Liquefaction determination method of ground

Abstract

To provide a liquefaction determination method of the ground allowing liquefaction determination to be easily and quickly carried out.SOLUTION: A liquefaction determination method is to determine liquefaction through a method of liquefaction potential damage determination such as an architectural H1-Dcy method using an estimated N value and estimated fine-grained percentage content Fc, each of the N value and the Fc being estimated through power regression analysis with explanatory variable of energy E0.25SL required to penetrate a penetration rod with a screw point provided on a tip. With this, estimated values of the N value and the fine-grained percentage content Fc required to determine the liquefaction determination can be acquired without requiring sampling and an indoor soil test, and by using these estimated values, the liquefaction determination can be carried out through the architectural H1-Dcy method and the like. Furthermore, fitting of the N value and the Fc acquired on the basis of a result of a standard penetration test through the power regression analysis is improved to enhance reliability of each of estimated values.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for determining ground liquefaction using data obtained by a screwdriver sounding test. [Background technology]

[0002] The soil constants used to assess soil liquefaction are typically determined by standard penetration tests. However, for small buildings and sites such as detached houses, the time and expense required for such tests necessitates the development of simpler techniques and methods for assessing soil liquefaction. Following the 2011 Tohoku-Pacific Ocean earthquake, the Housing Quality Assurance Promotion Act established a system for providing liquefaction information to homebuyers and other parties, and this law specifies a liquefaction assessment method using the screw weight penetration test (hereinafter referred to as the SWS test) specified in the Japanese Industrial Standard JISA1221. However, assessing liquefaction using the SWS test requires collecting samples at multiple depths underground and conducting indoor soil testing (grain size testing). However, many challenges remain in terms of sample collection methodology and cost, making this method ineffective.

[0003] On the other hand, in recent years, the screwdriver sounding test (hereinafter referred to as the SDS test), which is an extension of the SWS test, has appeared and its demand is expanding. As shown in Patent Documents 1 to 3, in the SDS test, the load W applied to the penetration rod in increments of 0.25 m during the process of rotating and penetrating the penetration rod into the ground is changed to a maximum of seven levels (250 N, 375 N, 500 N, 625 N, 750 N, 875 N, 1 kN), and the rotational load torque T acting on the penetration rod (more precisely, the screw point attached to the tip of the penetration rod) under each load, the number of half rotations Δn of the penetration rod, and the like are measured. ht , penetration amount ΔS t The test data is obtained by taking into account the torque T and the number of half rotations Δn in relation to the fluctuating load W in increments of 0.25 m.ht and penetration amount ΔS t The test is carried out 10 to 20 meters underground while recording the load W, torque T, and half-rotation speed Δn ht , penetration amount ΔS t By analyzing and evaluating parameters based on the above, it is possible to distinguish soil types at each penetration depth.

[0004] Furthermore, Patent Document 3 shows that by defining multiple parameters using SDS test data and performing multiple regression analysis using these as explanatory variables, it is possible to obtain estimated values ​​for the N value and the fine particle content Fc of the soil, which are basic data for liquefaction assessment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4705520 [Patent Document 2] Patent No. 5291329 [Patent Document 3] Patent No. 6159090 Summary of the Invention [Problem to be solved by the invention]

[0006] The liquefaction assessment method based on the method shown in Patent Document 3 estimates the N value and fine particle content from data obtained in the SDS test, and therefore has the advantage that liquefaction assessment can be performed without the need for sample collection or laboratory soil testing, compared to standard penetration tests or SWS tests. However, since there are multiple parameters that serve as explanatory variables for multiple regression analysis, there is a possibility that the values ​​may fluctuate greatly depending on the test data, reducing the reliability of the estimated values. In particular, the energy E required for penetration of 0.25 m may vary depending on the test data. 0.25 There was also a tendency for the increase or decrease to become larger. [Means for solving the problem]

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a method for determining ground liquefaction that enables liquefaction to be determined simply and quickly.

[0008] To achieve the above objectives, the present invention estimates the N-value through power regression analysis, using the energy required to penetrate a penetration rod equipped with a screw point at its tip into the ground as an explanatory variable, and uses this estimated N-value as a constant for liquefaction assessment. This makes it possible to obtain the estimated N-value required for liquefaction assessment without the need for sample collection or indoor soil testing. Furthermore, power regression analysis strengthens the fitting (correlation) with the N-value obtained by standard penetration testing, increasing the reliability of the estimated N-value.

