JP3173790U - Ground survey equipment - Google Patents

Abstract

An object of the present invention is to provide a ground surveying device capable of surveying the properties of the ground simply, accurately and stably.
Propagation speed detection means for detecting the propagation speed of an S wave, inflection point detection means for detecting an inflection point of the propagation speed, section determination means for determining a section between the inflection points, and section A stratum classification means for classifying the ground, an average propagation speed determination means for determining the average propagation speed of the section, and a ground characteristic estimation means for estimating the ground characteristics based on the average propagation speed. In the average propagation velocity determination means, different ground analysis calculation formulas 300 are used depending on the classified formation 100.
[Selection] Figure 1

Description

  The present invention relates to a geophysical exploration device for investigating the properties of the ground using a physical wave exploration technique using S waves in physical exploration for conducting ground surveys.

  Conventionally, in order to determine whether or not the ground can safely support structures and facilities, investigation of the properties of the ground has been performed. In this ground survey, for example, a geophysical exploration using the propagation speed of vibration is performed to investigate the amount of ground subsidence, the occurrence rate of liquefaction, and the like. By this ground survey, it is suitably determined whether or not the ground can safely support structures and facilities.

  As a method of geophysical exploration for conducting ground surveys, there is a surface wave exploration method using Rayleigh waves. Since this surface wave exploration method has the characteristic that the Rayleigh wave attenuates in proportion to the square root of the distance, the source of vibration is different from that of the physical exploration method using body waves such as P wave and S wave. And the position where the Rayleigh wave is detected can be separated from each other. In addition, this surface wave exploration method is a non-destructive exploration method in which the ground is surveyed by applying vibration to the ground with a vibrator, so that the ground survey is also performed in, for example, urban areas including paved roads and gravel-covered parking lots. It is also provided with the advantage that it can be performed easily. Furthermore, since the propagation characteristics of Rayleigh waves used in this surface wave exploration method are similar to the propagation characteristics of S waves, the analysis method used in the physical exploration method using body waves can be used as it is. It also has. And since it becomes possible to perform a ground investigation more simply by the above advantages, the surface wave exploration method using the Rayleigh wave has been suitably used in recent ground investigations.

  The surface wave exploration method using Rayleigh waves is an exploration method that uses the dispersion characteristics of Rayleigh waves. Here, the dispersion characteristic refers to the property that the propagation depth of the Rayleigh wave propagating through the ground having the water stratified structure changes depending on the vibration frequency of the exciter. The ground survey by the surface wave exploration method is usually performed as follows.

  First, an exciter for generating a Rayleigh wave and, for example, two detectors for detecting the Rayleigh wave generated by the exciter are separated from each other by a predetermined distance from the ground surface on which the ground survey is performed. Install. Next, a Rayleigh wave is generated in the ground within a predetermined frequency range by a vibrator, and the time when the two detectors detect the Rayleigh wave is measured. Then, based on the measured time difference and the interval between the two detectors, the propagation speed of the Rayleigh wave within the predetermined frequency range is calculated. That is, by using the Rayleigh wave dispersion characteristic, the correspondence relationship between the propagation speed of the Rayleigh wave propagating through the ground and the propagation depth is obtained. Next, the correspondence relationship between the obtained Rayleigh wave propagation velocity (Vr) and propagation depth (D) is plotted as a so-called D-Vr curve diagram. Here, the D-Vr curve diagram will be outlined.

  FIG. 8 is a schematic diagram showing an example of a D-Vr curve diagram created by surface wave exploration.

  In FIG. 8, the horizontal axis represents the Rayleigh wave propagation velocity scale, and the vertical axis represents the Rayleigh wave propagation depth scale. A curve C is a curve obtained by plotting a correspondence relationship between the propagation speed (Vr) of the Rayleigh wave and the propagation depth (D) obtained by using the dispersion characteristic. Inflection points 1 to 6 in the curve C represent the layer boundaries of the formation in the vertical direction of the ground to be investigated.

  Next, after the D-Vr curve diagram shown in FIG. 8 is drawn, layer classification in the vertical direction of the ground to be investigated is performed using this D-Vr curve diagram. Here, the method of classifying the ground into layers using the D-Vr curve diagram shown in FIG. 8 will be outlined.

  FIG. 9 is a schematic diagram in which the ground is layered in the vertical direction based on the example of the D-Vr curve diagram shown in FIG. 8.

  As shown in FIG. 9, the ground is divided into the first layer to the seventh layer so that the layer boundaries of the respective layers correspond to the inflection points 1 to 6 of the curve C in the D-Vr curve diagram shown in FIG. Layered. In addition, the code | symbol G in FIG. 9 represents the surface (ground surface) of the ground.

  Next, after the ground layer classification is performed as shown in FIG. 9, the average propagation velocity of Rayleigh waves in each of the first to seventh layers subjected to the layer classification is calculated. This is because of the propagation speed and propagation depth of Rayleigh waves at two inflection points (for example, inflection point 1 and inflection point 2 for the second layer shown in FIG. 9) that define each stratum classified into layers. This is done by substituting each value into an average propagation velocity calculation formula used in an analysis method called a matrix method. Finally, by substituting the value of the average propagation velocity of Rayleigh waves in each of the first to seventh layers calculated by the matrix method into a predetermined calculation formula related to the ground survey, the allowable stress of the ground Surveys on the degree, sinking amount and liquefaction are conducted. A ground survey by surface wave exploration using Rayleigh waves is usually carried out in this way.

