JP2004325287A - Method of evaluating excavated surplus soil containing igneous rock or mudstone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To classify excavated surplus soils into controlled disposal requiring one and controlled disposal not requiring one by a simple evaluation method, in the excavated surplus soils containing igneous rocks subjected to mineralization metamorphism or mudstones. <P>SOLUTION: When the excavated surplus soils are not a vein of ore or an ore, magnetic susceptibility of a collected sample, a pH of an elution water after one hour of lapse time, a sulfur content, a molar ratio of sulfur to calcium and a heavy metal content amount are measured, and the surplus soils are classified into the controlled disposal requiring one and the control disposal not requiring one, based on a level relation of measured results therein to preset set values therefor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

つまり、残土中の黄鉄鉱が酸素を溶存する雨水や地下水により二価の鉄と硫酸イオンに分解（式（１））され、生成した二価の鉄が三価の鉄にさらに酸化される（式（２））。次に、三価の鉄が水酸化物として沈殿する（式（４））とともに、強力な酸化剤として働いて黄鉄鉱の酸化を促進し、さらに硫酸イオンと水素イオンとを発生させる（式（４））。また、硫黄元素の酸素酸化による硫酸イオンの生成反応（式（５））がある。これらの反応は鉄酸化細菌およびそれと同じ環境下で共生する硫黄酸化細菌の作用により加速することが知られている。
このような残土のうち、鉱脈や鉱石（専門家であれば目視により識別できる）については多量の硫化鉱物等を含んでいると認められるから、初めから管理処分が必要なものとして分別され、問題はあまりないが、これらを一部含むものについてはその区別が難しく、このような硫化鉱物等を一部含有する残土を採掘した場合、これをそのまま野ざらしにすると前記反応が進行して酸性水が発生して環境汚染の原因となる。このため、このような硫化鉱物等を含有する残土は、管理設備で脱硫等の然るべき処理をして無害化してから廃土とする管理処分をする必要があるが、掘削した全ての残土に有害な硫化鉱物等が含まれているとは限らないことから、残土について、管理処分する必要があるか否かの評価をし、残土が環境汚染を引起す惧れがあるとされる基準値以上に硫化鉱物等を含有すると評価された残土については必要な管理処分をし、含有しないと評価された残土は管理処分をすることなくそのまま廃土とするという分別が要求される。
そこでこのような区別をする方法として、下記非特許文献１、２に記載されるように土懸濁液のｐＨ試験をする等して評価する方法が知られている。
【０００３】
【非特許文献１】
土質試験の方法と解説（第一回改訂版）（１５９頁〜１６４頁）平成１２年６月２６日訂正第３刷 社団法人地盤工学会発行
【非特許文献２】
産業廃棄物に含まれる金属等の検定方法 昭和４８年２月１７日環境庁告示第１３号
【０００４】
【発明が解決しようとする課題】
ところが前記従来の試験方法では、例えば浸盪時間だけでも６時間と長く、次から次に掘削される残土について、これら試験結果を待ってから管理処分が必要なものと必要でないものとに分別するのでは作業効率が悪いだけでなく、分別待ちの残土の置き場も必要になるなどの問題があり、ここに本発明の解決すべき課題がある。
【０００５】
【課題を解決するための手段】
本発明は、上記の如き実情に鑑みこれらの課題を解決することを目的として創作されたものであって、請求項１の発明は、鉱脈または鉱石でない火成岩あるいは泥岩を含む掘削残土について脱硫処理等の管理処分をする必要があるか否かの評価方法であって、該掘削残土の試料が火成岩を含む場合、予め設定される第一基準ｐＨ以下の酸性水溶出の可能性があると予測される試料について帯磁率と水溶液に溶出させた溶出水ｐＨとの測定結果から、前記第一基準ｐＨ以下の酸性水を溶出しないと予測される試料の帯磁率を設定して、評価しようとする試料が前記設定帯磁率以上の帯磁率を示す場合には、管理処分する必要がない掘削残土のものであると評価するようにしたことを特徴とする火成岩あるいは泥岩を含む掘削残土の評価方法である。
請求項２の発明は、鉱脈または鉱石でない火成岩あるいは泥岩を含む掘削残土について脱硫処理等の管理処分をする必要があるか否かの評価方法であって、該掘削残土の試料が火成岩を含む場合、予め設定される第一基準ｐＨ以下の酸性水溶出の可能性があると予測される試料について帯磁率と水溶液に溶出させた溶出水ｐＨとの測定結果から、前記第一基準ｐＨ以下の酸性水を溶出しないと予測される試料の帯磁率を設定すると共に、前記溶出液の予め設定される短い第一時間経過後と長い第二時間経過後との各溶出水ｐＨの測定結果から、第二時間経過後の溶出液ｐＨが予め設定される第二基準ｐＨ以下になると予測される第一時間経過後の溶出液ｐＨを設定して、評価しようとする試料が、前記設定帯磁率以上の帯磁率を示す場合には管理処分する必要がない掘削残土のもの、前記設定帯磁率未満の帯磁率を示しかつ設定溶出液ｐＨ以下の溶出液ｐＨを示す場合には、管理処分する必要がある掘削残土のものであると評価することを特徴とする火成岩あるいは泥岩を含む掘削残土の評価方法である。
請求項３の発明は、鉱脈または鉱石でない火成岩あるいは泥岩を含む掘削残土について脱硫処理等の管理処分をする必要があるか否かの評価方法であって、該掘削残土の試料が火成岩を含む場合、予め設定される第一基準ｐＨ以下の酸性水溶出の可能性があると予測される試料について帯磁率と水溶液に溶出させた溶出水ｐＨの測定結果から、前記第一基準ｐＨ以下の酸性水を溶出しないと予測される試料の帯磁率を設定し、かつ前記溶出液の予め設定される短い第一時間経過後と長い第二時間経過後の各溶出水ｐＨの測定結果から、第二時間経過後の溶出液ｐＨが予め設定される第二基準ｐＨ以下になると予測される第一時間経過後の溶出液ｐＨを設定し、さらに試料中の硫黄含有率と前記第二時間経過後の溶出液ｐＨ値との測定結果から、第二時間経過後の溶出液ｐＨが前記第二基準ｐＨ値以下になると予測される硫黄含有率を設定して、評価しようとする試料が、前記設定帯磁率以上の帯磁率を示す場合には管理処分する必要がない掘削残土のもの、設定帯磁率未満の帯磁率を示しかつ設定溶出液ｐＨ以下の溶出液ｐＨを示す場合には管理処分する必要がある掘削残土のもの、設定帯磁率未満の帯磁率を示し、設定溶出液ｐＨを超える溶出液ｐＨを示しかつ前記設定硫黄含有率以上の硫黄含有率を示す場合には管理処分する必要がある掘削残土のものであると評価するようにしたことを特徴とする火成岩あるいは泥岩を含む掘削残土の評価方法である。
請求項４の発明は、鉱脈または鉱石でない火成岩あるいは泥岩を含む掘削残土について脱硫処理等の管理処分をする必要があるか否かの評価方法であって、該掘削残土の試料が泥岩を含む場合、予め設定される第一基準ｐＨ以下の酸性水溶出の可能性があると予測される試料について溶出液の予め設定される短い第一時間経過後と長い第二時間経過後との各溶出水ｐＨの測定結果から、第二時間経過後の溶出液ｐＨが予め設定される第二基準ｐＨ以下になると予測される第一時間経過後の溶出液ｐＨを設定し、硫黄とカルシウムの含有率モル比（Ｓ／Ｃａ）と前記第二時間経過後の溶出液ｐＨ値との測定結果から、第二時間経過後の溶出液ｐＨが第二基準ｐＨ以下になると予測される含有率モル比を設定して、評価しようとする試料が設定溶出液ｐＨ以下の溶出液ｐＨを示す場合には管理処分する必要がある掘削残土のもの、設定溶出液ｐＨを超える溶出液ｐＨを示しかつ硫黄とカルシウムの前記設定含有率モル比以上の含有率モル比を示すものである場合には管理処分する必要がある掘削残土のものであると評価するようにしたことを特徴とする火成岩あるいは泥岩を含む掘削残土の評価方法である。
