Japanese Geotechnical Society Special Publication The 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering

In situ dynamic strength properties of the 3rd Meiji fortress reclaimed sands

Takaharu Shogaki

Department of Civil Engineering, National Defense Academy, 1-10-20 Hashirimizu, , 239-8686, Japan

ABSTRACT

Construction of the 3rd Meiji fortress, at a depth of approximately 40 m near the Kannon promontory in , was started in 1921 and lasted for 29 years. However, 35% of this 3rd fortress was submerged and all its functions suspended due to the liquefaction caused by the Great Kanto Earthquake of 1923. The measured relative density (Dr(m)) and stress ratios (RL20(m)) in a 20-cycle time frame values were 4.5% and 0.006, respectively, in mean values greater than those of the estimated in situ Dr(i) and RL20(i) values obtained with the economically feasible (EF) method. Thus, the Dr(m) and RL20(m) values overestimate the in situ values.

Keywords: earthquake, sand, 3rd Meiji fortress, liquefaction, sample disturbance, tube sampling, relative density

1. INTRODUCTION (2006). Therefore, the possibility of the 3rd Meiji fortress reclaimed sands liquefying is also discussed by Japan constructed 24 fortresses in the coastal area referring to the D and the stress ratio (R ) in a of , from the last days of the into the r L20 20-cycle time frame for the sands obtained from the site Meiji Period, to strengthen the defenses of the Tokyo concerned and the Niigata Meike sands. The metropolitan area against invasion by foreign enemies. applicability of the EF method (Shogaki and Sato, Three fortresses in were constructed on 2011; Shogaki and Kaneda, 2013), for estimating the in manmade islands. The 1st and 2nd fortresses were situ D and R values of the sand samples obtained constructed at depths of 5 m and 10 m, respectively, in r L20 from the 3rd Meiji fortress, is discussed together with Tokyo Bay near the Futtsu promontory in the sands from Niigata Meike, Niigata Airport, Niigata Prefecture, as shown in Fig, 1. Construction of the 3rd East Port and a port in Kansai. Meiji fortress, at a depth of approximately 40 m near the Kannon promontory in Kanagawa Prefecture, was started in 1921 and lasted for 29 years. However, 35% of the 3rd fortress was submerged and all its functions suspended due to the liquefaction caused by the Great Kanto Earthquake of 1923. Unfortunately, the maximum (emax) and minimum (emin) void ratios of the 3rd Meiji fortress reclaimed sands were not measured by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) (2002). Therefore, relative densities (Dr) were not measured for these sands in spite of the need for an estimation of the in situ dynamic strength 1st fort. properties using the economically feasible (EF) method 2nd fort. (Shogaki and Sato, 2011; Shogaki and Kaneda, 2013). rd In this paper, the 3 Meiji fortress reclaimed sands 3rd fort. Futtsu are identified by index and grain size distribution Hoshirimizu properties for sands obtained from Hashirimizu, Yokosuka Kurihama and Futtsu Beaches, since these sands were Tatarahama used as the reclaimed sands, as described in MLIT (2000). Niigata sands were liquefied during the Niigata ： Sampling sites 0 (㎞) 5 Earthquake of 1964. The grain size distribution Kurihama properties of the 3rd fortress reclaimed sands are similar to those of Niigata sands, as can be found in Shogaki, et al. (2006). The dynamic strength properties of the Fig. 1. Sites of fortresses and identification of 3rd Meiji fortress Niigata Meike sands were measured by Shogaki, et al. sands http://doi.org/10.3208/jgssp.JPN-016 2680 2. OUTLINE OF 3rd MEIJI FORTRESS IN 3. IDENTIFICATION OF 3rd MEIJI FORTRESS TOKYO BAY RECLAIMED SANDS

