JP2018188887A - Estimation method of liquefaction strength ratio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of estimating a liquefaction strength ratio with high accuracy while being a relatively simple method.SOLUTION: An estimation method comprises: a first step of obtaining infinitesimal deformation characteristic values (Vor G) of an original ground; a second step of obtaining infinitesimal deformation characteristic values (Vor G) and a liquefaction strength ratio (R) of a test sample having similar density to the original ground; and a third step of estimating a liquefaction strength ratio (R) of the original ground on the basis of the infinitesimal deformation characteristic values (Vor G) of the original ground, the infinitesimal deformation characteristic values (Vor G) of the test sample and the liquefaction strength ratio (R) of the test sample.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a technique for estimating a ground liquefaction strength ratio.

  As shown in the following Patent Document 1, a method for estimating the liquefaction strength ratio of the ground based on an in-situ test result (for example, an N value based on a standard penetration test) has been proposed. This method is usually called a simplified method. Although this simple method is easy to implement, it tends to be evaluated relatively safely. That is, even if the ground is difficult to liquefy, the liquefaction strength ratio tends to be estimated to be low. Then, for example, it leads to excessive design of the building, and there is a problem that the construction cost increases.

  On the other hand, a method (so-called detailed method) for estimating the liquefaction strength ratio by an indoor test using an undisturbed sample collected from the raw ground has been proposed. The estimation accuracy with this method depends on the quality of the undisturbed sample. In general, it is difficult and expensive to obtain a high quality undisturbed sample and perform the test in that state. Further, Non-Patent Document 2 shows a problem that high estimation accuracy cannot be expected in a test using a low-quality undisturbed sample.

  By the way, as general factors affecting the liquefaction strength ratio of sandy ground in a predetermined stress state, (1) density, (2) soil particle structure, (3) time (age) effect, (4 ) Stress history due to past earthquakes and environmental changes can be considered (Non-Patent Document 1 below). Here, it is considered that the effects of (3) and (4) are included in the influence of (2) soil particle structure. (3) includes a cementation effect, but it is considered that this does not need to be taken into account for ground that is subject to liquefaction estimation, such as landfills and young sediments. Non-patent documents 3 and 4 also introduce conventional liquefaction strength ratio estimation methods.

Based on the above background, the present inventors have developed a highly accurate liquefaction prediction method for the purpose of small deformation characteristics (shear wave velocity V _S and minute shear modulus G) and the liquefaction intensity ratio R _L The relationship has been examined (Non-Patent Document 5). Further, on the liquefaction intensity ratio (2) In order to evaluate only the effect of soil particle structure, to create a specimen having a different V _S under the condition that the density constant, has conducted a series of liquefaction test (non Patent Document 6). The following non-patent documents 7 to 10 show past studies in this field.

JP-A-5-93416

Seed, Jour. Geotech. & Geoenv. Eng. 105. ASCE 14380, 1979. Yoshimi, Earth and Foundation, 42 (4), 1994. Andrus & Stokoe, Jour. Geotech. & Geoenv. Eng. 126.11, 2000. Japan Road Association Road Bridge Specification and Explanation, 2012. Kiyota et al., S & F, 49 (2), 2009. Wu et al., JSCE Proceedings A1, 72 (4), 2016. Tokimatsu et al., S & F, 26 (1), 1986. Finn et al., Jour. Soil Mech. Div 96.SM6, 1970. Kiyota et al., S & F, 56 (4), 2016. Chiaro et al., JGS Special Publication, 2 (32), 2015.

The present inventor has conducted various tests in view of the above circumstances, the ratio of liquefaction strength ratio R _L ^* of liquefaction intensity ratio R _L and the test sample of original ground, small deformation characteristic value of the original ground It has been found that there is a high correlation between the ratio of (shear wave velocity V _S or shear rigidity G) and the small deformation characteristic value (shear wave velocity V _S ^* or shear rigidity G ^* ) of the test sample. . And it discovered that the liquefaction strength ratio of the original ground could be estimated with high accuracy using this relationship.

  The present invention has been made based on the above findings. The main object of the present invention is to provide a technique capable of estimating the liquefaction strength ratio with high accuracy while being a relatively simple method.

