浅谈沉积岩的分类及工程性质

浅谈沉积岩的分类及工程性质

The Discuss Classification and Engineering Properties of Sedimentary Rocks

学院：国际学院

班级：土木工程二班

姓名：杨良君

学号：631226010227

指导老师：肖巧林

浅谈沉积岩的分类及工程性质

杨良君

（重庆交通大学国际学院，土木工程专业二班学号：631226010227）摘要：沉积岩是地表环境中形成的一种地表面分布最广的岩石，它由碎屑物质、粘土矿物、化学沉积矿物和有机质及生物残骸组成。沉积岩记录了地球演化历史且蕴藏着占世界矿产资源总储量的80%能源矿产，对研究地球的演化和发展及能源开采有十分重要的理论价值。同时对地质工作也具有重要的意义。本文就沉积岩的组成、分类及工程性质进行研究。

关键词：沉积岩分类工程性质

中图分类号：P 文献标识码：A

（引言）

沉积岩，又称水成岩，是三种组成地球岩石圈的主要岩石之一。它是其他岩石的风化产物和火山喷发物，经过水流或冰川的搬运、沉积、成岩作用形成的岩石。地表岩石的70%都是沉积岩，它主要包括石灰岩、砂岩、页岩等。沉积岩地层蕴藏着绝大部分矿产，如能源、非金属、金属和稀有元素矿产，其次是化石。

1 沉积岩的组成

沉积岩主要由以下几种物质组成：

1.1 碎屑物质

碎屑物质是沉积岩的一种组分，它是由母岩经过机械风化作用产生的碎屑物质组成。由于它是经过物理风化作用形成的，因此其中大部分的化学成分、物理结构均没有较大的变化。常见的有陆源碎屑、内碎屑、火山碎屑。是碎屑岩、碎屑碳酸岩、火山碎屑岩等岩石的主要组成成分。

1.2 黏土物质

主要是由一些含铝、镁等为主的含水硅酸盐矿物的岩石，经化学风化作用形成的次生矿物。主要包括高岭石族、伊利石族、蒙脱石族、蛭石族以及海泡石等矿物。这类矿物的颗粒很细（<0.005mm)，具有很强的亲水性、可塑性及膨胀性。

1.3 化学沉积矿物

由生物化学作用或纯化学作用从溶液中沉积结晶产生的沉积矿物，如方解石、白云石、石膏、石盐、铁和锰的氧化物或氢氧化物等。

1.4 有机质及生物残骸

有机物质由生物作用或生物残骸堆积体经地质变化而成的物质，多半是盆地内的钙质壳生物碎屑或壳体堆积而成，如甲壳类和珊瑚等，也包括微体动物的壳和壳屑，以及藻类和藻类的碎屑等。

2 沉积岩的分类及其工程性质

按组成沉积岩的组分的大小、形状和排列方式进行分类，大致可以分为两类：一是陆源碎屑岩，主要由陆地岩石风化、剥蚀产生的各种碎屑物组成。按颗粒粗细分为砾岩、砂岩、粉砂岩和泥质岩。二是内积岩，主要指在盆地内沉积的化学岩、生物-化学岩，也可由风浪、风暴、地震和滑塌作用将未充分固结的岩石碎屑再堆积，成为内碎屑岩。沉积岩按造岩成分分为铝质岩、铁质岩、锰质岩、磷质岩、硅质岩、蒸发岩、可燃有机岩（褐煤、煤、油页岩）和碳酸盐岩（石灰岩、白云岩等）。

2.1 碎屑岩类

2.1.1火山碎屑岩

火山碎屑岩，是火山碎屑物质的含量占90%以上的岩石，火山碎屑物质主要有岩屑、晶屑和玻屑，因为火山碎屑没有经过长距离搬运，基本上是就地堆积，因此，颗粒分选和磨圆度都很差。

火山集块岩：主要由粒径>100mm的粗火山碎屑物质组成，胶结物主要为火山灰或熔岩，有时为碳酸钙、二氧化硅或泥质。

火山角砾岩：粒径一般为2~100mm的碎屑，占火山碎屑的90%，多呈棱角状，常为火山灰或硅质胶结。颜色呈暗灰、蓝灰或褐灰色。

凝灰岩：主要由粒径小于2mm的火山灰及细屑组成，主要由晶屑、玻屑及岩屑，以火山灰等为胶结物，其孔隙性高、容重小、易风化。

2.1.2 沉积碎屑岩

沉积碎屑岩又名正常碎屑岩，是经先成岩风化剥蚀的碎屑物质，经搬运、沉积、胶结而成的岩石。因为碎屑岩是由各种砾石或砂粒胶结而成的岩石，它的坚固性与胶结物的性质及胶结形式有着密切的关系。

