JP2002318285A - Bedrock strength analyzing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bedrock analyzing method which can easily find a permissible supporting force degree at a low cost according to the Rayleigh wave measured on the surface of a bedrock. SOLUTION: Through a Rayleigh wave survey, the speed of a Rayleigh wave in the object bedrock and the depth corresponding thereto are measured and then the curve showing the correlation between the measured speed and depth is found. Then, the curve is used to take a speed analysis of the Rayleigh wave. Through the speed analysis, inflection points of the curved in the object bedrock, i.e., the layer border speed and layer border depth at the border part of respective speed layers are analyzed and extracted. The propagation speed Vr of each speed layer is found from the extracted layer border speed and layer border depth. The propagation speed Vr of the each speed layer is substituted in the equation shown by a recurrence straight line 60 and then the permissible supporting force degree qa of each speed layer can be found and a distribution of values of permissible supporting force degrees qa in the depth direction of the object bedrock can be found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground strength analysis method capable of obtaining an allowable bearing strength indicating the strength of a ground by analyzing a velocity of a Rayleigh wave measured on the ground surface of the ground.

[0002]

2. Description of the Related Art Conventionally, various methods have been adopted as a method for judging the strength of the ground, but the method of judging the ground engineering standards (JGS1521-
195) is known as a flat plate loading test method.
In the flat plate loading test, a circular loading plate is installed on the ground surface,
A vertical load is applied to the ground surface via the loading plate, and from the relationship between the magnitude of the load and the amount of settlement of the loading plate, the deformation characteristics relating to the deformation of the ground to a predetermined depth (depth) and the ground strength are determined. This is a test for obtaining the permissible bearing strength indicated.

[0003]

However, in the above-described flat plate loading test, a load of about several tons may be applied to the ground via the loading plate, and accordingly, the equipment becomes large and the cost required for the test is high. In addition, there is a problem that a large space for installing such equipment is required. Moreover, the allowable bearing strength obtained by the flat plate loading test covers a depth (depth from the ground surface) up to about 1 to 2 times the diameter of the loading plate.

[0004] For this reason, when determining the ground strength at a portion deeper than the ground surface, it is necessary to dig down the ground surface and again perform a test by installing a loading plate on the bottom surface of the dug portion. . As a result, in order to know the strength of the ground in the deep part of the ground, additional steps such as excavation work of the ground and re-installation of equipment are required. Was.

On the other hand, ground survey methods for structural foundations, dams, tunnels, and slopes in the field of civil engineering include:
There is a surface wave exploration method as one of the physical exploration methods. In this surface wave exploration method, a search is often performed using a Rayleigh wave among surface waves, and a method using such a Rayleigh wave is referred to as a Rayleigh wave search. Rayleigh waves are surface waves with large energy that can be easily generated by applying vibration to the ground surface. Moreover, such a Rayleigh wave has a smaller geometrical attenuation, which is a decrease in energy density (a decrease in displacement amplitude), and is easier to measure than a P wave or an S wave, which are body waves, because the measurement device is small. You.

Therefore, as a method of determining the ground strength utilizing the Rayleigh wave, a method of measuring the allowable bearing strength of the ground described in Japanese Patent No. 3052224 has been proposed. According to this method, the Rayleigh wave velocity is measured on the ground to be measured, and the allowable bearing strength is obtained from the measured velocity.

However, this method for measuring the allowable bearing capacity of the ground measures the Rayleigh wave velocity in order to obtain the allowable bearing capacity, while the bearing capacity coefficient of the ground, the shape factor of the foundation constructed on the ground, It is necessary to determine various parameters such as the unit weight of the ground under the bottom and the minimum width of the base bottom. Therefore, since the allowable bearing strength is obtained from the determination result of various parameters and the Rayleigh wave velocity, the allowable supporting strength cannot be directly obtained from the Rayleigh wave velocity, and the determination of the ground strength becomes complicated. There was a point.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is an object of the present invention to easily and easily obtain an allowable bearing strength at low cost based on a measurement speed of a Rayleigh wave measured on the ground surface. The purpose is to provide a ground strength analysis method that can be performed.