  As a method for identifying the ground structure and soil properties of the ground to be investigated using Rayleigh waves, and investigating the properties of the ground using information on the identified ground structure and soil properties, boring is performed. There is a measurement method that performs appropriate liquefaction prediction according to the soil properties (see, for example, Patent Document 1).

  Further, even when the ground is composed of a plurality of layers, there is a method for measuring the amount of ground subsidence so that the boundary between each layer can be easily discriminated so that the amount of ground subsidence can be measured for each layer (see, for example, Patent Document 2).

JP 2002-055090 A JP 2002-006056 A

  By the way, in the method of calculating the average propagation velocity of Rayleigh waves for each formation layered by the D-Vr curve diagram as described above by the matrix method, the calculated average propagation velocity of Rayleigh waves is the true average propagation velocity. There may be a problem that it is significantly different from the speed. The reason why such a failure occurs is that the layer type (for example, diluvium, alluvium, sedimentary soil, or created soil) and soil quality (for example, viscous soil, sandy soil, This is because the average propagation velocity of Rayleigh waves is uniformly calculated by the matrix method without considering the difference in the type of soil layer and the soil quality, etc., even though the sedimentary soil is different. Therefore, by calculating the average propagation velocity of Rayleigh waves in each strata classified by the matrix method, and investigating the properties of the ground using the calculated average propagation velocity values of Rayleigh waves. However, there is a problem that it is difficult to accurately investigate the allowable stress level of the ground, the amount of settlement, and liquefaction.

  In addition, as described above, in consideration of the fact that the calculation accuracy of the average propagation velocity of Rayleigh waves in various layers may be lowered in the past, the value of the average propagation velocity of Rayleigh waves obtained by the matrix method is considered in advance. The average propagation velocity is corrected by multiplying by a predetermined correction value, and the value of the corrected average propagation velocity is substituted into a predetermined calculation formula related to the ground survey. We are investigating the nature of chemicalization. However, since the correction value is not always an appropriate value, there is a problem that it is difficult to accurately investigate the property of the ground to be investigated even by such a method.

  Furthermore, recently, in the surface wave exploration method using the Rayleigh wave, in order to confirm the propagation of the Rayleigh wave on the ground surface, the position of the source and the position where the Rayleigh wave is detected are separated by a certain distance or more ( For example, it has been found that it is necessary. In other words, it is scarce to confirm the propagation of Rayleigh waves on the ground surface in a relatively narrow land, particularly in a small residential land in an urban area. Therefore, the surface wave exploration method using Rayleigh waves is effective for ground surveys when constructing large-scale structures and facilities, but constructs small-scale structures such as ordinary houses. This is often not effective for ground surveys that target relatively narrow land.

  The present invention has been made to solve the above-mentioned problems, and performs a ground survey based on the types of geological layers constituting the ground and the soil properties of each of the geological layers, thereby easily and accurately determining the properties of the ground. The object of the present invention is to provide a ground surveying device that can be surveyed well and can be carried out even in a small residential area.

  The present invention has been made in view of the above circumstances, and the ground investigation device according to the present invention detects an S wave generated by vibrating the ground, and the properties of the ground based on the detected result. In the ground survey device for surveying, the respective geological layers constituting the ground and the soil quality of the respective geological layers are classified from the detected results, respectively, and ground analysis calculation is performed according to the classified geological layers and the soil quality A formula is selected, and the property of the ground is estimated based on the selected ground analysis calculation formula, the stratum and the soil quality.

  By adopting such a configuration, a ground analysis calculation formula is selected according to the type of strata constituting the ground to be investigated and the soil quality of each stratum, and the appropriate ground analysis calculation formula for each of the strata is selected. The nature of the formation can be investigated. As a result, it is possible to accurately investigate the allowable stress level of the ground, the amount of settlement, and liquefaction.

  In this case, each of the strata constituting the ground is classified into one of a surface layer, an alluvium layer, a diluvium layer, and a rock layer.

  By setting it as such a structure, when selecting the ground analysis arithmetic expression according to the kind of the stratum which comprises a ground, an optimal ground analysis arithmetic expression can be selected. As a result, it becomes possible to more accurately investigate the allowable stress level of the ground, the amount of settlement, liquefaction, and the like.

  In this case, the soil quality of each of the geological layers constituting the ground is classified into sedimentary soil, cohesive soil, sandy soil, consolidated sand, soil bedrock, and bedrock.

  By setting it as such a structure, when selecting the ground analysis arithmetic expression according to the soil quality of the stratum which comprises a ground, an optimal ground analysis arithmetic expression can be selected. As a result, it becomes possible to more accurately investigate the allowable stress level of the ground, the amount of settlement, liquefaction, and the like.

  In this case, the ground analysis calculation formula is a calculation formula for calculating the average propagation speed of the S wave in each formation forming the ground using the detected result.

  By adopting such a configuration, the average propagation speed of the S wave is one of important data that influences the investigation accuracy of the ground survey. You can investigate the nature accurately.

  In this case, the properties of the ground include the allowable stress level of the ground, the amount of immediate settlement and the amount of consolidation settlement, and the occurrence rate of ground liquefaction.

  With such a configuration, when building a house on the ground, a necessary and sufficient investigation can be performed so that the house does not collapse, sink, or incline over a long period of time. As a result, it is possible to prevent the house and the like from collapsing, sinking, and tilting for a long time.

  The present invention is implemented in the form as described above, and conducts ground surveys based on the types of strata that form the ground and the soil properties of each stratum, and easily and accurately investigates the properties of the ground. It is possible to provide a ground investigation device that can be used even in a small residential area.