Fig. 2 shows the cross sectional soil profile of the Fig. 4 shows the grain size distribution curves for 3rd fortress after its construction. The major and minor ～ axis lengths were 270 m and 167 m, respectively, and samples of z=2.5 m 27.5 m obtained from the the reclaimed soil volume was 332 million m3. The sampling sites, as shown in Fig. 3 together with foundation of the 3rd fortress is the Pliocene Kazusa Toyoura sand ( ▽ ). These sands are classified as stratum, and reclaimed sands obtained from “possible liquefaction”. The sands at z=2.5 m (＋), 7.5 Hashirimizu, Kurihama and Futtsu Beaches, shown in m (×) and 10.5 m (○) are classified as “high MLIT (2000), were used on top of the stone riprap liquefaction potential” by the Ports and Harbors Bureau placed on the base. The sampling sites of the of Japan (2013) as is the Toyoura sand. Table 1 shows Hashirimizu, Kurihama and Futtsu sands are also the grain size properties for samples at z=2.5 m, 7.5 m rd shown in Fig. 1 together with Tatarahama sand as a and 10.5 m obtained from the 3 fortress together with large amount of sediment sand in these areas. Control Toyoura, Hashirimizu 1 and 2, Kurihama, Tatarahama of the construction, using the above reclaimed sands, and Futtsu 1, 2 and 3 sands, described in next chapter. was conducted in a similar manner to the present-day The percentage (Fc) of grain sizes smaller than 0.075 rd preloading method and plate-loading test as mm at the 3 fortress are in the range of 3% to 8%, and technologies imported from European countries (MLIT, the uniformity coefficient (Uc) and the coefficient of 2000). In other words, control of the construction using curvature (U’c) are 2.0 to 3.8 and 0.9 to 1.1, reclaimed sands was conducted through plate-loading respectively, with the medium grain size (D50) being tests for both the weights of cannons and the reaction to 0.21 mm to 0.39 mm. their shooting, which resulted in a spreading depth of Fig. 5 shows the grain size distribution curves for the fill of 20 cm. These geotechnical techniques were the reclaimed sands (z=2.5, 7.5 and 10.5 m) and the rd quite progressive for that day and age, and they were identification the 3 fortress sands, as shown in Table 1. later exported to the United States of America (MLIT, 2000). 100 Fig. 3 shows the cross-sectional soil profiles after : Toyoura Great Kanto Earthquake of 1923. It can be determined 3rd Meiji fortress 80 z(m) from Figs. 2 and 3 that the main reason for the : 2.5 rd : 7.5 settlement of the 3 fortress was the collapse of the : 10.5 stone riprap and the liquefaction of the reclaimed sands 60 : 17.5 High liquefaction : 27.5 potential caused by the Great Kanto Earthquake of 1923. 40

+7.93 m +14.09 m +2.39 m Possible +12.97 m 20 liquefaction ±0.0 m +5.26 m Percentagefiner weight by (%) Reclaimed sand 0 0.001 0.01 0.1 1 10

Stone riprap -40.0 m Grain size, D(mm)

rd Pliocene Kazusa stratum Fig. 4. Grain size distribution curves (3 Meiji fortress).

100 Fig. 2. Cross-sectional soil profiles after establishment. 80

: Hashirimizu 1 60 : Hashirimizu 2 : Kurihama : Tatarahama 40 : Futtsu 1 : Futtsu 2 : Futtsu 3 3rd Meiji fortress 20 : 2.5m : 7.5m

Percentagefiner weight by (%) : 10.5m 0 0.01 0.05 0.1 0.5 1 5 10 Grain size, D(mm) Fig. 3. Cross-sectional soil profiles after Great Kanto Fig . 5 Grain size distribution curves (identification of 3rd Meiji Earthquake. fortress sands).

2681 Table. 1. Grain size distribution properties of sand samples.

ρ D D D D D Sand s F 10 30 50 60 max U U ' e e (g/cm3) c (mm) (mm) (mm) (mm) (mm) c c min max (%) 3rd fortress 2.724 8 0.127 0.265 0.394 0.482 9.50 3.8 1.1 - - (2.5m) 3rd fortress 2.736 3 0.122 0.165 0.212 0.243 4.75 2.0 0.9 - - (7.5m) 3rd fortress 2.727 6 0.115 0.166 0.220 0.254 4.75 2.2 0.9 - - (10.5m) Hashirimizu1 2.874 0.5 0.114 0.139 0.167 0.187 4.75 1.6 0.9 0.592 0.946 Hashirimizu2 2.727 0 0.120 0.225 0.345 0.449 9.50 3.7 0.9 - - Kurihama 2.776 2.4 0.114 0.144 0.181 0.206 4.75 1.8 0.9 0.634 0.977 Tatarahama 2.800 0.6 0.184 0.435 0.566 0.646 4.75 3.5 1.6 - - Futtsu 1 2.725 0 0.118 0.183 0.287 0.447 4.75 3.8 0.6 - - Futtsu 2 2.710 0.1 0.243 0.251 0.306 0.331 4.75 1.4 0.8 0.674 1.016 Futtsu 3 2.731 0 0.132 0.273 0.469 0.572 4.75 4.3 1.0 - -

