JP5150324B2 - Strength characteristic measuring method, strength characteristic measuring apparatus and program - Google Patents

Description

  The present invention relates to a strength characteristic measuring method, a strength characteristic measuring apparatus, and a program for measuring mechanical properties of a ground material at an original position, particularly strength properties.

  In general, regarding the mechanical properties of the ground material, it is difficult to reproduce the state of the original ground material (particle size distribution, compaction state, difference in consolidation process, etc.) by laboratory tests. Therefore, there is a demand for accurate and efficient measurement of the mechanical properties of various ground materials at the original position, but there is no effective measurement method that satisfies such demand in the prior art. For example, there are two conventional methods for measuring the strength characteristics of a ground material at an in-situ location: (1) an in-situ shear test method and (2) an intrusion test method.

FIG. 11 is a diagram illustrating the in-situ shear test method. In the in-situ shear test method, an in-situ shear test apparatus 51 shown in FIG. 11 is used to calculate the strength constant (adhesive force c, internal friction angle φ) of the ground material. Specifically, as shown in FIG. 11, a horizontal thrust is loaded on a specimen (block) 53 loaded with a certain vertical force. Then, the vertical force N _f and the horizontal thrust F _f when the specimen 53 shears and breaks at the shear surface 55 are measured, and the adhesive force c and the internal friction angle φ are estimated.

FIG. 12 is a diagram illustrating a method for estimating the adhesive force c and the internal friction angle φ. In the estimation method shown in FIG. 12, it is necessary to perform an in-situ shear test on two or more specimens 53. Each test point is calculated by an equation of σ = N _f / A and τ = F _f / A. Here, A is the area of the shear surface 55.

  However, in the in-situ shear test method, (b) a reaction force device is required, which requires a large amount of labor and a large amount of cost. (B) When the soil material is targeted, it is difficult to manufacture the specimen 53. There is a problem. As for (b), as shown in FIG. 11, a reaction force device for loading vertical force and horizontal thrust is required, and when a hard ground material such as a rock material is a target, The force is large and the reaction force device needs to be large. Regarding (b), since the sandy soil material has almost no adhesive force, it is difficult to produce the specimen 53 as shown in FIG. Thus, the in-situ shear test method is performed only on hard ground materials such as rock materials, with great effort and great expense. As described above, the in-situ shear test method cannot satisfy the demand for accurately and efficiently measuring the mechanical properties of various ground materials in the in-situ.

  The penetration type test method is a method in which a rod with a penetration tip (such as a cone) is penetrated into the ground material and the penetration resistance is measured. Then, the strength characteristic of the ground material is indirectly calculated from an empirical formula formulated based on the correlation between the penetration resistance and the strength characteristic measured with the same ground material in the past. The penetration test method has a simple test method and apparatus, and is widely used in the in-situ test.

  However, the penetration type test method (b) calculates strength characteristics indirectly using empirical formulas, so the measurement results depend greatly on the specifications (dimensions, etc.) of the test equipment and the target ground material. There are problems that the measurement accuracy on the surface is low, (c) the stress state is unclear, and (d) the tip area of the penetrating tip is small, resulting in large variations in measurement results. Thus, even the penetration type test method cannot satisfy the demand for accurately and efficiently measuring the mechanical properties of various ground materials in situ.

Along with the recent mechanization of construction, a drop-type device that does not require a large reaction force device as a method to obtain ground material in-situ with high work efficiency (a disk-like weight is dropped onto the target ground using a slider) Etc.), a method for easily obtaining the mechanical properties of the ground material has been developed. These representative methods and issues are summarized below. However, most of these methods are for determining the deformation characteristics of the ground material, and cannot determine the strength characteristics. Even if they are obtained, they are obtained indirectly by an empirical formula created based on the correlation between the measurement results obtained in the past for the same ground and the strength characteristics of the ground material.
(A) Dynamic response method: Typical methods include a response acceleration method, an impedance method, a resonance method, a wheel acceleration method, and the like. Although they are simple in-situ test methods, they are not so popular because the measurement results largely depend on the specifications of the test apparatus and the target ground.
(B) Dynamic loading test: A typical method is a small FWD (Falling Weight Deflectometer). In this method, the flat plate loading test generally performed for the purpose of obtaining the deformation characteristics of the in-situ ground material and the measuring method are almost the same. Therefore, it is widely used as a simple in-situ test method. However, this method has a large variation in measurement results due to reasons that skill is required in the measurement technique, for example, the ground surface is smoothed and a plate is installed.
Therefore, the present inventors have invented a measurement method using a drop-type device that can accurately and efficiently measure the mechanical properties of various ground materials in the original position (see Patent Document 1). In the measurement method disclosed in Patent Document 1, a rigid body to which an acceleration sensor is attached is dropped on a target ground material, an impact process is measured, and a contact time between the rigid body and the ground material is calculated from the measurement result. From the calculated contact time, the deformation characteristics (Young's modulus E, Poisson's ratio μ) of the ground material are calculated based on the Hertz impact theory. According to the measurement method disclosed in Patent Document 1, it is possible to accurately and efficiently measure the deformation characteristics of various ground materials at the original position.
JP 2002-30463 A

  In addition to the deformation characteristics of the ground material, the present inventors further provide a measurement method capable of accurately and efficiently measuring the strength characteristics (adhesive strength c, internal friction angle φ) of various ground materials in the original position. Invented.