It is the schematic diagram which showed the rule which selects a ground analysis calculation type | formula according to the formation and the kind of soil which concern on embodiment of this invention. It is an estimation figure which shows typically the propagation mechanism of a body wave in the ground of narrow land, such as a narrow residential land, and the generation mechanism of a surface wave. It is a conceptual diagram which shows typically the structure for enforcing the ground investigation method which concerns on Embodiment 1 of this invention. It is a conceptual diagram which shows typically the structure for enforcing the ground investigation method which concerns on Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the control arithmetic unit which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the D-Vs curve figure drawn by the body wave search in this Embodiment. FIG. 7 is a schematic diagram in which the ground is classified into layers in the vertical direction based on the example of the D-Vs curve diagram shown in FIG. 6. It is a schematic diagram which shows an example of the D-Vr curve figure produced by the conventional surface wave search. FIG. 9 is a schematic diagram in which the ground is layered in the vertical direction based on an example of the D-Vr curve diagram shown in FIG. 8.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
First, the propagation mechanism of body waves such as P waves and S waves and the generation mechanism of surface waves such as Rayleigh waves when conducting ground surveys in narrow residential areas will be described.

  FIG. 2 is an estimation diagram schematically showing the propagation mechanism of the body wave and the generation mechanism of the surface wave in the ground of a narrow land such as a narrow residential land. In FIG. 2, symbol A indicates an exciter, symbols a to c indicate detectors, and symbol G indicates the ground.

  As shown in FIG. 2, when conducting a ground survey, the weight (weight) of the vibrator A is vibrated up and down under predetermined vibration conditions (amplitude and frequency range, etc.). Then, the P wave propagates in the depth direction (vertical direction) of the ground due to the vertical vibration of the weight of the vibrator A. Here, the propagating P wave reaches a depth of λ / 2 in the depth direction of the ground. The symbol “λ” in “λ / 2” indicates the wavelength of the P wave.

  Now, when the P wave reaches a depth of λ / 2 in the ground, the S wave is dispersed from the reaching position so as to draw a concentric circle in the horizontal direction. Further, as shown in FIG. 2, the dispersed S wave sequentially emits P waves toward the surface of the ground G in the dispersion process. In the embodiment of the present invention, as shown in FIG. 2, by detecting P waves generated by S-waves dispersed in the horizontal direction toward the surface of the ground G by the detectors a to c, Measure the propagation speed. As shown in FIG. 2, in a region exceeding a predetermined separation distance Ls in the ground G, the S wave and the P wave are caused by resonance of energy due to repetition of the S wave propagating in the horizontal direction and the P wave propagating in the vertical direction. Rayleigh waves with less attenuation than that occur. Here, the region where the Rayleigh wave is generated is a region that is usually about 6 to 12 m or more away from the vibrator A because energy needs to resonate due to repetition of the S wave and the P wave. Therefore, when conducting a ground survey in a narrow residential land or the like, a ground survey using Rayleigh waves is difficult, and a ground survey using S waves that are body waves is effective.

  Next, the structure for implementing the ground investigation according to Embodiment 1 of the present invention will be described.

  FIG. 3 is a conceptual diagram schematically showing a configuration for carrying out the ground survey according to the first embodiment of the present invention.

  In FIG. 3, the code | symbol A has shown the exciter which is brought in to each investigation site | part of a ground investigation, and is used in order to install on the ground G and to generate an S wave. Reference symbols a and b are detectors for indirectly detecting S waves generated in the ground G due to the vertical vibration of the vibrator A.

  As shown in FIG. 3, the detectors a and b described above are separated by a predetermined distance L in order to measure the propagation speed of the S wave generated in the ground G by the excitation by the vibrator A, It is installed on the ground G. The exciter A and the detectors a and b control the amplitude and frequency at which the exciter A vibrates, and control operations for calculating signals detected by the detectors a and b. It is electrically connected to device B. The storage unit of the control arithmetic device B stores a predetermined arithmetic expression to be described later.

  Next, the ground investigation method according to the present embodiment will be described. It should be noted that all the arithmetic expressions used in the ground survey according to the present embodiment are derived from known relational expressions indicating the correspondence between the S wave velocity in the ground and various soil constants, and their known relational expressions. It is a relational expression.

  FIG. 5 is a flowchart showing the operation of the control arithmetic device according to the present embodiment. Hereinafter, the operation of the control arithmetic device will be described with reference to FIG.

  Prior to the ground survey, the site worker installs the vibrator A and the two detectors a and b in a straight line at appropriate positions on the ground G to be surveyed as shown in FIG. To do.

  After the exciter A and the detectors a and b are installed at predetermined positions, the site worker operates the control arithmetic device B to thereby change the vibration conditions (for example, amplitude and frequency) of the exciter A. Range, etc.) are set (step S1). Next, an S wave is generated inside the ground G by causing the weight of the vibrator A to vibrate up and down under the set vibration conditions (step S2). By this operation, the S wave generated by the vibration of the exciter A propagates in the horizontal direction at a depth corresponding to the frequency of the exciter A inside the ground G. At this time, the detectors a and b indirectly detect the S wave propagating in the ground G via the P wave, and the detection signal is transmitted to the control arithmetic unit B. In the control arithmetic unit B, the time when the detectors a and b detect the S wave is obtained, and the time difference between these times is calculated. Then, the propagation speed of the S wave generated by the vibration of the exciter A is calculated for each frequency by the following equation (1) (step S3).

