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1、地地 基基 处处 理理 技技 术术Ground Improvement Techniques章荣军章荣军 (Rongjun ZHANG)华中科技大学华中科技大学Huazhong University of Science & Technology 1Office: 207#, South No.2 Building ( (南二楼南二楼 207 房间）房间）Contact Information：E-mail: ce_QQ: 40228415WeChat: zhangrongjun1984Tel: 15827157841 (Mobile)About MyselfPrefaceDr. Rongju
2、n ZHANG (章荣军章荣军)Preferred2It is my pleasure to know all of you!Preface3 Bilingual (双语双语) Course (Mandarin & English) Excellent Course in HUST Textbook (Edited by Prof. ZHENG Junjie ) Website of This Course: http:/ Exam: Class performance (30%) + Final examination (70%) (open-book)About this coursePr
3、efaceGround Improvement Techniques4Chapter 1 Introduction5 1.1 What is Ground Improvement?Chapter 1 Introduction 1.2 Why do We Improve Ground? 1.3 What Contents in this Course?61.1 What is Ground Improvement? l1.1.2 Definition of Ground Improvementl1.1.3 Function of Ground ImprovementChapter 1l1.1.1
4、 Two basic terminologies -Ground (地基地基) Foundation (基础基础)7Chapter 11.1.1 Two basic terminologiesMetaphorically, a tree is like a structure.FoundationGroundFoundation(基基础础) ): :建建筑筑底底部部与与地地基基接接触触的的承承重重构构件件，它它的的作作用用是是把把建建筑筑上上部部的的荷荷载传给地基。载传给地基。Ground(地地基基) ): :建建筑筑物物下下面面支支承承基基础础的的土土体体或或岩岩体体。有有天天然然地地基基和
5、和人人工工地地基基两两类类。天天然然地地基基是是不不需需要要人人加加固固的的天天然然土土层层。人人工工地地基基需需要要人人加固处理。加固处理。8Chapter 11.1.1 Two basic terminologiesIn low-rise structuresSpread foundationGround91.1.1 Two basic terminologiesIn high-rise structuresChapter 1Pile foundationGround101.1.1 Two basic terminologiesIn bridge towersChapter 1Ground
6、Open caisson foundation111.1.1 Two basic terminologiesIn high embankmentsChapter 1Artificial Ground - Composite Ground (including piles)121.1.1 Two basic terminologiesChapter 1Difference between Composite Ground and Pile Group Foundation:p Connection to Superstructurep Load Bearing Ratio of Soilp Lo
7、ad Transfer MechanismTo summarize:Ground (地基地基) Foundation (基础基础)This course focuses only on GROUND.13If the engineering performance of natural ground cannot meet the requirements of the structure to be constructed, the natural ground must be improved to form a new type of artificial ground to achie
8、ve the goal and ensure the safety of the structure.This improvement is named as Ground Improvement or Ground Treatment.1.1.2 Definition of Ground ImprovementChapter 1Natural groundImproved ground14 (1) enhancing shear strength of soils, (2) reducing compressibility of soils, (3) improving performanc
9、e of water-proof, (4) mitigating liquefaction, and (5) improving collapsible / expansive soils The function of ground improvement includes:1.1.3 Function of Ground ImprovementChapter 115l1.2.1 Some Typical Case Historiesl1.2.2 Poor Engineering Properties of Weak Soilsl1.2.3 Special Requirements of S
10、tructures to be Constructed1.2 Why do We Improve Ground? Chapter 116(1) Leaning Tower of Pisa8 floors, 55 m high, total weight = 145 MN.Average pressure acted on ground = 50 kPa. Construction began in 1173, paused at the 4th floor with the height of 29 m due to significant slant, completed in 1370.