請求項５の発明は、鉱脈または鉱石でない火成岩あるいは泥岩を含む掘削残土について脱硫処理等の管理処分をする必要があるか否かの評価方法であって、該掘削残土の試料が火成岩を含む場合、予め設定される第一基準ｐＨ以下の酸性水溶出の可能性があると予測される試料について帯磁率と水溶液に溶出させた溶出水ｐＨとの測定結果から、前記第一基準ｐＨ以下の酸性水を溶出しないと予測される試料の帯磁率を設定し、かつ前記溶出液の予め設定される短い第一時間経過後と長い第二時間経過後との各溶出水ｐＨの測定結果から、第二時間経過後の溶出液ｐＨが予め設定される第二基準ｐＨ以下になると予測される第一時間経過後の溶出液ｐＨを設定して、評価しようとする試料が、前記設定帯磁率以上の帯磁率を示す場合には管理処分する必要がない掘削残土のもの、設定帯磁率未満の帯磁率を示しかつ設定溶出液ｐＨ以下の溶出液ｐＨを示す場合には管理処分する必要がある掘削残土のもの、設定帯磁率未満の帯磁率を示し、設定溶出液ｐＨを超える溶出液ｐＨを示しかつ試料中の重金属含有率が予め設定される設定含有率以上である場合には管理処分をする必要がある掘削残土のものであると評価することを特徴とする火成岩あるいは泥岩を含む掘削残土の評価方法である。
請求項６の発明は、火成岩あるいは泥岩を含有する掘削残土について脱硫処理等の管理処分をする必要があるか否かの評価方法であって、鉱脈または鉱石でないと判断される掘削残土の試料が予め設定される第一基準ｐＨ以下の酸性水溶出の可能性があると予測される試料について帯磁率と水溶液に溶出させた溶出水ｐＨとの測定結果から、前記第一基準ｐＨ以下の酸性水を溶出しないと予測される試料の帯磁率を設定し、かつ前記溶出液の予め設定される短い第一時間経過後と長い第二時間経過後との各溶出水ｐＨの測定結果から、第二時間経過後の溶出液ｐＨが予め設定される第二基準ｐＨ以下になると予測される第一時間経過後の溶出液ｐＨを設定し、さらに試料中の硫黄含有率と前記第二時間経過後の溶出液ｐＨ値との測定結果から、第二時間経過後の溶出液ｐＨが前記第二基準ｐＨ値以下になると予測される硫黄含有率を設定し、さらにまた試料が泥岩である場合の硫黄とカルシウムの含有率モル比（Ｓ／Ｃａ）と前記第二時間経過後の溶出液ｐＨ値との測定結果から、第二時間経過後の溶出液ｐＨが第二基準ｐＨ以下になると予測される含有率モル比を設定して、測定しようとする試料が泥岩でない場合、該試料が、前記設定帯磁率以上の帯磁率を示す場合には管理処分する必要がない掘削残土のもの、設定帯磁率未満の帯磁率を示しかつ設定溶出液ｐＨ以下の溶出液ｐＨを示す場合には管理処分する必要がある掘削残土のもの、さらに設定帯磁率未満の帯磁率を示しかつ設定溶出液ｐＨを超える溶出液ｐＨを示したものについて、設定硫黄含有率以上の硫黄含有率を示すか、試料中の重金属含有率が予め設定される設定含有率以上を示すかの少なくとも一つである場合には管理処分をする必要がある掘削残土のもの、設定帯磁率未満の帯磁率を示しかつ設定溶出液ｐＨを超える溶出液ｐＨを示したものについて、設定硫黄含有率未満の硫黄含有率を示しかつ試料中の重金属含有率が予め設定される設定含有率未満である場合のものは管理処分を必要としない残土のものであると評価し、また、測定しようとする試料が泥岩である場合、該試料が、設定溶出液ｐＨ以下の溶出液ｐＨを示す場合には管理処分する必要がある掘削残土のもの、さらに設定溶出液ｐＨを超える溶出液ｐＨを示したものについて、設定硫黄含有率以上の硫黄含有率を示すか、硫黄とカルシウムの含有率モル比が前記設定含有率モル比以上を示すか、試料中の重金属含有率が予め設定される設定含有率以上を示すかの少なくとも一つの場合ものは管理処分をする必要がある掘削残土のもの、設定溶出液ｐＨを超える溶出液ｐＨを示したものについて、設定硫黄含有率未満の硫黄含有率を示し、硫黄とカルシウムの含有率モル比が設定含有率モル比未満を示しかつ試料中の重金属含有率が予め設定される設定含有率未満を示すものは管理処分を必要としない残土のものであると評価するようにしたことを特徴とする火成岩あるいは泥岩を含む掘削残土の評価方法である。
そしてこれらのようにすることで、火成岩あるいは泥岩を含む掘削残土について、管理処分が必要であるか否かの評価が短時間に簡単にできることになる。
また請求項７の発明は、請求項１、２、３、５または６において、設定帯磁率値は５０×１０^−６ｅｍｕ／ｃｍ^３であることを特徴とすることができる。
請求項８の発明は、請求項２、３、４、５または６において、１０ｍｍ以下に粉砕した試料１００重量部と蒸留水５００重量部とを容器に入れ、３分間浸盪後静置したものにおいて、第一時間は１時間であり、溶出水の設定ｐＨは６．０であることを特徴とすることができる。
請求項９の発明は、請求項３または６において、設定硫黄含有率は２．０ｗｔ％であることを特徴とすることができる。
請求項１０の発明は、請求項４または６において、硫黄とカルシウムの設定含有率モル比は１．０であることを特徴とすることができる。
【０００６】
【発明の実施の形態】
【０００７】
前記発明において、第一、第二基準ｐＨは同じであっても異なっていても良く、具体的数値としては、例えば排水の排出基準である５．８とすることができるが、この数値に限定されるものではなく、求められる排出環境によって調整されるものであることはいうまでもなく、また各測定結果から設定される設定帯磁率、設定溶出ｐＨ、設定硫黄含有率、硫黄、カルシウムの設定モル比、そして設定重金属含有率は、掘削現場の成分組成によって種々異なるものであり、これについても、求められる排出環境によって調整されるものであることはいうまでもない。
【０００８】
本発明は、東北新幹線八甲田トンネルを掘削した際に発生した残土について縷々検討した結果、完成したものである。八甲田トンネルは、七戸・新青森間に位置する全長２６ｋｍを越える長大トンネルであって、トンネル周辺には大小の旧金属鉱山が存在し、しかもトンネルのほぼ全域に渡り鉱化変質作用を受けた岩石が存在することが知られている。鉱化変質作用を受けた岩石についての物理的、化学的特徴を把握し、これらから簡易的な評価方法がないか検討するため、簡易溶出試験、硫黄含有量、帯磁率等の測定を試みた。
【０００９】
［簡易溶出試験］
事前調査として、トンネル周辺で地表から２０〜３５ｍの短尺ボーリングを行い、代表的な岩種を採取して簡易溶出試験（短尺ボーリング試料）を行った。またさらに本トンネルの斜路および本坑掘削時に採取した切羽試料および先進ボーリング試料（トンネル試料）をそれぞれ採取して簡易溶出試験を行った。簡易溶出試験は、採取試料を乾燥させ、１０ｍｍ以下に粉砕した試料１００ｇと蒸留水５００ｇを容器に入れ、３分間浸盪させた後、静置する。静置後１０分、１時間、７、１４、３０（２８）、４２、５６日経過後に、それぞれの溶出水（溶出液）ｐＨを測定することにより行った。
【００１０】
短尺ボーリングをして得た試料の簡易溶出試験における溶出水のｐＨの経時変化を図１に示す。図１によると、３０日後に酸性を示す試料は、何れも１０分後のｐＨが６以下を示し、１０分後のｐＨが６以上のものは酸性化していないことが確認される。この結果から、１０分後のｐＨの値は、酸性水発生の有無を判断するうえで重要な指標になると判断される。
一方、図２に短尺ボーリングして得た試料とトンネル切羽から得た試料の経時変化を示す。図２では、５６日後の溶出水のｐＨに対して各試料の１０分後から２８日後の溶出水ｐＨの変化を矢印で示した。これによると、トンネル試料に比べて短尺ボーリング試料はｐＨ変化が小さいことが確認される。このことからも、短尺ボーリング試料は１０分経過後にほぼ最終的なｐＨに近い状態に達するが、トンネル試料の溶出水ｐＨの変化は遅く、最終的なｐＨに達するまでに時間を要することも確認された。このような短尺ボーリング試料とトンネル試料の溶出水の酸性化傾向の違いは、短尺ボーリング試料は地表に近いため、すでに化学風化作用により黄鉄鉱の酸化と方解石等の緩衝鉱物の溶脱が進んだ試料であった可能性があるのに対し、斜路トンネル内の試料はほぼ新鮮な岩石であって化学風化作用が殆ど進んでいないことによるものと推定される。そして現に、トンネル試料においても、地表からの深度の浅い場所の試料の１０分後のｐＨは比較的低く、深部に掘り進むに従い高くなる傾向が確認された。
図３にトンネル試料について１０分後、１時間後の溶出水ｐＨと５６日後の溶出水ｐＨとの関係を示すが、これによると、１０分後の溶出水のｐＨを見ると、６．０以下のものは認められず、また１時間後のｐＨでは、６．０以下のものが少数観測され、７．０以下の試料の大部分が５６日後に酸性を示していることが確認された。このことから、１時間後の溶出水ｐＨを設定溶出水ｐＨと設定し、測定される試料の１時間後の試料の溶出水ｐＨがこの設定ｐＨ値より大きいか小さいかにより酸性化の有無の評価ができるといえることが確認された。そしてこの八甲田トンネルでは溶出水酸性化に関する過大評価を避けるためから、１時間後溶出水ｐＨが６．０以下を適宜処理が必要な管理型と判定することにしている。