  Means for solving the above-described problems can be described as follows.

(Item 1)
A first step of acquiring a micro deformation characteristic value (V _S or G) of the original ground;
A second step of obtaining a microdeformation characteristic value (V _S ^* or G ^* ) and a liquefaction strength ratio (R _L ^* ) for a test sample having a density equivalent to that of the original ground;
The liquefaction strength ratio (R _L ) of the original ground, the microdeformation characteristic value (V _S or G) of the original ground, the micro deformation characteristic value (V _S ^* or G ^* ) of the test sample, and the test sample A liquefaction strength ratio estimation method comprising: a third step of estimating from a liquefaction strength ratio ( _RL ^* ) of

  Here, there is no restriction | limiting in particular in the order of a 1st step and a 2nd step, which may be implemented first.

(Item 2)
The estimation method according to Item 1, wherein the minute deformation characteristic value is a shear wave velocity (V _S ).

(Item 3)
The estimation method according to Item 1, wherein the minute deformation characteristic value is a shear rigidity (G).

(Item 4)
The estimation method according to any one of Items 1 to 3, wherein the test sample is a reconstructed sample or an undisturbed sample collected from a raw ground.

(Item 5)
The estimation method according to any one of Items 1 to 4, wherein the third step is executed when the undisturbed sample obtained from the raw ground is evaluated and it is determined that the quality of the undisturbed sample is insufficient.

(Item 6)
A first step of acquiring a micro deformation characteristic value (V _S or G) and a liquefaction strength ratio (R _L ) of the original ground;
A second step of obtaining a microdeformation characteristic value (V _S ^* or G ^* ) and a liquefaction strength ratio (R _L ^* ) for a test sample having a density equivalent to that of the original ground;
The ratio of the microdeformation characteristic value (V _S or G) of the original ground to the microdeformation characteristic value (V _S ^* or G ^* ) of the test sample, the liquefaction strength ratio (R _L ) of the original ground, and the And a third step of acquiring a relationship with the ratio of the liquefaction strength ratio (R _L ^* ) of the test sample.

(Item 7)
A computer program for causing a computer to execute each step according to any one of items 1 to 6.

  This computer program is stored in an appropriate recording medium (for example, an optical recording medium such as a CD-ROM or a DVD disk, a magnetic recording medium such as a hard disk or a flexible disk, or a magneto-optical recording medium such as an MO disk). Can be stored. This computer program can be transmitted via a communication line such as the Internet.

(Item 8)
The ratio between the microdeformation characteristic value (V _S or G) of the original ground and the microdeformation characteristic value (V _S ^* or G ^* ) of the test sample, the liquefaction strength ratio (R _L ) of the original ground, and the test sample Data representing the relationship with the ratio of the liquefaction strength ratio (R _L ^* ) of
Here, the test sample has a density equivalent to the original ground,
The liquefaction strength ratio (R _L ) of the original ground, the microdeformation characteristic value (V _S or G) of the original ground, the micro deformation characteristic value (V _S ^* or G ^* ) of the test sample, and the test sample Data used for processing estimated from the liquefaction strength ratio (R _L ^* ).

  This data is stored in an appropriate recording medium (for example, an optical recording medium such as a CD-ROM or a DVD disk, a magnetic recording medium such as a hard disk or a flexible disk, or a magneto-optical recording medium such as an MO disk). can do. This data can be transmitted via a communication line such as the Internet.

(Item 9)
A first measurement unit that measures a minute deformation characteristic value (V _S ^* or G ^* ) of a test sample having a density equivalent to that of the original ground;
A second measuring unit for measuring a liquefaction strength ratio (R _L ^* ) for the test sample;
The liquefaction strength ratio (R _L ) of the original ground, the minute deformation characteristic value (V _S or G) of the original ground, the minute deformation characteristic value (V _S ^* or G ^* ) of the test sample, and the test sample A liquefaction strength ratio estimation device comprising: an estimation unit that estimates from a liquefaction strength ratio (R _L ^* ).

  According to the present invention, it is possible to provide a technique capable of estimating the liquefaction strength ratio with high accuracy while being a relatively simple technique.