Vs = L / ΔT (1)
Here, Vs indicates the propagation speed (m / s) of the S wave. L represents the separation distance (m) between the detectors a and b. ΔT indicates a time difference (s) between the times when the detectors a and b detect the S wave.

  Next, using the calculated value of the propagation speed of the S wave and the value of the vibration frequency of the exciter A, the depth at which the S wave propagates is calculated by the following equations (2) and (3). (Step S4).

D = λ / 2 (2)
λ = Vs / F (3)
Here, D indicates the propagation depth (m) of the S wave, λ indicates the wavelength (m) of the S wave, and F indicates the frequency of the exciter A, that is, the frequency (Hz) of the S wave.

  After the propagation depth of the S wave is calculated in step S4, it is determined whether or not the measurement related to the ground survey has been performed to a predetermined depth (step S5). If it is determined in step S5 that the measurement has not been performed to a predetermined depth (NO in step S5), the process returns to step S1 and vibration conditions are set again, and the measurement has reached a predetermined depth. Until it is confirmed (YES in step S5), step S1 to step S4 are repeated.

  After confirming that the measurement related to the ground survey has been performed up to a predetermined depth in step S5, using the calculated propagation speed Vs of the S wave and the propagation depth D, D-Vr in the case of using the Rayleigh wave A “D-Vs curve diagram” corresponding to the curve diagram is drawn (step S6). Here, the D-Vs curve diagram in the present embodiment will be described with reference to FIG.

  FIG. 6 is a schematic diagram showing an example of a D-Vs curve diagram drawn by body wave exploration in the present embodiment.

  In FIG. 6, the horizontal axis represents the S-wave propagation velocity scale, and the vertical axis represents the S-wave propagation depth scale. Curve C is a curve obtained by plotting the correspondence relationship between the propagation speed and propagation depth of the S wave obtained by using the dispersion characteristic. Inflection points 1 to 6 in the curve C represent the layer boundaries of the formation in the vertical direction of the ground to be investigated.

After the D-Vs curve diagram is drawn in step S6, the S-wave propagation speed and propagation depth at the inflection points 1 to 6 shown in FIG. 6 are analyzed based on the drawn D-Vs curve diagram. Is done. Here, the propagation speed Vs and the propagation depth D of the S wave at the inflection points 1 to 6 are D ₁ and V ₁ at the inflection point ₁ , and D ₂ and V ₂ at the inflection point 2, Inflection point 3 is D ₃ and V ₃ , inflection point 4 is D ₄ and V ₄ , inflection point 5 is D ₅ and V ₅ , and inflection point 6 is D _6. , it is a _{V 6.} Further, the propagation velocity Vs and the propagation depth D when the propagation depth is 0 m are D ₀ and V ₀ , and when the propagation depth is 10 m, they are D ₇ and V ₇ .

  Next, after the D-Vs curve diagram illustrated in FIG. 6 is drawn in step S6, the stratum classification in the vertical direction of the ground to be investigated is performed again based on this D-Vs curve diagram (step). S7). Here, a method for classifying the ground using the D-Vs curve diagram illustrated in FIG. 6 will be described.

  FIG. 7 is a schematic diagram in which the ground is classified into layers in the vertical direction based on the example of the D-Vs curve diagram shown in FIG. 6.

  As shown in FIG. 7, the ground is classified into formations 10 to 70 such that the layer boundaries of the respective formations correspond to the inflection points 1 to 6 of the curve C in the D-Vs curve diagram shown in FIG. Yes. And each type (surface layer, alluvium layer, diluvium layer, bedrock layer, etc.) and soil quality (viscous soil, sandy soil, sedimentary soil, etc.) of the formations 10 to 70 are shown in the D-Vs curve diagram shown in FIG. 7 are classified as shown in FIG. 7 based on the information obtained from the curve C in FIG. That is, in FIG. 7, the stratum 10 is the surface layer (deposited soil), the strata 20 to 40 are alluvium (from the surface side, viscous soil, sandy soil, sedimentary soil), and the strata 50 to 60 are the diluvium (from the surface side, The consolidated sand 70 and the ground layer 70 are the bedrock layer (bedrock). The symbol G represents the surface (ground surface) of the ground.

  In addition, the classification of the soil quality of each region performed based on the attenuation rate of the S wave is performed as follows. That is, the S wave generated inside the ground due to the vibration of the exciter A is gradually attenuated as it spreads to the surroundings, and the amplitude of the S wave becomes smaller as the distance from the exciter A increases. For example, in the configuration shown in FIG. 3, when the amplitudes of the S waves (actually the amplitudes of the P waves) detected by the detectors a and b installed on the ground G are compared, The amplitude of the S wave detected by the detector a arranged at a position close to A is larger than the amplitude of the S wave detected by a detector b arranged at a position far from the vibrator A. . Based on the difference in the amplitude of the S wave, the attenuation rate of the S wave in each region is accurately calculated by using predetermined calculation means. After the S-wave attenuation rate is calculated for each layer, a preliminary test is performed to determine the soil quality of the formation based on the calculated S-wave attenuation rate and the S-wave propagation velocity calculated as described above. By referring to the soil classification information obtained in this way, the soil classification of each region is implemented.

