報告書番号

380050

タイトル（和文）

セメント系地盤改良の耐震効果に関する研究－原位置調査・試験からみた改良効果－

タイトル（英文）

ASEISMIC EFFECT CEMENT-MIXED SOIL IMPROVEMENT -THE EFFECTS THROUGH THE RESULT OF THE IN SITU TEST-

概要 （図表や脚注は「報告書全文」に掲載しております）

地盤改良による耐震効果を調べるため，手賀沼東部の超軟弱地盤をセメント系深層混合攪拌工法により地盤改良を施して，（１）地盤物性調査・試験，（２）振動試験，（３）地震観測，等の諸試験を実施した。このうち本報告は，（１）の地盤調査・試験のうち原位置試験結果についてまとめたものである。得られた結果は次の通りである。（１）セメント深層混合処理による改良の前後で湿潤密度はほとんど変化していない。（２）静的・動的孔壁加圧試験により，改良地盤の強度及び変形性は著しく増大していることがわかった。（３）改良地盤の一軸圧縮強度の深度分布にはむらがあり強度は一様ではない。しかし圧縮強度の平均値は１０／平方■以上あり設計強度の６（■／平方■）を上まわっていた。（４）続報の室内試験結果と合せて地震応答解析用の地盤モデルを作成して示した。

概要 （英文）

SOME EXPERIMENTS AND ANALYSIS HAVE BEEN CARRIED OUT,IN ORDER TO EXAMINE THE SEISMIC EFFECTS OF THE GROUND IMPROVEMENT BY THE DEEP MIXING IMPROVEMENT WITH CEMENT TO THE SOFT GROUND. IN-SITU TESTS PERFORMED FOR TWO KINDS OF IMPROVED GROUNDS AND A NATURAL GROUND. THESE ARE CALLED HERE IMPROVED GROUND A , IMPROVED GROUND B AND UN-IMPROVED GROUND C ,RESPECTIVELY. IMPROVED GROUND B IS THE GROUND WITH THE IMPROVED SURFACE OF ABOUT 30M IN DIAMETER AND 2M IN DEPTH. IMPROVED GROUND A IS THE GROUND WHOSE SURFACE WAS IMPROVED SAME AS THE B AND MORE OVER,ITS CENTER PART OF SURFACE WAS IMPROVED TO 23M IN DEPTH INTHE SHAPE OF THE COLUMN 10M X 10M IN PLANE. THE MODEL FOUNDATIONS MADEOF CONCRETE BLOCK(3.5MX3.5M IN PLANE,1M IN HIGH)WERE SET ON THE ESCH CENTER OF A , B AND C ,RESPECTIVELY.THESE FOUNDATIONS WERE VIBRATED BY THE MECHANICAL VIBRATOR AND THEIR DYNAMIC BEHAVIORS WERE EXAMINED. THISPAPER DESCRIBES THE RESULTS OF THE GROUND SURVEY AND TESTS IN-SITU.THEMETHODS OF IN-SITU TESTINGS USED HERE ARE SHOWN AS FOLLOWS. 1)STATIC AND DYNAMIC PRESSUREMETER TESTS. 2)SEISMIC VELOSITY TESTS. 3)STANDARD PENETRATION TESTS. 4)THE CONTINUOUS PENETRATION TESTS BY ROTARY BORING. THE RESULTS OF THIS SURVEY AND TESTS ARE SUMARIZED AS FOLLOWS. (1)PROFILE OF THE LAYER OF THE SITE. THE KINDS OF LAYER AND THE DISTRIBUTION OF S.P.T.N VALUES ARE SHOWN AS FIG.5. (2)EFFECTS OF THE IMPROVEMENT ON MECHANICAL PROPERTIES. THE WET DENSITY OF IMPROVED AND UN-IMPROVED SOILS ARE NOT CHANGED. ON THE OTHER HAND THE SHEAR STRENGTH AND SHEAR MODULUS OF IMPROVED SOILS ARE REMARKABLY ADVANCED AS SHOWN IN TABLE 1.

報告者

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