[0009] To achieve the above objective, the present invention estimates the fines content Fc by power regression analysis, using the energy required to penetrate a screw-pointed penetration rod into the ground as an explanatory variable, and uses this estimated Fc as a constant for liquefaction assessment. This makes it possible to obtain the estimated fines content Fc required for liquefaction assessment without the need for sample collection or laboratory soil testing. Furthermore, power regression analysis strengthens the fit with Fc obtained based on the results of standard penetration tests, increasing the reliability of the estimated Fc.

[0010] Furthermore, to achieve the above-mentioned objectives, the present invention is characterized by estimating the N-value and fines content Fc through power regression analysis, using the energy required to penetrate a screw-pointed penetration rod into the ground as an explanatory variable, and then using these estimated N-values ​​and Fc to assess liquefaction using the Building H1-Dcy method. This allows for the estimation of the N-value and fines content Fc required for liquefaction assessment without the need for sample collection or indoor soil testing, and these can be used to assess liquefaction using the Building H1-Dcy method. Furthermore, power regression analysis strengthens the fit with the N-value and Fc obtained based on the results of standard penetration tests, increasing the reliability of each estimated value.

[0011] In estimating the N value, the energy required to penetrate the penetration rod into the ground is the energy E required to penetrate the screw point into the ground every 0.25 m. 0.25SL The following power regression equation with N SDS =3.01×E 0.25SL 0.65 Therefore, the estimated value of N is SDS It is preferable to calculate the estimated value of N by this regression equation. SDS This provides a good fit with the N-value obtained based on the results of the standard penetration test.

[0012] In addition, in estimating the fine particle content Fc, the following power regression equation is used, in which the ratio of the rotational energy ET of the penetration rod when rotating and penetrating the ground to the penetration energy EW due to the load is used as an explanatory variable. Fc SDS =86.13×(ET / EW) -0.60 Therefore, the estimated fine particle content Fc is SDS It is desirable to calculate the estimated fine particle content Fc using this regression equation. SDS This provides a good fit with the fine particle content Fc obtained based on the results of the standard penetration test.

[0013] Furthermore, when determining liquefaction using the above-mentioned Building H1-Dcy method, the energy required to penetrate the penetration rod into the ground is calculated as the energy E required to penetrate the screw point into the ground every 0.25 m. 0.25SL The following power regression equation with N SDS =3.01×E 0.25SL 0.65 Therefore, the estimated value of N is SDS The following power regression equation is used as an explanatory variable: the ratio of the rotational energy ET of the penetration rod when it is rotated and penetrated into the ground to the penetration energy EW due to the load. Fc SDS =86.13×(ET / EW) -0.60 Therefore, the estimated fine particle content Fc is SDS It is desirable to obtain the estimated N value, N SDS and the estimated fine particle content Fc SDS This provides a good fit with the N value and fine particle content Fc obtained based on the results of the standard penetration test.

[0014] The energy E required to penetrate the screw point into the ground every 0.25 m 0.25SL It is desirable to set the value obtained by proportionally converting the multiple energies obtained in each 0.25 m penetration section for each penetration section. 0.25 This has a better correlation with the N value than using [Effects of the Invention]