【００１１】
［硫黄含有量の検討］
工事着工前のトンネル計画段階において、（Ｉ）近傍のトンネルの掘削残土（硫黄（Ｓ）含有量２．０ｗｔ％）、（ＩＩ）八甲田トンネルルート近傍に掘削した調査坑の掘削残土（Ｓ含有量２．３ｗｔ％）および（ＩＩＩ）近傍の鉱山の掘削残土（Ｓ含有量１５ｗｔ％）の残土に石灰岩砕石を混入したものの３種類を１０年間自然状態に置き、排出水のｐＨを測定したところ、（ＩＩＩ）の残土はｐＨが１．３〜２．８のあいだと強い酸性度を示し、（Ｉ）および（ＩＩ）のものでもｐＨは最低で６．３であった。この結果から、Ｓ含有量が２．０ｗｔ％を基準値とし、これ以上の硫黄含有量があるものを脱硫処理等の管理が必要な管理処分型とし、それ未満を処理が必要でない非管理処分型として設定し、これの信憑性についてさらに検討した。
【００１２】
次に、八甲田トンネルの切羽試料のうち、泥岩（泥岩については後述する）以外の試料に関する硫黄含有量と簡易溶出試験５６日後の溶出水ｐＨとの関係を図４に示す。これによると、５６日後の溶出水ｐＨが水の排出基準の５．８以下を示す試料はＳ含有量が２．０ｗｔ％以上のものが殆どで、２．０ｗｔ％未満でｐＨ５．８以下となるものは１８２１試料中、７試料（０．４％）であることが確認され、このことから、八甲田山トンネルにおいて、管理処分型とするか否かの設定Ｓ含有率値を２．０ｗｔ％とすることは妥当であると判断できる。
【００１３】
［帯磁率の検討］
黒鉱地域の火成岩は、熱水変質作用を受けると一般に帯磁率が低下し、硫黄含有量が増加することが知られている。その原因の一つとして、磁鉄鉱が黄鉄鉱等の硫黄に富み磁性の弱い鉱物に変質することが考えられている。このことから、帯磁率は鉱化変質の程度を判断する有効な指標となることが考えられる。このようなことから、トンネル切羽から採取した試料について、帯磁率と、簡易溶出試験５６日後溶出水のｐＨ並びにＳ含有量との測定結果をプロットしたものをそれぞれ図５、６に示す。これらのグラフ図から、八甲田トンネルにおける試料では、酸性水溶出の可能性があると考えられるＳ含有量２．０ｗｔ％以上の試料は、何れも帯磁率が５０×１０^−６ｅｍｕ／ｃｍ^３以下であった。また、溶出水がｐＨ５．８以下となる試料の帯磁率は３×１０^−６ｅｍｕ／ｃｍ^３以下であった。このことから、八甲田トンネル周辺に分布する火成岩については、５０×１０^−６ｅｍｕ／ｃｍ^３より大きい帯磁率のものは鉱化変質作用を受けていないことが確認され、そこでこの値を設定帯磁率とした。なお、帯磁率の測定は次の通りに行った。
ｉ．試料調整：岩石試料を２〜４ｍｍに調整し、１０ｍｌ容器につめる。
ｉｉ．帯磁率測定：バーティントン社製ＭＳ２型帯磁率計を用いて調整試料の帯磁率を測定する。
ｉｉｉ．調整試料の体積測定：一定量の水を入れたメスシリンダーにｉｉ．の試料を入れ、体積測定をする。
ｉｖ．ｉｉ．で測定した帯磁率をｉｉｉ．で測定した体積で除して単位体積あたりの帯磁率を算出する。
【００１４】
［泥岩に対する検討］
火成岩は、主として熱水変質作用を受けることにより黄鉄鉱が生成されるのに対し、泥岩は、その堆積時に初生的な黄鉄鉱が生成すると考えられており、Ｓ含有量の値が低い場合でも酸性水が発生する場合があると考えられる一方で、泥岩には方解石や斜長石のようなＣａ（カルシウム）含有鉱物が含まれている。そしてこれらの鉱物は、次式（６）（７）のような反応で硫酸を消費することにより、岩石と接する水のｐＨの低下を抑制するものと推定される。

つまり、泥岩の場合、酸性水が生じるか否かは、黄鉄鉱の酸性化により生成される硫酸量と、方解石や斜長石などＣａ含有鉱物（緩衝鉱物）の分解により消費される硫酸量の関係によるものであると考えられ、火成岩とは異なった基準を設けることが必要となる判断した。つまり泥岩は、緩衝鉱物がカルシウムを含む鉱物であることから、緩衝鉱物の含有量は全岩のＣａ含有量で置き換えられると仮定し、これと岩石の黄鉄鉱含有量の指標となるＳ含有量との比率が、溶出水のｐＨに関与するのではないかと類推し、そこで図７に、トンネル試料についてＳ／Ｃａモル比と簡易溶出試験５６日の溶出水ｐＨとの関係を示す。これによると、Ｓ／Ｃａモル比が１．０以上の泥岩はｐＨが排水基準の５．８以下になっていることが確認され、そこでこの値を設定Ｓ／Ｃａモル比とした。
さらにまた、方解石は溶解速度が速いことから、全岩Ｓ含有量が高い場合はＣａ含有量が大きくても方解石などの緩衝鉱物が黄鉄鉱よりも早期に溶解し、将来的に溶出水が酸性化する可能性が考えられる。そこで、泥岩以外の岩石と同様に硫黄含有量が２．０ｗｔ％以上を管理処分型に区分することとした。
ちなみに、Ｓ含有量とＣａ含有量は、例えば蛍光Ｘ線分析装置等の分析装置によって同時に、かつ迅速に分析できる。
【００１５】
［全岩化学組成分析の検討］
岩石中に含まれる硫黄鉱物の分解により酸性水が溶出すると同時に重金属イオンも溶出することが想定され、そこで試料について蛍光Ｘ線分析装置（理学電機工業社製：ＺＳＸ１００ｅ）を用いて銅（Ｃｕ）、鉛（Ｐｂ）、亜鉛（Ｚｎ）、砒素（Ａｓ）、カドニウム（Ｃｄ）、クロム（Ｃｒ）、ニッケル（Ｎｉ）、セレン（Ｓｅ）、バリウム（Ｂａ）の各種重金属元素の濃度を検量線法で行った。分析は、乾燥させた試料を７５μｍ以下の粉末状に粉砕したものを加圧成形して分析試料とした。
これら重金属は環境省の指針により土壌に関する基準値が既に規定されており、このためこの該基準値を超えるものについては脱重金属処理をする必要がある管理処分型のものであると評価する。
【００１６】
次に、図８に前記検討結果に基づき、火成岩あるいは泥岩を含有する掘削残土について、脱硫等の適宜の管理処分をする必要があるものと必要がないものとの区分けをするフローチャート図を示す。これによると、掘削した残土について、これがまず鉱脈あるいは鉱石であるかを肉眼で確認し、鉱脈または鉱石である場合には管理処分をする必要があるものとして区分けする。ついで、鉱脈または鉱石でない残土について、これが火成岩であってかつ測定した帯磁率が設定帯磁率である５０×１０^−６ｅｍｕ／ｃｍ^３以上のものは鉱化変質作用を受けていないものとして一般処理型に区分けすることができる。一方、前記設定帯磁率未満の試料については、１時経過後の溶出水ｐＨが設定溶出水ｐＨである６．０以下であれば、これを管理処分する必要があるものとして区分けする。さらに設定溶出水ｐＨである６．０を超えるものについては、泥岩であるか否かの判断をし、泥岩でない場合には、試料の硫黄含有率が２．０ｗｔ％以上か、含有重金属量が既に設定されている基準値以上のものは管理処分が必要であるとして区分し、そうでないものはそのまま廃棄できる非管理処分型として区分する。
一方、泥岩であると判断されたものについては、試料の硫黄含有率が２．０ｗｔ％以上か、含有重金属量が既に設定されている基準値以上のものの他に、さらに硫黄／カルシウムのモル比が設定モル比である１．０以上のものについては管理処分が必要であると区分し、未満のものについてはそのまま廃棄できる非管理処分型のものとして区分することができる。
【００１７】
因みに本発明を実施するにあたり、前述した第１〜第６の発明についてそれぞれ実施することができ、各発明において評価された残土が多量で、残りの残土が少ない場合には、第６の発明のように最後まで評価する必要がないもので、この場合、第１〜第５の発明において各残った残土中には管理処分する必要があるものが残留する可能性があるので、管理処分されるものとして評価される。
【００１８】
【効果】
このように本発明は、火成岩あるいは泥岩を含有する掘削残土について、脱硫等の管理処分をするものとする必要がないものとの区分けが、従来のように長時間を要する試験をしないでよく、短時間のうちに効率よくできることになって、トンネルやダム工事のように連続して掘削残土を排出する現場での区分け作業が効率化することになる。
【図面の簡単な説明】
【図１】短尺ボーリングして得た試料を簡易溶出試験した溶出水ｐＨの経時変化を表すグラフ図である。
【図２】短尺ボーリングして得た試料とトンネル切羽から得た試料の溶出水ｐＨの経時変化を示すグラフ図である。
【図３】トンネル試料について１０分後、１時間後の溶出水ｐＨと５６日後の溶出水ｐＨとの関係を示すグラフ図である。
【図４】泥岩以外の試料に関する硫黄含有量と簡易溶出試験５６日後の溶出水ｐＨとの関係を示すグラフ図である。
【図５】トンネルから得た火成岩の試料の帯磁率と簡易溶出試験５６日後の溶出水ｐＨとの関係を示すグラフ図である。
【図６】トンネルから得た火成岩の試料の帯磁率と硫黄含有量との関係を示すグラフ図である。
【図７】トンネルから得られた泥岩試料についてＳ／Ｃａモル比と簡易溶出試験５６日の溶出水ｐＨとの関係を示すグラフ図である。
