JP2014122464A - Subsurface exploration method and subsurface exploration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subsurface exploration method and apparatus enabling a dynamic strength (penetration resistance value) of a subsurface in a testing depth and physical properties such as soil property discrimination for each depth to be easily evaluated and also enabling a liquefaction strength at any arbitrary point to be easily measured.SOLUTION: A subsurface exploration method includes penetrating a rod 3 in which a removable penetration body 2 is mounted in a distal end 3a, and exploring the subsurface (t) by penetrating the penetration body 2 in a depth direction of the subsurface (t). By penetrating the penetration body 2 into the subsurface (t), a penetration displacement amount of the penetration body 2 is measured, and a penetration resistance value in the subsurface depth is analyzed using the obtained penetration displacement amount. The penetration body 2 is penetrated into a preset subsurface depth and the rod 3 is then pulled out, thereby measuring each of a pull-out displacement amount and a pull-out resistance value. Physical properties including at least soil property discrimination are analyzed using each of the obtained measurements and the penetration resistance value, and a liquefaction strength of the subsurface is analyzed using the obtained physical properties and the penetration resistance value.

Description

  The present invention relates to a ground investigation method and a ground investigation apparatus for evaluating the dynamic strength and liquefaction strength of a ground and analyzing physical and mechanical characteristics of the ground.

  Usually, when constructing civil engineering / architectural structures, etc. on the ground made of natural or artificial objects, it is necessary to grasp the physical and mechanical characteristics of the ground in advance and to carry out an appropriate structural design based on it. . Therefore, various ground investigation methods and apparatuses have been proposed and put into practical use.

  By the way, it has been reported that in soft land near the coast of Japan, great damage was caused by liquefaction of the ground due to past earthquakes. Therefore, in the evaluation of liquefaction strength, indoor soil test data such as repeated undrained triaxial tests of soil is required using undisturbed samples collected in-situ, but at present, detailed liquefaction is required. Intensity has been evaluated only at limited points. For this reason, the liquefaction strength in a certain area must be evaluated based on poor data.

  On the other hand, past surveys on earthquake damage show examples where the degree of damage changes significantly even in places that are only a short distance away. Therefore, a more accurate evaluation is required to perform a highly reliable design for ground liquefaction. However, it is very difficult to carry out conventional tests at many points because it increases the cost of investigation. Thus, from an engineering point of view, there is a need for an investigation method that can be performed more inexpensively, simply, and with high accuracy.

  For example, a typical penetration test method (JIS A 1219) defined by Japanese Industrial Standards is a typical method of a dynamic penetration test for investigating the mechanical properties of the ground. This standard penetration test method is a test method for obtaining an N value for knowing the relative values of the hardness and firmness of the soil in the original position.

  In this standard penetration test method, a standard penetration test sampler is attached to the tip of the rod, lowered to the bottom of the drilled boring hole, and the rod is hit on the ground by a free fall (fall height 78 cm) of a hammer (63.5 kg). The number of hits (N value) required to penetrate 15 to 45 cm (30 cm) from the hole bottom is obtained. The N value obtained by this test method has been used for many years as a design index for structures in Japan with a complex ground structure.

  However, in the standard penetration test method, there is a problem that a boring machine and a boring pump are required for digging the test hole, which increases costs. In addition, mud water (construction sludge) is forced to be used to stabilize the hole wall during excavation, and further investigation work such as slime removal work at the bottom of the hole and pre-working work of 15 cm are complicated during the test. At the same time, there is a problem that it takes experience and takes time to investigate.

  Further, as an alternative to the standard penetration test method, there are various sounding methods (for example, automatic ram sounding) classified into dynamic penetration test methods. These various sounding methods are, for example, methods in which a rod having a conical penetrating body attached to the tip is continuously hit into the ground by a free fall of a hammer and the number of hits per fixed penetration length is obtained ( Non-patent document 1).

