A land slide occurred at Kashio Town near Nigawa Railway Station on the Imazu line of the Hankyu Electric Railway Co. on July 13th, 1951. During this landslide the foundation rose. The inclined surface which had kept balance during the last ten and over years slid, though little change was noted in the external condition. The authors investigated the cause of the land slide from the physico-chemical standpoint

MATSUO, Shin-ichiro

MISE, Tadashi

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RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:A Study on the Analysis of LandSlide in the Kashio DistrictMATSUO, Shin-ichiro; MISE, TadashiMATSUO, Shin-ichiro ...[et al]. A Study on the Analysis of Land Slide in the Kashio District.Memoirs of the Faculty of Engineering, Kyoto University 1956, 18(2): 65-721956-07-20http://hdl.handle.net/2433/28034765 A Study on the Analysis of Land Slide m the Kashio District By Shin-ichiro MATSUO and Tadashi MISE Department of Civil Engineering (Received January 27, 1956) Synopsis A land slide occurred at Kashio Town near Nigawa Railway Station on the Imazu line of the Hankyu Electric Railway Co. on July 13th, 1951. During this landslide the foundation rose. The inclined surface which had kept balance during the last ten and over years slid, though little change was noted in the external condition. The authors investigated the cause of the land slide from the physico-chemical standpoint. 1. Local condition at Kashio The location of the landslide is shown in Fig. 1, the photographical features in Fig. 2 and the nature of soils in Fig. 3. As is clear from Fig. 2, the land slide occur-red at the saddle, a position where water springs even at the ground surface. The section after the slide and the natural features made clear by boring are represented in Fig. 4 (A), (B). N + ki /////!I ///1; '/ Fig. 1. 66 Shin-ichiro 11 ~ .t -= . h" MISE d Tadas 1 MATSUO an 0 wa,(t -f:::=:::~~=,1/=::Tti:=o =:;Tr,.;:=tt:ka.::l"a. =;: ~ - di _11! 11 ~/ ,1/ ;L .IL JL Fig. 2. Fig. 3. . r A Study on the Analysis oj Land Slide in the Kashio District Fig. 4 (A). Piel 0 3/tJ Clo.ye-! S Cl./>1A.- 1 soo 9ro..vd.. 2$00 cf.4...,1 2600 mo da..Jqyra.vet 3630 ~ra..vet Ua..J 4-ISO SI.SO 6000 3050 Fig. 4 (B). 2. Chemical analysis _J_ 400 67 The soil and the rain water of the Kashio district were chemically analysed. The places where underground water ard soil samples were taken are marked A, B, •·· and 1, 2, · · · respectively. The underground water from A, B, · · · and F were collected into glass bottles from drainage holes, and the soils were taken out with a soil auger. The underground water samples were analysed quantitatively by spectral analysis and poralography, then quantitatively for all the existing cations and anions. The soil samples were leached with lN-NH,Cl solutions and lN-NaCl for 24 hrs., and then filtered. The filtrates were analysed quantitatively for the cations and anions. The exchange capacity was determined by the ordinary lN-ammonium acetate method. 68 Shin-ichiro MATSUO and Tadashi MrsE The results of the chemical analysis are shown in Table 1 and Table 2. From the results of the analysis, it was found that there was no appreciable difference between the underground water and rain water. However the Ca content alone of the underground water was much larger than that of the rain water itself. The calcium leached out from the content with the underground water. Table 1. Samples I Unit I A I B I C I D I E I F I G I H ! atom. temp. oc I 32.5 31.0 31.8 I 32.2 32.2 27.5 ! water temp. oc 22.2 26.5 22.1 23.5 20.8 19.0 25.0 pH 5.6 5.8 5.8 6.3 5.9 5.8 5.8 5.4 alka!ity m.e./l 8.2 30.24 16.80 7.92 6.20 HCO3' free m.e./l 8.2 30.2 16.8 7.9 6.2 carbonate p.p.m. 2.4 1.8 22.1 11.00 12.8 acidity m.e./l 2.8 2.1 25.1 12.5 14.5 dissolved 0 2 p.p.m. 0.9 0.8 0.7 1.1 0.8 Cl' mg/I 1.4 2.2 2.4 3.5 1.6 PO,' mg/! 36.6 26.3 23.8 29.5 31.0 SiO/' mg/! 36.7 29.0 31.3 27.5 38.9 Ca .. mg/! 70.8 : 103.1 64.7 62.9 65.0 I Mg"" mg/! 11.7 colour- I 13.3 16.9 19.4 18.1 colour slight slight light muddy less I I muddy yellow . velocity of flow c.c./sec. 23.3 2.7 3.3 I 1.3 50.0 I I Table 2. Sample Unit I exc1i;;ge I H" I Na" I K" I Ca"" I Mg·· I Fe·· I Al""" I Mn"" I NH; I capac1 y rain water m.e .. 