【図８】火成岩あるいは泥岩を含有する掘削残土の評価手順を示すフローチャート図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of a method for evaluating excavated soil including igneous rock or mudstone containing sulfide minerals such as pyrite discharged when excavating a mine or tunnel.
[0002]
[Prior art]
When excavating tunnels and mines, igneous rocks (volcanic rocks) that have undergone mineralization and alteration containing sulfide minerals such as pyrite and mudstones containing pyrite at the beginning may be discharged. When such residual soil comes into contact with water (water such as rainwater and groundwater), acidic water and heavy metals are eluted to cause environmental pollution, which is a problem. Of the sulfide minerals contained in the mineralized alteration surplus soil, those that are generally the most abundant are pyrite (FeS). ₂ ), The process in which pyrite reacts with water and is oxidized is represented by the following reaction formula.

In other words, pyrite in the remaining soil is decomposed into divalent iron and sulfate ions by rainwater or groundwater in which oxygen is dissolved (formula (1)), and the generated divalent iron is further oxidized to trivalent iron (formula (1)). (2)). Next, trivalent iron precipitates as a hydroxide (Equation (4)), acts as a strong oxidizing agent to promote the oxidation of pyrite, and further generates sulfate ions and hydrogen ions (Equation (4)). )). Further, there is a reaction (formula (5)) for producing sulfate ions by oxygen oxidation of a sulfur element. It is known that these reactions are accelerated by the action of iron-oxidizing bacteria and sulfur-oxidizing bacteria that coexist in the same environment.
Of these remnants, veins and ores (which can be visually identified by specialists) are considered to contain a large amount of sulfide minerals, etc. Although it is not so much, it is difficult to distinguish those containing a part of them, and when mining residual soil partially containing such sulfide minerals etc., if this is left open as it is, the above-mentioned reaction proceeds and acid water is generated. It can cause environmental pollution. For this reason, it is necessary to detoxify the residual soil containing such sulfide minerals by appropriate treatment such as desulfurization in the management facility and then treat it as waste soil. Since it does not necessarily contain any sulfide minerals, etc., it is necessary to evaluate whether or not it is necessary to manage and dispose of the surplus soil. It is required to perform necessary management and disposal on residual soil that is evaluated to contain sulfide minerals, etc., and to discard the remaining soil that is evaluated as not containing it without management disposal.
Therefore, as a method of making such a distinction, a method of performing an evaluation by performing a pH test of an earth suspension or the like as described in Non-Patent Documents 1 and 2 below is known.
[0003]
[Non-patent document 1]
Soil test method and explanation (1st revised edition) (pp. 159 to 164) Revised June 26, 2000 Third printing Published by Japan Geotechnical Society
[Non-patent document 2]
Testing method for metals etc. contained in industrial waste February 13, 1973 Notification No. 13 of the Environment Agency
[0004]
[Problems to be solved by the invention]
However, in the above-mentioned conventional test method, for example, the shaking time alone is as long as 6 hours, and the remaining soil to be excavated next is separated into those requiring management disposal and those not requiring management after waiting for these test results. However, there is a problem that not only the work efficiency is poor, but also a place for storing the remaining soil waiting for separation is required, and there is a problem to be solved by the present invention.
