the structure of the perforated pipe | tube as an penetration body used with the ground injection construction method of an Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining the flow of the ground evaluation method of the present embodiment. FIG. 2 is a diagram showing a schematic configuration of a drilling system for obtaining measurement values necessary for the evaluation of the ground.

  First, the drilling system will be described with reference to FIG. The hole drilling machine described in the present embodiment is a vibro drill 1. The vibro drill 1 is a small drilling machine capable of propelling a rod to the ground at a penetration speed similar to that of a striking drilling machine by applying vibration (vibro).

  The vibro drill 1 is mainly configured by a base portion 11 that can be traveled by a crawler, a leader 12 that stands up in a vertical direction or an inclination direction, and a propulsion device 13 that moves along a guide cell 12a of the leader 12.

  A chuck 13a is attached to the tip of the propulsion device 13, and the upper end of the penetrating body that allows the chuck 13a to penetrate the ground is gripped. Various rods, steel pipes, casings, sampler pipes, augers and the like are examples of the penetrating body that penetrates into the ground.

  The vibro drill 1 pushes the penetrating body into the ground by giving the penetrating force or the feeding force and the vibro to the penetrating body by the propulsion device 13. At the time of construction by the vibro drill 1, metal hitting sound that is generated at the time of construction of the percussion drilling machine is not generated, and noise can be greatly reduced. Moreover, since the vibro drill 1 is provided with a turning or swing mechanism, the hole core at the drilling position can be quickly obtained.

  A hydraulic meter 2 and a displacement meter 3 for measuring the feeding force and the penetration speed acting on the penetrating body are attached to the vibro drill 1 configured as described above. The oil pressure gauge 2 is a measuring instrument that measures the propulsion oil pressure of the propulsion device 13. A method of converting the measured propulsion oil pressure into a feed force will be described later.

  On the other hand, the displacement meter 3 is a measuring instrument that measures the amount of displacement of the propulsion device 13. The displacement meter 3 includes a fixing part 32 that is fixed to the apex of the reader 12 and protrudes laterally, a cable 31 whose end is connected to the fixing part 32, and a winder 33 that winds or feeds the cable 31. It is mainly equipped with.

  The displacement meter 3 is a winding type displacement meter that measures the length of the cable 31 wound or fed by the winder 33 as a displacement amount. Here, since the propulsion device 13 and the penetrating body are directly connected, the displacement amount of the propulsion device 13 per unit time is the penetration speed of the penetrating body.

  The oil pressure gauge 2 and the displacement gauge 3 are connected to the data logger 4 via the switch box 41. The data logger 4 is operated by a DC power source 42. In the data logger 4, the measurement values measured by the oil pressure gauge 2 and the displacement gauge 3 are sequentially accumulated.

  Next, a ground evaluation method using the above-described drilling system will be described with reference to the flowchart of FIG.

  First, as shown in step S1, the propulsion oil pressure and the feeding force measured by the oil pressure gauge 2 are calibrated. When performing this calibration, a load cell (not shown) is installed on the ground, the chuck 13a at the tip of the propulsion device 13 is applied to the load cell, and the propulsion hydraulic pressure and the load cell value are measured simultaneously.

  That is, since the value measured by the load cell can be assumed to be the feed force, if the propulsion oil pressure at this time is read by the oil pressure gauge 2, the relationship between the propulsion oil pressure and the feed force becomes clear.

  FIG. 3 is a diagram showing the relationship between the propulsion hydraulic pressure and the feed force measured in this way. There is a clear correlation between the two forces as shown in FIG. The following formula (1) is a formula showing the relationship between the propulsion oil pressure P and the feed force F obtained from FIG.

F = 1.751 x P + 1.654 (1)
By using this equation (1), the propulsion oil pressure P measured by the oil pressure gauge 2 can be immediately converted into a measured value of the feed force F.

  After performing calibration in this way, the upper end of a rod (not shown) is connected to the chuck 13a of the vibro drill 1, and the rod penetrates into the ground (step S2).

  The penetration of the rod into the ground is promoted by a feed force applied to the rod from the propulsion device 13. In addition, when it is desired to increase the penetration speed or when the ground is hard and the penetration does not progress, vibration (vibro) can be added by the propulsion device 13. However, since the measured value of the hydraulic pressure gauge 2 when the vibro is added is substantially constant and does not serve as an index indicating the hardness of the ground, the calculation of the estimated N value described later is performed when the vibro is not added. This is done using the measured value.