Next, as shown in FIG. 7, after classifying the soil layer and the soil structure constituting the investigation target ground, the S wave average propagation speeds Vs _{1 to} Vs ₇ in the formations 10 to 70 are respectively calculated. (Step S8). Here, in the first embodiment of the present invention, the average propagation velocity Vs ₁ ～Vs ₇ S-wave in the strata shown in FIG. 7, based on the combination of geological 100 and soil 200 as shown in FIG. 1 Ground A predetermined ground analysis calculation formula is selected from the analysis calculation formula 300, and the selected ground analysis calculation formula is used to calculate each. In FIG. 1, V _S indicates the average propagation speed (m / s) of the S wave. V _U and V _L are the propagation speeds (m / s) of S waves on the surface side and the ground side of the two inflection points related to the investigation target layer of the curve C in the D-Vs curve diagram shown in FIG. Is shown. Further, D _U, and D _L represents the surface side and Chikaku side of S-wave propagation depth of the inflection point (m).

Hereinafter, a more specific method for calculating the S wave average propagation velocities Vs _{1 to} Vs ₇ in the present embodiment will be described in detail with reference to FIGS. 1 and 7.

As described above, FIG. 1 shows rules for selecting an arithmetic expression to be used for calculating the average propagation speed of S waves according to the type and soil quality of the formation. An arithmetic expression for selecting the type of formation from the formation 100 and the soil quality of each formation from the soil 200 and calculating the average propagation velocity of the S wave corresponding to the combination of the selections. Is selected from the ground analysis formula 300. That is, in the present embodiment, when calculating the average S-wave propagation velocity Vs ₁ of the formation 10 shown in FIG. 7, the type of the formation is the surface layer, and the soil is sedimentary soil. The average propagation velocity Vs ₁ of the S wave is calculated by the corresponding ground analysis calculation formula (4) shown in FIG. In addition, Formula (4) is applied also when the soil quality of the stratum 10 is a created soil.

V _S = V _L (4)
Here, V _S is the average propagation velocity of the S wave (m / s), V _L Chikaku side of S-wave propagation velocity of the two inflection points of the surveyed layer of curve C (m / s) Is shown. Therefore, the average propagation velocity Vs ₁ of the S wave in the formation 10 is obtained as shown in Equation (5).

Vs ₁ = V ₁ (5)
When calculating the average S-wave propagation velocity Vs ₂ of the formation 20 shown in FIG. 7, the type of the formation is alluvium, and the soil is viscous soil (in this case, the internal friction angle = 0 °). since a to), by the corresponding soil analysis arithmetic expression shown in FIG. 1 (6), to calculate the average propagation velocity Vs ₂ of the S-wave.

V _S = (V _U + V _L ) / 2 (6)
Here, V _S is the average propagation velocity of the S wave (m / s), V _U and V _L propagation of surface side and Chikaku side of the S-wave two inflection points of the surveyed layer of curve C Each speed (m / s) is shown. Thus, the average propagation velocity Vs ₂ of the S wave of the formation 20 is obtained by the equation (7).

Vs ₂ = (V ₁ + V ₂ ) / 2 (7)
When calculating the average S-wave propagation speeds Vs ₃ and Vs ₄ of the formations 30 and 40 shown in FIG. 7, the type of formation is alluvium, and the soil is sandy or sedimentary soil. Therefore, the average propagation speeds Vs ₃ and Vs ₄ of the S wave are calculated by the above equation (4) from FIG. Accordingly, the average propagation speeds Vs ₃ and Vs ₄ of the S waves in the formations 30 and 40 are obtained as shown in the equations (8) and (9).

Vs ₃ = V ₃ (8)
Vs ₄ = V ₄ (9)
In addition, when calculating the average S-wave propagation speeds Vs ₅ and Vs ₆ of the formations 50 and 60 shown in FIG. 7, the type of the formation is the divergent layer, and the sand and earthen soil solidified. Since it is a board, the average propagation speeds Vs ₅ and Vs ₆ of the S wave are calculated by the corresponding ground analysis formula (10) shown in FIG. In addition to the solid sand and earthen basin, the soil of this basin includes bedrock, a solid gravel layer, and the like.

V _S ≈ ((V _L ² D _L −V _U ² D _U ) / (D _L −D _U )) ^(1/2) (10)
Here, V _S indicates the average propagation velocity (m / s) of the S wave. V _U and V _L , D _U and D _L are the same as described above. Accordingly, the average propagation speeds Vs ₅ and Vs ₆ of the S waves in the formations 50 and 60 are obtained as shown in Expression (11) and Expression (12).

Vs ₅ ≈ ((V ₅ ² D ₅ -V ₄ ² D ₄ ) / (D ₅ -D ₄ )) ^(1/2) (11)
Vs ₆ ≈ ((V ₆ ² D ₆ −V ₅ ² D ₅ ) / (D ₆ −D ₅ )) ^(1/2) (12)
In addition, said Formula (10) is an arithmetic formula used when calculating | requiring the average propagation speed of S wave of each layer which comprises the ground by the matrix method in the conventional ground investigation.

Further, when calculating the average propagation velocity Vs ₇ of the S wave in the formation 70 shown in FIG. 7, since the type of the formation is a rock formation and the soil is a rock formation, the S wave of FIG. The average propagation velocity Vs ₇ is calculated by the equation (10). Therefore, the average propagation velocity Vs ₇ of the S wave in the formation 70 is obtained as shown in Equation (13).

Vs ₇ ≈ ((V ₇ ² D ₇ −V ₆ ² D ₆ ) / (D ₇ −D ₆ )) ^(1/2) (13)
As described above, the average propagation speeds Vs _{1 to} Vs _{7 of} the S waves are calculated based on the types and soil properties of the various layers 10 to 70.