11、1.2.1 Some Typical Case HistoriesChapter 117TheThebearingbearingsubsoilsubsoilisismealymealysand,sand,whichwhichisisunderlainunderlainbysiltandsoftclay.bysiltandsoftclay.DifferentialDifferentialsettlementsettlementbetweenbetweennorthernnorthernandandsouthernsouthern sidessides isis 1.81.8mm duedue t
12、oto thethe unevenunevensoilsoillayers.layers.TheThedeviationdeviation ofof towertowercentercenter isis 5.275.27 mm andandthethe towertower hashas a a slantslantdegreeof5.5degreeof5.5. .It was a dangerous tower!(1) Leaning Tower of Pisa1.2.1 Some Typical Case HistoriesChapter 118Slant rectification(1
13、) Leaning Tower of Pisa1.2.1 Some Typical Case HistoriesChapter 119(2) Huqiu Tower in SuzhoulBuilt in Song Dynasty (more than 1000 years). 7-floor brick tower, 47.5 m in height, 13.66 m in diameter, and total weight = 63000 kN. lIn 1978, maximum deviation = 2.3 m, many cracks. lCauses: non-homogeneo
14、us subsoils and unimproved ground. Before slant rectification1.2.1 Some Typical Case HistoriesChapter 120lGround improvement started in 1978 and completed in 1983. The settlement rate tended to stability.After slant rectification(2) Huqiu Tower in Suzhou1.2.1 Some Typical Case HistoriesChapter 121l6
15、5 silos, 59.44m in length, 23.47m in width and 31.00 m in height; reinforced mat foundation: thickness = 61 cm, and embedded depth = 3.66m. l Structure weight = 20000 t, almost 42.5% of the total weight after it was fully filled with the grain. Before filling grain(3) Transcona Grain Elevator in Can
16、ada1.2.1 Some Typical Case HistoriesChapter 122Grain volume 31822m3, settlement increment in 1h = 30.5cm. It slanted and collapsed 24h later, the west portion subsided 7.32m, and the east heaved 1.52 m, the slanting angle is 27. Cause: Assumed bearing capacity = 352 kPa but actual bearing capacity =
17、 193.8 276.6 kPa, which is much lower than the design value!(3) Transcona Grain Elevator in Canada1.2.1 Some Typical Case HistoriesChapter 123The super-structure was still in good condition though the ground failed. The grain elevator continued to be used after it had been lifted by 388 jacks, and e
18、ach jacks capacity is 50 t, but the elevation was 4 m lower than the original position. After lifted by jacks(3) Transcona Grain Elevator in Canada1.2.1 Some Typical Case HistoriesChapter 124In 1955, 10 grain silos collapsed due to ground failure in Fargo, North Dakota, USA. (4) Grain Silos in USA 1
19、.2.1 Some Typical Case HistoriesChapter 125Forage capacity = 25000t, and built on soft clay. In the 1st use, ground failed because the filling was too fast and subsoils had not been fully consolidated. (5) Forage Silo in Canada1.2.1 Some Typical Case HistoriesChapter 126A building in Mexico City. Di
20、fferential settlement can be obviously seen. The soil has very high water content up to 650%，and extremely high compressibility (6) Building in Mexico1.2.1 Some Typical Case HistoriesChapter 127Buildings collapsed due to liquefaction induced by 1964 Niigata(新泻新泻) earthquake.(7) Buildings after Earth
21、quake 1.2.1 Some Typical Case HistoriesChapter 128A bridge collapsed due to liquefaction induced by 1964 Niigata earthquake.(8) Bridge after Earthquake 1.2.1 Some Typical Case HistoriesChapter 129(9) Settlement of Kansai International Airport1.2.1 Some Typical Case HistoriesChapter 1Ground condition
22、 of the seabedCondition of the settlement30(9) Settlement of Kansai International Airport1.2.1 Some Typical Case HistoriesChapter 1Settlement per yearElevations on the island (as of Dec. 2015)Measure against settlement31Weak soils usually include:l(1) Soft clays,l(2) Fills (artificial fill, miscella
23、neous fill, or hydraulic fill),l(3) Some sands and silts,l(4) Organic soils and peatsl(5) Special soils (collapsible soils, expansive soils, frozen soils, or salty soils)l(6) Karst groundl(7) Landfill soils.1.2.2 Poor Engineering Properties of Weak SoilsChapter 1321.2.2 Poor Engineering Properties o
24、f Weak SoilsChapter 1(1) For soft clay Key Engineering issues:lLow bearing capacity,lHigh compressibility lLow permeabilitylRheological properties331.2.2 Poor Engineering Properties of Weak SoilsChapter 1(2) For fills Key Engineering issues:lHigh compressibility (under-consolidated) lHighly heteroge