  During the operation of pushing the rod into the ground by the vibro drill 1, the measurement values measured by the hydraulic gauge 2 and the displacement gauge 3 are sequentially accumulated in the data logger 4. The measurement values obtained by the oil pressure gauge 2 and the displacement gauge 3 are converted into a measurement value of the feeding force and a measurement value of the penetration speed (step S3).

  In step S4, the estimated N value of the ground is calculated from the measured values of the feeding force and the penetration speed measured during the drilling. The estimated N value of the ground can be calculated by the following estimation formula (2).

Estimated N value = (b−a × V) × F (2)
Here, V is a measured value of the penetration speed, F is a measured value of the feeding force, and a and b are coefficients specified for each ground. Subsequently, the coefficients a and b specified for each ground will be described.

  These coefficients a and b are set before the estimated N value is calculated. The set time may be before the rod is penetrated into the ground (before step S2) or after the feeding force and the penetration speed are measured (after step S3). In any case, it may be set before step S4.

  In order to set the coefficients a and b, test drilling is performed. FIG. 4 shows the measured value of the feeding force and the measured value of the penetration speed measured during the test drilling in correspondence with the depth. In addition, although the measured value of penetration speed is obtained with a point as shown in FIG. 5 mentioned later, in order to make a figure legible, it showed with the line.

  For comparison, the N value of the same ground obtained by Swedish sounding is shown on the same figure as the converted N value. That is, the converted N value is obtained from the result of the survey boring performed near the test drilling location.

  FIG. 5 is a diagram in which FIG. 4 is redrawn from the relationship between the penetration speed and the ratio of the feed force to the converted N value. When the relational expression is derived from the plot of FIG. 5 by the least square method, the following linear approximation expression (3) is obtained.

y = −0.0079X + 0.6662 = aX + b (3)
Therefore, the coefficients a and b specified for each ground are a = −0.0079 and b = 0.6666 in the description of the present embodiment. In addition, since these coefficients a and b may differ depending on the ground, when the construction target ground changes, the setting is reset.

  Such test drilling and survey boring are performed only at one point or several points on the construction target ground, but the above-mentioned measurement of the feeding force and penetration speed by the vibro drill 1 is performed at all points where construction is performed ( All holes).

  By the way, it is possible to assume that the measured value of the feeding force or the measured value of the penetration speed can be close to the converted N value obtained by Swedish sounding.

  As can be seen from FIG. 4, the gradient of the feeding force is different between when the penetration speed is fast and when the penetration speed is slow. It turns out that it cannot be said that a value can be expressed.

  On the other hand, FIG. 6 shows the result of calculating the estimated N value by adding the coefficients a and b specified by the expression (3) to the above estimated expression (2) (estimated N value by the present method) and the conversion N It is the figure which contrasted the value (the conversion N value obtained by Swedish type sounding).

  As can be seen from FIG. 6, an N value substantially the same as the converted N value can be calculated by the estimation formula (2). In short, it can be understood that if a measured value of the feeding force and a measured value of the penetration speed for each depth are obtained, a highly accurate N value can be easily estimated.

  Next, the effect | action of the ground evaluation method of this Embodiment is demonstrated.

  The ground evaluation method of the present embodiment configured as described above is based only on the measured values of the feed force and the penetration speed of the penetrating body that are measured even when a small and simple drilling machine called the vibro drill 1 is used. Use to estimate the N value of the ground.

  As a result, it is possible to easily obtain an accurate estimated N value of the ground in real time. Moreover, since the penetration speed is measured and input, it becomes possible to drill holes at an arbitrary penetration speed, and efficient construction can be performed.

  For example, in the Cone Penetration Test, an internationally established in-situ test method, test results cannot be obtained unless the rod is penetrated at a constant speed (standard is 10 mm / sec). Thus, if the ground cannot be evaluated unless it penetrates at a constant penetration speed, the time required for drilling work cannot be shortened. In addition, drilling work to maintain a constant penetration speed for ground of different hardness is a highly difficult work that requires abundant experience. Will have to.