[0015] According to the present invention, the N value and fines content Fc can be estimated from the data obtained by the SDS test, which has the advantage of enabling simple and rapid liquefaction assessment without the need for sample collection or laboratory soil testing, compared to standard penetration tests and SWS tests. In addition, the explanatory variables used in estimating the N value and Fc are simplified, which has the advantage of being less susceptible to fluctuations in test data than conventional methods that use multiple parameters as explanatory variables. Furthermore, by using power regression to obtain estimated values ​​of the N value and Fc, the fitting with the N value and fines content Fc obtained by the standard penetration test can be strengthened, thereby increasing the reliability of liquefaction assessment results based on each estimated value. Furthermore, the energy E proportionally converted for each 0.25 m section of the penetration length of the penetration rod can be calculated. 0.25SL By using as an explanatory variable, E, which attempts to average the energy in a 0.25 m penetration section by data regression, as shown in Patent Document 3, 0.25 This has the advantage of providing a better correlation with the N value than using the conventional method, and increasing the reliability of liquefaction assessment results. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a perspective view of an automatic penetration testing machine for carrying out SDS test data. [Figure 2] FIG. 10 is an explanatory diagram showing a graph of a method for calculating E0.25SL. [Figure 3] This is an explanatory graph showing the relationship between the N value obtained by the standard penetration test and E0.25SL. [Figure 4] This is an explanatory graph showing the relationship between the N-value obtained by the standard penetration test and the estimated N-value obtained by existing technology using E0.25. [Figure 5] FIG. 10 is an explanatory graph showing the results of power regression analysis relating to the estimation of the N value. [Figure 6] This is an explanatory graph showing the relationship between the N value obtained by the standard penetration test and the estimated N value NSDS based on the SDS test results. [Figure 7] FIG. 1 is an explanatory graph showing the results of power regression analysis relating to the estimation of the fine particle content Fc. [Figure 8] This is an explanatory graph showing the relationship between the fine particle content Fc obtained from the results of the standard penetration test and the estimated value FcSDS based on the SDS test results. [Figure 9] FIG. 10 is an explanatory diagram showing a comparison of FL values. [Figure 10] FIG. 10 is an explanatory diagram showing a comparison of dcy values. [Figure 11] FIG. 1 is an explanatory diagram showing the relationship between the results of boring surveys and the Dcy values ​​obtained from SDS test results. [Figure 12] This is a judgment diagram using the architectural H1-Dcy method based on the results of drilling surveys and SDS tests. [Figure 13] This is an explanatory diagram showing the correlation between the results of drilling surveys and SDS test results based on the judgment made by the architectural H1-Dcy method. [Figure 14] This is a depth distribution map of the test site (Inzai City, Chiba Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 15] This is a depth distribution map of the test site (Urayasu City, Chiba Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 16]This is a depth distribution map of the test site (Katsushika Ward, Tokyo) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 17] This is a depth distribution map of the test site (Kumamoto City, Kumamoto Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 18] This is a depth distribution map of the test site (Ichihara City, Chiba Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 19] This is a depth distribution map of the test site (Moriyama City, Shiga Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 20] This is a depth distribution map of the test site (Niigata City, Niigata Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 21] This is a depth distribution map of the test site (Sakaiminato City, Tottori Prefecture) used to examine the validity of liquefaction assessment based on SDS test results. [Figure 22] This is a depth distribution map and liquefaction risk assessment map for the test site (Urayasu City, Chiba Prefecture). [Figure 23] This is a depth distribution map and liquefaction risk assessment map for the test site (Sakaiminato City, Tottori Prefecture) for liquefaction assessment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (Summary of the liquefaction assessment method according to the present invention) The following describes an embodiment of the method for determining ground liquefaction according to the present invention. The method for determining ground liquefaction according to the present invention complies with the architectural H1-Dcy method (hereinafter simply referred to as the H1-Dcy method), which is a method based on the relationship between the amount of ground surface displacement (Dcy value) and the non-liquefaction layer thickness (H1 value) set forth in the "Technical Guidelines for Determining the Possibility of Liquefaction Damage to Residential Land" of the Ministry of Land, Infrastructure, Transport and Tourism.

[0018] First, the soil quality targeted for liquefaction assessment in this invention is soil that is determined to be sandy soil by the SDS test. In this case, the soil fine particle content (Fc) is approximately 50% or less, which is considered to be a condition that includes the target ground in the H1-Dcy method.

[0019] Next, the N value of the ground used to calculate the safety factor against liquefaction (FL value) is the estimated N value based on the SDS test results: N SDS This N SDS is the energy required to penetrate the screw point 0.25 m: E 0.25SL This is calculated based on E 0.25SL In the Better Living Foundation's Examination Certification-011 (December 2013), it was confirmed that there is a high correlation between the N value and the "energy required to penetrate the screw point 0.25m: E 0.25 " is an energy value that has been reorganized for the ground used in the liquefaction study to improve the estimation accuracy. 0.25SL and E 0.25 The difference between these two will be explained later. In addition, the fine particle content Fc is estimated by the correlation equation established by the parameter ET / EW related to the internal friction angle of the soil obtained from the SDS test results. SDS is used.

[0020] For the target soil set as above, the estimated N value N SDS and estimated Fc SDS The Dcy value is calculated based on the above, and liquefaction assessment is performed using the H1-Dcy method.

