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第二篇A Very Slow Ride The surface of the earth may seem very stable to you.But you might be amazed if you knew some of the things that are going on under that surface. The earth has an outer shell of rigid pieces called tectonic plates (地壳构造板块).The plates include both ocean floor and dry land.Some have whole continents on top of them.The continents on top of the plates are just going along for a slow ride,moving only about four inches per year.But even this small movement causes three types of big interactions. One type is ocean ridges.These ridges develop in places where two plates are moving away from each other.As the plates separate,hot magma(岩浆)flows up to fill the space.New crust(地壳)builds up on the plate boundaries and causes ocean ridges.These ridges form long mountain ranges,which only rise above the ocean surface in a few places. Another type of reaction-trenches-occurs between two plates that are moving toward each other.As the plates meet,one bends downward and plunges undemeath the other.This forms deep ocean trenches.The Marianas Trench off Guam in the western Pacific Ocean has a depth of more than 36,000 feet.This is the lowest point on the ocean floor.If the leading edges of the two colliding plates carry continents,then the layers of rock in the overriding plate crumple(变皱)and fold.A plate that carried what is now lndia collided with the southern edge of the plate that carried Europe and most of Asia.This caused the Himalayas,the world’s highest mountains. The third reaction is transform faults(转换断层).These faults occur where two plates that are traveling in opposite directions slide past each other.Severe earthquakes can occur.The San Andreas Fault in Califomia is a good example of this type of movement. To explain the effect of trenches,the writer gives the example of
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第二篇A Very Slow Ride The surface of the earth may seem very stable to you.But you might be amazed if you knew some of the things that are going on under that surface. The earth has an outer shell of rigid pieces called tectonic plates (地壳构造板块).The plates include both ocean floor and dry land.Some have whole continents on top of them.The continents on top of the plates are just going along for a slow ride,moving only about four inches per year.But even this small movement causes three types of big interactions. One type is ocean ridges.These ridges develop in places where two plates are moving away from each other.As the plates separate,hot magma(岩浆)flows up to fill the space.New crust(地壳)builds up on the plate boundaries and causes ocean ridges.These ridges form long mountain ranges,which only rise above the ocean surface in a few places. Another type of reaction-trenches-occurs between two plates that are moving toward each other.As the plates meet,one bends downward and plunges undemeath the other.This forms deep ocean trenches.The Marianas Trench off Guam in the western Pacific Ocean has a depth of more than 36,000 feet.This is the lowest point on the ocean floor.If the leading edges of the two colliding plates carry continents,then the layers of rock in the overriding plate crumple(变皱)and fold.A plate that carried what is now lndia collided with the southern edge of the plate that carried Europe and most of Asia.This caused the Himalayas,the world’s highest mountains. The third reaction is transform faults(转换断层).These faults occur where two plates that are traveling in opposite directions slide past each other.Severe earthquakes can occur.The San Andreas Fault in Califomia is a good example of this type of movement. According to the passage,the earth is
（三）背景资料某施工总承包单位承担一项建筑基坑工程的施工。基坑开挖深度12m，基坑南侧距坑边6m 处有一栋6 层住宅楼。基坑土质状况从地面向下依次为：杂填土0～2m，粉质土2～5m，砂质土15～10m，粘性土哟10 ～12m，砂质土12～18m。上层滞水水位在地表以下5m（渗透系数为0.5m／d）,地表下18m 以内无承压水。基坑支护设计采用灌注桩加锚杆。施工前，建设单位为节约投资，指示更改设计，除南侧外其余三面均采用土钉墙支护，垂直开挖：基坑在开挖过程中北侧支护出现较大变形，但一直未被发现，最终导致北侧支护部分坍塌。事故调查中发现：（1）施工总承包单位对本工程作了重大危险源分析，确认南侧毗邻建筑物、临边防护、上下通道的安全为重大危险源，并制订了相应的措施，但未审批。（2）施工总承包单位有健全的安全制度文件。（3）施工过程中元任何安全检查记录、交底记录及培训教育记录等其他记录资料。问题 本工程基坑最小降水深度应为多少？降水宜采用何种方式？
第二篇A Very Slow Ride The surface of the earth may seem very stable to you.But you might be amazed if you knew some of the things that are going on under that surface. The earth has an outer shell of rigid pieces called tectonic plates (地壳构造板块).The plates include both ocean floor and dry land.Some have whole continents on top of them.The continents on top of the plates are just going along for a slow ride,moving only about four inches per year.But even this small movement causes three types of big interactions. One type is ocean ridges.These ridges develop in places where two plates are moving away from each other.As the plates separate,hot magma(岩浆)flows up to fill the space.New crust(地壳)builds up on the plate boundaries and causes ocean ridges.These ridges form long mountain ranges,which only rise above the ocean surface in a few places. Another type of reaction-trenches-occurs between two plates that are moving toward each other.As the plates meet,one bends downward and plunges undemeath the other.This forms deep ocean trenches.The Marianas Trench off Guam in the western Pacific Ocean has a depth of more than 36,000 feet.This is the lowest point on the ocean floor.If the leading edges of the two colliding plates carry continents,then the layers of rock in the overriding plate crumple(变皱)and fold.A plate that carried what is now lndia collided with the southern edge of the plate that carried Europe and most of Asia.This caused the Himalayas,the world’s highest mountains. The third reaction is transform faults(转换断层).These faults occur where two plates that are traveling in opposite directions slide past each other.Severe earthquakes can occur.The San Andreas Fault in Califomia is a good example of this type of movement. This passage is mostly about
案例分析题某城市跨线立交桥工程，桥梁全长811m，共计24跨，桥梁下部结构有22根直径1.5m的钻孔灌注桩，采用反循环钻机成孔。项目部针对钻孔桩数量多，经招标程序将钻孔作业分项工程分包给甲机械施工公司，由甲公司负责组织钻孔机械进行钻孔作业。施工过程中现场发生如下事件：事件一：项目部在现场文明施工检查时发现：原有泥浆沉淀池已淤积，正在进行钻孔施工的泥浆水沿排水沟直接流到工地附近的河道里，现场土堆旁有未燃尽的油毡碎片。事件二：甲公司液压起重机起吊钢筋笼时，因钢筋笼的U形吊环与主筋焊接不牢，起吊过程中钢筋笼倾倒，所幸作业人员及时避开，没有造成人员伤亡，但将泥浆搅拌棚砸坏。项目经理组织人员清理现场，并开展事故调查分析，对分包方进行罚款处理，调查报告完成后，经项目经理签字，上报了企业负责安全的部门。事件三：受钻孔机械故障影响，项目部要求甲公司增加钻孔机械，以保障钻孔作业的计划进度。因甲公司钻机在其他工地，需等5d后才能运到现场，等到该桥全部钻孔桩完成时已拖延工期13d。问题： 背景中选用反循环钻机成孔，则此处钻孔灌注桩作业的地层条件可能是什么样的？
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