[0009]

According to a first aspect of the present invention, there is provided a ground strength analysis method for analyzing a measurement speed (Vrm) of a Rayleigh wave measured on the ground surface of a ground, and analyzing the measured velocity in the ground. Velocity of a Rayleigh wave propagating through
r), and using the propagation velocity (Vr), a predetermined coefficient (A), and a predetermined index (B) obtained by the propagation velocity analysis step to calculate the allowable bearing capacity (qa) of the ground. ,

Vr = A · qa^B  And an allowable bearing strength analysis process determined by:
The value of (A) is in the range of approximately 17.0 to approximately 17.1;
And the value of the index (B) is from about 0.440 to about 0.4
41.

According to the ground strength analysis method of the present invention, the measurement speed (Vrm) of the Rayleigh wave is measured on the surface of the ground by the Rayleigh wave exploration which is a kind of the surface wave exploration. ), The propagation speed (Vr) of the Rayleigh wave propagating in the searched ground
Is analyzed and obtained. The analysis value of the propagation velocity (Vr) is substituted into Expression 4, the value of the coefficient (A) in Expression 4 is set in a range of approximately 17.0 to approximately 17.1, and the exponent (B ) Is calculated in the range of approximately 0.440 to approximately 0.441, the value of the allowable bearing strength (qa) indicating the strength in the ground is obtained.

According to a second aspect of the present invention, in the method for analyzing a ground strength according to the first aspect, the step of analyzing the propagation velocity includes the step of determining the depth (D) at which the Rayleigh wave of the measured velocity (Vrm) passes through the Rayleigh wave. From the wavelength (λ) of

[Mathematical formula-see original document] Based on a depth analysis process obtained by D = [lambda] / 2 and a dispersion characteristic of a measurement speed (Vrm) with respect to the depth (D) obtained by the depth analysis process, a stratum structure in the ground is estimated, and Data of the measurement speed (Vrm _n-1 ) and depth (D _n-1 ) at one boundary surface and the measurement speed (Vrm _n ) and depth (D _n ) at the other boundary surface in Propagation in the formation using the extraction process to be extracted and the measurement speed (Vrm _n−1 , Vrm _n ) and depth (D _n−1 , D _n ) in the formation targeted for data extraction by the extraction process Rayleigh wave propagation velocity (Vr)

Vr = ｛(Vrm _n ² · D _n −Vrm _n−1 ²
A process of calculating a propagation velocity obtained by (D _n-1 ) / (D _n -D _{n- 1} )｝ ^1/2 .

According to a third aspect of the present invention, there is provided the ground strength analysis method according to the first or second aspect, wherein the propagation speed analysis step includes a step of calculating a density (ρ) in the ground analyzed by the propagation speed analysis step. ) Is substantially equal to the depth (D) direction.

[0013]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an electrical configuration diagram of a measurement system 1 used for Rayleigh wave exploration performed at a stage before a ground strength analysis method according to one embodiment of the present invention. Rayleigh wave exploration detects Rayleigh waves propagating in the target ground E at the ground surface E _0, measuring velocity of the Rayleigh wave from the detection result (hereinafter, simply referred to as "measurement speed".) Is calculated Vrm, This is an exploration method for estimating the underground structure (stratum structure) of the target ground E based on the measured speed Vrm. The unit of the measurement speed Vrm is “m / s”.

[0014] Measurement system 1 observes the Rayleigh wave is a kind of surface wave at the ground surface E ₀ of the target ground E, is a system for calculating the measured velocity Vrm from the observation result.
The measurement system 1 mainly includes a CPU 2 and a ROM 3
, A RAM 4, a control circuit 5, and a floppy (registered trademark) disk drive (hereinafter, referred to as "FDD") 6.
, A seismometer 7, a first detector 8, a second detector 9, an operation panel 10, an oscillator 11, a power amplifier 12, and an exciter 13.

The CPU 2 is an arithmetic unit that operates based on a control program stored in the ROM 3, and performs various types of information processing. The ROM 3 is a non-rewritable memory for storing various data in addition to a control program for operating the CPU 2, and the RAM 4 is a rewritable memory for temporarily storing various data. The control circuit 5 is mutually connected to the CPU 2, the ROM 3, the RAM 4, the FDD 6, the seismograph 7, the operation panel 10, and the oscillator 11 by an address bus, a data bus, a control signal line, and the like, and functions as an interface between them. Circuit.