  An object of the present invention is to provide a strength property measurement method and the like that can accurately and efficiently measure strength properties (adhesive strength c, internal friction angle φ) of various ground materials in situ.

In order to achieve the above-mentioned object, the first invention is a strength characteristic measuring method for measuring the strength characteristics of a ground material at an original position, wherein a rigid body to which an acceleration sensor is attached is dropped from a certain height. A measurement step for measuring an impact process, and a contact time between the rigid body and the ground material is calculated based on the measured impact process, and the contact time, the mass of the rigid body, and from the center of the rigid body to the outer periphery. Calculating the deformation characteristics of the ground material from a first theoretical formula based on Hertz's impact theory, showing the relationship between the distance, the height, the rigid body and the deformation characteristics of the ground material, and the measured impact Based on the process and the calculated deformation characteristics of the ground material, the deformation characteristics of the ground material, the distance from the center point of the rigid body to the outer periphery, and the maximum settlement point of the ground material from the center point of the rigid body Using the distance from the straight line drawn to the point where the compressive stress of the contact surface of the rigid body and the ground material becomes zero, the force that contributes to the deformation of the ground material is not converted to the inertial force of the impact force. Calculate the average compressive stress divided by the area of the contact surface, the average compressive stress of the contact surface, the distance from the center point of the rigid body at the time of dropping to the boundary of the plastic region of the ground material, The second theoretical formula based on Vesic's cavity expansion theory, showing the relationship between the distance from the center point to the outer periphery, the strength characteristics of the ground material, and the density of the ground material , is calculated as the average compressive stress of the contact surface. And calculating a strength characteristic of the ground material by solving using the average compressive stress . According to the first invention, the strength characteristics of various ground materials can be accurately and efficiently measured at the original position.

The second theoretical formula in the first invention takes into account the inertial force . By considering the inertial force, a highly accurate measurement result can be obtained.

  In the first aspect of the invention, it is preferable that the measurement step is repeated a plurality of times, and the average of the intensity characteristics is calculated by statistical processing using a harmonic average method. By using the harmonic averaging method, for example, even if a case where a large stone is included in the ground material is included in the measurement result, the influence can be reduced.

A second invention is a strength characteristic measuring apparatus for measuring the strength characteristics of a ground material at an in-situ position, wherein measurement data obtained by measuring a shock process by dropping a rigid body to which an acceleration sensor is attached from a certain height is obtained. Calculate the contact time between the rigid body and the ground material based on the input means and the input measurement data, the contact time, the mass of the rigid body, the distance from the center of the rigid body to the outer periphery, Means for calculating the deformation characteristics of the ground material from a first theoretical formula based on Hertz's impact theory, showing the relationship between the height, the rigid body and the deformation characteristics of the ground material, and the measured impact process and calculation Based on the deformation characteristics of the ground material, the deformation characteristics of the ground material, the distance from the center point of the rigid body to the outer periphery, and the straight line drawn from the center point of the rigid body to the maximum settlement point of the ground material Or From the distance to the point where the compressive stress of the contact surface between the rigid body and the ground material becomes zero, the force that contributes to the deformation of the ground material without being converted into the inertial force is applied to the contact surface. Calculate the average compressive stress divided by the area, the average compressive stress of the contact surface, the distance from the center point of the rigid body to the boundary of the plastic region of the ground material when dropped, the outer periphery from the center point of the rigid body 2nd theoretical formula based on Vesic's cavity expansion theory showing the relationship between the distance to the surface, the strength characteristics of the ground material, and the density of the ground material , and the calculated average compressive stress as the average compressive stress of the contact surface by solving with a strength characteristic measuring apparatus characterized by comprising a means for calculating the strength properties of the ground material.

  The third invention is a program for causing a computer to function as the strength characteristic measuring device of the second invention.

  According to the present invention, it is possible to provide a strength characteristic measuring method and the like that can accurately and efficiently measure the strength characteristics (adhesive strength c, internal friction angle φ) of various ground materials in situ.

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

  FIG. 1 is a diagram showing an outline of an apparatus used for an intensity characteristic measuring method. As shown in FIG. 1, in the strength characteristic measuring method according to the embodiment of the present invention, the rigid body 1, the computer 5, the power supply 15, the A / D board 17 and the like are used at the original position of the target ground material 3.