There are no samples of the 3rd fortress sands obtained those of Niigata Meike under the same z. Niigata Meike from the tube sampling. In Fig. 6, the grain size sands, as shown in Fig. 6, liquefied in the Niigata distribution curve at z=2.5 m (●) of the 3rd fortress is Earthquake of 1964 and Niigata City suffered terrible similar to that of Futtsu 2 (◇), while the curves of damage due to this earthquake. It can be seen that the rd z=7.5 m (×) and 10.5 m (■) are similar to Hashirimizu 1 3 fortress reclaimed sands are also liquefied sand in

(▽) or Kurihama (＋), respectively. The D50, Uc and the sense of the dynamic strength properties. The EF method for estimating the in situ void ratio U’c of those samples, shown in Table 1, are similar and reflect similar grain size distribution curves. The (e0), Dr, RL20 and the initial modulus of rigidity (G0) of samples of Hashirimizu 2 (△), Tatarahama (▲) and the sand samples, utilizing the changes in density, was proposed through element and model tests on Toyoura Futtsu 1 (◆) include many shell chips and the D50 are larger by 0.1 to 0.2 mm. Therefore, it can be judged sand (Shogaki and Sato, 2011). In situ e (=e(i)), Dr from the viewpoint of grain size distribution that the (=Dr(i)), RL20 (=RL20(i)) and G0(CTX) (i) values using the EF reclaimed sands obtained from the 3rd fortress at z=2.5 method, for which (m) stands for the measured value. m are Futtsu 2, and those obtained at z=7.5 m and 10.5 m are Hashirimizu 1 or Kurihama sands. The emax and Table. 2. Measured and estimated in situ e, D and R values. rd r L20 emin values of the 3 fortress sands were not measured by MLIT (2002). Therefore, in the next chapter, the Dr Depth Measured value Estimated in situ value values for the 3rd fortress sands are calculated from the Dr(m) Dr(i) z (m) e(m) RL20(m) e(i) RL20(i) measured emax and emin, as shown in Table 1, to estimate (%) (%) the in situ strength properties. 2.5 0.701 69.2 0.238 0.708 65.8 0.236

7.5 0.694 71.2 0.228 0.694 71.2 0.228 4. IN SITU DYNAMIC STRENGTH 10.5 0.711 66.4 0.196 0.720 60.8 0.186 PROPERTIES OF 3rd MEIJI FORTRESS RECLAIMED SANDS 0 : Niigata Meike (TS) : Niigata Meike (FS) : The 3rd Meiji fortress (TS) The RL20 values at z=2.5 m, 7.5 m and 10.5 m are 2 obtained as 0.238, 0.228 and 0.196, respectively, as

4 (m) shown in Table 2. The measured Dr and RL20 values z obtained from the TS (◎) of the 3rd fortress, together 6 with the frozen sampling of Niigata Meike, namely, Depth, 8

(FS) (＋) and TS (○), are plotted against z in Figure 6. 10 rd The Dr values for the 3 fortress are in the range of 66.4% to 71.2% and higher than those of Niigata sands. 12 rd These higher Dr values for the 3 fortress are 20 40 60 80 100 0.2 0.3 0.4 considered with soil compaction control during Relative density, Dr(%) Stress ratio, RL20 rd construction. However, the RL20 values of the 3 rd considered with soil compaction control during fortress Fig. 6 Relationships among Dr, RL20 and depths (3 Meiji are in the range of 0.196 to 0.238 and are lower than fortress and Niigata Meike sands).

2682 Fig.8. Relationship between measured RL20(m) and Dr(m).

more realistic values for in situ R and D . 0.6 L20(i) r(i) : Niigata Meike Toyoura The measured and estimated e, Dr and RL20 values Niigata 0.5 : Niigata Airport sand are also summarized in Table 2. The Dr(m) and RL20(m)

: Niigata East Port Meike(FS) are 4.5% and 0.006, respectively, in mean values L20(m)

R : Kansai port 0.4 greater than those of Dr(i) and RL20(i). Then, the Dr(m) and

， : The 3rd Meiji fortress RL20(m) values overestimate the in situ values. The rd 0.3 quantitative estimation for the liquefaction of the 3 fortress’s reclaimed sands was shown in this paper. 0.2 The term “liquefaction” is well known by the Stress ratio Stress general public in present-day Japan. The common sense 0.1 that has existed in geotechnical engineering since the 0 20 40 60 80 100 Alaskan and Niigata Earthquakes of 1964 did not exist Relative density ，Dr(m) (%) in the Meiji or Taisho Period; and thus, sands with a rd Fig . 7. Relationship between measured RL20(m) and Dr(m). high potential for liquefaction were used for the 3 fortress’s reclaimed sands.