The FDD 6 is a drive device for writing data to a floppy disk mounted on the FDD 6. The FDD 6 associates a measured speed Vrm used for Rayleigh wave speed analysis described later with a depth D and stores the data on the floppy disk. can do. The measured speed Vrm and the depth D stored on the floppy disk are transmitted to a personal computer (hereinafter referred to as “P”) via the floppy disk.
C ". ) And other computers (not shown)
The computer is used for Rayleigh wave velocity analysis.

A computer such as a PC may be connected to the measurement system 1 via an interface (not shown). In such a case, the measured speed Vrm and the data of the depth D can be directly transmitted to the computer and stored in a storage medium in the computer, and the computer receiving the data can transmit the Rayleigh wave described later. Speed analysis and ground strength analysis can also be performed immediately on site.

The seismometer 7 amplifies the detection signals from the first detector 8 and the second detector 9, and the first detector 8
And a second detector 9 is a vibration detection sensor of a piezoelectric element type which detects the vibration of the ground surface E ₀ (displacement). Detectors 8, 9
Is installed apart on the ground surface _{E 0} of the target ground E by a distance L, the distance L is substantially 0.5~1.0m approximately. The operation panel 10 is a panel for setting a value of a vibration frequency f, which is a vibration frequency of the vibration generator 13. The unit of the vibration frequency f is “s ⁻¹ = Hz”.

The oscillator 11 generates a sinusoidal waveform signal based on the value of the vibration frequency f set by the operation panel 10, and outputs the waveform signal to the power amplifier 12. The power amplifier 12 amplifies the waveform signal input from the oscillator 11 and outputs the amplified signal to the vibrator 13. Exciter 13, based on the waveform signal amplified by the power amplifier 12 is a device for applying (excitation) on the ground surface E ₀ the vibration force of the excitation frequency f by an electromagnetic method, vibration force excitation frequency f is, for example, in the range of several Hz to several hundred Hz. Further, the exciter 13, 'is installed on the ground surface E ₀ spaced apart by this distance L' first detector 8 and the distance L is substantially 0.5~1.0m about.

Next, the Rayleigh wave search using the measurement system 1 will be described. First, when the measurement system 1 is started, the control program stored in the ROM 3 is executed by the CPU 2, and the CPU 2 starts controlling the measurement system 1 according to the control program. here,
When the vibration frequency f is set by the operation panel 10, C
The PU 2 instructs the oscillator 11 to generate a waveform signal, generates a waveform signal based on the oscillation frequency f, and outputs the waveform signal to the power amplifier 12. This waveform signal is amplified by the power amplifier 12 and output to the vibrator 13. The vibrator 13 that has received the waveform signal generates the vibration frequency f
Vibration was applied to the ground surface E ₀ of the ground surface E ₀ is vibrated in the vertical direction by this application, the Rayleigh wave is generated in the target ground E.

The Rayleigh wave deforms the ground surface E ₀ when propagating in the target ground E. Deformation of the ground surface E ₀ by the Rayleigh wave, with the propagation of the Rayleigh wave, after being detected by the first detector 8, is detected by the second detector 9. Here, the delay time between the detection timings of the Rayleigh waves by the two detectors 8 and 9, that is, the time required for the Rayleigh waves to pass through the distance L (hereinafter, referred to as “passage time”).
T is calculated by the CPU 2. The unit of the units of the distances L and L 'is "m", and the unit of the transit time T is "s".
It is.

The measurement speed Vrm is obtained from the relationship between the distance L between the detectors 8 and 9 and the transit time T of the Rayleigh wave passing through the distance L.

Vrm = L / T Here, “/” in Equation 7 is a division operator, and indicates that the variable before “/” is divided by the variable after “/” (the same applies hereinafter). Based on this equation 7,
The value of the measured speed Vrm is calculated by the CPU 2 and
It is temporarily stored in M4 or stored in a floppy disk mounted on FDD6.