  The rigid body 1 is made of metal, for example, spherical or hemispherical. However, the shape is not limited to these, and the surface layer portion of the rigid body 1 that contacts at least the ground material 3 when it is dropped may be spherical.

  An acceleration sensor 7 and a handle 11 are attached to the rigid body 1. The acceleration sensor 7 measures the acceleration when the rigid body 1 is dropped. The acceleration sensor 7 is connected to the power supply 15 and the A / D board 17 via the cable 13. The A / D board 17 is connected to the computer 5 and converts the voltage signal from the acceleration sensor 7 into a digital signal. The computer 5 records and analyzes signals from the A / D board 17 and calculates deformation characteristics, strength characteristics, and the like of the ground material 3.

  In the strength characteristic measuring method according to the embodiment of the present invention, the rigid body 1 is pulled up to a certain height (for example, 50 cm), the rigid body 1 is dropped freely, and the impact process between the rigid body 1 and the ground material 3 is measured. To do.

  FIG. 2 is a view showing the inside of the rigid body 1 and the handle 11. As shown in FIG. 2, the acceleration sensor 7 is built in the rigid body 1 and is fixed by, for example, a screw or the like. The cable 13 passes through the inside of the handle 11 and is connected to the acceleration sensor 7. The rigid body 1 and the handle 11 are fixed by screws or the like, for example.

  FIG. 3 is a hardware configuration diagram of the computer 5. Note that the hardware configuration in FIG. 5 is merely an example, and various configurations can be employed depending on the application and purpose. In the computer 5, a control unit 21, a storage unit 22, a media input / output unit 23, a communication control unit 24, an input unit 25, a display unit 26, a peripheral device I / F unit 27 and the like are connected via a bus 28.

  The control unit 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

The CPU calls a program stored in the storage unit 22, ROM, recording medium or the like to a work memory area on the RAM and executes it, drives and controls each device connected via the bus 28, and is described later by the computer 5. To achieve the process.
The ROM is a non-volatile memory, and permanently stores a boot program for the computer 5, a program such as BIOS, data, and the like.
The RAM is a volatile memory, and temporarily stores a program, data, and the like loaded from the storage unit 22, ROM, recording medium, and the like, and includes a work area used by the control unit 21 for performing various processes.

The storage unit 22 is an HDD (hard disk drive), and stores a program executed by the control unit 21, data necessary for program execution, an OS (operating system), and the like. As for the program, a control program corresponding to an OS (operating system) and an application program corresponding to processing described later are stored.
Each of these program codes is read by the control unit 21 as necessary, transferred to the RAM, read by the CPU, and executed as various means.

  The media input / output unit 23 (drive device) inputs / outputs data, for example, a floppy (registered trademark) disk drive, a CD drive (-ROM, -R, -RW, etc.), a DVD drive (-ROM, -R). , -RW, etc.) and media input / output devices such as MO drives.

  The communication control unit 24 includes a communication control device, a communication port, and the like, and is a communication interface that mediates communication between the computer 5 and the network 29, and performs communication control between other computers via the network 29.

The input unit 25 inputs data and includes, for example, a keyboard, a pointing device such as a mouse, and an input device such as a numeric keypad.
An operation instruction, an operation instruction, data input, and the like can be performed on the computer 5 via the input unit 25.

  The display unit 26 includes a display device such as a liquid crystal panel and a logic circuit (a video adapter or the like) for realizing the video function of the computer 5 in cooperation with the display device.

  The peripheral device I / F (interface) unit 27 is a port for connecting the peripheral device to the computer 5, and the computer 5 transmits and receives data to and from the peripheral device via the peripheral device I / F unit 27. The peripheral device I / F unit 27 is configured based on standards such as USB, IEEE 1394, RS-232C, and a PC card interface, and usually includes a plurality of peripheral devices I / F. The connection form with the peripheral device may be wired or wireless.

  The bus 28 is a path that mediates transmission / reception of control signals, data signals, and the like between the devices.

  Next, the theoretical background of the present invention will be described with reference to FIGS. FIG. 4 is a diagram for explaining the cavity expansion theory. FIG. 5 is a diagram showing the distribution of impact stress.

  The cavity expansion theory proposed by Vesic is (1) based on the spherical expansion phenomenon, (2) suitable for deep foundations (equal stress is applied), (3) volumetric strain of the material in the plastic region (4) The material must have deformation characteristics. For (4), the deformation characteristics of the ground material 3 can be calculated by the method disclosed in Patent Document 1. On the other hand, with respect to (1) to (3), it is necessary to modify the theory in consideration of the characteristics of the strength characteristic measurement method according to the embodiment of the present invention. This is because the inertial force is generated because the rigid body 1 is dropped and a dynamic load is applied to the material.