0.6 5. CONCLUSIONS : Niigata Meike Toyoura 0.5 : Niigata Air Port sand It was judged from the sense of grain size : Niigata East Port distribution that the reclaimed sands obtained from the L20(i) 0.4 rd R : Kansai port 3 Meiji fortress at z=2.5 m were Futtsu 2 and those : The 3rd Meiji fortress ， 0.3 obtained at 7.5 m and 10.5 m were Hashirimizu 1 or Kurihama sands. The 3rd Meiji fortress reclaimed sands 0.2 were liquefied sands in terms of the dynamic strength properties. The measured Dr(m) and RL20(m) values were

Stress ratio Stress 0.1 4.5% and 0.006, respectively, in mean values greater Niigata Meike(FS ） 0 than those of the estimated in situ Dr(i) and RL20(m) 0 20 40 60 80 100 values obtained from the economically feasible (EF) Relative density ，Dr(i) (%) method. Then, the Dr(m) and RL20(m) values are seen to Fig. 8. Relationship between estimated in situ RL20(i) and Dr(i). overestimate the in situ values.

REFERENCES Fig. 7 shows the relationship between the measured 1) Ministry of Land, Infrastructure, Transport and Tourism RL20(m) and Dr(m), together with the regression line for the results obtained from Toyoura sands (Shogaki and Kanto Regional Bureau Office (2000) (MLIT, 2000): The construction history of 3rd fortress in Tokyo bay (in Sato, 2011; Shogaki and Kaneda, 2013), Niigata Meike Japanese). (×) and Niigata Airport (＋) sands (Shogaki, et al., 2) Ministry of Land, Infrastructure, Transport and Tourism 2010), Niigata East Port sand (●) (Yoshizu, et al. 2014), Kanto Regional Bureau Office (2002 (MLIT, 2002): 2002 a port in Kansai (◎) (Shogaki and Yoshizu, 2013) and soil investigation report on Uraga channel route (in Japanese). the 3rd fortress (▲). 3) Shogaki, T., Sakamoto, S., Nakano, Y. and Shibata, A. Fig. 8 shows the in situ values estimated by the EF (2006): Applicability of the small diameter sampler for method using the measured RL20(m) and Dr(m). The Niigata sand deposits, Soils and Foundations, 46 (1), measured RL20(m) values in Fig. 7 are in the range of 0.1 pp.1-14. 4) Shogaki, T. and Sato, M. (2011): Estimating in-situ dynamic to 0.33 and constant for Dr(m). However, their plots and th regression curves for the estimated in situ R values strength properties of sand deposits, The 14 Asian L20(i) Regional Conference on Soil Mechanics and Geotechnical increase with an increasing Dr(i), as shown in Fig. 8, Engineering, Hong-Kong, CDR. where (i) stands for the estimated in situ value obtained 5) Shogaki, T. and Kaneda, K. (2013): A feasible method, by the EF method. The same tendency was observed for utilizing density changes, for estimating in-situ dynamic Toyoura sand as well as the sands of Niigata Meike, strength and deformation properties of sand samples, Soils Niigata Airport, Niigata East Port, a port in Kansai and and Foundations, 53 (1), pp. 64-76. the 3rd fortress, as shown in the same figure. The R 6) Shogaki, T. and Yoshizu, T. (2013): Improving estimation L20(i) of in situ dynamic strength properties of sands, Proc. of the values increase with increasing Dr(i) values for the 23rd Int. Offshore and Polar Engineering, Anchorage, pp. Toyoura sand (Shogaki and Sato, 2011), as shown by 532-537. the broken line located at the top of the plots, since 7) Yoshizu, T., Shogaki, T. and Nakano, Y., (2014): Toyoura sand does not include particles smaller than Applicability of improving estimation of in-situ dynamic strength properties of Niigata east port sand, 49th Annual 0.075 mm. The relationship between in situ RL20(i) and Conf. of Japanese Geotechnical Society, (in Japanese). Dr(i), shown in Fig. 8, is consistent with the test results for Toyoura sand. Using the EF method, we obtained

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