25、neous properties341.2.2 Poor Engineering Properties of Weak SoilsChapter 1(3) For some sands and silts - Coarse sandsKey Engineering issue:lHigh permeability (Hydraulic cutting-off walls are needed)351.2.2 Poor Engineering Properties of Weak SoilsChapter 1(3) For some sands and silts - Saturated fin
26、e sands & silts36Video 1Video 21.2.2 Poor Engineering Properties of Weak SoilsChapter 1(3) For some sands and silts - Saturated fine sands & siltsKey Engineering issue:lLiquefaction371.2.2 Poor Engineering Properties of Weak SoilsChapter 1(4) Organic soils and peatsKey Engineering issues:lLow bearin
27、g capacity,lHigh compressibility lRheological propertieslPoor chemical stability381.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils- Collapsible loess 宁夏扶贫扬黄工程宁夏扶贫扬黄工程11号泵站号泵站 的大厚度自重湿陷性黄土地基试坑浸水试验的大厚度自重湿陷性黄土地基试坑浸水试验391.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5)
28、Special soils- Collapsible loess 新疆伊犁黄土现场浸水试验新疆伊犁黄土现场浸水试验避开另选避开另选（浸水第二天湿陷量达（浸水第二天湿陷量达2m, 2m, 最终最大湿陷量最终最大湿陷量3.2m)3.2m)401.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils- Collapsible loess Key Engineering issue:lCollapsibilityMechanism:Mechanism:lClosureofvoidsClosureofvoidslS
29、olutionofsolubleSolutionofsolublecomponentscomponents411.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils- Expansive soilsKey Engineering issues:lSwelling in wateringlShrinking in dewatering Repeatedly!421.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils
30、- Expansive soils陶岔渠首深层滑坡陶岔渠首深层滑坡 长长300m300m左右，左右， 厚厚24m24m，9m9m深度处见水，深度处见水， 约约200,000m200,000m3 3431.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils- Expansive soils镇江南徐大道黄山段滑坡。第二地质土层为膨胀土，综合坡比镇江南徐大道黄山段滑坡。第二地质土层为膨胀土，综合坡比1 1：3 31 1：5 5。0303年年6 6月道路月道路开挖，滑坡逐步向上发展开挖，滑坡逐步向上发展( (只
31、要下雨，就向上发展只要下雨，就向上发展) )。范围：纵向。范围：纵向100m100m，横向，横向300m300m左右。左右。441.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils- Frozen soilsKey Engineering issues:lSwelling and shrinkinglStrength decreasing with load duration451.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Sp
32、ecial soils- Salty soilsKey Engineering issues:lSwelling and shrinkinglCorrosivity461.2.2 Poor Engineering Properties of Weak SoilsChapter 1(5) Special soils- Salty soils471.2.2 Poor Engineering Properties of Weak SoilsChapter 1(6) Karst groundKey Engineering issues:lLarge deformation and collapselW
33、ater burst481.2.2 Poor Engineering Properties of Weak SoilsChapter 1(7) Landfill soilKey Engineering issues:lLow strengthlHigh compressibilitylHighly heterogeneous propertieslContamination49TosummarizeTosummarize: :WeaksoilsareusuallynotabletoshowadequateWeaksoilsareusuallynotabletoshowadequateprope
34、rtiestosatisfythepropertiestosatisfytheconstructionrequirementsconstructionrequirements inthefollowingaspects:inthefollowingaspects:Strengthandbearingcapacity;Strengthandbearingcapacity;Stability;Stability;Displacement;Displacement;Hydraulicseepagecondition;Hydraulicseepagecondition;Dynamiccharacter
35、isticsDynamiccharacteristics1.2.2 Poor Engineering Properties of Weak SoilsChapter 1501.2.3 Special Requirements of Structures to be ConstructedChapter 1For instance: Super large-scale construction 51 Adjacent to existing important structures 1.2.3 Special Requirements of Structures to be Constructe
36、dChapter 1XunlimenStation,Line2ofWuhanSubwayXunlimenStation,Line2ofWuhanSubway52Specifically, 8 ground improvement techniques are to be introduced in this course:l Replacement and Cushion Method,l Consolidation Method, l Dynamic Compaction Method, l Sand / Stone Column Method, l Lime Column Method,
37、l Soil-Cement Mixing Method, l Cement-Flyash-Gravel Column Method, l Jet Grouting Method.1.3 What Contents in This Course? Chapter 153(1) Reading the history of every technique(2) Understanding its mechanism(3) Mastering the design methodology(4) Knowing about the construction methods(5) Grasping quality assessment methods(6) Studying case historiesMethods for Learning This CoursesChapter 11.3 What Contents in This Course? 54Class overThanks for your attention !55