'l 0.07 0.16 0.07 0.01 I 0.0005 0.02 - 0.0002 ground water m.e./l 0.07 0.18 1.13 0.02 0.00008 0.02 trace 0.003 blue clay i leachate m.e./lO0g 21.0 1.0 0.82 0.65114.42 4.03 0.0027 0.01 0.045 0.238 red clay m.e./l00g 12.5 2.8 1.12 0.10 8.37 0.13 0.0077 0.03 0.05 -leachate 3. Shear-test It is acknowledged that the shearing strength of a given soil sample changes variously according to the quantity and the quality of the absorbed cations. The order of the strengh of soil, exchanged by H-ion at first and by others secondarily, is given as NH4 , H, K, Fe, Al, Mg, Ba, Ca, Na and Li, as the result of Sullivan's experiment.1J The author also recognized that the position in the plasticity-chart moves almost parallel to A-line by the ion-exchange.2J From this fact, and the fact that the quantity of exchanged Ca in Kashio-soils is very large, but is merely three-fourths of the A Study on the Analysis of Land Slide in the Kashio District 69 quantity of the saturation, there will be a great difference in the shearing strength and other characteristic between Ca-soils that exist and saturated Ca-soils that are presumed to have existed. Concerning stability, it is considered that there is great difference in the safety factor. Taking these points into consideration, the authors compared natural-soils with saturated Ca-soils by the shear-test, as the shearing strength of soils differs with the moisture-content. In this case, various proportions of water were added to sample of Kashio air-dried soils and were left to stand for 24 hrs, after which the shear-test was made. To determine the value of the moisture. content, the four values were measured after the shear-test and the average takes. The particle-size distribution curves of the soils are represented in Fig. 5, and the results obtained by the shear-test are represented in Fig. 6 and Fig. 7. 20 0 -~ ' 0.•••5 o.oo I t2----+--~ j I' / / / V o.os a/ f'a.rlide Size (m.ht) Fig. 5. "' ~,-----+-----llll~>r-----o.!; LO 0 3~0~--~--~~-----16110.._ __ 1.1,,.o ___ .Jo l1o;stt1..re. ~111.en.t (Y.> Fig. 6. 70 Shin-ichiro MATSUO and Tadashi MISE 03t-----t----+----l-------f 0 ----·------~---..._-""-_.., 3D 1io so 60 Mots tu.re ccn,ten.:t"(r,J Fig. 7. 70 Judging from the above results, when the moisture content is normal, the fric-tional angle is 0.45° and 0.06°, and cohesion 0.163 kg/cm2, and 0.08 kg/cm2 for the Ca-soils and the normal soils respectively. 4. Stability analysis Fig. 8 indicates a longitudinal section of the terrain. In Fig. 8 the oblique line is nearly a straight line before the slide, and so if it is assumed as a straight line, f 400 0 /00 0 S /I> I• <D;t Fig. 8. A Study on the Analysis of Land Slide in the Kashio District 71 the plane of the upper border of the clay layer, considered the sliding surface, is nearly parallel to the surface of the earth. It is considered that the sliding surface of the upper and lower end of this straight line is round. The results of the stability computation of the straight and round sliding surface is shown in Table 3 and Fig. 8. Table 3. ------------- -----~--~-~--~---~----~---= j Unit j Cl' [ SO4" [ PO4" [ SiO3" i Acidity [ Alkality [ ca;b:iate Sample I---------~---:---: ,_u_n_d_:_r:_i:o_:_n_:_e_:_a_te_r_~l _:_:_~1_t ~1-~_:~: I ~:~~: I 0~80 j4;54 I ~:~;9:.=~~-/ 11 0.247~.e.// ~I __ ~---~_!9_8 The factor of safety computed by the angle of friction and the cohesion from Table 4 is shown in Table 5 ; namely the factor of safety of Ca-soil is 1.3, while that of the natural soil is 0.6. Therefore, in soil which is saturated with Ca and is static-ally stable, the adhered Ca is substituted by other cations and by this it is considered that the strength of the soil is changed and the land sliding is brought about. , Table 4. -· ----Parts I 1 I 2 I 3 I 4 I 5 I 6 I 7 I 8 I Sum I □ FBCE I A(m2) 3.7 4.0 5.9 9.1 10.1 9.9 8.7 5.1 56.5 193.0 g(t/m3) 1.65 " " " " " " " " " W(t) 6.1 6.6 9.7 15.0 16.7 16.3 14.4 8.4 93.2 318.5 T(t) -4.6 -3.9 -3.4 -1.5 3.6 8.3 10.6 6.9 16.0 75.2 ' N(t) 4.3 5.4 9.0 15.0 16.3 13.1 9.2 2.8 75.1 ' 308.1 I L(m) 20.4 I . 37.4 <p(o) 139 Table 5. I II I tan II [ c(t/m2) I Ms I M, I Ds D, I s [ Natural water content I I I I I Ca-clay I 0.45 0.00791 1.63 I 134.4 306 75.2 63.2 I 1.3 -natural soil 0.06 0.0018 0.68 134.4 127 75.2 26.0 0.6 60.21% 5. The counter-measure From the above investigation and research, the measures to be taken hereafter against this land slide are considered as follows : 1 ) The necessary step to prevent future land slide is to maintain the terrain in its present state. To make a big change in the local topography, especially to bank the upper part of the surface of the slope or add other loads, would very likely cause a new land slide. 72 Shin-ichiro MATSUO and Tadashi MISE 2) For the period that the present state can be maintained the practice of chemical analysis and the test of soil properties, are useful in predicting the occur-rence of land sliding. 3) A positive measure for maintaining the stability of the slope is to dig holes near the upper border of the slope and supplement Ca-ion. Bibliography 1) Sullivan, J. D., Physico-chemical Control of Properties of Clays, Trans. Electrochem. Soc., 1939. 2) Matsuo, S., Characteristics of Consistency of Soil Shown in Plasticity Chart, Proc. First Japan National Congress for Applied Mechanics, 1951. 

A Study on the Analysis of Land Slide in the Kashio District

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A Study on the Analysis of Land Slide in the Kashio District

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