(Theoretical formula of the internal friction angle φ and influence range R _p)
First, assuming that the adhesive strength c of the ground material 3 which is one of the strength characteristics is 0, the internal friction angle φ (unit: °) and the influence range R _p (unit: m) which are the other strength characteristics are The theoretical formula will be described. In the following, (assuming 1) since the support force against the fall of the rigid body 1 is mainly provided with a conical region having the center of the rigid body 1 as a vertex (O-ABCD in FIG. 4), the scope of application of the theory is Limited to the ABCD region (plastic region 31 shown in FIG. 4), (Assumption 2) Targeting the non-viscous ground material 3, (Assumption 3) The volume strain of the material in the plastic region 31 shown in FIG. Assuming that

但し、ｒは剛性体１の中心点からの距離（単位：ｍ）であり、地盤材料３の自重は無視
する。 In the static state, the equilibrium relationship between the stresses σ _r and σ _θ in the spherical portion of the rigid body 1 satisfies the following equation.

However, r is the distance (unit: m) from the center point of the rigid body 1, and the weight of the ground material 3 is ignored.

In the plastic region 31, the Mohr-Column theory expressed by the following equation holds.

ここで、Ｒは剛性体１の半径（単位：ｍ）、ｐ_ｕは剛性体１と地盤材料３との接触面における平均圧縮応力（単位：Ｐａ）である。 Substituting equation (2) into equation (1), taking into account the constraints sigma _{r =} p _u at the contact surface r = R the rigid body 1 and the ground material 3, the following equation is obtained.

Here, R represents the rigid body 1 radius (unit: m), p _u is the average compressive stress in the contact surface of the rigid body 1 and the ground material 3 (unit: Pa) is.

ここで、ｄを剛性体１による圧縮量（単位：ｍ）とすると、次式を得る。

但し、ｄ_ｐ、ｄ_ｐ−ｕは、次式のとおりである。

式（６）、（８）から、次式が成り立つ。

更に、ｕ_ｐの二乗以上の項を無視すると、式（４）、（５）、（９）から、次の関係式が成り立つ。

If the displacement in the r direction at the boundary (r = R _p ) of the plastic region 31 is u _p , the volume change in the plastic region 31 is 0 (see (Assumption 3)).

Here, when d is a compression amount (unit: m) by the rigid body 1, the following equation is obtained.

_{However, d p,} d _p-u are as follows.

From the expressions (6) and (8), the following expression is established.

Moreover, ignoring the square or more terms of _{u p,} Equation (4), (5), (9), holds the following relationship.

但し、ｑは塑性領域３１の境界部（ｒ＝Ｒ_ｐ）における平均圧であり、次式のとおりである。

Further, according to the equation of Lame, _{u p} is expressed by the following equation.

However, q is an average pressure in the boundary part (r = _Rp ) of the plastic area | region 31, and is as following Formula.

また、式（１１）、（１２）、（１３）から、次式を得る。

更に、ｒ＝Ｒ_ｐを式（３）に代入すると、次式を得る。

従って、式（１３）、（１５）から、次式を得る。

ここで、σ_θとｐ_ｕが求まれば、式（１４）、（１６）によって、影響範囲Ｒ_ｐと内部摩擦角φを同時に求めることができることになる。 On the other hand, since the formula (2) is also established at the boundary portion (r = R _p ) of the plastic region 31, when the formula (2) is deformed, the following formula is obtained.

Further, the following equation is obtained from the equations (11), (12), and (13).

Furthermore, substituting r = R _p into equation (3) yields:

Therefore, the following equation is obtained from equations (13) and (15).

Here, if Motomare is sigma _theta and _{p u,} equation (14), so that can be obtained simultaneously by the influence range _{R p} and the internal friction angle phi (16).

但し、γは地盤材料３の密度（ｋｇ／ｍ^３）である。式（１３）を式（１４）、（１６）に代入すると、次式を得る。

ここで、ζを次式のように定義する。

そして、式（２０）を用いて、式（１８）を変形すると、次式を得る。

更に、後述するように、本発明の実施の形態における強度特性測定方法においては、ｄおよびｐ_ｕも求めることができることから、式（２１）を式（１９）に代入すると、Ｒ_ｐが唯一の未知量となり、数値解析によってＲ_ｐを求めることができ、更に内部摩擦角φも求めることができる。 In the strength characteristic measuring method according to the embodiment of the present invention, when σ _θ is a passive earth pressure, the following equation is established.

However, (gamma) is the density (kg / m < ³ >) of the ground material 3. FIG. Substituting equation (13) into equations (14) and (16) yields:

Here, ζ is defined as follows.

Then, when equation (18) is transformed using equation (20), the following equation is obtained.

Furthermore, as will be described later, in the intensity characteristic measurement method according to the embodiment of the present invention, d and p _u can also be obtained. Therefore, when equation (21) is substituted into equation (19), R _p is the only one. becomes unknown quantity, can be obtained R _p by a numerical analysis, it can be further determined even φ internal friction angle.