[0005]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made with the object of solving these problems. The invention of claim 1 provides desulfurization treatment for excavated soil containing igneous rocks or mudstones that are not veins or ores. It is a method of evaluating whether or not it is necessary to perform a management disposal of the excavated soil, when the sample of the excavated remains contains igneous rock, it is predicted that there is a possibility of elution of acidic water having a predetermined first reference pH or lower. From the measurement results of the magnetic susceptibility and the pH of the eluted water eluted into the aqueous solution for the sample, the sample to be evaluated is set by setting the magnetic susceptibility of the sample that is predicted not to elute the acidic water having the first reference pH or lower. If the susceptibility indicates a susceptibility greater than or equal to the set susceptibility, the method for evaluating excavated remains including igneous rock or mudstone is characterized by evaluating the excavated remains without the need for management and disposal. .
The invention of claim 2 is a method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rocks or mudstones that are not veins or ores, wherein the sample of the excavated remains contains igneous rocks From the measurement results of the magnetic susceptibility and the pH of the eluted water eluted in the aqueous solution for a sample predicted to have a possibility of eluting the acidic water having a predetermined first reference pH or less, the acidity of the first reference pH or less is measured. Along with setting the magnetic susceptibility of the sample that is not expected to elute water, from the measurement results of the pH of each elution water after the elapse of a preset first short time and after the elapse of a long second time of the eluate, The eluate pH after elapse of two hours is set to be the eluate pH after elapse of the first time, which is predicted to be equal to or lower than the second reference pH that is set in advance, and the sample to be evaluated has a magnetic susceptibility greater than or equal to the set magnetic susceptibility. When indicating susceptibility Excavated soil that does not need to be disposed of, if it shows a susceptibility lower than the set susceptibility and an eluate pH that is equal to or lower than the set eluate pH, indicates that the excavated surplus soil needs to be managed and disposed of. This is a method for evaluating excavated soil containing igneous rock or mudstone, which is characterized by being evaluated.
The invention according to claim 3 is a method for evaluating whether it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rocks or mudstones that are not veins or ores, wherein a sample of the excavated remains contains igneous rocks From the measurement results of the magnetic susceptibility and the pH of the eluted water eluted in the aqueous solution for a sample predicted to have a possibility of elution of acidic water having a preset first reference pH or lower, the acid water having the first reference pH or lower is measured. The magnetic susceptibility of the sample that is not expected to elute is set, and from the measurement results of the pH of each elution water after the elapse of the preset first short time and after the elapse of the long second time of the eluate, the second time Set the pH of the eluate after the elapse of the first time when the eluate pH after the elapse is predicted to be equal to or lower than the second reference pH set in advance, and further determine the sulfur content in the sample and the elution after the elapse of the second time From the measurement results with the liquid pH value If the eluate pH after the elapse of the second time is set to the sulfur content that is predicted to be equal to or lower than the second reference pH value, and the sample to be evaluated has a magnetic susceptibility equal to or higher than the set magnetic susceptibility, Excavated excavated soil that does not need to be disposed of by management, if it shows a susceptibility lower than the set susceptibility and shows an eluate pH that is less than or equal to the set eluent pH, it must be managed and disposed of, but less than the set susceptibility Indicate the magnetic susceptibility of, indicate the eluate pH exceeding the set eluent pH and if the sulfur content is equal to or higher than the set sulfur content, so as to evaluate that the soil is excavated soil that needs to be managed and disposed of This is a method for evaluating excavated soil containing igneous rock or mudstone, characterized by the following.
The invention according to claim 4 is a method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone that is not a vein or an ore, wherein the sample of the excavated earth contains mudstone. Each eluted water after a predetermined short first time elapse and a long second time elapse of the eluate for a sample predicted to have a possibility of elution of acidic water having a predetermined first reference pH or less. From the pH measurement results, set the eluate pH after the first time period, at which the eluate pH after the second time period is predicted to be equal to or lower than the preset second reference pH, and determine the sulfur and calcium content moles. From the measurement results of the ratio (S / Ca) and the pH of the eluate after the lapse of the second time, the content molar ratio is set that the eluate pH after the lapse of the second time is predicted to be equal to or lower than the second reference pH. Sample to be evaluated Excavated soil that needs to be managed and disposed of when the eluate pH is lower than the liquid pH, the eluate pH exceeds the set eluate pH, and the content mole of sulfur and calcium is equal to or higher than the set content mole ratio. A method for evaluating excavated soil containing igneous rock or mudstone is characterized in that when the ratio indicates a ratio, it is evaluated that the excavated earth must be managed and disposed of.
The invention of claim 5 is a method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rocks or mudstones that are not veins or ores, wherein the sample of the excavated remains contains igneous rocks From the measurement results of the magnetic susceptibility and the pH of the eluted water eluted in the aqueous solution for a sample predicted to have a possibility of elution of acidic water having a preset first reference pH or less, the acidity of the first reference pH or less is measured. The magnetic susceptibility of the sample that is not expected to elute water is set, and from the measurement results of the pH of each elution water after a predetermined short first time and after a long second time of the eluate, The eluate pH after the elapse of the first time is predicted to be equal to or lower than the second reference pH set in advance after the elapse of two hours, and the sample to be evaluated has a magnetic permeability of the set magnetic susceptibility or more. Control when indicating susceptibility Excavation surplus soil that does not need to be separated, if it shows a susceptibility less than the set susceptibility and shows an eluate pH that is less than or equal to the set eluate pH, it must be managed and disposed of. It shows susceptibility, shows an eluate pH that exceeds the set eluate pH, and when the heavy metal content in the sample is equal to or higher than a preset content, it is excavated soil that requires management disposal This is an evaluation method for excavated soil containing igneous rock or mudstone.
The invention of claim 6 is a method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone. From the measurement results of the magnetic susceptibility and the pH of the eluted water eluted into the aqueous solution for a sample predicted to be likely to be eluted with an acidic water having a first reference pH or less set in advance, the acid water having the first reference pH or less is measured. The magnetic susceptibility of the sample that is not expected to elute is set, and from the measurement results of the pH of each elution water after the elapse of a preset first short time and after the elapse of a long second time of the eluate, Set the eluate pH after elapse of the first time, the eluate pH after elapse is predicted to be equal to or lower than the second reference pH that is set in advance, further, the sulfur content in the sample and the elapse of the second time after elapse From the measurement results with the eluate pH value The sulfur content rate at which the eluate pH after the elapse of the second time is predicted to be equal to or lower than the second reference pH value is set, and further, when the sample is mudstone, the sulfur / calcium content molar ratio (S / Ca) ) And the pH value of the eluate after the lapse of the second time, set the molar ratio of the content that is expected to make the pH of the eluate after the lapse of the second time equal to or lower than the second reference pH. If the sample is not mudstone, if the sample has a magnetic susceptibility greater than or equal to the set magnetic susceptibility, it is not necessary to control and dispose of the excavated soil. If the following eluate pH is shown, the excavated soil that needs to be managed and disposed of, as well as those that show a susceptibility lower than the set susceptibility and an eluate pH that exceeds the set eluate pH, contain the set sulfur content. Rate of sulfur content In other words, if the heavy metal content in the sample is at least one of indicating a predetermined content or more, the excavated soil that needs to be managed and disposed of, indicates a susceptibility less than the set susceptibility. In addition, if the eluate pH is higher than the set eluate pH, it is controlled if the sulfur content is lower than the set sulfur content and the heavy metal content in the sample is lower than the predetermined set content. If the sample to be measured is mudstone and the sample shows an eluate pH below the set eluate pH, it must be managed and disposed of. Certain excavated soil, and those showing an eluate pH exceeding the set eluate pH, show a sulfur content that is equal to or higher than the set sulfur content, or the sulfur and calcium content molar ratios are equal to the set content molar ratio. Less than At least one of the cases where the above is shown or the heavy metal content in the sample is equal to or higher than the preset set content is the excavated soil that needs to be disposed of by management, the eluate exceeding the set eluate pH For those indicating pH, the sulfur content is less than the set sulfur content, the sulfur content and the calcium content mole ratio are less than the set content mole ratio, and the heavy metal content in the sample is the predetermined content. The method for evaluating excavated surplus soil containing igneous rock or mudstone is characterized in that the one showing a rate lower than the rate is evaluated as surplus soil that does not require management disposal.