  However, in the above sounding method, although the dynamic strength (penetration resistance value) of the ground at the test depth can be evaluated from the number of hits, since soil samples cannot be collected at each depth, evaluation of physical characteristics such as soil discrimination There is a problem that can not be.

"Ground evaluation by small automatic ram sounding test" Yoshiyuki Ito et al. [2002] 37th Geotechnical Engineering Conference (Osaka) p.103-104

  Therefore, the present inventor, in the dynamic penetration test method (for example, automatic ram sound, etc.), incorporate a recovery-type tip cone into the rod tip penetrator, and calculate from the amount of penetration in the ground around the penetrator at the time of hitting penetration. By detecting and analyzing the dynamic strength (penetration resistance value), and the displacement and pulling force (drawing resistance value) at the time of pulling out after reaching the planned depth of investigation, the soil classification and liquefaction strength of the ground can be determined. It was found that it can be evaluated.

  The present invention has been made in view of such circumstances, and the evaluation of physical properties such as the dynamic strength (penetration resistance value) of the ground at the test depth and the soil discrimination at each depth, and the liquefaction strength at an arbitrary point. It is an object of the present invention to provide a ground survey method and apparatus that enable simple measurement.

  In order to solve the above-mentioned problem, the invention according to claim 1 investigates the ground by hitting a rod having a detachable penetrating body attached to the tip and penetrating the penetrating body in the depth direction of the ground. In this method, the penetration displacement of the penetration body is measured by penetrating the penetration body into the ground, and the penetration resistance value of the ground depth is analyzed from the obtained penetration displacement amount and set in advance. After penetrating the penetrating body up to the determined ground depth, each of the displacement amount and the pulling resistance value is measured by pulling out the rod, and at least the soil determination is made from each of the obtained measured values and the penetrating resistance value. It is characterized by analyzing the physical properties including, and analyzing the liquefaction strength of the ground from the obtained physical properties and the penetration resistance value.

  The invention according to claim 2 is the invention according to claim 1, wherein when the penetration body penetrates in the depth direction of the ground, the percussion obtained by continuously hitting and penetrating. Analyzing the penetration resistance value of the ground depth and continuously measuring the pulling displacement amount and pulling resistance value when pulling out the rod, respectively, so that the behavior of the ground during impact penetration and the behavior during withdrawal From the above, analyze the physical characteristics including at least soil judgment, analyze the liquefaction strength of the ground from the obtained physical characteristics and the penetration resistance value, and continuously display the analysis results along the depth direction It is characterized by.

  According to a third aspect of the present invention, in the ground surveying device used in the ground surveying method according to the first or second aspect, the rod having the penetrating body detachably attached to the tip, and the rod On the end side, the hammer penetrates the penetrating body in the depth direction of the ground, the pulling device for pulling out the penetrating body penetrating in the depth direction together with the rod, and the penetrating body by striking the hammer. A displacement sensor for detecting the amount of penetration displacement when penetrating into the ground and the amount of pulling displacement when the penetrating device is pulled out from the ground by the pulling device, and the pulling resistance value when pulling out the penetrating member from the ground by the pulling device , A displacement sensor, a measurement device that converts a detection signal from the load sensor into a digital signal by A / D conversion, and data of the measurement device And it is characterized in that it comprises a personal computer for analysis.

  According to the first to third aspects of the present invention, the amount of penetration displacement of the penetrating body is obtained by striking a rod having a penetrating pendant attached to the tip and penetrating the penetrating body in the depth direction of the ground. The penetration resistance value of the ground depth is analyzed from the obtained penetration displacement amount, and after the penetration body penetrates to a preset ground depth, the withdrawal displacement amount and the withdrawal resistance are obtained by pulling out the rod. Each value is measured, and physical properties including at least soil determination are analyzed from each obtained measurement value and the above penetration resistance value, and the liquefaction strength of the ground is analyzed from the obtained physical property and the above penetration resistance value. Therefore, it is possible to evaluate physical properties such as soil discrimination, which has been difficult until now, by a simple method of measuring the amount of displacement and resistance of pulling, and evaluating the liquefaction phenomenon that occurs during an earthquake. It can be also carried out.