  Next, after the average propagation velocity of the S wave of each layer constituting the ground is obtained as described above, each of the formations 10 to 70 constituting the ground is obtained using the value of the average propagation velocity. The ground characteristics related to the formation are estimated (step 9).

  First, a method for calculating the allowable stress level will be described in detail. The allowable stress level is conventionally called “ground strength”.

  When calculating the allowable stress level of each stratum constituting the ground, first, using the value of the average propagation velocity of the S wave of each stratum, the following formula (14) and formula (15) are used for each stratum. Calculate uniaxial compressive strength and consolidation yield stress.

qu = (V _S / 134) ^{(1 / 0.443)} (14)
Py = (V _S /99.6) ^{(1 / 0.510)} (15)
Here, V _S represents the average propagation velocity (m / s) of the S wave, qua represents the uniaxial compressive strength (kgf / cm ² ), and Py represents the consolidation yield stress (kgf / cm ² ).

  Then, using the values of uniaxial compressive strength and consolidation yield stress calculated for each stratum, the following formulas (16) and (17) are used to determine the adhesive strength of each stratum and the yield load by the plate loading test. Calculate half the value.

C = qu / 2 (16)
qt = Py / 2 (17)
Here, C is the adhesive strength (kgf / cm ² ) of the formation, qt is a half value (kgf / cm ² ) of the yield load by the plate loading test, and q u is the uniaxial compressive strength (kgf / cm ^2). ) And Py indicate consolidation yield stress (kgf / cm ² ), respectively.

  Furthermore, when calculating the allowable stress level of each stratum, the value of the adhesive strength C regarding each stratum constituting the ground is compared with the half value qt of the yield load degree by the plate loading test. The calculation is performed using a parameter (C or qt) indicating a small value. However, when the soil quality of the formation can be confirmed to be sandy soil, the allowable stress level is calculated by adopting a value qt that is a half of the yield load by the flat plate loading test only for the formation. If the soil layer is cohesive and it can be confirmed that the internal friction angle is 0 °, the allowable stress level is calculated by adopting the layer adhesive force value C only for that layer.

  For calculating the allowable stress level of each layer constituting the ground, the formula (18) or the formula (19) conventionally used in calculating the allowable stress level is properly used according to the adopted parameter (C or qt). By doing. That is, Expression (18) is an expression used when calculating the allowable stress level using the value of the adhesive strength C, while Expression (19) is a value qt that is a half of the yield load level in the flat plate loading test. This is an equation used when calculating the allowable stress level.

_{qa = (i c αCN c +} i γ βγ 1 BNγ + i q γ 2 D f N q) / 3 ··· (18)
qa = qt + (N′γ ₂ D _f ) / 3 (19)
Here, in Expression (18), qa represents the allowable stress level (kN / m ² ), i _c = i _q = (1−θ / 90) ² , i _γ = (1−θ / φ) ² , θ is the inclination angle (°) with respect to the vertical direction, φ is the internal friction angle (°), α and β are the shape factors related to the shape of the foundation bottom, and C is the adhesive force (kgf / cm) of the formation below the foundation bottom ² ), B is the length (m) of the short side of the base bottom surface, N _c , N _γ and N _q are bearing force coefficients, D _f is the depth (m) to the base bottom surface, γ ₁ and γ ₂ indicates the unit volume weight (kN / m ³ ) of the ground below the foundation load surface. In Equation (19), qt is a half value (kgf / cm ² ) of the yield load in the plate loading test, N ′ is a coefficient corresponding to the type of ground below the foundation load surface, respectively. Show. In Equation (19), γ ₂ and D _f are equivalent to those in Equation (18). In this way, the allowable stress level qa of each layer constituting the ground is obtained.

  Next, a method for calculating the amount of settlement for each layer constituting the ground will be described.

The subsidence amount is calculated by substituting the average propagation velocity Vs _{1 to} Vs ₇ of the S wave calculated based on the type and soil quality of each region into a predetermined mathematical formula for calculating the subsidence amount. The subsidence amount of the formation is analyzed by dividing it into an immediate subsidence amount that considers subsidence in a relatively short period and a consolidation subsidence amount that considers subsidence in a long period (about 10 years). In addition, when it is confirmed that the soil of the formation is sandy soil, sandy soil is highly permeable and has no adhesive force, so that it is shown that the analysis of the consolidation settlement amount is omitted. In addition, if the soil layer is cohesive, the cohesive soil is not permeable and will cause consolidation settlement over a long period of time. Therefore, it is necessary to consider both the immediate settlement amount and the consolidation settlement amount in order to predict the settlement amount. It is shown.

  The amount of immediate subsidence is calculated as follows for each region using the average propagation velocity of S waves in each region.

  First, the average propagation velocity of the S wave is substituted into the following equation (20) to calculate the rigidity factor of the ground.

G = (1 / g) ρV _S ² (20)
Here, G is the ground rigidity (kN / m ² ), g is the gravitational acceleration (m / s ² ), ρ is the ground density (kg / m ² ), and V _S is the average propagation of the S wave. Each speed is shown.

  After calculating the rigidity modulus G of the ground according to the equation (20), the Young's modulus of the ground is calculated by substituting the value of the calculated rigidity modulus G into the following equation (21).

E = 2 (1 + ν) G (21)
Here, E represents the Young's modulus of the ground, ν represents the Poisson's ratio of the ground, and G represents the rigidity of the ground (kN / m ² ). Then, after the Young's modulus E of the ground is calculated by Expression (21), the calculated value of the Young's modulus of the ground is substituted into Expression (22) shown below to calculate the amount of immediate settlement of the ground.