It is a graph which shows the relationship between the relative density (horizontal axis) of a sample, and a liquefaction intensity ratio (vertical axis). It is a graph which shows the relationship between the shear wave velocity (horizontal axis) of a sample, and liquefaction intensity ratio (vertical axis). Relationship between the ratio (horizontal axis) of shear wave velocities V _S and V _S ^{* of} test samples having the same density and different soil particle structures and the ratio (vertical axis) of liquefaction strength ratios R _L and R _L ^* It is a graph which shows. It is a flowchart which shows the outline of the estimation method which concerns on one Embodiment of this invention. It is a flowchart for demonstrating in detail some procedures in FIG. It is a flowchart for demonstrating in detail some procedures in FIG. It is a block diagram which shows an example of the estimation apparatus for enforcing the method of FIG.

A method for estimating a liquefaction strength ratio according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the present specification, the liquefaction strength ratio includes various parameters (for example, parameters that can be calculated linearly) that can be uniquely derived from the liquefaction strength ratio. Therefore, it is expressed as a liquefaction strength ratio. In the following description, an example is shown in which the shear wave velocity V _S is used as the minute deformation characteristic value. However, various parameters that can be uniquely derived from the shear wave velocity V _S can be substituted for this. Is available.

(Premise of this embodiment)
First, the knowledge of the present inventor will be described in detail as a premise for describing the present embodiment. In order to evaluate the influence of the soil particle structure on the liquefaction strength ratio, the present inventor created specimens (that is, test samples) having different shear wave velocities V _S under the condition of constant density, and the following liquids The test was conducted (see Non-Patent Document 6 described above).
・ Testing machine: Triaxial testing machine;
・ Experiment sample: Toyoura sand;
Relative density Dr: 3 series of 50%, 65%, 75%.

In this experiment, the density was adjusted by the air drop method, and after saturation / consolidation (σ _C ′ = 100 kPa), in each series, stress history due to repeated loading of undrained / undrained was given to the specimen, and the soil particle structure was changed. I tried to do that. This technique follows Non-Patent Documents 7 and 8. Is appropriately changed cyclic loading number, the shear wave velocity V _S of the specimen was adjusted to different values. However, the density of the specimen after the stress history was set to be the target density of each series. Therefore, the difference in the shear wave velocity V _S in the condition that the density constant can be interpreted as corresponding to the difference in soil particle structure. Thereafter, a liquefaction test was carried out under the condition of repeated shear stress ratio constant. For this experimental technique, see Non-Patent Document 6 described above.

(Experimental result)
FIG. 1 shows the relationship between the liquefaction strength ratio R _L defined by both amplitude axis strains ε _V (DA) = 5% and 20 repetitions and the relative density of the specimen. FIG. 2 shows the relationship between the liquefaction strength ratio _RL and the Vs of the specimen measured before the liquefaction test. In these drawings, “cycle” indicates the number of repetitions during the repeated drainage loading history, and “Reliq” indicates a specimen having a non-drained repeated loading history (so-called liquefaction history).

In FIG. 1, liquefaction strength ratios _{RL that} are two or more times different are obtained for the same sample (Toyoura sand) and with an equivalent relative density Dr depending on the difference in soil particle structure. Many similar reports have been made so far (Non-Patent Documents 7 and 8 described above). Further, from FIG. 2, a good correlation was confirmed between the shear wave velocity V _S and the liquefaction strength ratio R _L , but it can be confirmed that the relationship varies greatly depending on the relative density Dr. According to these results, only using only relative density Dr only or shear wave velocity V _S it can be seen that it is difficult to estimate the liquefaction strength.

On the other hand, FIG. 3 shows the relationship between the ratio of the shear wave velocities V _S and V _S ^* and the ratio of the liquefaction strength ratios _RL and _RL ^{* of} samples having different soil particle structures in each density series. Here, as V _S ^* and R _L ^* , values of specimens having no stress history are set in each density series. From FIG. 3, a good correlation was observed between V _S / V _S ^* and R _L / R _L ^* regardless of the relative density Dr. The figure also shows the results of various ground samples including undisturbed samples that were frozen and collected. By fitting with an exponential function, a high correlation of R ² = 0.9 or more was obtained. Note that the relationship shown in FIG. 3 is established regardless of the density and restraint pressure if the density of the original ground and the test sample are equal.