  On the other hand, if drilling can be performed at an arbitrary penetration speed, the drilling operation can be shortened and an automatic control device is not required, so that construction can be efficiently performed with a simple configuration.

  Moreover, by using the vibro drill 1 in the drilling machine, it is possible to efficiently penetrate the penetrating body such as a rod while giving the vibro to the hard ground. That is, a place where the evaluation of the ground is not necessary (for example, a place where the ground is hard and the N value is obviously greater than or equal to a predetermined value and the N value does not need to be estimated, or the ground injection described later is not performed). Can be passed efficiently by giving vibro.

  Furthermore, since the vibro drill 1 can use a smaller machine than the rotary percussion drill, it can cope with a small construction site.

  Next, the ground injection method using the ground evaluation method described in the above embodiment will be described with reference to FIGS. The description of the same or equivalent parts as the contents described in the above embodiment will be described with the same terms and the same reference numerals.

  First, the ground injection method will be described with reference to FIGS. In the ground injection method described in this embodiment, a well is constructed in the ground, and a liquid such as water or a chemical solution is injected into the ground using this well, or air is injected into the ground. In addition, the well is used as an observation well for collecting underground groundwater for the purpose of investigation, as a gas suction well for sucking up harmful gases contained in contaminated soil, and as a pumping well. It can also be used.

  In such a well, for example, a perforated tube 51 as shown in FIG. The perforated pipe 51 is provided with slits 511,... As a plurality of openings on the outer periphery, and the slit 511 communicates with the inside and outside to take in groundwater or gas into the interior, Or send it in.

  This perforated tube 51 is a screen provided with a downward conical tip 51a, a cylindrical tip-side non-hole 51c formed thereabove, and slits 511,. It has the part 51b and the cylindrical upper non-hole part 51d formed on it.

  The tip 51a is formed to have a sharp tip so that the perforated tube 51 can be pushed into the ground by pressing with the vibro drill 1. Further, the tip 51a is formed of a material having high strength because a larger force acts than other portions when driven.

  The perforated tube 51 is a long hollow member, and the tip is closed by the tip 51a, so that dirt and foreign matter that have entered the tube are trapped in the tip 51a and the tip-side non-hole 51c. Can be deposited.

  Further, a plurality of slits 511,... Provided in the screen portion 51b are formed at intervals in a range where groundwater or the like is to be collected. The slit 511 is formed in a size that prevents entry of large foreign matters such as earth and sand and does not hinder the passage of water or air.

  In addition, a screw groove (not shown) for connecting the non-porous tube 52 is formed on the upper end of the upper non-hole portion 51d formed above the screen portion 51b. For example, as the perforated pipe 51 and the non-porous pipe 52, a steel pipe having an inner diameter of 40 mm, an outer diameter of 48.6 mm, a thickness of 3.5 mm, and a length of 1 m can be used. The combined length of the tip 51a and the tip-side non-hole 51c of the perforated tube 51 can be about 30 cm, the screen 51b can be about 50 cm, and the upper non-hole 51d can be about 20 cm. The slits 511 are provided in a staggered arrangement as rectangular openings having a length of 50 mm and a width of 2 mm so that the predetermined strength of the perforated tube 51 can be maintained.

  Furthermore, although not shown, a wire mesh filter is disposed on the inner periphery of the screen portion 51b of the perforated pipe 51. The metal mesh filter is a metal cylindrical mesh material, and has a function as a strainer for preventing earth and sand that has passed through the slit 511 from entering the pipe.

  Then, the construction method of a well is demonstrated, referring FIG. First, the upper end of the perforated pipe 51 serving as a penetrating body is connected to the chuck 13 a of the vibro drill 1. And the perforated pipe | tube 51 is penetrated into the ground G with the feeding force and vibro given by the propulsion apparatus 13 (process 1).

  The perforated tube 51 is driven until the upper portion of the perforated tube 51 protrudes slightly from the ground G. At that point, the driving is temporarily stopped and the chuck 13 a is separated from the upper end of the perforated tube 51.