  According to invention of Claim 2, when penetrating the said penetration body in the depth direction of the ground, the said penetration resistance value of the ground depth for every said strike obtained by hitting continuously and penetrating is obtained. Analyze and measure the pulling displacement amount and pulling resistance value continuously when pulling out the rod, so that the physical characteristics including at least soil judgment from the behavior when the ground hits and the behavior when pulling out In order to analyze the liquefaction strength of the ground from the obtained physical characteristics and the above penetration resistance value, the pulling force (pullout resistance value) is recorded for every single stroke when hitting and for every fixed displacement when pulling. Therefore, not only a significant improvement in work efficiency but also continuous measurement with high density (high resolution) in the depth direction can be performed.

  In addition, by continuously displaying the analysis results along the depth direction, when estimating the liquefaction strength and performing the liquefaction determination, the penetration resistance value (dynamic strength) at the time of impact penetration, and the extraction From the pulling resistance value (pulling force) at the time, it is possible to easily visually evaluate the fine particle content estimated by the soil determination and the ground liquefaction safety factor.

  According to the third aspect of the present invention, the rod having the penetrating body detachably attached to the tip, a hammer and a drawing device on the other end side of the rod, and the amount of penetration displacement and the amount of withdrawal displacement are detected. A displacement sensor, a load sensor for detecting a pulling resistance value, a measuring device for converting the displacement sensor and a detection signal from the load sensor into a digital signal by A / D conversion, and a personal computer for analyzing data of the measuring device Even with simple equipment, it is possible to measure not only the penetration resistance value (dynamic strength) but also the pulling resistance value (pulling force) as the mechanical properties of the ground. It can be easily moved and installed in a short time. Thereby, investigation time and investigation cost can be reduced.

1 shows an embodiment of a ground investigation device used in the ground investigation method of the present invention, (a) is a schematic diagram showing a state in which an penetration body attached to the tip of a rod penetrates into the ground by hammering, (b) It is the schematic which shows a rod and the penetration body in the drawing | extracting state from a ground with a drawing-out apparatus. It is a front view of the penetration body used for the ground investigation apparatus used for the ground investigation method of the present invention. It is an example of the data processing flowchart which evaluates liquefaction intensity | strength from the ground investigation method of this invention. It is an example of the soil classification chart used for the ground investigation method of this invention. It is the graph analyzed based on the data detected by the ground investigation method of this invention.

  As shown in FIG. 1, the ground investigation device 1 used in the ground investigation method of the present invention includes a rod 3 having a penetrating body 2 detachably attached to a tip 3 a and a penetrating on the other end 3 b side of the rod 3. A hammer 4 that strikes and penetrates the body 2 in the depth direction of the ground t, a pulling device 5 that pulls the penetrating body 2 that penetrates in the depth direction together with the rod from the ground t, and a penetration displacement amount and a pulling displacement of the penetrating body A displacement sensor 6 for detecting the amount, a load sensor 7 for detecting a pulling resistance value, a measuring device 8 for converting detection signals from the displacement sensor 6 and the load sensor 7, and a personal computer 9 for analyzing data of the measuring device 8. Is generally configured.

  Here, the rod 3 has a length dimension necessary to penetrate and withdraw the penetrating body 2 in the depth direction of the ground t, and has a diameter of, for example, 28 mm. As for this rod 3, the penetration body 2 is provided in the front-end | tip 3a side so that attachment or detachment is possible. As shown in FIG. 2, the penetrating body 2 includes a mantle 2a formed in a columnar shape, a cone tip 2b formed in a conical shape (vertical angle 90 ° in the figure) on the tip side of the mantle 2a, An extension rod 2c is connected to the base end side of the mantle 2a via a connecting portion 2f.