From the above results, it can be seen that once the relationship as shown in FIG. 3 is obtained, the liquefaction strength ratio _RL of the original ground can be estimated with high accuracy from the other three parameters.

(Method of this embodiment)
Based on the above description, the method for estimating the liquefaction strength ratio according to the present embodiment will be described with further reference to FIGS.

(Step SA-1 in FIG. 4)
First, as shown in FIG. 3, the relationship between R _L / R _L ^* and V _S / V _S ^* is acquired. Details of this procedure will be described with further reference to FIG.

(Step SB-1 in FIG. 5)
First, a plurality of pairs of V _S , V _S ^* , R _L , and R _L ^* at the same density are acquired. Here, the same density means that the density is the same in one set. Thus, the density may be different between different sets. Further, the same density may be the same density as long as there is no practical problem, and what density is the same can be determined experimentally or empirically. Acquisition of a set of V _S , V _S ^* , R _L , and R _L ^* at the same density may be obtained by acquiring data from the actual ground and a test sample, for example, or shown in previous studies. It may be obtained by collecting these data. The example of FIG. 3 includes both data. Note that various existing methods can be used as an acquisition method for acquiring these data, and thus detailed description thereof will be omitted.

(Steps SB-2 to SB-3 in FIG. 5)
Next, R _L / R _L ^* and V _S / V _S ^* are calculated using the obtained data sets (V _S , V _S ^* , R _L , R _L ^* ) for each density. This process is performed for each group. The relationship between the calculation results can be approximated using, for example, the least square method.

In the present embodiment, the relationship between the liquefaction strength ratio R _L and (V _S , V _S ^* , R _L ^* ) is fitted to an appropriate curve (an exponential function or a polynomial function) to obtain a relationship between them. Can be obtained. For example, when fitting to an exponential function,
R _L = R _L ^* × (V _S / V _S ^* ) ^ b (1)
It can be expressed as. Here, b is a coefficient obtained by fitting, for example.

In addition, when fitting to a polynomial function, if R _L ^* × (V _S / V _S ^* ) is X,
R _L = a ₀ + a ₁ X + a ₂ X ² +,..., + _An X ⁿ (2)
A _i (where i = 0, 1,..., N) is a coefficient obtained by fitting, for example. The appropriate degree of the polynomial can be determined experimentally.

When the above relationship is generalized, the function F () for estimating the liquefaction strength ratio _RL can be expressed as follows.
R _L = F (V _S , V _S ^* , R _L ^* ) (3)

The steps so far can be said to be preparation steps for performing actual estimation. Therefore, in general, it is preferable to obtain a relational expression for calculating the liquefaction strength ratio _RL using the above-described procedure before actual estimation. However, the present invention is not limited to this, and a procedure for acquiring the above-described relational expression in parallel with actual estimation is possible.

(Step SA-2 in FIG. 4)
Next, a data set (V _S , V _S ^* , R _L ^* ) is acquired for the raw ground for which the liquefaction strength ratio R _L is to be estimated.

  Hereinafter, this step will be described in detail with further reference to FIG.

(Step SC-1 in FIG. 6)
First obtains the shear wave velocity V _S and the density of the original ground. These can be obtained by, for example, a boring survey on the original ground, but are not limited to this method. Further, if the density of the test sample to be described later is considered to be equivalent to the density of the original ground, it is not necessary to acquire the density of the original ground at this point.

(Steps SC-2 and SC-3 in FIG. 6)
Next, an undisturbed sample is collected from the ground. Thereafter, the quality of the sample is evaluated by a laboratory test. As a quality evaluation method, as shown in Non-Patent Document 10, there is a method of confirming the equivalence of the shear wave velocity V _S and the density of the original ground and collected samples. Moreover, when the undisturbed sample is not collected and the reconstructed sample is used, steps SC-2 and SC-3 can be omitted.

(Step SC-4 in FIG. 6)
If the quality of the sample is sufficient, the liquefaction strength ratio _RL can be estimated using the sample. In this case, the subsequent procedure can be omitted.