[0021] (SDS test) The SDS test is performed using an automatic penetration testing machine shown in Figure 1. This automatic penetration testing machine 1 holds a penetration rod 3, which has a screw point 2 attached to its tip, in a chuck unit 5 of a lifting platform 4, and acquires various test data as the penetration rod 3 penetrates the ground. The chuck unit 5 is configured to be rotated by a rotation motor 6, and the lifting platform 4 is configured to be able to rise and fall along a support 8 by driving a lifting motor 7. When the penetration rod 3 penetrates the ground, the load applied to the penetration rod 3 can be changed by adjusting the load due to the mass of the lifting platform 4 (see Patent Documents 1 to 3, etc., mentioned above, for details).

[0022] The SDS test is performed by rotating and penetrating a penetration rod 3 into the ground using an automatic penetration testing machine 1, and during this process, the load W applied to the penetration rod 3 is changed to a maximum of seven levels (250N, 375N, 500N, 625N, 750N, 875N, 1kN) for each penetration distance of 0.25m, and test data is measured under each load. The measured test data includes the rotational load torque T (hereinafter simply referred to as torque T) acting on the screw point 2 under each load, the penetration distance ΔS of the screw point 2, and the load W applied to the penetration rod 3. t , the number of half rotations of the penetration rod 3 Δn ht (number of rotations, counting one rotation of the penetration rod 3 as 2) and elapsed time t. In this way, test data is measured every 0.25 m, and the test is carried out to 10 to 20 m underground. The test data obtained from this SDS test (load W, torque T, penetration amount ΔS t , half rotation speed Δn ht , elapsed time t), parameters are calculated using a plasticity analogy model, and analysis is performed. Analysis based on this SDS test data is described in detail in Patent Publication No. 4705520, Patent Publication No. 5291329, Patent Publication No. 5320081, etc.

[0023] (Method of determining liquefaction using SDS test results) The method for determining ground liquefaction according to the present invention is based on the "Guidelines for Design of Building Foundation Structures" by the Architectural Institute of Japan, a general incorporated association, and the N value and fine particle content Fc of the ground are examined using estimated values ​​calculated from the results of SDS tests.

[0024] Since the reliability of the SDS test in the depth direction is about 10 m underground, the liquefaction consideration depth of the liquefaction assessment method of this invention is set to about GL-10 m. In addition, since the SDS test is a test in which the load change step is repeated with 0.25 m of screw point penetration as one cycle, the liquefaction consideration interval is every 0.25 m. The constants used in the liquefaction study are as follows:

[0025] (1) Unit volume weight of soil The unit weight of soil was 18 (kN / m 3 ), and 16 (kN / m 3 However, if there is indoor soil test data from a standard penetration test (boring survey) nearby, the analyst may set an appropriate value.

[0026] (2) Groundwater level When assessing liquefaction using the SDS test, the groundwater level is measured on-site, and this measured water level is used as the calculated value. Groundwater level measurements are carried out by measuring the water level in an SDS test hole, i.e., a hole created by inserting a penetration rod during the SDS test. However, when considering seasonal fluctuations in the groundwater level, etc., the water level can be set appropriately by clarifying the criteria for assessment.

[0027] (3)N SDS Calculation of The estimated N value from the SDS test results SDS To do this, first calculate the energy E required to penetrate the screw point 0.25 m for each 0.25 m of penetration. 0.25SL The penetration energy under each load is expressed by the following equation 1.

[0028]

number

[0029] In the above formula 1, ΔE: Penetration energy at each load stage T: Torque at each load stage Δn ht : Half rotation W: Load ΔS t : Penetration amount The torque T and load W are corrected values ​​taking into account the soil resistance component acting on the penetration rod as shown in Japanese Patent No. 5320081.