  The extension rod 2c has one end inserted into the distal end side of the rod 3, and the other end screwed with a male screw portion 2d screwed into the connecting portion 2f of the mantle 2a. Further, a through-hole portion 2e penetrating in the radial direction is formed in the center of the extension rod 2c in the longitudinal direction. When the through-hole portion 2 e is inserted into the tip end side of the rod 3, the through-hole portion 2 e is locked to a locking protrusion (not shown) provided on the inner peripheral surface of the rod 3.

  As shown in FIG. 1A, when the penetrating body 2 is penetrated into the ground t by hammering, the hammer 4 is disposed on the other end 3b side of the rod 3. The hammer 4 is formed in a cylindrical shape and is inserted on the other end 3 b side of the rod 3. For example, the hammer 4 having a weight of 30 kg is used. The hammer 4 may be forcibly dropped by a machine using a hydraulic motor or an electric motor, and the hammer 4 may be dropped freely after being lifted by a hydraulic motor or an electric motor to a drop height position. .

  Further, an anvil 11 is fixed to the other end 3b side of the rod 3 so that the rod 3 and the penetrating body 2 are penetrated in the depth direction of the ground t by being hit by the hammer 4 falling. The anvil 11 is detachably attached to the rod 3.

  In addition, a displacement sensor 6 for detecting the displacement amount (penetration amount) of the anvil 11 in the depth direction due to the hammer 4 is provided on the sensor stand 13. The sensor stand 13 is provided with a bar member erected in the depth direction, and a leg portion is formed to be foldable. The displacement sensor 6 is, for example, a non-contact type magnetostrictive displacement meter.

  And the displacement sensor 6 is attached to the said base end side of the sliding member 6a by which the base end part was provided in the said rod member of the sensor stand 13 so that sliding was possible. The sliding member 6a is provided extending in the radial direction of the bar member. Further, the sensor stand 13 is provided with a proximity sensor 10 that detects the timing of hitting the hammer 4 against the anvil 11. The proximity sensor 10 is provided on the distal end side of the sliding member 6a so as to be slidable in the axial direction of the rod member together with the displacement sensor 6. Further, the tip of the sliding member 6 a is disposed below the anvil 11.

  Further, the displacement sensor 6 and the proximity sensor 10 are connected to the measuring device 8 and the cable 12. The measuring device 8 includes an A / D converter that digitizes detection signals from the displacement sensor 6 and the proximity sensor 10, and a digital recording unit that records the digitized data. Further, a personal computer 9 for processing data recorded in the digital recording unit is connected to the measuring device 8.

  Further, as shown in FIG. 1B, when the penetrating body 2 is pulled out from the ground t by the pulling device 5, the pulling device 5 is disposed on the other end 3 b side of the rod 3. For example, a hydraulic jack 5 is used as the drawing device 5. The hydraulic jack 5 is formed such that the rod 3 can be inserted through the center, and a locking mechanism is provided that allows the rod 3 to be attached and detached at the tip of a forward / backward rod that can be advanced and retracted. In addition, a load sensor 7 that detects a pulling force (pulling resistance value) is provided below the hydraulic jack 5.

  And the displacement sensor 6 which detects the displacement amount (drawing amount) in the depth direction by the advancement of the advance / retreat rod of the hydraulic jack 5 is provided on the rod member of the sensor stand 13 via the sliding member 6a. . The displacement sensor 6 and the sensor stand 13 are the same as those used when the penetrating body 2 penetrates. In addition, the front-end | tip part of the sliding member 6a is arrange | positioned in the upper part of the other end 3b of the rod 3, and detects the displacement amount (drawing amount) of the said depth direction.

  Further, the displacement sensor 6 and the load sensor 7 are connected to the measuring device 8 and the cable 12. The measuring device 8 includes an A / D converter that digitizes detection signals from the displacement sensor 6 and the load sensor 7, and a digital recording unit that records the digitized data. Further, a personal computer 9 for processing data recorded in the digital recording unit is connected to the measuring device 8.