(Step SC-5 in FIG. 6)
If undisturbed samples are not collected in step SC-2, or if it is determined that the sample quality evaluation in step SC-3 is insufficient, reconstructed samples with the same density as the original ground will be used in laboratory tests. prepare. Alternatively, if the density of the undisturbed sample is equivalent to that of the original ground, the undisturbed sample can be used. In the following description, both are generically referred to as a sample. Here, it should be noted that no special consideration is required for the difference in soil particle structure between the sample and the ground.

(Step SC-6 in FIG. 6)
Next, the shear wave velocity V _S ^* of the sample is measured by a laboratory test. This measurement method is not particularly limited, and for example, various existing methods can be used.

(Step SC-7 in FIG. 6)
At the same time as or before or after Step SC-6, the liquefaction strength ratio R _L ^* of the sample is measured by a laboratory test. This measurement method is not particularly limited, and for example, various existing methods can be used.

(Step SC-8 in FIG. 6)
Next, the liquefaction strength ratio _RL of the original ground can be estimated using the obtained data set (V _S , V _S ^* , R _L ^* ), for example, using the relationship shown in FIG.

According to the present embodiment, the liquefaction strength ratio _RL of the original ground can be estimated using the relationship shown in FIG. 3 (for example, the above-described equation (1)). Since this relationship does not depend on the difference in the soil particle structure between the raw ground and the sample, the estimation method of this embodiment can obtain high estimation accuracy even when a high-quality undisturbed sample cannot be obtained. There is an advantage that can be.

  Moreover, the relationship as shown in FIG. 3 is established regardless of the density of the original ground and the restraint pressure (however, each plot point has the same density and restraint pressure). Therefore, since the relationship in FIG. 3 can be obtained in advance and estimation can be performed on various grounds using the relationship, there is an advantage that the cost in estimation work can be kept low.

  In addition, since high estimation accuracy can be obtained without using a high-quality undisturbed sample, according to the present embodiment, it is possible to reduce costs in this respect.

(Estimation device)
Hereinafter, an example of the estimation apparatus for performing the above-described procedure will be described with reference to FIG.

This estimation apparatus includes a first measurement unit 1 that measures a shear wave velocity V _S ^* for a test sample having a density equivalent to that of the original ground, and a second measurement that measures a liquefaction strength ratio R _L ^* for the test sample. The liquefaction strength ratio _RL of the part 2 and the original ground is estimated from the shear wave velocity V _S of the original ground, the shear wave velocity V _S ^* of the test sample, and the liquefaction strength ratio _RL ^* of the test sample. And an estimation unit 3. Furthermore, in this embodiment, the output part 4 which outputs an estimation result is additionally provided.

As the first measurement unit 1, a bender element, an accelerometer, or a disk transducer that can measure the shear wave velocity V _S (or shear rigidity due to repeated static loading) of a specimen under a predetermined restraining pressure can be used. . However, these are not limited as long as a desired function can be exhibited.

  As the 2nd measurement part 2, the various test apparatuses which can perform a liquefaction test, for example, a triaxial test apparatus or a torsional shear test apparatus, can be used. However, these are not limited as long as a desired function can be exhibited.

  The estimation unit 3 can be implemented by a computer that stores programs and data necessary for the estimation process or that can use them via a network. However, it is possible to make an estimation by an operator using the above-described relationship without using a computer.

  The output unit 4 is a functional element for displaying an estimation result to a target person or sending data to a related device. For example, a display, a printer, or various storage devices can be used as the output unit 4.

(data)
In the above-described embodiment, the data as shown in FIG. 3 indicates that “the liquefaction strength ratio (R _L ) of the original ground, the shear wave velocity V _S of the original ground, the shear wave velocity V _S ^{* of the} test sample, This corresponds to an example of “data used for processing estimated from the liquefaction strength ratio R _L ^* of the test sample”.

  The contents of the present invention are not limited to the above embodiments. In the present invention, various modifications can be made to the specific configuration within the scope of the claims.