S _E = I _s ((1-ν ² ) / E) σB (22)
Here, the immediate subsidence of S _E is ground with (cm), the coefficient determined by the shape and stiffness of I _s the basic bottom, [nu is the Poisson's ratio of the ground, E is the Young's modulus of the ground, sigma Fundamentals the load of the compression (kN / ^{m 2),} B is the length of the short side of the basis of (m), respectively show. As described above, an immediate subsidence S _E of the ground is determined.

  On the other hand, the amount of consolidation settlement is calculated for each stratum using predetermined parameters as follows.

First, the volume compression coefficient (m _v ) of the ground to be investigated is calculated by using a predetermined calculation formula relating to the calculation of the volume compression coefficient of the ground. Then, after the volume compression coefficient of the ground is calculated, the value of the volume compression coefficient of the calculated ground is substituted into the following equation (23) to calculate the consolidation settlement amount of the ground.

S _c = m _v Δτh (23)
Here, consolidation settlement of _{S c} is ground with (cm), _{m v} is the volume compressibility coefficient of the ground, .DELTA..tau increase effective underground stress (kN / ^{m 2),} h is consolidated layer thickness (m) to , Respectively. Note that the consolidation settlement amount of the ground may be calculated by the following equation (24).

S _c = h (C _c / 1 + e) log (1+ (Δτ / σ _z )) (24)
In equation (24), S _c is the consolidation settlement amount (cm) of the ground, h is the consolidation layer thickness (m), C _c is the compression index, e is the initial gap ratio, Δτ is the effective effective ground stress (KN / m ² ) and σ _z indicate underground stress (kN / m ² ) before construction, respectively. As described above, consolidation settlement amount S _c of the ground is determined.

  Next, a method for calculating the occurrence rate of liquefaction for each layer constituting the ground will be described.

The liquefaction rate is calculated based on the estimated seismic intensity and scale of earthquakes other than the average S-wave propagation speeds Vs _{1 to} Vs ₇ calculated based on the type and soil quality of the various layers that make up the ground. And using characteristic values relating to various properties of the ground to be investigated. Then, by substituting each prepared value into a predetermined mathematical formula relating to calculation of the occurrence rate of liquefaction, this is performed as follows.

  First, the repeated shear stress ratio of the ground to be investigated is calculated using the following equation (25).

S _w = γ _n (αmax / g) (κ _z / κ _z ′) γ _d (25)
Here, _Sw is the repeated shear stress ratio, γ _n is the correction factor based on the expected earthquake magnitude, α max is the expected earthquake magnitude (Gal), g is the gravitational acceleration (Gal), κ _z = _{ηH (η:} sandy soil density, H: obtaining _{depth), κ z '= ηL +} (η-9.8) (H-L) (η: sandy soil density, L: groundwater normal level, H: (Required depth) and γ _d respectively indicate reduction coefficients based on the desired depth H.

  Next, the liquefaction resistance ratio of the ground to be investigated is calculated using the following formula (26).

R = τ ₁ / κ _z ′ (26)
Here, R represents the liquefaction resistance ratio, and τ ₁ represents the liquefaction resistance (kN / m ² ) in the horizontal plane. Incidentally, kappa _z in Equation (26) 'are, kappa _z in the above formula (25)' is the same as.

Finally, the value of the cyclic shear stress ratio S _w calculated by equation (25), by substituting the value of liquefaction resistance ratio R calculated by Equation (26) into equation (27) shown below, The occurrence rate of liquefaction is calculated.

F = R / S _w (27)
Here, F represents the occurrence rate of liquefaction, R represents the liquefaction resistance ratio, and _Sw represents the repeated shear stress ratio. In interpreting the rate of occurrence of liquefaction, it is understood that liquefaction does not occur when F <1.0. In this way, the occurrence rate F of ground liquefaction is obtained.

  As described above, the allowable stress level indicating the properties of the ground, the immediate settlement amount and the consolidation settlement amount, and the occurrence rate of liquefaction are obtained. In the embodiment of the present invention, the average propagation velocity of the S wave used when determining the properties of the ground is calculated in consideration of the type and soil quality of each layer constituting the ground. The average propagation speed can be accurately calculated. As a result, it is possible to easily and accurately determine the allowable stress level indicating the nature of the ground, the immediate settlement amount and the consolidation settlement amount, and the occurrence rate of liquefaction.

(Embodiment 2)
FIG. 4 is a conceptual diagram schematically showing a configuration for carrying out a ground investigation according to Embodiment 2 of the present invention.

  In FIG. 4, a symbol A indicates an exciter that is brought into each ground survey site and installed on the ground G to be used to generate an S wave that is a body wave. Reference symbols a, b and c are detectors for detecting S waves generated in the ground G due to the vertical vibration of the vibrator A.

  As shown in FIG. 4, these detectors a, b, and c each have a predetermined distance L in order to measure the propagation speed of the S wave generated in the ground G by the excitation by the exciter A. It is installed on the ground G. The exciter A and the detectors a, b, and c control the amplitude and frequency at which the exciter A vibrates, and calculate signals detected by the detectors a, b, and c. Is electrically connected to a control arithmetic unit B.

  Next, the ground investigation method according to the present embodiment will be described. The operation of the control arithmetic unit B in the present embodiment is the same as that in the first embodiment. In addition, the method of drawing the D-Vs curve diagram, the method of layer classification in the vertical method of the ground to be investigated, the method of determining the type and soil quality of each layer, the method of investigating the properties of the ground, etc. are also the case of the first embodiment. It is the same. Therefore, the description about each is abbreviate | omitted.