  By using the ground investigation device 1 having the above-described configuration, the recovery type penetration body 2 is incorporated at the tip of the rod 3 by a dynamic penetration test method (for example, automatic ram sound), and the ground around the penetration body at the time of impact penetration By detecting and analyzing the dynamic strength (penetration resistance value) calculated from the penetration amount and the pulling displacement amount and pulling force (pull resistance value) at the time of withdrawal after reaching the planned depth of investigation, It becomes possible to evaluate soil determination and liquefaction strength of the ground t from the relationship between the amount of penetration and the pulling force (pulling resistance value) at the time of pulling.

  This is because, for example, in the case of uniform loose sandy soil, the surrounding area of the intruder becomes undrained at the time of intrusion, and the dynamic strength (penetration resistance value) decreases due to the generated positive excess pore water pressure. The dynamic strength (penetration resistance value) increases due to the negative excess pore water pressure generated. On the other hand, since the drainage condition is in the ground t around the penetrating body during static drawing, the difference in strength due to the excess pore water pressure generated in the ground t becomes smaller than in the impact penetration under the non-drainage condition.

  Furthermore, as the content of fine particles is mixed from uniform sandy soil and the soil classification is close to that of viscous soil, the excess pore water pressure response generated at the time of impact penetration becomes dull, and the impact penetration depends on the proportion of fine particles. The ratio response of the dynamic strength at the time (penetration resistance value) and the drawing force at the time of static drawing (drawing resistance value) changes.

  From these, by measuring the dynamic strength (penetration resistance value) and the pulling force (pullout resistance value) at the time of impact penetration, not only the dynamic strength (penetration resistance) of the ground t at the depth but also physical The characteristics (soil discrimination) can be estimated and the liquefaction strength of the ground t can be evaluated.

Next, the ground survey method will be specifically described.
First, as shown in FIG. 1A, in order to penetrate the penetrating body 2 in the depth direction of the ground t, the penetrating body 2 is attached to the tip 3a side of the rod 3, and the tip of the mantle 2a of the penetrating body 2 is attached. The cone tip 2b formed on the side is brought into contact with the ground surface.

  Next, the anvil 11 is fixed to the other end 3 b side of the rod 3. At this time, for example, when the height of the free fall of the hammer 4 having a weight of 30 kg is set to 35 cm, the anvil 11 is fixed to a height of about 50 cm from the other end 3 b of the rod 3.

  Further, the displacement sensor 6 for detecting the displacement amount (penetration amount) of the anvil 11 in the depth direction is set on the sensor stand 13. At that time, the sliding member 6 a provided so as to be slidable in the axial direction of the rod member of the sensor stand 13 is arranged so that the tip of the sliding member 6 a is located below the anvil 11. Further, the proximity sensor 10 is set on the upper end of the sliding member 6a.

  Further, the displacement sensor 6 and the proximity sensor 10 are connected to the measuring device 8 via the cable 12. This measuring device 8 is connected to a personal computer 9.

Note that the number of impacts (N _d value) required for the penetrating body to penetrate 20 cm in the depth direction using a Swedish lamb sound testing device that is roughly equivalent to the N value (N _spt value) obtained in the standard penetration test. Have the following relationship:
N _spt ≒ N _d
The test conditions at that time are as follows.
Rod: 32mm in diameter
Penetration body: diameter 45mm, length 90mm, vertex angle 90 °
Hammer: weight 63.5kg, drop height 50cm

And the hammer 4 is continuously hit | damaged to the anvil 11 of the rod 3 mechanically, for example with a hydraulic motor. The penetration resistance value (dynamic strength) is obtained as the number of hits (N _m value) necessary for the penetration body 2 to penetrate 20 cm in the depth direction.
The test conditions at this time are as follows.
Rod: 28mm in diameter
Penetration body: Diameter 36.6mm, length 69mm, vertex angle 90 °
Hammer: Weight 30kg, Drop height 35cm
The number of hits (N _m value) using the ground investigation device of the present invention is approximately equal to half of the N value (N _d value) of the standard penetration test.
N _spt ≒ N _d ≒ 1 / 2N _m
Thus, when the ground survey device of the present invention is used, the penetration resistance value (dynamic strength) is obtained as the number of impacts (N _m value) required for the penetration body 2 to penetrate 20 cm in the depth direction. Can do.