For example, in the above-described embodiment, as small deformation characteristic value, was used the shear wave velocity V _S, instead of this, various parameters can now practically uniquely derived, is possible to use, for example, shear modulus G it can. When the shear rigidity G is used, the shear wave velocity V _S or V _S ^* may be read as the shear rigidity G or G ^{* in} the above description.

  A plurality of coefficients in the above-described formula (1) or (2) may be determined according to the type of ground. In this case, a coefficient to be used can be determined according to the type of raw ground, and the same estimation as described above can be performed using the coefficient.

  Furthermore, each component described above may exist as a functional block, and does not need to exist as independent hardware. As a mounting method, hardware or computer software may be used. Furthermore, one functional element in the present invention may be realized by a set of a plurality of functional elements, and a plurality of functional elements in the present invention may be realized by one functional element.

  Moreover, the functional element may be arrange | positioned in the position physically separated. In this case, the functional elements may be connected by a network. It is also possible to realize functions or configure functional elements by grid computing or cloud computing.

1 first measurement unit 2 second measurement unit 3 estimation unit 4 output unit G shear modulus R _L liquefaction intensity ratio V _S shear wave velocity

Claims (9)

A first step of acquiring a micro deformation characteristic value (V _S or G) of the original ground;
A second step of obtaining a microdeformation characteristic value (V _S ^* or G ^* ) and a liquefaction strength ratio (R _L ^* ) for a test sample having a density equivalent to that of the original ground;
The liquefaction strength ratio (R _L ) of the original ground, the microdeformation characteristic value (V _S or G) of the original ground, the micro deformation characteristic value (V _S ^* or G ^* ) of the test sample, and the test sample A liquefaction strength ratio estimation method comprising: a third step of estimating from a liquefaction strength ratio ( _RL ^* ) of The estimation method according to claim 1, wherein the minute deformation characteristic value is a shear wave velocity (V _S ).   The estimation method according to claim 1, wherein the minute deformation characteristic value is a shear rigidity modulus (G). The estimation method according to any one of claims 1 to 3, wherein the test sample is a reconstructed sample or an undisturbed sample collected from a raw ground. The estimation method according to any one of claims 1 to 4, wherein the third step is executed when the undisturbed sample acquired from the raw ground is evaluated and it is determined that the quality of the undisturbed sample is insufficient. . A first step of acquiring a micro deformation characteristic value (V _S or G) and a liquefaction strength ratio (R _L ) of the original ground;
A second step of obtaining a microdeformation characteristic value (V _S ^* or G ^* ) and a liquefaction strength ratio (R _L ^* ) for a test sample having a density equivalent to that of the original ground;
The ratio of the microdeformation characteristic value (V _S or G) of the original ground to the microdeformation characteristic value (V _S ^* or G ^* ) of the test sample, the liquefaction strength ratio (R _L ) of the original ground, and the And a third step of acquiring a relationship with the ratio of the liquefaction strength ratio (R _L ^* ) of the test sample.   The computer program for making a computer perform each step of any one of Claims 1-6. The ratio between the microdeformation characteristic value (V _S or G) of the original ground and the microdeformation characteristic value (V _S ^* or G ^* ) of the test sample, the liquefaction strength ratio (R _L ) of the original ground, and the test sample Data representing the relationship with the ratio of the liquefaction strength ratio (R _L ^* ) of
Here, the test sample has a density equivalent to the original ground,
The liquefaction strength ratio (R _L ) of the original ground, the microdeformation characteristic value (V _S or G) of the original ground, the micro deformation characteristic value (V _S ^* or G ^* ) of the test sample, and the test sample Data used for processing estimated from the liquefaction strength ratio (R _L ^* ). A first measurement unit that measures a minute deformation characteristic value (V _S ^* or G ^* ) of a test sample having a density equivalent to that of the original ground;
A second measuring unit for measuring a liquefaction strength ratio (R _L ^* ) for the test sample;
The liquefaction strength ratio (R _L ) of the original ground, the minute deformation characteristic value (V _S or G) of the original ground, the minute deformation characteristic value (V _S ^* or G ^* ) of the test sample, and the test sample A liquefaction strength ratio estimation device comprising: an estimation unit that estimates from a liquefaction strength ratio (R _L ^* ).