By doing so, it is possible to easily and quickly evaluate whether or not management disposal is required for excavated soil containing igneous rock or mudstone.
According to a seventh aspect of the present invention, in the first, second, third, fifth or sixth aspect, the set susceptibility value is 50 × 10 ^-6 emu / cm ³ It can be characterized by the following.
According to an eighth aspect of the present invention, in the second, third, fourth, fifth or sixth aspect, 100 parts by weight of a sample pulverized to 10 mm or less and 500 parts by weight of distilled water are placed in a container, and left to stand after being stirred for 3 minutes. , The first time is 1 hour, and the set pH of the elution water is 6.0.
According to a ninth aspect of the present invention, in the third or sixth aspect, the set sulfur content is 2.0 wt%.
According to a tenth aspect of the present invention, in the fourth or sixth aspect, the set content molar ratio of sulfur to calcium is 1.0.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
[0007]
In the above invention, the first and second reference pHs may be the same or different, and a specific numerical value may be, for example, 5.8 which is a drainage discharge standard, but is not limited to this numerical value. It is needless to say that the set susceptibility, the set elution pH, the set sulfur content, the set sulfur and the set calcium, which are set from each measurement result, needless to say, are adjusted according to the required discharge environment. The molar ratio and the set heavy metal content vary depending on the component composition at the excavation site, and it goes without saying that this is also adjusted according to the required discharge environment.
[0008]
The present invention has been completed as a result of a detailed examination of the residual soil generated when the Hakkoda tunnel of the Tohoku Shinkansen was excavated. The Hakkoda Tunnel is a long tunnel with a total length of more than 26 km, located between Shichinohe and Shin-Aomori. There are large and small old metal mines around the tunnel, and rocks that have been mineralized and altered throughout almost the entire area of the tunnel. Is known to exist. In order to understand the physical and chemical characteristics of mineralized alteration rocks and to determine if there is a simple evaluation method from these, a simple dissolution test, sulfur content, magnetic susceptibility measurement, etc. were attempted. .
[0009]
[Simple dissolution test]
As a preliminary survey, a short boring of 20 to 35 m was performed from the surface of the ground around the tunnel, representative rock types were collected, and a simple dissolution test (short boring sample) was performed. Further, a face sample and an advanced boring sample (tunnel sample) collected during the excavation of the slope and the shaft of the tunnel were respectively subjected to a simple dissolution test. In the simple dissolution test, a collected sample is dried, 100 g of a sample pulverized to 10 mm or less and 500 g of distilled water are put in a container, shaken for 3 minutes, and then allowed to stand. After 10 minutes, 1 hour, 7, 14, 30 (28), 42, 56 days after standing, the pH of each eluted water (eluate) was measured.
[0010]
FIG. 1 shows the change over time in the pH of the elution water in a simple elution test of a sample obtained by short boring. According to FIG. 1, it is confirmed that all the samples showing acidity after 30 days have a pH of 6 or less after 10 minutes, and those having a pH of 6 or more after 10 minutes are not acidified. From these results, it is determined that the pH value after 10 minutes is an important index for determining whether or not acidic water is generated.
On the other hand, FIG. 2 shows the change over time of the sample obtained by short boring and the sample obtained from the tunnel face. In FIG. 2, the change in the pH of the elution water from 10 minutes to 28 days after the elapse of each sample with respect to the pH of the elution water after 56 days is indicated by an arrow. According to this, it is confirmed that the pH change of the short boring sample is smaller than that of the tunnel sample. From this, it was also confirmed that the short boring sample reached a state close to the final pH after 10 minutes, but the pH of the elution water of the tunnel sample changed slowly and it took time to reach the final pH. Was done. The difference in the acidification tendency of the eluted water between the short boring sample and the tunnel sample is that the short boring sample is close to the surface of the ground, so the oxidation of pyrite and the leaching of buffer minerals such as calcite have already progressed due to chemical weathering. It is presumed that the sample in the ramp tunnel was almost fresh rock and chemical weathering had hardly progressed. In fact, even in the tunnel sample, it was confirmed that the pH of the sample at a shallow place from the ground surface after 10 minutes was relatively low, and tended to increase as it was dug deeper.
FIG. 3 shows the relationship between the pH of the eluted water after 10 minutes and 1 hour and the pH of the eluted water after 56 days for the tunnel sample. According to this, the pH of the eluted water after 10 minutes is 6.0. The following were not observed, and at pH after 1 hour, a small number of samples having a pH of 6.0 or less were observed, and it was confirmed that most of the samples having a pH of 7.0 or less exhibited acidity after 56 days. . From this, the pH of the elution water after 1 hour is set as the set elution water pH, and the presence or absence of acidification is determined depending on whether the pH of the elution water of the sample after 1 hour of the sample to be measured is larger or smaller than the set pH value. It was confirmed that evaluation could be performed. In order to avoid overestimation of acidification of the elution water in the Hakkoda tunnel, the pH of the elution water after 1 hour is determined to be 6.0 or less as a control type requiring appropriate treatment in order to avoid overestimation.
[0011]
[Study of sulfur content]
At the tunnel planning stage before the construction commencement, (I) excavated soil from the tunnel near (I) (sulfur (S) content 2.0 wt%), (II) excavated soil from the investigation pit excavated near the Hakkoda tunnel route (S content) 2.3 wt%) and (III) mining excavated soil (S content: 15 wt%) were mixed with limestone crushed stone in the remaining soil for 10 years, and the pH of the discharged water was measured. The residual soil of (III) showed a strong acidity when the pH was between 1.3 and 2.8, and the pH of the soil of (I) and (II) was at least 6.3. Based on this result, the S content was set to 2.0 wt% as the reference value, those with a sulfur content higher than this were regarded as the controlled disposal type requiring management such as desulfurization treatment, and those with less than that were unmanaged disposal requiring no treatment. It was set as a type, and its authenticity was further examined.
[0012]
Next, FIG. 4 shows the relationship between the sulfur content and pH of the elution water 56 days after the simple elution test for samples other than the mudstone (mudstone will be described later) among the face samples of the Hakkoda tunnel. According to this, most of the samples in which the pH of the eluted water after 56 days is 5.8 or less of the water discharge standard have an S content of 2.0 wt% or more, and the S content is less than 2.0 wt% and the pH is 5.8 or less. It was confirmed that 7 out of 1821 samples (0.4%) were obtained. From this fact, in the Hakkoda Tunnel, the set S content value for determining whether or not to use the controlled disposal type was 2.0 wt%. Is appropriate.
[0013]
[Study of magnetic susceptibility]
It is known that igneous rocks in the Kuroko area generally have a lower magnetic susceptibility and a higher sulfur content when subjected to hydrothermal alteration. As one of the causes, it is considered that magnetite is transformed into a mineral rich in sulfur and weak in magnetism such as pyrite. From this, it is considered that the magnetic susceptibility is an effective index for judging the degree of mineralization alteration. For this reason, FIGS. 5 and 6 show plots of the measurement results of the magnetic susceptibility, the pH of the eluted water 56 days after the simple elution test, and the S content of the sample collected from the tunnel face. From these graphs, it can be seen from the graphs at the Hakkoda Tunnel that any of the samples having an S content of 2.0 wt% or more, which is considered to have a possibility of eluting the acidic water, has a magnetic susceptibility of 50 × 10 4. ^-6 emu / cm ³ It was below. The magnetic susceptibility of the sample in which the elution water has a pH of 5.8 or less is 3 × 10 ^-6 emu / cm ³ It was below. From this, the igneous rocks distributed around the Hakkoda tunnel are 50 × 10 ^-6 emu / cm ³ It was confirmed that those with higher magnetic susceptibility did not undergo mineralization alteration, and this value was taken as the set magnetic susceptibility. The susceptibility was measured as follows.
i. Sample adjustment: Adjust the rock sample to 2 to 4 mm and pack in a 10 ml container.
ii. Magnetic susceptibility measurement: The magnetic susceptibility of the adjusted sample is measured using an MS2 type magnetic susceptometer manufactured by Bertington.
iii. Volume measurement of adjusted sample: ii. , And measure the volume.
iv. ii. The magnetic susceptibility measured at iii. The susceptibility per unit volume is calculated by dividing by the volume measured in.