By the way, in a semi-infinite elastic body, such as a target ground E, most of the Rayleigh wave is the wavelength λ, the area in the horizontal direction from the ground surface E ₀ to a depth D of wavelength λ substantially equivalent (FIG. 1 In the direction of arrow X). Therefore, measuring the rate Vrm of the Rayleigh wave passing through the region from the ground surface E ₀ to the wavelength lambda is substantially equivalent depth D is approximated as the average velocity of the Rayleigh wave in the half-wavelength lambda / 2 is substantially equivalent to the depth D Can be used for

Therefore, the depth D through which the Rayleigh wave having the measurement speed Vrm passes is determined by the wavelength λ of the Rayleigh wave and the measurement speed Vrm.
And the relationship with the excitation frequency f,

D = λ / 2 = Vrm · (2 · f)^-1  Is required. Here, “•” in Equation 8 is a multiplication operation
Multiply the variable before "•" and the variable after "•" as a child
(The same applies hereinafter). Based on this equation 8,
And the value of the depth D at which the Rayleigh wave at the measurement speed Vrm propagates
Is calculated by the CPU 2 (depth analysis process), and the calculation
In the RAM 4 corresponding to the measurement speed Vrm used for
Flow stored temporarily or attached to FDD6
It is stored on a floppy disk.

Therefore, for example, if the excitation frequency f is changed (variable) in the range of several Hz to several hundred Hz and a Rayleigh wave is generated on the ground surface E0 by the exciter 13, the above _equation 7 Based on Equation 8, the depth D at which the Rayleigh wave propagates and the measurement speed Vrm at that depth D are obtained, and the dispersion characteristics of the measurement speed Vrm in the depth D direction can be obtained (see FIG. 2).

The depth D is the ground surface E of the target ground E.
_The distance from ₀ to the vertical downward direction (downward in FIG. 1). The unit of the depth D and the wavelength λ of the Rayleigh wave are both “m”.

Referring to FIGS. 2 and 3, a method of analyzing the speed of a Rayleigh wave using the results of the above-described Rayleigh wave search (a propagation speed analysis process) will be described. FIG. 2A is a graph showing a relationship between the measured speed Vrm and the depth D of the target ground E, and FIG. 2B is a graph showing a stratum (velocity stratum) in the target ground E derived from FIG. It is sectional drawing which shows a section.
In FIG. 2A, the horizontal axis and the vertical axis indicate the measured speed Vr.
m and depth D are shown, and both the measurement speed Vrm and the depth D are set to “0” at the origin.

A curve 20 in FIG. 2A shows a plurality of data points (circles in the figure) for the measured velocity Vrm measured by the above-described Rayleigh wave exploration and the depth D corresponding thereto.
Is a curve formed by plotting
And the depth D of the target ground E. The Rayleigh wave velocity analysis is performed based on the curve 20.

First, an inflection point on the curve 20 (eg, a non-linear step portion, a dense portion of data points, or a curve 2
Are analyzed, and the measured speed Vrm and the depth D are calculated or read from the data points located at the inflection points 21, 21,. (Extraction process). Each inflection point 21, 21, ... in the curve 20 indicates a boundary of a stratum having different properties or ground strength.

Hereinafter, the depth D of the stratum boundary portion indicated by each inflection point 21, 21,... Is referred to as the stratum boundary depth D ₁ , D ₂ ,.
, D _n−1 , D _n, and each layer boundary depth D ₁ , D ₂ ,
..., measurement speeds V corresponding to D _n-1 and D _n respectively
rm is the layer boundary speed Vrm ₁ , Vrm ₂ ,..., Vrm
called _n-1, Vrm _n, further strata boundary first speed layer formation in between _{E 1,} second speed layer _E 2, · · ·, (n-1) th speed layer _{E n-1} , referred to as the n-th speed layer _{E n.}
Note that the above suffixes “1”, “2”,.
1 "," n "indicates the order counted from the ground surface E ₀ (ordinal number) (hereinafter, the same.).

As a result, as shown in FIG.
Ground E is ground surface E₀From the first velocity layer E₁, Second velocity layer
E₂,..., The (n-1) th velocity layer E_n-1, Nth speed
Layer E _nAnd ground surface E₀From each speed layer E₁,
E₂, ..., E_n-1, E_nThe depth D to the lower surface of
Layer boundary depth D₁, D₂, ..., D_n-1, D_nAnd analysis
Is done.

By the way, in general, the rigidity G of the ground (the ground includes a stratum; the same applies hereinafter), the density ρ of the ground, and the speed of the S wave which is one of the body waves (hereinafter referred to as “S wave”) The speed is referred to as "speed."