充填于碎屑颗粒空隙中的化学沉淀物质和黏土物质称为碎屑岩的胶结物，常见的有硅质、钙质、铁质和泥质。硅质胶结的岩石密度、强度高；钙质胶结的岩石能溶于酸；铁质胶结的岩石常为红色或紫红色，强度也比较高；黏土胶结的岩石质地松软、强度低、易湿软、易风化。因而在工程上必须注意钙质和黏土胶结的岩石，钙质岩石应避免与酸接触，黏土胶结岩石应避免承受过重的荷载，以免结构物坍塌。

常见的沉积碎屑岩主要由以下几种：

砾岩和角砾岩：砾岩和角砾岩主要由50%以上大于2mm的粗大碎屑胶结而成，黏土含量小于25%。由浑圆状砾石胶结而成的称为砾岩；由棱角状的角砾胶结而成的称为角砾岩。角砾岩的岩性单一，砾岩的岩性比较复杂，经常由多种岩石的碎屑和矿物颗粒组成。

砂岩：粒径在0.05~2mm的砂粒经胶结而成的岩石，砂粒的质量分数大于50%。砂岩的主要成分是石英、长石、云母等岩石碎屑。主要用于工程上的装饰材料。

粉砂岩：由粒径在0.005~0.5mm的碎屑物质的质量分数大于50%的碎屑岩。胶结物质主要是黏土。其结构疏松，强度和稳定度不高。主要用于工艺品的原料，如瓷砖。

2.2 黏土岩

黏土岩石沉积岩中分布最广的一类岩石。其黏土矿物的含量通常大于50%，粒径在0.005~0.0039mm。主要由高岭石、多水高岭石、水云母、绿泥石、蒙脱石和伊利石矿物组成。黏土岩致密均一，不透水，性质软弱，硬度低，易产生压缩变形，抗风化能力弱，尤其是蒙脱石类矿物，遇水后易膨胀、崩解等性质，不适宜作大型水工建筑物的地基。

常见的黏土岩主要由页岩和泥岩。

页岩是页片构造发育的黏土岩。它能沿层理面分裂成薄片或页片，具有清晰的层理，风化成碎片状。大部分岩性软弱，易风化成碎片，强度低，与水反应易丧失稳定性。主要用于作铁矿石，提炼石油，用作制砖、水泥和陶粒等产品的原料。

泥岩是一种成厚层状的黏土岩，层岩中层理不清，风化后成碎块状。以高岭石为主要成分的泥岩呈灰白色或黄白色，吸水性强，遇水后易软化。

如果黏土岩夹在坚硬的岩层中，浸水后易软化滑动，在工程上应该严加重视。

2.3 化学岩和生物化学岩

常见的化学岩和生物化学岩主要分一下几种：

2.3.1 石灰岩

石灰岩主要是由方解石组成。纯的石灰岩呈灰白色，含杂质的成灰色到灰黑色。石灰岩根据白云石和黏土矿物的含量分别达到25%~50%分为白云质灰岩和泥灰岩。颜色一般较浅，岩石呈致密状。石灰岩分布广，岩性均一，易开采，是用途很广的工程建筑材料。石灰岩主要用于制造水泥和石灰及铺路基石，冶金工业中作熔剂，环保中用于软化饮用水及污水处理，农业中作土壤调节剂、家禽饲料添加剂，还可用于轻工、化工、纺织、食品等工业。由于石灰岩容易溶解在水中，在石灰岩发育地区，常形成石林、溶洞等景观，是宝贵的旅游资源。

2.3.2 白云岩

主要由白云石构成，也含有方解石和黏土矿物，结晶结构。纯的白云岩为白色，随杂质的不同也会呈现不同的颜色。性质与石灰岩类似，但其强度和稳定性比较高。白云岩风化后常呈乱刀砍状的溶蚀沟纹。外貌特征与石灰岩类似，可以用稀硫酸反应程度加以判定。白云岩在建材上主要用于玻璃、陶瓷、铸石配料和含镁水泥原料及建筑用石料等。

结语

沉积岩不仅分布极为广泛，而且记录着地壳演变的漫长历史。现已知地壳上最老的岩石年龄为46亿年，而沉积岩圈中年龄最老的岩石就36亿年。沉积岩中蕴藏着大量的沉积矿产，如煤、石油、天然气、盐类等，而且在金属矿产中沉积类型的也占有很大的比例。而且沉积岩分布地区又是水文地质和工程地质的主要场所。因此，研究沉积岩对发展地质科学理论，寻找丰富的沉积矿产以及水文地质和工程地质工作均具有重要意义。

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The Discuss Classification and Engineering Properties of Sedimentary

Rocks

Yang Liangjun

(Chongqing Jiaotong University International College, School of Civil Engineering professional

second class number: 631226010227)

Keywords : sedimentary rock classification engineering properties

Abstract：Sedimentary rock cover most of the Earth’s surface b y area, it consists of detrital rock, clay rock, biochemical sedimentary rock and organic chemical rocks. Sedimentary rock recording tales of ancient events and ancient environments on the ever-changing face of the Earth. It covers more than 80% of the Earth's surface, Nevertheless, it contains the bulk of our energy resources. So the study of Earth's evolution and development of minerals and energy have important theoretical value, it also has important significance for geological works. This paper main study the composition of sedimentary rocks, classification and engineering properties.