At this time, the displacement sensor 6, the penetration body 2 detects whether it has 20cm penetration in the depth direction, the hit number (N _m value), by a proximity sensor provided on the sliding member 6a, the hammer 4 is an anvil 11 And how many times the sensor is struck, these detection signals are transmitted to the measuring device 8 and the detected vibration is digitized by the A / D converter, and then the digitized data is stored in the digital storage unit. To be recorded.

  In addition, when penetrating the penetrating body 2 in the depth direction, in addition to a method of hitting the hammer 4 mechanically using the hydraulic motor or a method of hitting the hammer 4 by free fall, a hammer drill, an impact drill, or the like There is also a method of obtaining the striking energy from the relationship between the striking load and the penetration speed by using the ratchet method or the striker or air cushion method.

  Next, after the penetration resistance value of the penetration body 2 is recorded in the digital storage part of the measuring device 8, the rod 3 is pulled out from the ground t. At that time, the hammer 4 and the anvil 11 disposed on the other end 3b side of the rod 3 are removed. Then, the hydraulic jack 5 is disposed on the rod 3. At that time, after inserting the rod 3 into the hole at the center of the advance / retreat rod of the hydraulic jack 5 and placing the hydraulic jack 5 on the ground, the advance / retreat rod is fixed to the rod 3 by the locking mechanism at the tip thereof. To do.

  Further, the tip of the sliding member 6 a provided with the displacement sensor 6 is placed on the upper part of the other end 3 b of the rod 3. In addition, a load sensor 7 is disposed below the upper advance / retreat rod of the hydraulic jack 5, and the load sensor 7 and the measuring device 8 are connected by a cable 12.

Then, by operating the hydraulic jack 5, the rod 3 and the penetrating body 2 provided at the tip 3a of the rod 3 are pulled upward in the depth direction, and the displacement sensor 6 continuously measures the pulling displacement amount, The pulling resistance value (pulling force) is continuously measured by the load sensor 7. At that time, the drawing displacement amount is continuously measured up to 20 cm, for example.
The pulling resistance value (pulling force) at a certain depth is a load (F _s ) measured by the load sensor 7 every several centimeters.

  The detection signals detected by the displacement sensor 6 and the load sensor 7 are transmitted to the measuring device 8 via the cable 12. The transmitted detection signal is digitized by the A / D converter and recorded in the digital storage unit.

  The digital data recorded in the digital storage section of the measuring device 8 is analyzed by the personal computer 9 for physical characteristics including soil determination, and further, the liquefaction strength of the ground t is analyzed, and the liquefaction strength. Is evaluated.

  The data processing for evaluating the liquefaction strength is as shown in the flowchart of FIG. In the processing flow of FIG. 3, all data excluding the unit volume weight and the groundwater level are measured values obtained by the ground investigation device 1 having the above-described configuration. Then, according to this processing flow, analysis processing is performed by the analysis program of the personal computer 9.

If the unit volume weight is about 17 to 18 kN / m ³ unless it is special soil, there will be no significant error. This may, if cohesive soil system 17 kN / m ³ approximately, a 18 kN / m ³ approximately as long as sandy soil system, since the material discrimination is a value that can be assumed if possible, there is no particular problem even if you can not actually measured. In addition, the groundwater level is confirmed using a water level gauge or the like in an investigation boring hole left after the rod 3 is pulled out.

And dynamic strength at the time of impact penetration (penetration resistance value: resistance value converted to N _spt value (number of _impacts = N _d value)), pulling force at the time of drawing (drawing resistance value: F _s value), groundwater level Based on the calibration result, the pore pressure estimated from the above is converted into force and arranged into the following various quantities.