(Correction of theory considering inertia)
Expressions (1), (2), (3), and (15) showing the dispersion relation of the stress σ _r are all obtained by static stress equilibrium conditions. In the strength characteristic measuring method according to the embodiment of the present invention, it is expected that the stress is further dispersed by the inertial force. Therefore, the theory must be corrected in consideration of the inertial force. Here, along with modifications of theory considering the inertial force, the formula (19), the amount of compression (hereinafter, referred to as the maximum subsidence.) Contained in the (20) describing calculation of d and average compressive stress p _u.

In general, the attenuation of dynamic amplitude with distance is proportional to distance, so equations (3), (16), and (19) can be modified as follows.

The average compressive stress p _{u at the} contact surface cannot be obtained by dividing the measured impact force F _max by the contact area. The cause is that the impact force includes one that contributes to the deformation of the ground material 3, one that is converted into the inertial force of the ground material 3, one that is converted into heat, and the like. Therefore, among these, calculates a contributing force F ^* to the deformation of the ground material 3, it is necessary to determine the average compressive stress p _u from F ^*.

Hereinafter, a deformation characteristics of ground material 3 Young's modulus E (unit: Pa), the method of calculating the average compressive stress p _u will be described with reference to Poisson's ratio mu. The Young's modulus E and Poisson's ratio μ can be calculated by the method disclosed in Patent Document 1, and are also calculated among the strength characteristic measuring methods in the embodiment of the present invention.

従って、Ｆ^＊は次式のとおり表すことができる。

ここで、ａとｄとの間には、次式に示す関係式が成り立つ。

式（２６）を式（２５）に代入すると、次式を得る。

The stress distribution between the rigid body 1 and the ground material 3 can be modeled as shown in FIG. Here, p ₀ is a compressive stress at the maximum settlement point of the contact surface 33. Also, p is, r of the contact surface 33 (r is the distance from a line drawn to the maximum subsidence point from the center point of the rigid body 1) is a compression stress at a point, with a shown in p ₀ and 5 following It can be expressed by a formula.

Therefore, F ^* can be expressed as:

Here, the relational expression shown below is established between a and d.

Substituting equation (26) into equation (25) yields:

式（２８）を積分すると、最大沈下量ｄは次式のとおり求めることができる。

次に、式（２９）に応力分布の関係を示す式（２４）を代入すると、次式を得る。

次に、式（３０）を式（２７）に代入すると、Ｆ^＊は次式のとおり求めることができる。

一方、平均圧縮応力ｐ_ｕは、式（３１）に示すＦ^＊によって、次式のとおり表すことができる。

ここで、Ａ_ｍａｘは接触面積であり、例えば、球冠の表面積とすると、次式を得る。

従って、平均圧縮応力ｐ_ｕは、次式のとおり求めることができる。

式（３４）、（２１）を式（２３）に代入し、Ｒ_ｐについて解けば、影響範囲Ｒ_ｐが求まる。更に、求めたＲ_ｐを式（２１）に代入すれば、内部摩擦角φが求まる。尚、地盤材料３の粘着力ｃは０と仮定している。 According to Bosinesq's solution, when the concentrated load P is acting vertically on the ground surface, the amount of settlement on the ground surface that is r away from the loading point can be expressed by the following equation.

When the equation (28) is integrated, the maximum subsidence amount d can be obtained as follows.

Next, substituting Expression (24) indicating the relationship of stress distribution into Expression (29), the following expression is obtained.

Next, by substituting equation (30) into equation (27), F ^* can be obtained as follows.

On the other hand, the average compressive stress p _u can be expressed by the following formula using F ^* shown in formula (31).

Here, A _max is the contact area. For example, when the surface area of the crown is given, the following equation is obtained.

Therefore, the average compressive stress p _u can be obtained as follows.

By substituting the equations (34) and (21) into the equation (23) and solving for R _p , the influence range R _p can be obtained. Furthermore, if the calculated R _p is substituted into the equation (21), the internal friction angle φ is obtained. In addition, the adhesive force c of the ground material 3 is assumed to be zero.

  As described above, the theory is corrected in consideration of the inertial force, and the internal friction angle φ, which is one of the strength characteristics of the ground material 3, is directly calculated from the above-described theoretical formula by the strength characteristic measurement method according to the embodiment of the present invention. Can be sought.

  On the other hand, when the target is the ground material 3 with φ = 0 such as saturated clay, by removing the assumption about the adhesive strength c and placing the assumption of φ = 0, the adhesive strength c is set in the same manner as described above. Can be sought. When both the adhesive force c and the internal friction angle φ are unknown amounts, for example, the internal friction angle φ can be obtained by setting an empirical value for the adhesive force c.