[0014]
[Study on mudstone]
Igneous rocks are primarily subjected to hydrothermal alteration to produce pyrite, while mudstone is thought to produce primary pyrite during its deposition, and acidic water is produced even when the S content is low. It is thought that mudstone may contain Ca (calcium) -containing minerals such as calcite and plagioclase. It is presumed that these minerals suppress the decrease in pH of water in contact with rocks by consuming sulfuric acid in reactions such as the following equations (6) and (7).

That is, in the case of mudstone, whether or not acid water is generated depends on the relationship between the amount of sulfuric acid generated by acidification of pyrite and the amount of sulfuric acid consumed by the decomposition of Ca-containing minerals (buffer minerals) such as calcite and plagioclase. It was decided that it was necessary to set a different standard from igneous rock. In other words, mudstone assumes that the buffer mineral content is replaced by the Ca content of the whole rock, since the buffer mineral is a mineral containing calcium, and this and the S content, which is an indicator of the pyrite content of the rock, It is presumed that the ratio of (1) is related to the pH of the elution water, and FIG. 7 shows the relationship between the S / Ca molar ratio and the pH of the elution water on day 56 of the simple elution test for the tunnel sample. According to this, it was confirmed that the pH of the mudstone having an S / Ca molar ratio of 1.0 or more was 5.8 or less as the drainage standard, and this value was set as the set S / Ca molar ratio.
Furthermore, since calcite has a high dissolution rate, buffer minerals such as calcite dissolve earlier than pyrite even if the Ca content is high, and the eluted water will be acidified in the future when the whole rock S content is high. It is possible. Therefore, as in the case of rocks other than mudstone, the sulfur content of 2.0 wt% or more was classified as a controlled disposal type.
Incidentally, the S content and the Ca content can be simultaneously and rapidly analyzed by an analyzer such as a fluorescent X-ray analyzer.
[0015]
[Examination of whole rock chemical composition analysis]
It is assumed that acidic water is eluted due to the decomposition of sulfur minerals contained in the rock, and heavy metal ions are eluted at the same time. Therefore, the sample is made of copper (Cu) using a fluorescent X-ray analyzer (Rigaku Corporation: ZSX100e). The concentration of various heavy metal elements such as lead, lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni), selenium (Se), and barium (Ba) is determined by a calibration curve method. I went in. In the analysis, the dried sample was pulverized into a powder having a size of 75 μm or less and subjected to pressure molding to obtain an analysis sample.
For these heavy metals, standard values for soil have already been specified by the guidelines of the Ministry of the Environment. Therefore, those exceeding these standard values are evaluated as being of a controlled disposal type that needs to be treated with heavy metals.
[0016]
Next, FIG. 8 is a flow chart for classifying the excavated soil containing igneous rock or mudstone into those that need to be subjected to appropriate management and disposal such as desulfurization and those that do not need to be based on the above examination results. According to this, the excavated soil is first visually checked whether it is a vein or ore, and if it is a vein or ore, it is classified as having to be managed and disposed. Then, for the vein or the non-ore ore soil, this is an igneous rock, and the measured susceptibility is 50 × 10 which is the set susceptibility. ^-6 emu / cm ³ The above can be classified into general treatment types as those not subjected to mineralization alteration. On the other hand, a sample having a magnetic susceptibility lower than the set magnetic susceptibility is classified as having to be managed and disposed if the pH of the elution water after 1 hour is equal to or lower than the set elution water pH of 6.0. Further, if the pH exceeds the set elution water pH of 6.0, it is determined whether the sample is mudstone. If the sample is not mudstone, the sulfur content of the sample is 2.0 wt% or more, or the heavy metal content is Those that are higher than the standard values already set are classified as requiring management disposal, and those that are not are classified as non-management disposal types that can be discarded as they are.
On the other hand, for those judged to be mudstone, the sulfur content of the sample is not less than 2.0 wt% or the content of heavy metals is not less than the preset reference value, and the sulfur / calcium molar ratio Can be classified as requiring management disposal, and those with less than 1.0, which is the set molar ratio, can be classified as non-management disposal types that can be discarded as they are.
[0017]
By the way, in carrying out the present invention, the above-described first to sixth inventions can be carried out, respectively. When the remaining soil evaluated in each invention is large and the remaining soil is small, the sixth invention In this case, it is not necessary to evaluate to the end. In this case, in the first to fifth inventions, there is a possibility that there is a possibility that some of the remaining soil may need to be disposed of by management. Will be evaluated as something.
[0018]
【effect】
Thus, the present invention, the excavated residual soil containing igneous rock or mudstone, the separation from those that do not need to be subjected to management disposal such as desulfurization, it is not necessary to perform a long test as in the past, Since it can be efficiently performed in a short time, the sorting operation at the site where the excavated soil is continuously discharged, such as tunnel and dam construction, becomes more efficient.
[Brief description of the drawings]
FIG. 1 is a graph showing the change over time in the pH of elution water in a simple elution test of a sample obtained by short boring.
FIG. 2 is a graph showing changes over time in the pH of elution water of a sample obtained by short boring and a sample obtained from a tunnel face.
FIG. 3 is a graph showing the relationship between the pH of the elution water after 10 minutes, 1 hour, and the pH of the elution water after 56 days for the tunnel sample.
FIG. 4 is a graph showing the relationship between the sulfur content of samples other than mudstone and the pH of dissolution water after 56 days of a simple dissolution test.
FIG. 5 is a graph showing the relationship between the magnetic susceptibility of a sample of igneous rock obtained from a tunnel and the pH of elution water after 56 days of a simple elution test.
FIG. 6 is a graph showing the relationship between the magnetic susceptibility and the sulfur content of a sample of igneous rock obtained from a tunnel.
FIG. 7 is a graph showing the relationship between the S / Ca molar ratio and the pH of the elution water for 56 days in a simple elution test for a mudstone sample obtained from a tunnel.
FIG. 8 is a flowchart illustrating a procedure for evaluating excavated soil containing igneous rock or mudstone.