  And as shown in (process 2) of FIG. 8, the non-porous tube 52 which forms a penetration body in the upper end of the perforated tube 51 is connected. This non-porous pipe 52 is a cylindrical steel pipe in which no opening is formed on the outer periphery. The connection between the perforated pipe 51 and the non-porous pipe 52 can be made through a thread groove, and a water sealing treatment is performed by applying a curing seal tape having a smooth surface from the outside of the joint.

  Subsequently, the chuck 13a is connected to the head of the newly connected non-porous pipe 52, and driving by the vibro drill 1 is resumed. From the ground G to the upper part of the non-porous pipe 52 as shown in (Step 3) of FIG. In a state where the protrusion protrudes slightly, driving is stopped and the chuck 13a is separated.

  In this way, the operation of connecting and driving the non-porous pipe 52 is repeated until the perforated pipe 51 arranged at the tip of the penetrating body is penetrated to a predetermined position (step 4). Here, the perforated pipe 51 is penetrated to the groundwater level W or lower.

  In this way, whether or not the perforated pipe 51 is driven to a predetermined position (the formation) can be properly determined during construction by applying the above-described ground evaluation method of the present embodiment. It becomes like this.

  FIG. 7 is a flowchart showing a processing flow of the ground injection method according to the embodiment. First, in step S11, an injection tube is installed. Here, the injection tube is composed of a perforated tube 51 at the tip and a non-porous tube 52 connected to the necessary number behind the tube (see FIG. 8). The propulsion hydraulic pressure and the propulsion amount of the injection pipe (injection pipe displacement) are measured by the oil pressure gauge 2 and the displacement gauge 3 in the drill hole that penetrates the injection pipe into the ground G.

  And when performing formation evaluation, it transfers to step S12. In step S12, the penetration speed is calculated from the relationship between the measured time and the injection tube displacement. On the other hand, in step S13, as described in the above embodiment, the feed force is calculated from the propulsion oil pressure. In addition, in order to transfer to step S13, the calibration of propulsion hydraulic pressure and feed force must be performed in advance (step S10).

  In step S14, the estimated N value is calculated from the measured values of the penetration speed and the feed force using the estimation formula (2) described in the above embodiment. Further, looking at the calculated estimated N value, in step S15, it is determined whether or not the formation into which the perforated pipe 51 is inserted is a formation suitable for injection.

  If it is determined in step S15 that the formation is suitable for injection, the adjustment of the injection pipe depth in step S16 has been completed, so the slit G1, 51,... Then, air, a chemical solution, or the like is discharged (step S17).

  Steps S16 (including step S15 when determining the injection depth) and step S17 are repeated as many times as necessary when air or a chemical solution is injected from a plurality of depths in one well. . And when injection | pouring of air, a chemical | medical solution, etc. in a predetermined position (geosphere) is completed, an injection | pouring pipe is pulled up and collect | recovered (step S18).

  In this way, if the formation evaluation using the measurement value obtained during drilling is performed, it is determined whether or not the perforated pipe 51 is arranged in a desired formation (a formation suitable for injection in this embodiment). It will be possible to make a proper judgment in real time.

  Other configurations and functions and effects are substantially the same as those in the above-described embodiment, and thus description thereof is omitted.

  The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to this embodiment or example, and the design changes are within the scope of the present invention. Are included in the present invention.

  For example, in the above-described embodiment and examples, the vibro drill 1 has been described as a drilling machine, but the present invention is not limited to this, and the feeding force and the penetration speed are measured when the penetration body penetrates the ground. Anything is possible.

1 Vibro drill (drilling machine)
2 Hydraulic gauge 3 Displacement gauge 51 Perforated pipe (penetrating body)
52 Non-porous pipe (penetrating body)
G ground

Claims (3)

A ground evaluation method using measured values obtained during drilling,
A step of measuring a feeding force and a penetration speed acting on a penetrating body penetrating into the ground by a drilling machine;
A ground evaluation method comprising: a step of estimating the N value of the ground by an estimation formula using the measured value of the feeding force and the measured value of the penetration speed as variables as measured by the above steps.   The ground drilling method according to claim 1, wherein the drilling machine is a vibro drill.   The N value estimation formula is expressed as (b−a × V) × F, where F is the measured value of the feeding force, V is the measured value of the penetration speed, and a and b are coefficients for specifying the ground. The ground evaluation method according to claim 1, wherein the ground evaluation method is expressed.