CLC: P Document code: A

Introduction

Sedimentary rock is one of the three main rocks of the Earth's lithosphere. Rock and other volcanic eruption broken down and worn away by wind and water , and then slowly turn into rock.it covers 70% of the surface rock, which include limestone, sand stone, shale and so on. Sedimentary rock contain most of the minerals, such as energy, non-metallic, metal and rare metal.

1.The Classification and Engineering Properties of Sedimentary Rock

Sedimentary rock composed mainly of the following substances:

1.1 Detrital (or Clastic) Sedimentary Rocks

Detrital sedimentary rocks are formed by the particles or clasts that are cemented together to form the rock.Because it is formed through physical and weathering effect, most of them retain its' inherent chemical properties and physical structure.

Rock name Comments Clast size

Conglomerate Consists of rounded pebbles,cobbles,or boulders;some conglomerates are formed entirely of like-sized clasts cemented together,while some consist of large clasts surrounded by smaller

1.2 Clay rock Clay rock is the most widely spread rock.The diameter of the particle is less than 0.005mm.And it mainly composed of kaolinite,halloysite,mica,chlorite,smectite and illite minerals.Clay rock dense uniform,impervious nature weak,mild low,easy to produce compressive deformation,wind capacity is weak,especially montmorillonite rock,it can easy expansio n when water in it.

1.2.1 Shale

Shale have a construction like paper.it's characteristic are that it split along bedding planes into sheets or plates with clear bedding,after weathered showed pieces.Most of shale are weak,easy weathered into pieces,low-intensity ,react with water can easy lose its original stability .

1.2.2 Mud stone

Mud stone is a rock have a thick layer of clay ,the middle layer of rocks are disarray ,after weathered will become into pieces.Kaolinite as the main component of mud stone ,it's color always show gray or yellowish-white,high absorbent water,and easy to soften when run into water.

If it existence in the middle layer of hard rocks, easy to soften slide and flooding, should be strictly attention in the project.

1.3 Biochemical and Organic Sedimentary Rocks

Biological or organic sedimentary rocks are rocks that owe their existence to biological processes.When the organisms die, the solid material in the shells turn into sediment that eventually becomes incorporated in the class of sedimentary rocks called biochemical sedimentary rocks.Plants and yield materials incorporated in sedimentary rocks called organic rocks.

1.3.1 Limestone (biochemical type)

Limestone reach 25% to 50% into dolomitic limestone and marl are based on the content of dolomite and clay minerals.Color are generally shallow,rocky showed a dense shape.Limestone widely distributed,lithology uniform,easy to exploit,and it's a very useful engineering building clasts —the smaller clasts compose the matrix of the conglomerate.

Coarse Breccia

Consists of angular (sharp-edged) rock fragments

Sandstone

Consists of angular-sized grains; typically, sandstones consist almost entirely of quartz sand, because quartz is a durable mineral.But some sandstones consist of other minerals. Medium Arkose

Consists of mixture of sand-sized grains of quartz and feldspar. Siltstone

Consists of silt-size grains, usually composed of quartz. Fine Shale

Composed of clay flakes; shale forms by the lithification of mud. V ery fine

materials and valuable tourism resources.

1.3.2 Dolostone

Composed mainly of dolomite,calcite and clay minerals also contain the crystalline structure.Pure dolomite is white,with different impurities will show different colors.Similar in nature and limestone,but its strength and stability is relatively high.After weather ed dolomite always showed knifed shaped chaos grooves.Physical characteristics similar to limestone,can be distinguished by the reaction of acid.

Summary

Sedimentary rock not only spread everywhere,but also record the history of the evolution of the Earth's crust.It is known that the oldest rocks on the Earth's crust age is 4.6 billion years,and the age of the oldest sedimentary rock is 3.6 billion years.Sedimentary sock vast deposits of minerals,such as coal,oil,gas,salt,etc,and metal minerals also account for a large proportion.The place of sedimentary rock also is the main place of hydrogeology and engineering geology.Therefore,the research on the development of sedimentary geology scientific theories,to find a rich sediment mineral,to hydrogeology and engineering work has important significance.

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