Tip support force: q _c (cone cross-sectional area: equivalent to support force divided by A _p , q _c = 392 N _d (kN / m ² ))
However, the coefficient 392 in the above equation is a standard value for fine sand and silty sand that can be easily liquefied, and is 200 (soil with a lot of fine particles) according to the soil estimated by the soil determination. 1 to 600 (containing a large amount of coarse particles). This setting is processed by the personal computer 9.
Pulling frictional force: f _s :( pullout resistance: frictional force of F _s value obtained by dividing by the surface area A _m of the mantle)
Pore water pressure: u

(Equation 1) Tip bearing force considering the influence of pore water pressure: q _t

(Equation 2) Normalized tip support force: Q _t

(Equation 3) Normalized pulling friction force: F _t

Ａ_e ：ロッド断面積（ｍ²）
Ａ_p ：コーンの底面積（ｍ²）
Ａ_m ：マントルの表面積（ｍ²）
ｕ₀ ：当該深さにおける静水圧（ｋＮ／ｍ²）
σ_r0 ：当該深さにおける鉛直全応力（ｋＮ／ｍ²）
σ_r0’：当該深さにおける鉛直有効応力（ｋＮ／ｍ²） (Equation 4) Normalized pore water pressure: B _q

A _e : Rod cross-sectional area (m ² )
A _p : Bottom area of cone (m ² )
A _m : Mantle surface area (m ² )
u ₀ : Hydrostatic pressure at the depth (kN / m ² )
σ _r0 : Total vertical stress at the depth (kN / m ² )
σ _{r0 ′} : Effective vertical stress at the depth (kN / m ² )

From the normalized tip support force (Q _t ), the normalized pulling friction force (F _t ), and the normalized pore water pressure (B _q ) according to the above formula, for example, the soil classification chart ( Source: Robertson, PK: Soil classification using the cone penetration test, Canadian Geotechnical Journal, Vol. 27, No. 1, pp 151-158).

FIG. 5 shows an example in which the liquefaction strength according to the present invention is estimated and the liquefaction determination is performed. In this example, the fine grain content estimated by performing soil judgment from the dynamic strength at the time of impact penetration (penetration resistance value: N _d value) and the drawing force at the time of drawing (drawing resistance value: F _s value): It is possible to visually evaluate F _c and the liquefaction safety factor F _L of the ground t evaluated from these.

  According to the ground investigation method and the ground investigation device according to the above-described embodiment, the rod 3 with the detachable penetrating body 2 attached to the tip 3a is hit and the penetrating body 2 is penetrated in the depth direction of the ground t. Then, the penetration displacement amount of the penetration body 2 is measured, the penetration resistance value of the ground depth is analyzed from the obtained penetration displacement amount, and after penetrating the penetration body 2 to a preset ground depth, the rod 3 is pulled. The pulling displacement amount and the pulling resistance value are measured by pulling out, and from each of the obtained measured values and the above penetration resistance values, the physical characteristics including at least soil determination are analyzed, and the obtained physical characteristics and the above penetration resistance values are measured. In order to analyze the liquefaction strength of the ground t, it is possible to evaluate the physical properties such as soil determination, which has been difficult until now, by a simple method of measuring the drawing displacement amount and the drawing resistance value. , It can also be carried out evaluation of liquefaction phenomenon that occurs at the time of the earthquake.

  Moreover, when penetrating the penetration body 2 in the depth direction of the ground t, the penetration resistance value of the ground depth for each hit obtained by continuously hitting and penetrating is analyzed, and the rod 3 is pulled out. In this case, by continuously measuring the pulling displacement amount and the pulling resistance value, the physical characteristics including at least soil determination were obtained from the behavior of the ground t at the time of intrusion and the behavior at the time of drawing. In order to analyze the liquefaction strength of the ground t from the physical characteristics and the above penetration resistance value, the pulling force (drawing resistance value) is recorded for each hitting penetration and for every fixed displacement when pulling. Not only a significant improvement in efficiency, but also continuous measurement with high density (high resolution) in the depth direction.