[Mathematical formula-see original document] There is a relationship represented by G = Vs ² · ρ, where S wave velocity Vs and measured velocity Vrm
Between

## EQU10 ## There is a relationship represented by Vs ≒ Vrm.

The relationship of Equations 9 and 10 is expressed by
E₁, E₂, ..., E_n-1, E _nApplied to each
And in normal ground, each velocity layer E₁, E₂, ...
・, E_{n -1}, E_nDensity ρ at₁, Ρ₂, ...,
ρ_n-1, Ρ_nIs approximately uniform,

[Mathematical formula-see original document]₁≒ ρ₂≒ ・ ・ ・ ≒ ρ_n-1≒ ρ_n  Then, the n-th velocity layer E_nRayleigh propagating in
Wave propagation speed (hereinafter simply referred to as “propagation speed”) Vr
_nIs the n-th velocity layer E_nLayer boundary velocity Vrm_nAnd layer boundaries
Depth D_n, And the (n-1) th velocity layer E_n-1Layer boundaries
Speed Vrm_n-1And layer boundary depth D_n-1Using,

Equation 12] ^{_{Vr n = {(Vrm n 2}} · D n -Vrm
obtained by ^_n-1 2 · D _{n-1) / (D} n -D ^{_n-1)} 1/2.} When applying Equation 12, "１２
｝ ^1/2 ”indicates that the expression in“ ｛... ”Is raised to the 乗 power, n is a natural number, and the value of D ₀ is“ 0 ”.

According to this _equation 12, the number (n = 1, 2, 3,...) Counted from the ground surface E ₀ in the velocity layer to be obtained
If Atehamere a.), The propagation velocity Vr ₂ of the Rayleigh wave propagating its velocity layer is determined (propagation speed calculation step). For example, when the speed to be obtained layer is a second velocity layer E _2, if calculation by fitting a "2" in the subscript of each variable having 12 "n", Rayleigh propagating the second speed layer E in ₂ The wave propagation velocity Vr is determined. Similarly,
Each of the other velocity layer _{E 1, E 3, ···,} E n-1, propagation velocity _Vr in _{E n 1, Vr 3, ···} , Vr n-1, V
r _n can also be determined respectively.

FIG. 3A shows five speed layers E ₁ -E.
₅ (that is, n = 5), the measured velocity Vrm measured by the Rayleigh wave survey and the target ground E
FIG. 3B is a graph showing the relationship between the depth and the depth D of FIG.
3 (a) and a graph showing the propagation velocity _Vr 1 through Vr ₅ of each velocity layer _E 1 to E ₅ which is analyzed using Equation 12. In FIG. 3A, the horizontal axis and the vertical axis indicate the measured speed Vrm and the depth D, and both the measured speed Vrm and the depth D are set to “0” at the origin. FIG.
In (b), the horizontal axis and the vertical axis indicate the propagation speed Vr and the depth D, and the value of both the propagation speed Vr and the depth D is “0” at the origin.

As shown in FIG. 3A, the speed of the Rayleigh wave
According to the degree analysis, the target ground E is the inflection point 3 of the curve 30
Each speed layer E from 1, 31, ...₁~ E₅And the five-layer structure
Estimated and each of these velocity layers E₁~ E₅At the border of
Layer boundary velocity Vrm₁~ Vrm ₅Value and layer boundary depth D₁
~ D₅Is parsed and read. This read
Layer velocity Vrm₁~ Vrm₅Value and layer boundary depth
D₁~ D₅By substituting the value of
Degree E₁~ E₅Velocity Vr at₁~ Vr₅But it
Each is required.

The analysis diagram 32 of FIG.
₁ to E is a graph showing the change in propagation velocity _Vr 1 through Vr ₅ in _5, as shown in this graph, the propagation velocity Vr of the Rayleigh wave propagation speed Vr which different for each velocity layer _E 1 to E ₅ has become ₁ through Vr _5, it is changed stepwise in the depth D direction. As described above, the stratum structure of the target ground E is analyzed from the values of the measured speed Vrm of the Rayleigh wave and the corresponding depth D measured by the Rayleigh wave exploration, and the propagation speed Vr propagating for each layer in each region. Can be obtained.