[0030] Energy E required to penetrate the screw point 0.25 m 0.25SL As shown in Figure 2, the cumulative penetration energy ΣΔE up to the final load of the penetration section 0.25m is simply converted proportionally to the energy per 0.25m of penetration. The energy E required to penetrate a conventional screw point 0.25m is 0.25 is an attempt to average the energy in a 0.25 m penetration section by data regression, as shown in the above-mentioned Patent Document 3, but has the drawback that the value fluctuates greatly depending on the SDS test data. 0.25SL The calculation method is simple, and E 0.25 Although the energy is not averaged as in the case of E, as shown in Figures 3 and 4, the correlation with the N value obtained by the standard penetration test is 0.25 than the estimated N value obtained using E 0.25SL The results showed that E 0.25SL The effectiveness of estimating the N value using this method is recognized. Bor and E 0.25SL Figure 4 shows the relationship between N Bor and E 0.25 The relationship between the estimated N value obtained by existing technology using

[0031] The estimated value N of the N value in the present invention SDS E 0.25SL is calculated by power regression with E as an explanatory variable. 0.25SL by N SDS The power regression results of the following equation 2 are shown in Figures 5 and 6. The N value obtained by the standard penetration test: N Bor and SDS test parameter E 0.25SL There is a correlation as shown in Figure 5, and the correlation is enhanced by fitting by changing the regression from a straight line to a power regression of a convex curve. Note that data where N=0 cannot be regressed, so it is deleted for convenience.

[0032]

number

[0033] In addition, Figure 6 shows the N SDS and the N value obtained by the standard penetration test: N Bor The figure shows the correlation between the two, and the results show that the correlation is generally good.

[0034] (4) Fc SDS Calculation of (estimation of Fc) Only soils determined to be "sand" from the SDS test results are subject to the estimation of the fine particle content Fc, assuming that they have the potential for liquefaction. Soil layers determined to be other than sand (clay soil) are treated as non-liquefaction layers. This Fc estimation is based on the estimated fine particle content Fc from the SDS test results. SDS This is calculated by the following formula 3. SDS The calculation was performed by power regression analysis using the SDS test parameter ET / EW as the explanatory variable.

[0035]

number

[0036] Fine content Fc:Fc obtained from the results of standard penetration tests Bor There is a correlation between Fc and the SDS test parameter ET / EW as shown in Figure 7, and a generally good correlation can be obtained by fitting the power regression curve of the above formula 3. Bor and Fc SDS It can be seen that the correlation between the two is generally good.

[0037] In addition, Fc SDS The upper limit was set at 35% to be on the safe side in the calculation. Also, ET / EW is the energy component due to rotation in the calculation formula for penetration energy in the SDS test (Equation 1 above), ET = πTΔn ht and the energy component due to the load EW=WΔS t This is a parameter that is thought to have a high correlation with soil quality.

[0038] As mentioned above, the Fc estimate is only made for soils that are judged to be "sand," but the judgment of whether the soil is "sand" or "other than sand" is based on a judgment method that applies the concept of Mahalanobis distance, as presented in the Better Living Foundation's Examination Certification-011 (December 2013). This judgment method uses the parameters dT / dWD and W obtained from past SDS test results. 0.25 This utilizes the characteristic that the relationship between the two soil types forms different populations for "sand" and "non-sand." Since each population shows an elliptical spread, normal distributions are taken for the directions of the major and minor axes, and the intersection of the medians of each distribution is set as the center of each population. 0.25 The distance to the center of each population is compared based on the relationship between the distance and the center of each population. Based on the results of this comparison, the point is classified into the soil type with the shorter distance. Here, dT is the torque at each load stage in the SDS test, dW is the load value at each load stage in the SDS test, D is the diameter of the penetration rod, and W 0.25 is the load value required to penetrate 0.25 m (maximum load value in a 0.25 m section).

[0039] Liquefaction is judged using the H1-Dcy method, using the non-liquefaction layer thickness H1 from the ground surface and the ground surface displacement Dcy as indicators based on the constants obtained above.

[0040] (Validity verification) The validity of the liquefaction assessment method using SDS test results according to the present invention is examined by comparing the results with liquefaction assessment results based on boring surveys (standard penetration tests) (hereinafter referred to as boring assessment). To start with, the results of the validity study showed that seven of the eight test sites where liquefaction assessment was conducted either had the same assessment category, or the assessment category using the SDS test results was on the side with a higher probability of damage (safe side). Table 1 shows the eight test sites where the SDS test data and boring survey data used in the validity comparison were obtained.

[0041] [Table 1]

[0042] The validity of the liquefaction assessment based on the SDS test results (hereinafter referred to as SDS assessment) was examined using the FL values ​​(FL values ​​obtained from the results of both the boring survey and the SDS test at the eight locations shown in Table 1 above) Bor , SDS test: FL SDS ) and dcy values. Validity was also examined from the results of the liquefaction risk assessment using the H1-Dcy method. Although the SDS test allows for more detailed test data to be obtained at depths of 0.25 m increments compared to drilling surveys, the SDS assessment in this validity study only used test data from depths where data was obtained in the drilling surveys.