Claims (10)

A method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone that is not a vein or ore,
When the sample of the excavated soil contains igneous rocks, the measurement results of the magnetic susceptibility and the pH of the eluted water eluted in the aqueous solution for the sample predicted to have a possibility of eluting the acidic water having a predetermined first reference pH or lower. From, to set the magnetic susceptibility of the sample is predicted not to elute the acidic water below the first reference pH,
When the sample to be evaluated has a magnetic susceptibility equal to or higher than the set magnetic susceptibility, the excavated soil containing igneous rock or mudstone is characterized in that it is evaluated as excavated soil that does not need to be disposed of by management. Evaluation method. A method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone that is not a vein or ore,
When the sample of the excavated soil contains igneous rocks, the measurement results of the magnetic susceptibility and the pH of the eluted water eluted in the aqueous solution for the sample predicted to have a possibility of eluting the acidic water having a predetermined first reference pH or lower. From, while setting the magnetic susceptibility of the sample is predicted not to elute the acidic water below the first reference pH,
From the measurement results of the eluate water pH after the elapse of a short first time and after the elapse of a long second time of the eluate, a second reference pH at which the eluate pH after the elapse of the second time is preset Set the eluate pH after the first time is expected to be less than
If the sample to be evaluated has a magnetic susceptibility that is equal to or higher than the set magnetic susceptibility, it is not necessary to manage and dispose of the excavated soil,
If the susceptibility indicates a susceptibility lower than the set susceptibility and indicates an eluate pH equal to or lower than the set eluate pH, igneous rock or mudstone characterized by being evaluated as being of excavated soil that needs to be disposed of by management How to evaluate excavated soil including. A method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone that is not a vein or ore,
When the excavated soil sample contains igneous rocks, the magnetic susceptibility and the pH of the eluted water eluted into the aqueous solution were measured from a sample predicted to have a possibility of elution of acidic water having a predetermined first reference pH or lower. Set the magnetic susceptibility of the sample that is not expected to elute acidic water below the first reference pH,
And from the measurement result of each eluate water pH after the elapse of a short first time and after the elapse of a long second time of the eluate, a second reference pH at which the eluate pH after the elapse of the second time is preset Set the eluate pH after the first time, which is expected to be below,
Further, from the measurement results of the sulfur content in the sample and the eluate pH after the lapse of the second time, the sulfur content at which the eluate pH after the lapse of the second time is predicted to be equal to or less than the second reference pH value And set
If the sample to be evaluated has a magnetic susceptibility that is equal to or higher than the set magnetic susceptibility, it is not necessary to manage and dispose of the excavated soil,
Excavated soil that needs to be disposed of by management if it shows a magnetic susceptibility lower than the set magnetic susceptibility and shows an eluate pH that is equal to or lower than the set eluate pH,
It indicates a magnetic susceptibility lower than the set magnetic susceptibility, indicates an eluate pH higher than the set eluent pH, and indicates a sulfur content equal to or higher than the set sulfur content. A method for evaluating excavated soil including igneous rock or mudstone, characterized in that it is evaluated. A method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone that is not a vein or ore,
When the sample of the excavated soil includes mudstone, the sample is predicted to have a possibility of elution of the acidic water having a predetermined first reference pH or lower, and after a lapse of a predetermined short first time of the eluate, it is long. From the measurement results of each eluate water pH after the elapse of the second time, the eluate pH after the elapse of the first time is predicted that the eluate pH after the elapse of the second time is equal to or less than a preset second reference pH. Set,
From the measurement results of the sulfur-to-calcium content molar ratio (S / Ca) and the eluate pH value after the second time, it is predicted that the eluate pH after the second time has become equal to or lower than the second reference pH. Content molar ratio
If the sample to be evaluated shows an eluate pH lower than the set eluate pH, excavated soil that needs to be managed and disposed of,
If it shows an eluate pH exceeding the set eluate pH and shows a content molar ratio of sulfur and calcium that is equal to or higher than the set content molar ratio, it is evaluated as being excavated soil that needs to be disposed of by management. A method of evaluating excavated soil containing igneous rock or mudstone, characterized in that: A method for evaluating whether or not it is necessary to perform management disposal such as desulfurization treatment on excavated soil containing igneous rock or mudstone that is not a vein or ore,
When the sample of the excavated soil contains igneous rocks, the measurement results of the magnetic susceptibility and the pH of the eluted water eluted in the aqueous solution for the sample predicted to have a possibility of eluting the acidic water having a predetermined first reference pH or lower. From, to set the magnetic susceptibility of the sample is predicted not to elute the acidic water below the first reference pH,
From the measurement results of the pH of each elution water after the elapse of a short first time and after the elapse of a long second time, the eluate pH after the elapse of the second time is set to a second reference value. Set the eluate pH after the first time, which is expected to be below pH,
If the sample to be evaluated has a magnetic susceptibility that is equal to or higher than the set magnetic susceptibility, it is not necessary to manage and dispose of the excavated soil,
Excavated soil that needs to be disposed of by management if it shows a magnetic susceptibility lower than the set magnetic susceptibility and shows an eluate pH that is equal to or lower than the set eluate pH,
Excavation that shows a susceptibility lower than the set susceptibility, shows an eluate pH that exceeds the set eluate pH, and requires heavy disposal when the heavy metal content in the sample is equal to or higher than a preset content. A method of evaluating excavated surplus soil containing igneous rock or mudstone, which is evaluated as surplus soil. A method for evaluating whether it is necessary to perform management disposal such as desulfurization of excavated soil containing igneous rock or mudstone,
The sample of the excavated soil that is judged not to be a vein or an ore has a magnetic susceptibility and a pH of the eluted water eluted in the aqueous solution for a sample predicted to have a possibility of elution of acidic water having a predetermined first reference pH or less. From the measurement results, set the magnetic susceptibility of the sample predicted not to elute the acidic water below the first reference pH,
From the measurement results of the pH of each elution water after the elapse of a short first time and after the elapse of a long second time, the eluate pH after the elapse of the second time is set to a second reference value. Set the eluate pH after the first time, which is expected to be below pH,
Further, from the measurement results of the sulfur content in the sample and the eluate pH after the lapse of the second time, the sulfur content at which the eluate pH after the lapse of the second time is predicted to be equal to or less than the second reference pH value And set
Furthermore, from the measurement results of the sulfur-to-calcium content molar ratio (S / Ca) when the sample is mudstone and the eluate pH after the second time, the eluate pH after the second time has passed. By setting the content molar ratio expected to be below the second reference pH,
If the sample to be measured is not mudstone, if the sample shows a magnetic susceptibility greater than or equal to the set magnetic susceptibility, it is not necessary to manage and dispose of excavated soil,
Excavated soil that needs to be disposed of by management if it shows a magnetic susceptibility lower than the set magnetic susceptibility and shows an eluate pH that is equal to or lower than the set eluate pH,
Further, for those exhibiting a magnetic susceptibility lower than the set magnetic susceptibility and exhibiting an eluate pH exceeding the set eluate pH, exhibiting a sulfur content higher than the set sulfur content or setting a heavy metal content in the sample in advance. Excavation surplus soil that needs to be disposed of if at least one of the specified content rates or higher is indicated,
For those exhibiting a susceptibility lower than the set susceptibility and exhibiting an eluate pH exceeding the set eluate pH, a setting wherein the sulfur content is less than the set sulfur content and the heavy metal content in the sample is set in advance If the content is less than the content, it is judged that it is the remaining soil that does not require management disposal,
In addition, when the sample to be measured is mudstone, if the sample shows an eluate pH equal to or lower than the set eluate pH, the excavated soil must be managed and disposed of,
Further, for those showing an eluate pH exceeding the set eluate pH, whether the sulfur content is equal to or higher than the set sulfur content, or the sulfur and calcium content molar ratios are equal to or higher than the set content molar ratio, the sample At least one of the cases where the heavy metal content in the steel indicates a predetermined content or more is the excavated soil that needs to be disposed of by management,
For those showing an eluate pH exceeding the set eluate pH, a sulfur content lower than the set sulfur content is indicated, a sulfur / calcium content molar ratio is less than the set content molar ratio, and a heavy metal content in the sample. A method for evaluating excavated surplus soil containing igneous rock or mudstone, wherein a material whose rate is less than a preset content rate is evaluated as surplus soil that does not require management disposal. The method according to claim 1, 2, 3, 5, or 6, wherein the set susceptibility value is 50 × 10 ⁻⁶ emu / cm ³ . The method according to claim 2, 3, 4, 5, or 6, wherein 100 parts by weight of a sample pulverized to 10 mm or less and 500 parts by weight of distilled water are put into a container, and left to stand after shaking for 3 minutes. A method for evaluating excavated soil including igneous rock or mudstone, wherein the time is a time and the set pH of the elution water is 6.0. The method according to claim 3 or 6, wherein the set sulfur content is 2.0 wt%. The method according to claim 4 or 6, wherein the set molar ratio of sulfur to calcium is 1.0.

Images