FIG. 4 is a sectional view of the target ground E on which the flat plate loading test is performed. The flat plate loading test is a test for obtaining a correlation between the propagation velocity Vr analyzed by the above-described propagation velocity analysis and an allowable bearing capacity (long-term allowable bearing capacity) qa. Loading test method "(JGS1521-195). As shown in FIG. 4, the flat plate loading test is performed on the target ground E on which the Rayleigh wave search by the measurement system 1 has been performed.

In the flat plate loading test, the ground surface E _{0 of the} target ground E was
It is performed by installing the loading plate 41 on the bottom surface of the concave portion 40 dug by the height H from the ground surface E ₀ to unify from such test conditions that If is is often being artificially disturbed . Here, the footing (base) is constructed by concrete casting in the foundation work of a house building, but in such construction, the footing is usually dug approximately 0.50 m below the ground surface. Therefore, in this embodiment, substantially 0.5 the height H is the amount digging the ground surface E ₀ practicing the flat loading test
0 m.

The flat plate loading test is performed together with the Rayleigh wave search by the measurement system 1 on 72 target grounds E having different geology, topography, and soil quality.
The geological features of the 72 target grounds E are Tertiary Pliocene, Tertiary Flood, Quaternary Alluvium or Quaternary Flood, topography is around Lake Kata, back marsh, river terrace, lowland plain, valley, Natural embankments, hilly terrain, alluvial terrain, plains, hilly valleys or coastal terraces, as well as embankment sandy clay, silty clay, clayey sand, embankment and cohesive soil, sandy clay, gravel, embankment and clayey,
It has properties such as embankment and gravel, gravel clay, weathered tuff or weathered mudstone.

FIG. 5 is a diagram showing the correspondence between the propagation velocity Vr, which is the result of the above-mentioned Rayleigh wave velocity analysis, and the allowable bearing strength qa, which is the result of the above-mentioned flat plate loading test.
The correspondence table 50 shown in FIG. 5 has three columns 51 to 53 in the horizontal direction.
Are provided, and each of the columns 51 to 53 is vertically divided into 72 sections.

In column 51, sample numbers 1 to 72 of the target ground E at 72 locations where the Rayleigh wave exploration and the plate loading test were performed are described. The column 52 describes the propagation velocity Vr analyzed for the target ground E corresponding to each sample number. In the column 53, the value of the allowable bearing force qa measured by the flat plate loading test performed on the target ground E corresponding to the sample number is described. The unit of the propagation speed is “m / s”, and the unit of the allowable bearing strength qa is “10 ³ N / m ² = kN”.
/ A ^{m 2} ".

In the flat plate loading test, the strength can be determined only up to a depth of about 1 to 2 times the diameter d of the loading plate 41. Specifically, when a circular loading plate 41 is used, in the above-described JGS1521-195 test, the diameter d of the loading plate 41 is approximately 0.30 m, and the depth D at which the strength can be determined is approximately 0.30 to 0.30 m. It is about 0.60 m. Therefore, in the velocity analysis based on the results of the Rayleigh wave exploration, the propagation velocity Vr with respect to the depth that can be determined by the flat plate loading test is analyzed. That is, the value of the propagation velocity Vr at the depth D of about 1 to 2 times the diameter d of the loading plate 41 is shown in the column 52 of FIG.

FIG. 6 shows the propagation speed Vr and the allowable bearing strength qa.
Is a logarithmic scale on both the horizontal axis and the vertical axis, and the horizontal axis and the vertical axis show the allowable bearing force qa and the propagation velocity Vr. In the graph of FIG. 6, 72 data points (● in the figure) 61, 61,... Are plotted for the 72 samples shown in FIG. 5, and the analysis was performed based on these data points. A regression line 60 based on the power method is shown.

Based on this regression line 60, the propagation velocity V
Using a coefficient A and an index B between r and the permissible bearing capacity qa,

Vr = A · qa^B  Is required. Here, the coefficient A of Expression 13 and
The value of exponent B is

A = 17.6653, B = 0.404
04, the standard deviation can be set to 0.3339613, and a high correlation between the propagation velocity Vr and the allowable bearing strength qa can be obtained.