[0043] (1) Conditions for examining liquefaction The liquefaction assessment method and calculation formulas were basically based on the "Guidelines for Design of Building Foundations," and the factors considered were N-value, Fc, and groundwater level. The liquefaction assessment conditions are summarized in Table 2. Regarding liquefaction assessment based on SDS test results, if a single, non-continuous liquefiable layer (FL<1) was present, and two or more layers (0.5m) of non-liquefiable layers (FL≥1) were present above and below it, the layer was considered to be a thin layer with low liquefaction risk and evaluated as a non-liquefiable layer (however, this does not apply to areas directly below the groundwater level). The symbol for ground deformation due to liquefaction is dcy, which represents the amount of ground deformation at each depth where test data was obtained, and Dcy, which represents the amount of ground deformation at the ground surface at each test site. Dcy at each test site is the sum of the above dcy values ​​for that test site, i.e., Σdcy.

[0044] [Table 2]

[0045] (2) Liquefaction study results N value and estimated Fc values ​​based on SDS test results SDS ,Fc SDS FL value obtained from the results of liquefaction studies using: FL sds The FL value obtained from the liquefaction study results using the N value and Fc based on the results of the boring survey: FLBor A comparison of the dcy values ​​is shown in Figure 9, and a comparison of the dcy values ​​is shown in Figure 10.

[0046] In comparison of FL values, approximately 65% ​​of the total number were FL Bor >FL SDS (White plot in Figure 9). This is because FL SDS FL Bor It is also a safe rate for FL. Bor , F.L. SDS Quadrant 3 where both are less than 1 and FL Bor , F.L. SDS In quadrant 2 or quadrant 4, where either of these is less than 1, FL SDS It can be seen that the variations are offset, with 26.4% of cases being on the safe side and 25.5% being on the dangerous side.

[0047] When comparing the dcy values, as shown in Figure 10, the overall average was almost equal, with the boring survey (Bor) overall average = 0.42 cm and the SDS test (SDS) overall average = 0.39 cm, which offsets the differences in FL quadrants 2 and 4, which correspond to the quadrants in Figure 9.

[0048] The determination of liquefaction is not reliable for the actual situation, even if the N value and Fc obtained from the boring survey are used. Depending on the results of the validity study, the estimated N value based on the SDS test results: N SDS ,Fc estimate Fc SDS It is also necessary to consider multiplying each by a safety factor. However, as mentioned above, when comparing the FL value and dcy value, the variability in the SDS judgment, which was sometimes on the safe side and sometimes on the dangerous side compared to the boring judgment, was almost canceled out overall. Compared to the boring judgment, it is "not too safe, not too dangerous," and we have determined that this level of condition (without multiplying by a safety factor) is appropriate in practice.

[0049] The liquefaction risk assessment results using the H1-Dcy method, based on the liquefaction assessment results for the eight test sites, and the ground surface Dcy, are summarized in Figures 11 through 13. According to the H1-Dcy method, the drilling assessment and SDS assessment were consistent at five sites, the SDS assessment was safer than the drilling assessment at two sites, and the drilling assessment was safer than the SDS assessment at one site. Depth distribution maps for each of the eight sites are also shown in Figures 14 through 21. These Figures show that the values ​​obtained from the drilling survey and SDS test follow roughly similar trends. These results also demonstrate the validity of the SDS assessment compared with the drilling assessment. Incidentally, the data marked c in Figures 14 through 21 were determined to be "other than sand" using the Mahalanobis distance described above. Fc was not estimated for the non-liquefaction layer assessment.

[0050] It should be noted that this validation study only used SDS test data at the depths where the boring survey data was measured, as mentioned above, and did not use all of the data obtained from the SDS test. Because SDS tests collect data in 0.25 cm intervals, it may be possible to make more detailed liquefaction assessments in practice by using all of this data. Examples demonstrating this possibility are shown in Figures 22 and 23. These show the results of liquefaction assessments using all of the SDS test data for Urayasu City, Chiba Prefecture, and Sakaiminato City, Tottori Prefecture, two of the eight test sites mentioned above (depth distribution maps for both test sites and liquefaction risk assessment results using the H1-Dcy method).