(Calculation of deformation characteristics)
Here, an outline of a method for calculating the deformation characteristics of the ground material 3 by the method disclosed in Patent Document 1 will be described. Similarly to the strength characteristic measuring method according to the embodiment of the present invention, the method disclosed in Patent Document 1 allows the rigid body 1 to freely fall and measure the contact time with the ground material 3. Based on the contact time, the deformation characteristics of the ground material 3 are calculated from a theoretical formula based on the Hertz impact theory.

According to the impact theory of Hertz, falling sphere (e.g., a rigid body 1) the contact time _{T c} of the elastic body plane (e.g., ground material 3), (1) Deformation of the sphere (Young's modulus _{E 1} and Poisson Ratio μ ₁ ), (2) deformation characteristics of the elastic body plane (Young's modulus E ₂ and Poisson's ratio μ ₂ ), (3) sphere mass M ₁ , sphere radius R _1, and drop height h.

ここで、δ_ｉ＝（１−μ_ｉ ^２）／（Ｅ_ｉπ）（ｉ＝１、２）である。また、ｇは重力加速度であり、ｇ＝９．８（ｍ／ｓ^２）である。 When a sphere of mass M ₁ and radius R ₁ is dropped from the drop height h onto the elastic body plane, the contact time T _c between the sphere and the elastic body plane is expressed by the following equation.

Here, δ _i = (1−μ _i ² ) / (E _i π) (i = 1, 2). Further, g is a gravitational acceleration, and g = 9.8 (m / s ² ).

From the equation (35), the contact time T _c between the sphere and the elastic body plane is the sphere mass M ₁ , the sphere radius R ₁ , the drop height h, and the deformation characteristics of the sphere (Young's modulus E ₁ and Poisson's ratio μ ₁ ). And the deformation characteristics of the elastic body plane (Young's modulus E ₂ and Poisson's ratio μ ₂ ). The contact time T _c can be measured, and the sphere mass M ₁ , the sphere radius R ₁ , the drop height h, and the deformation characteristics of the sphere (Young's modulus E ₁ and Poisson's ratio μ ₁ ) are known. The unknown amount is two of deformation characteristics (Young's modulus E ₂ and Poisson's ratio μ ₂ ) of the elastic body plane. Therefore, if an elastic plane (for example, ground material 3 at the same location) having the same deformation characteristics is dropped twice under different drop conditions, the deformation characteristics (Young's modulus E ₂ and Poisson's ratio) of the elastic plane μ ₂ ) can be estimated.
Alternatively, regarding the Poisson's ratio μ ₂ among the unknown quantities, values corresponding to the target elastic body plane (for example, rock: 0.2, gravel soil: 0.2, sandy soil: 0.3, viscous soil: 0.4, etc.) are used. . Therefore, if the sphere is dropped once with respect to the elastic body plane, the deformation characteristic (Young's modulus E ₂ ) of the elastic body plane can be estimated.
As described above, the deformation characteristics of the ground material 3 can be calculated in the strength characteristic measurement method according to the embodiment of the present invention.

  Next, the details of the strength characteristic measuring method according to the embodiment of the present invention will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of the intensity characteristic measuring method.

  As shown in FIG. 6, the measurer inputs known data (for example, the radius of the rigid body 1, the density of the ground material 3, etc.) via the input unit 25 of the computer 5 (step 101). The control unit 21 of the computer 5 stores the input known data in the storage unit 22.

Next, when the measurer lifts the rigid body 1 to a certain height (for example, 50 cm) and drops it onto the ground material 3 (step 102), the acceleration sensor 7 measures the acceleration of the rigid body 1 (step 103). ). The measurement result is converted into a digital signal by the A / D board 17 and input to the computer 5 via the peripheral device I / F unit 27 of the computer 5. The control unit 21 of the computer 5 stores the input measurement result (time series data of acceleration of the rigid body 1) in the storage unit 22.
It should be noted that the position where the rigid body 1 is dropped in the process of step 102 is preferably a flat place, avoiding places where the surface is disturbed and stones. Further, the processing of step 102 may be such that the rigid body 1 is mounted on the vehicle, the vehicle automatically determines the drop position, and the rigid body 1 is allowed to fall freely.

  Next, the control part 21 of the computer 5 performs the process etc. which reduce the noise of the measurement result memorize | stored in the memory | storage part 22 (step 104).

  Next, the control unit 21 of the computer 5 obtains the deformation coefficient and the strength constant for each measurement time from the above-described theoretical formula based on the measurement result (step 105). Specifically, the Young's modulus E and the Poisson's ratio μ are calculated from the theoretical formula based on the Hertz impact theory described above. Further, the internal friction angle φ or the adhesive force c is calculated from the theoretical formula based on the above-described Vesic's cavity expansion theory.

Next, the control unit 21 of the computer 5 confirms whether or not the scheduled number of measurements has been reached (step 106).
If the scheduled number of measurements has not been reached, the process is repeated from step 102.
If the scheduled number of measurements has been reached, the process proceeds to step 107.