Further, in deriving Equations (13) and (14), the safety factor is tripled in the plate loading test in which the allowable bearing strength qa is measured. The value of the allowable bearing strength qa obtained from Equations (13) and (14) is , Can be practically within the standard deviation. Preferably, the values of the coefficient A and the exponent B shown in the above equation 14 may be used, but in practice, the value of the coefficient A shown in the above equation 13 is approximately 17.
The value of exponent B in Expression 13 is set in a range of approximately 0.440 to approximately 0.441, and the value of exponent B in Expression 13 is set in a range of approximately 17.1 to approximately 17.1.
3, the allowable supporting force qa can also be obtained.

Next, a method of analyzing the ground strength of the target ground E will be specifically described. For example, when analyzing the ground strength in the direction of the depth D of the target ground E shown in FIG.
First, by the above-mentioned Rayleigh wave exploration, the measured speed Vrm of the Rayleigh wave and the corresponding depth D are measured for the target ground E in FIG. 3A, and the correlation between the measured speed Vrm and the depth D in FIG. A curve 30 is determined. Thereafter, the velocity analysis of the Rayleigh wave described above is performed using the curve 30.

[0048] In speed analysis of the Rayleigh wave, the inflection point 31 and 31 of curve 30 in the subject ground E, ···, that is, speed layer _E 1 layer boundary speed _Vrm 1 boundary portion definitive of ~E ₅ ~
And values of the layer boundary depth _D 1 to D ₅ of Vrm ₅ is extracted is analyzed. Each of the extracted layer boundary velocities Vrm _1-
By substituting the value of Vrm _{5 and} the values of the layer boundary depths D _{1 to} D ₅ into the above Equation 12, as shown in FIG. 3B, the propagation velocities Vr ₁ to Vr in the respective velocity layers E _{1 to} E ₅ are obtained. Vr ₅ is determined respectively.

[0049] Then, the value of the propagation velocity _Vr 1 through Vr ₅ at each velocity layer _E 1 to E ₅ of the target ground E obtained by the velocity analysis of the Rayleigh wave, by substituting the number 13 of the respective velocity layer The permissible bearing capacity qa in each of E _{1 to} E ₅ is obtained (permissible bearing capacity analysis process), and the target ground E
Depth D direction (e.g., the depth D from the ground surface _{E 0} 10 m of
(A range up to the extent), the distribution (change) of the value of the allowable bearing strength qa can be obtained.

As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the gist of the present invention. Can easily be inferred.

In the present embodiment, the measurement system 1 has been described as an example of the device used for the Rayleigh wave search, but the configuration of the device used for the Rayleigh wave search is not necessarily limited to this. Wave measurement speed V
What is necessary is just to be able to measure the correlation between rm and the depth D at which it propagates.

In this embodiment, the S-wave velocity Vs and the measured velocity Vrm of the Rayleigh wave are set to be substantially equal in Equation 9, but the S-wave velocity Vs and the measured velocity Vrm of the Rayleigh wave are set.
Is not necessarily limited to this, and the relationship between the S-wave velocity Vs and the measured velocity Vrm changes according to the Poisson's ratio of the ground.

[Formula 15] It may be 0.8 · Vrm ≦ Vs ≦ Vrm.

[0053]

According to the ground strength analysis method of the present invention,
Since the allowable bearing capacity indicating the strength of the ground is obtained from the propagation speed of the Rayleigh wave propagating in the ground, there is no need to secure large equipment such as a flat plate loading test and its installation space to determine the ground strength Accordingly, the determination of the ground strength can be simplified and the cost can be reduced. In addition, there is an effect that an allowable bearing strength substantially equal to the allowable bearing strength obtained by the flat plate loading test can be obtained from the propagation speed of the Rayleigh wave.

Further, since the propagation speed of the Rayleigh wave in the deep part of the ground is also obtained by analyzing the measurement speed of the Rayleigh wave, the permissible bearing strength in the deep part of the ground away from the surface of the ground is obtained from the propagation speed. There is an effect that the ground strength in the deep part can also be determined. That is, the flat plate loading test is performed by digging the ground when obtaining the allowable bearing capacity of the deep part of the ground, but even without such digging, by measuring the measurement speed of the Rayleigh wave on the ground surface, the ground The effect is that the allowable bearing strength of the deep part can be easily obtained.