  As shown in FIG. 4, the site worker installs the vibrator A and the three detectors a, b, and c in a straight line at appropriate positions on the ground G to be investigated, and performs control computation. By operating the device B, the weight of the vibrator A is vibrated up and down within a predetermined amplitude and frequency range. By this operation, the S wave generated by the vibration of the weight of the vibrator A propagates in the ground G at a depth corresponding to the frequency of the vibrator A. At this time, the detectors a, b, and c indirectly detect the S wave propagating in the ground G via the P wave, and transmit the detection signal to the control arithmetic unit B. Here, in the present embodiment, three types of D-Vs curve diagrams are drawn for each of the detectors a and b, the detectors b and c, and the detectors a and c. Then, the obtained three types of D-Vs curve diagrams are respectively compared and examined. From among them, D which has not been subjected to interference of standing waves generated by combining the traveling wave and the reflected wave of the S wave. Select a -Vs curve diagram or a D-Vs curve diagram with relatively little interference of standing waves. Then, various ground investigations are performed based on the selected D-Vs curve diagram.

  In this way, by using the three detectors a, b, and c, a high-quality D-Vs curve diagram can be selected from a plurality of D-Vs curve diagrams, so a more accurate ground survey is performed. It becomes possible. Others are the same as those in the first embodiment.

  In this embodiment, three detectors a, b, and c are used. However, the number of detectors is not limited to three, and may be three or more.

  In the above description, an example of body wave search using S waves as body waves has been described. However, the present invention can be applied even when other body waves are used. Furthermore, the present invention can be applied to general geophysical exploration for investigating the properties of the ground.

  The ground investigation device according to the present invention is capable of conducting a ground investigation based on the types of strata constituting the ground and the soil quality of each stratum, and capable of investigating the properties of the ground simply, accurately and stably. It can be used industrially as a ground survey device that can be implemented even in small residential areas.

1 to 6 Inflection points 10 to 70 Formation 100 Formation 200 Soil 300 Ground analysis formula A Exciter B Control computation device C Curve G Ground surface a to c Detector

Claims (8)

A propagation speed detecting means for detecting a propagation speed according to the depth of the S wave generated by vibrating the ground;
An inflection point detecting means for detecting an inflection point in a change according to the depth of the detected propagation velocity;
Section determining means for determining a plurality of sections sandwiched between adjacent inflection points;
For each of the sections, based on the detected propagation velocity, a stratum classification means for classifying the section into a stratum shallower than the alluvium and a stratum deeper than the diluvium,
The average propagation velocity determination that determines the average propagation velocity of the section by using different ground analysis calculation formulas for the section classified as the shallow formation below the alluvium and the section classified as the formation deeper than the diluvium. Means,
A ground characteristic estimating means for estimating a ground characteristic for each of the sections based on the average propagation speed,
Ground survey device. Soil analysis arithmetic expression of the alluvial shallower formations to the classified section of the average propagation velocity of the section and V _S, among the inflection points sandwiching the section, the propagation speed at the inflection point of Chikaku side When V _L is the propagation velocity at the inflection point on the surface side, V _U ,
V _S = V _L or V _S = (V _U + V _L ) / 2
And
Soil analysis arithmetic expression of the classified strata of diluvial deeper interval, the average propagation velocity of the section and V _S, among the inflection points sandwiching the section, the propagation speed at the inflection point of Chikaku side When V _L , the propagation velocity at the inflection point on the surface layer side is V _U , the depth of the inflection point on the core side is D _L , and the depth of the inflection point on the surface layer side is D _U ,
V _S = ((V _L ² D _L −V _L ² D _U ) / (D _L −D _U )) ^(1/2)
The ground investigation device according to claim 1 which is.   The ground investigation device according to claim 1, wherein the ground characteristic is at least one characteristic selected from the group consisting of an allowable stress level, a subsidence amount, and an occurrence rate of liquefaction. In the ground investigation device that detects the S wave generated by vibrating the ground and investigates the property of the ground based on the detected result,
Formation determination means for determining each formation forming the ground from the detected result;
Soil quality judging means for judging the soil quality of each of the formations;
A ground analysis calculation formula selecting means for selecting a ground analysis calculation formula according to the determined formation and the soil;
A ground survey apparatus comprising: estimation means for estimating a property of the ground based on the selected ground analysis calculation formula and the determined stratum and the soil quality.   The stratum judgment means for judging each stratum constituting the ground comprises classification means for classifying the ground into one of a surface layer, an alluvium, a diluvium, and a bedrock layer. Ground survey device.   The soil judgment means for judging the soil quality of each of the geological layers constituting the ground is classified into one of sedimentary soil, viscous soil, sandy soil, consolidated sand, soil bedrock, and bedrock. The ground investigation device according to claim 4, further comprising classification means for performing the classification.   Calculation for calculating an average propagation velocity of S waves in each of the formations constituting the ground, using the detected result, a ground analysis calculation expression selection means for selecting a ground analysis calculation expression according to the formation and the soil 5. The ground investigation device according to claim 4, further comprising identification means for identifying an expression.   Estimating means for estimating the properties of the ground based on the selected ground analysis calculation formula, the formation and the soil, the allowable stress level of the ground, the amount of immediate settlement and consolidation settlement, the liquefaction of the ground The ground survey device according to claim 4, further comprising a calculation means for calculating an occurrence rate.

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