  Next, the control unit 21 of the computer 5 obtains an average, a standard deviation, and the like of the deformation coefficient and the intensity constant by statistical processing from the measurement results measured by the processing from step 102 to step 105 (step 107). Here, the statistical processing may use not only a commonly used simple average method but also a harmonic average method.

調和平均法を用いることで、例えば、地盤材料３に大きな石が含まれていたような場合が測定結果に含まれていても、その影響を軽減することができる。 The harmonic average method is calculated by, for example, the following formula for n pieces of data x ₁ ,..., X _n .

By using the harmonic average method, for example, even if a case where a large stone is included in the ground material 3 is included in the measurement result, the influence can be reduced.

  Next, examples according to the embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a diagram illustrating an example of a screen that displays the measured waveform. FIG. 8 is a diagram illustrating an example of a screen that displays a waveform after performing noise processing and the like. FIG. 9 is a diagram illustrating an example of a screen that displays a result of statistical processing. FIG. 10 is a diagram showing an example of comparison of measurement results between the present invention and an indoor triaxial compression test.

  The impact process between the rigid body 1 and the ground material 3 begins to receive upward resistance from the moment when the rigid body 1 and the ground material 3 come into contact with each other, until the rigid body 1 and the ground material 3 are separated. Directional resistance continues. Since the direction of the external force coincides with the direction of the measured acceleration, the time until the sign of the acceleration changes is the contact time 35 as shown in FIG.

  In this embodiment, as shown in FIG. 7, when the rigid body 1 is dropped at the original position of the ground material 3, the control unit 21 of the computer 5 displays the acceleration waveform measured by the acceleration sensor 7 as the display unit of the computer 5. 26. Then, as illustrated in FIG. 8, when the control unit 21 of the computer 5 performs noise processing or the like, the control unit 21 displays the waveform after the noise processing or the like on the display unit 26 of the computer 5. As shown in FIG. 8, the control unit 21 of the computer 5 calculates an internal friction angle, an influence range, and the like and displays them on the display unit 26 of the computer 5. When the scheduled number of measurements is completed, the control unit 21 of the computer 5 performs statistical processing. For example, as shown in FIG. 9, the measurement result and calculation result of each time and the result of statistical processing are displayed on the display unit 26 of the computer 5. To display. Thus, in addition to the ease of measurement work, in this embodiment, the measurement result can be confirmed in real time at the original position.

  In order to verify the measurement accuracy by the strength characteristic measurement method according to the embodiment of the present invention, the inventors measured the strength characteristic measurement according to the embodiment of the present invention at the original position on the same ground material 3. The measurement by the method and the measurement by the indoor triaxial compression test (consolidation undrained condition) were performed. FIG. 10 is a comparison of both measurement results.

  As shown in FIG. 10, the measurement result of the internal friction angle φ by the indoor triaxial compression test for the slag 1 and the slag 2 is 27.4 to 33.4. On the other hand, the measurement result of the internal friction angle φ by the strength characteristic measurement method according to the embodiment of the present invention is 27.1 for slag 1 and 31.8 for slag 2. That is, it can be seen that the measurement results of the slag 1 and the slag 2 are substantially the same. In addition, the measurement result of the internal friction angle φ by the indoor triaxial compression test for fine-grained pebbles is 38.0. On the other hand, the measurement result of the internal friction angle φ by the strength characteristic measurement method according to the embodiment of the present invention is 37.6. That is, it can be seen that the measurement results of both particles are almost the same for the fine-grained gravel. Thus, it can be seen that the strength characteristic measuring method according to the embodiment of the present invention can not only work efficiently at the original position but also accurately measure the strength characteristics of various ground materials 3.

  In general, when the contact surface is spherical, the boundary conditions are complicated compared to the measurement method using a flat plate loading device, and theoretical analysis for evaluating stress distribution and the like becomes difficult. However, in the strength characteristic measurement method according to the embodiment of the present invention, a theoretical formula is derived from Hertz's impact theory and Vesic's cavity expansion theory, and the derived theoretical formula is modified to a theoretical formula suitable for this method. As a result, a highly accurate measurement result could be obtained.

  The embodiments of the present invention have been described in detail above with reference to the drawings. Since the shape of the conventional drop-type device is a disk shape, a slider is required to drop the fallen object horizontally with the target ground material 3, and it is common to install a plate on the ground surface. . Moreover, since the conventional fallen object is a surface contact, the loading area is large, and the impact force which destroys the ground material cannot be loaded.

  On the other hand, in the strength characteristic measuring method according to the embodiment of the present invention, since the contact surface between the rigid body 1 and the ground material 3 is spherical, a device such as a slider or a plate is unnecessary, and the measuring operation is easily performed. be able to. Further, in the strength characteristic measuring method according to the embodiment of the present invention, since the contact is point contact, the contact area is small, and local fracture of the ground material 3 can be caused relatively easily by stress concentration. Furthermore, since the contact area becomes smaller as the ground material 3 becomes harder, a larger impact force can be loaded on the hard ground material 3.