Furthermore, as in the conventional method for measuring the allowable bearing capacity using Rayleigh waves, the bearing capacity coefficient of the ground, the form factor of the foundation constructed on the ground, the unit weight of the ground below the base of the foundation, and the Since the allowable bearing strength is directly obtained from the propagation speed of the Rayleigh wave without using various parameters such as the minimum width of the base bottom, there is an effect that the determination of the ground strength can be performed more easily. Moreover,
Since the density in the ground analyzed by the propagation velocity analysis process is assumed to be substantially equal to the depth direction of the ground, it is possible to easily obtain the allowable bearing capacity even when determining the strength of the ground where multiple layers of layers are stacked. effective.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an electrical configuration of a measurement system used for Rayleigh wave exploration performed at a stage before a ground strength analysis method according to an embodiment of the present invention.

FIG. 2A is a diagram illustrating a relationship between a measurement speed and a depth of a target ground, and FIG. 2B is a cross-sectional view illustrating a stratum division in the target ground derived from FIG.

FIG. 3A is a graph showing the relationship between the measured speed measured by Rayleigh wave exploration and the depth of the target ground for five target grounds, and FIG. It is a graph shown.

FIG. 4 is a sectional view of a target ground on which a flat plate loading test is performed.

FIG. 5 is a diagram showing a correspondence between a propagation velocity as a result of Rayleigh wave velocity analysis and an allowable bearing strength as a measurement result of a flat plate loading test.

FIG. 6 is a graph showing a correlation between a propagation speed and an allowable bearing strength.

[Explanation of symbols]

1 measuring system A coefficient B exponent E target ground (ground) _{E n} ground surface (ground surface) _{E 0} n-th speed layer (given formation portion of the formation structure in the ground) _E 1 _{to E n-1} speed layer ( Part of the stratum structure in the ground) D depth D _n-1 stratum boundary depth (depth at _one interface in a given stratum) D _n stratum boundary depth (depth at the other interface in a given stratum) qa Permissible bearing strength Vr Propagation velocity Vrm Measurement velocity Vrm _n-1 layer boundary velocity (measurement velocity at one boundary surface in a predetermined stratum) Vrm _n layer boundary velocity (measurement velocity at the other boundary surface in a predetermined formation) λ Rayleigh wave wavelength ρ Velocity layer density (density in the stratum)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2D043 AB07 AB08 2G064 AB05 AB09 AB19 AB23 BD18 CC13 CC47 DD23

Claims (3)

[Claims] 1. A Rayleigh wave meter measured on the surface of the ground
Analyzing the velocity measurement (Vrm), the sound propagating in the ground
Propagation velocity analysis process for finding the propagation velocity (Vr) of an illy wave
And the propagation velocity (V
r), using a predetermined coefficient (A) and a predetermined index (B)
The allowable bearing capacity (qa) of the ground is expressed as follows: Vr = A · qa^B  And a value of the coefficient (A) is in a range of approximately 17.0 to approximately 17.1.
And the value of the index (B) is from approximately 0.440.
Ground having a range of approximately 0.441
Strength analysis method. 2. The method according to claim 1, wherein the step of analyzing the propagation speed comprises measuring the speed (V
rm) Rayleigh wave at the depth (D) through which the Rayleigh wave passes
From the relationship with the wavelength (λ), the depth analysis process obtained by D = λ / 2 and the depth (D) obtained by the depth analysis process
Formation in the ground based on the dispersion characteristics of the measurement speed (Vrm)
Estimate the structure and calculate the total at one boundary in a given stratum.
Speed measurement (Vrm_n-1) And depth (D_n-1)And its
Measurement speed (Vrm) at the other interface_n) And depth
(D_n) And the extraction process to extract the data
Measurement speed (Vrm _n-1, Vrm_n) And depth (D
_n-1, D_n), The Rayleigh that propagates in the formation
-The propagation speed of the wave (Vr) is given by: Vr = Ｖ (Vrm_n ²・ D_n-Vrm_n-1 ²
・ D_n-1) / (D_n-D_{n- 1})｝^1/2 And the process of calculating the propagation velocity determined by
The ground strength analysis method according to claim 1, wherein 3. A method according to claim 1, wherein said propagation velocity analysis step is such that the density (ρ) in the ground analyzed by the propagation velocity analysis step is substantially equal to the depth (D) direction. Ground strength analysis method described in 1.