  Then, by continuously displaying the analysis result along the depth direction, the liquefaction strength is estimated, and when performing liquefaction determination, the penetration resistance value (dynamic strength) at the time of impact penetration, and the extraction Based on the pulling resistance value (pulling force) at the time, it is possible to easily visually evaluate the fine grain content estimated by performing soil judgment and further the liquefaction safety factor of the ground t.

  Furthermore, the rod 3 having the penetrating body 2 detachably attached to the tip 3a, the hammer 4 and the drawing device 5 on the other end 3b side of the rod 3, and a displacement sensor 6 for detecting the amount of penetration displacement and the amount of withdrawal displacement. A load sensor 7 for detecting a pulling resistance value, a measuring device 8 for converting a detection signal from the displacement sensor and the load sensor into a digital signal by A / D conversion, and a personal computer 9 for analyzing data of the measuring device 8 Even with a simple device, it is possible to measure not only the penetration resistance value (dynamic strength) but also the pulling resistance value (pulling force) as the mechanical characteristics of the ground t. Can be easily moved and installed in a short time. Thereby, investigation time and investigation cost can be reduced.

  In the above embodiment, the ground surveying device 1 used for the ground surveying method can be used by using various sounding methods classified into the dynamic penetration test method, for example, devices used for automatic ram sounding. is there.

  It can be used when evaluating the dynamic strength and liquefaction strength of the ground.

DESCRIPTION OF SYMBOLS 1 Ground investigation apparatus 2 Intrusion body 3 Rod 3a Tip 3b Other end 4 Hammer 5 Pull-out device 6 Displacement sensor 7 Load sensor 8 Measuring device 9 Personal computer t Ground

Claims (3)

It is a ground investigation method for investigating the ground by striking a rod attached with a detachable penetrating body at the tip and penetrating the penetrating body in the depth direction of the ground,
By penetrating the penetrating body into the ground, the penetrating displacement amount of the penetrating body is measured, and the penetration resistance value of the ground depth is analyzed from the obtained penetrating displacement amount, and the penetrating body is set up to a preset ground depth. After the penetration, the pulling displacement amount and the drawing resistance value are measured by pulling out the rod, and from the obtained measured values and the penetration resistance value, the physical characteristics including at least soil determination are analyzed and obtained. A ground investigation method characterized by analyzing the liquefaction strength of the ground from the obtained physical properties and the penetration resistance value.   When penetrating the penetrating body in the depth direction of the ground, analyzing the penetration resistance value of the ground depth for each hit obtained by continuously hitting and penetrating, when pulling out the rod, By continuously measuring the pulling displacement amount and the pulling resistance value, the physical characteristics including at least soil judgment are analyzed from the behavior when the ground hits and the pulling behavior, and the obtained physical characteristics and the above The ground investigation method according to claim 1, wherein the liquefaction strength of the ground is analyzed from the penetration resistance value, and the analysis result is continuously displayed along the depth direction. A ground survey device used in the ground survey method according to claim 1,
The rod having the penetrating body detachably attached to the tip, the hammer for striking the penetrating body in the depth direction of the ground and penetrating the other end of the rod, and the penetrating body penetrating in the depth direction A pulling device for pulling out the rod together with the rod, and a displacement for detecting the amount of penetration displacement when the penetrating body penetrates into the ground by hammering and the amount of pulling displacement when the penetrating device is pulled out from the ground by the pulling device. A sensor, a load sensor for detecting a pulling resistance value when the penetrating body is pulled out from the ground by the pulling device, and a measurement for converting detection signals from the displacement sensor and the load sensor into digital signals by A / D conversion A ground surveying device comprising a device and a personal computer for analyzing data of the measuring device.

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