  The preferred embodiments of the strength characteristic measuring method and the like according to the present invention have been described above, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. Understood.

The figure which shows the outline | summary of the apparatus used for an intensity | strength characteristic measuring method The figure which shows the inside of the rigid body 1 and the handle 11 Hardware configuration diagram of computer 5 Diagram explaining cavity expansion theory Diagram showing the distribution of impact stress Flow chart showing the flow of strength characteristic measurement method The figure which shows the example of the screen which displays the measured waveform The figure which shows the example of the screen which displays the waveform after performing noise processing etc. The figure which shows the example of the screen which displays the result of statistical processing The figure which shows an example of the comparison of the measurement result of this invention and an indoor triaxial compression test Diagram explaining the in-situ shear test method The figure explaining the estimation method of adhesive force c and internal friction angle (phi)

Explanation of symbols

1 ... Rigid body 3 ... Ground material 5 ... Computer 7 ... Accelerometer 11 ... Handle 13 ... Cable 15 ... Power supply 17 ... A / D board 21 ......... Control unit 22 ......... Storage unit 23 ......... Media input / output unit 24 ......... Communication control unit 25 ......... Input unit 26 ......... Display unit 27 ......... Peripheral device I / F unit 28 ......... Bus 29 ……… Network 31 ……… Plastic region 33 ……… Contact surface 35 ……… Contact time

Claims (5)

A strength property measurement method for measuring the strength property of a ground material at an original position,
A measurement step for measuring an impact process by dropping a rigid body to which an acceleration sensor is attached from a certain height;
The contact time between the rigid body and the ground material is calculated based on the measured impact process, and the contact time, the mass of the rigid body, the distance from the center of the rigid body to the outer periphery, the height, the rigidity Calculating the deformation characteristics of the ground material from a first theoretical formula based on Hertz's impact theory, showing the relationship between the body and the deformation characteristics of the ground material;
Based on the measured impact process and the calculated deformation characteristics of the ground material, the deformation characteristics of the ground material, the distance from the center point of the rigid body to the outer periphery, the maximum of the ground material from the center point of the rigid body Using the distance from the straight line drawn to the settlement point to the point where the compressive stress of the contact surface between the rigid body and the ground material becomes zero, the impact force is not converted to the inertial force and contributes to the deformation of the ground material. Calculate the average compressive stress by dividing the force by the area of the contact surface,
Average compressive stress of the contact surface, the distance from the center point of the rigid body at the time of dropping to the boundary of the plastic region of the ground material, the distance from the center point of the rigid body to the outer periphery, the strength characteristics of the ground material, By solving the second theoretical formula based on Vesic's cavity expansion theory showing the relationship of the density of the ground material, using the calculated average compressive stress as the average compressive stress of the contact surface , Calculating an intensity characteristic;
A strength characteristic measuring method comprising: The intensity characteristic measuring method according to claim 1 , further comprising calculating the average of the intensity characteristics by statistical processing using a harmonic averaging method by repeating the measurement step a plurality of times. A strength characteristic measuring device that measures the strength characteristics of a ground material in its original position,
Means for inputting measurement data obtained by dropping a rigid body to which an acceleration sensor is attached from a certain height and measuring an impact process;
Calculate the contact time between the rigid body and the ground material based on the input measurement data, the contact time, the mass of the rigid body, the distance from the center of the rigid body to the outer periphery, the height, Means for calculating the deformation characteristics of the ground material from a first theoretical formula based on Hertz's impact theory, showing the relationship between the rigid body and the deformation characteristics of the ground material;
Based on the measured impact process and the calculated deformation characteristics of the ground material, the deformation characteristics of the ground material, the distance from the center point of the rigid body to the outer periphery, the maximum of the ground material from the center point of the rigid body Using the distance from the straight line drawn to the settlement point to the point where the compressive stress of the contact surface between the rigid body and the ground material becomes zero, the impact force is not converted to the inertial force and contributes to the deformation of the ground material. Calculate the average compressive stress by dividing the force by the area of the contact surface,
Average compressive stress of the contact surface, the distance from the center point of the rigid body at the time of dropping to the boundary of the plastic region of the ground material, the distance from the center point of the rigid body to the outer periphery, the strength characteristics of the ground material, By solving the second theoretical formula based on Vesic's cavity expansion theory showing the relationship of the density of the ground material, using the calculated average compressive stress as the average compressive stress of the contact surface , Means for calculating strength characteristics;
An intensity characteristic measuring device comprising: 4. The intensity characteristic measuring apparatus according to claim 3 , further comprising means for calculating an average of the intensity characteristics by statistical processing using a harmonic average method with a plurality of the measurement data as inputs. The program which functions a computer as an intensity | strength characteristic measuring apparatus in any one of Claim 3 or Claim 4 .

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