[0051] In the results for Urayasu City, Chiba Prefecture, shown in Figure 22, both the boring judgment results (plot of Bor judgment) and the SDS judgment results (plot of SDS judgment (Bor comparison)) were rated A, but the judgment results using all SDS test data (plot of SDS judgment (25cm)) were rated B. Since the original SDS judgment tended to be closer to a B than the boring judgment, it is believed that the actual situation was identified by the judgment using all SDS test data.

[0052] In the results for Sakaiminato City, Tottori Prefecture, shown in Figure 23, the boring assessment and SDS assessment were separated near the boundary between the A and B evaluation areas, but the assessment using all the SDS test data resulted in the same A rating as the boring assessment. When assessing areas near the boundary of evaluation areas, it is expected that the accuracy of identifying the evaluation area can be improved by using all the SDS test data.

[0053] In addition, in the method for determining liquefaction of ground according to the present invention, an example of determination by the H1-Dcy method has been shown, but as shown in the stage of validity examination, the estimated N value according to the present invention: N SDS and estimated Fc:Fc SDS The usefulness of the FL value is also evident. Therefore, it is considered to be effective when applied to the FL method. It can also be applied to other liquefaction damage possibility assessments, such as the Building H1-PL method and the Road Safety H1-PL method, which use the FL value. In this way, the estimated N value: N SDS and estimated Fc:Fc SDS By using this method, it becomes possible to easily perform liquefaction assessment even when assessing the possibility of liquefaction damage using methods other than the H1-Dcy method. [Explanation of symbols]

[0054] 1 Automatic penetration testing machine 2 screw points 3 Penetration Rod 4 Lifting platform 5 Chuck unit 6 Rotation motor 7 Lifting motor 8 pillars

Claims

1. A method for determining ground liquefaction, characterized in that the N value is estimated by power regression analysis using the energy required to penetrate a penetration rod equipped with a screw point at the tip into the ground as an explanatory variable, and this estimated N value is used as a constant for determining liquefaction.

2. A method for determining ground liquefaction, characterized in that the fine particle content Fc is estimated by power regression analysis using the energy required to penetrate a penetration rod equipped with a screw point at the tip into the ground as an explanatory variable, and this estimated Fc is used as a constant for determining liquefaction.

3. A method for assessing ground liquefaction, characterized in that the N value and fine particle content Fc are estimated by power regression analysis using the energy required to penetrate a penetration rod equipped with a screw point at the tip into the ground as an explanatory variable, and the estimated N value and estimated Fc are used to assess the possibility of liquefaction damage.

4. The energy required to penetrate the penetration rod into the ground is the energy E required to penetrate the screw point into the ground every 0.25 m. 0.25SL The following power regression equation with N SDS =3.01×E 0.25SL 0.65 Therefore, the estimated value of N is SDS The method for determining liquefaction of ground according to claim 1 or 3, further comprising:

5. The energy E required to penetrate the screw point into the ground every 0.25 m 0.25SL The method for determining ground liquefaction according to claim 4, characterized in that the energy values ​​obtained in each 0.25 m penetration section are proportionally converted for each penetration section.

6. The following power regression equation is used as an explanatory variable: the ratio of the rotational energy ET of the penetration rod when it is rotated and penetrated into the ground to the penetration energy EW due to the load. c SDS The -0.60 Thus, the estimated fine particle content Fc SDS The method for determining ground liquefaction according to claim 2 or 3, further comprising:

7. The energy required to penetrate the penetration rod into the ground is the energy E required to penetrate the screw point into the ground every 0.25 m. 0.25SL The following power regression equation with N SDS =3.01×E 0.25SL 0.65 Therefore, the estimated value of N is SDS Seeking In addition, the following power regression equation is used as an explanatory variable: the ratio of the rotational energy ET of the penetration rod when it is rotated and penetrated into the ground to the penetration energy EW due to the load. c SDS The -0.60 Thus, the estimated fine particle content Fc SDS The method for determining liquefaction of ground according to claim 3, further comprising:

8. The energy E required to penetrate the screw point into the ground every 0.25 m 0.25SL The method for determining ground liquefaction as described in claim 7, characterized in that the energy values ​​obtained in each 0.25 m penetration section are proportionally converted for each penetration section.

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