基坑降水引起的相邻建筑物直接经济损失预测研究实用教案

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1、11 Study backgroundMore and more skyscrapers: deep foundation pitsmore and more underground projects Metro underground shop mallResult in: Deep excavation第1页/共54页第一页，共55页。Zhengzhou International Conference and Exhibition Center (ICEC)2第2页/共54页第二页，共55页。Zhengzhou ICEC Hotel3第3页/共54页第三页，共55页。Zijingshan

2、 Metro Station:In the future, the L-2 Metro line will run beneath this station. Here will be a busy transfer center for travelers.4第4页/共54页第四页，共55页。Adjacent ground settlement and crack caused by ground water pumping in construction pit5第5页/共54页第五页，共55页。Pipeline cut by ground settlement that resulted

3、 from ground water pumping6第6页/共54页第六页，共55页。Residential buildings damaged by ground settlement that resulted from ground water pumping7第7页/共54页第七页，共55页。How far?Magnitude?Is settlement magnitude the only factor?8第8页/共54页第八页，共55页。Construction pit ground water pumpingDetermining of ground water table a

4、nd contour after pumpingBuilding direct loss vs. ground settlement gradientGround settlement gradientDetermining of ground settlement and contourAdjacent building direct loss prediction9第9页/共54页第九页，共55页。2 Ground water table and contour after pumping2.1 General algorithm for water table determiningA-

5、Solution of fluid mechanism: strict analytic solutionB-Solution of hydraulics: approximate solution(3-D stable flow)(2-D stable flow)10第10页/共54页第十页，共55页。C- Numerical simulationPore water pressure numerical simulation-111第11页/共54页第十一页，共55页。Pore water pressure numerical simulation-212第12页/共54页第十二页，共55

6、页。Ground settlement numerical simulation-113第13页/共54页第十三页，共55页。Ground settlement numerical simulation-214第14页/共54页第十四页，共55页。However, these algorithms are too complicated to be applied in practical project! On the other hand, most of the Chinese civil engineers are used to following the national code

7、s system This must be taken into consideration!15第15页/共54页第十五页，共55页。16第16页/共54页第十六页，共55页。17 Assumptions:2-dimension stable flow, without water cutting wall surrounding the pitDetermining of ground water table after pumpingThe ground water table may be obtained by(Dupuits equation)第17页/共54页第十七页，共55页。

8、18Loess geological areaAlluvion geological area第18页/共54页第十八页，共55页。19Before applying, the validity of the formula has to be checkedSix projects are chosen as cases study, and only one is discussed hereZhengzhou Metro Station:Athlete Center Station 第19页/共54页第十九页，共55页。20第20页/共54页第二十页，共55页。21第21页/共54页第二

9、十一页，共55页。22第22页/共54页第二十二页，共55页。locationSW-70SW-67SW-68SW-69monitored water table(m)-10.62-11.47-12.02-10.8Calculated water table (m)-10.95-9.69-9.69-8.74Distance to the edge of pit (m)-26-40-40-52Calculated water table and monitored water table23第23页/共54页第二十三页，共55页。24Calculated water table and monit

10、ored water tableAfter verification in six projects, it is found that the Dupuits equation can be used to determine the water table after pumping第24页/共54页第二十四页，共55页。3.1 Algorithm-soil compression accumulation (SCA) For the convenience of engineers, the algorithm stipulated in Chinese National Code (S

11、CA) is employed:3 Ground settlement caused by water pumping25第25页/共54页第二十五页，共55页。26 S2-usually very small, may be neglected According to the National Code, in order to obtained S1, the modification factor has to be determined firstmodification factor : _determined by local engineering geology condit

12、ion. (3.1)第26页/共54页第二十六页，共55页。No.Water tableCalculated settlement (mm)Monitored settlement (mm)110.7991.3527.00.2956210.4389.0324.90.2797312.16100.8733.60.3331413.8411433.80.2965515.15125.635.50.2826614.52119.9429.70.2476714.76122.1234.80.2850814.62120.8336.30.3004915.14125.5137.50.2988Modification

13、factor27第27页/共54页第二十七页，共55页。modification factor 28第28页/共54页第二十八页，共55页。Presume comply with the standard normal distribution29， 第29页/共54页第二十九页，共55页。Take as 0.29, then the settlement calculation error No.Modified calculation settlement (mm)S=S1Monitored settlement (mm)error1 126.4926.4927271.88%1.88%2

14、225.8225.8224.924.93.69%3.69%3 329.2529.2533.633.62.94%2.94%4 433.0633.0633.833.82.19%2.19%5 536.4236.4235.535.52.60%2.60%6 634.7834.7829.729.71.71%1.71%7 735.4135.4134.834.81.77%1.77%8 835.0435.0436.336.33.47%3.47%9 936.4036.4037.537.52.94%2.94%30第30页/共54页第三十页，共55页。 4 Building loss results from gro

15、und settlement 4.1 Main assumption Only direct loss is taken into consideration31第31页/共54页第三十一页，共55页。32 4.2 Algorithm(1) The ground near the construction pit is divided into a series of donuts. (2) Equation (3.1) is employed to determine the settlement of each donut (the middle line of each donut is

16、 taken as target).(3) Settlement gradient between bordered donuts is obtained.(4) Economic loss rate vs. ground settlement gradient is set up.(5) A certain scope around the pit is chosen, all buildings loss in the scope is accumulated. 第32页/共54页第三十二页，共55页。33第33页/共54页第三十三页，共55页。4.3 Donuts4.3.1 Usuall

17、y, the geometric center of pit is set as the center of all donuts4.3.2 The affecting scope (taken as 5Sw, Sw-the depth of water table falling beneath the pit ground ) is divided into a series of donuts with the increment as 0.2Sw34第34页/共54页第三十四页，共55页。4.4 ground settlement gradientNo.G1G2G3G4G5G6G7G8

18、Gi0.320.3.0.270.250.230.220.200.19No.G9G10G11G12G13G14G15G16Gi0.180.170.210.220.200.190.180.17No.G17G18G19G20G21G22G23G24Gi0.160.150.140.220.240.250.220.1835Ground settlement gradient in the Case Project第35页/共54页第三十五页，共55页。36Generally, the further the distance from the pit edge is, the smaller the g

19、round settlement gradient is. 第36页/共54页第三十六页，共55页。37However, if a donut runs across over the soil surface which is below and above the water table before and after pumping, the gradient here is likely to leap significantly. 第37页/共54页第三十七页，共55页。38For the sake of security, 1 is taken as the threshold

20、of ground settlement gradient.4.5 The threshold of difference settlement building第38页/共54页第三十八页，共55页。394.6 The relationship between ground settlement gradient (G) and economic loss rate () of building1 When G is smaller than 1 , = 0.2 Theoretically, when G approaches , = 1.3 Several historical cases

21、 are employed to set the relationship between G and , such as (Above parameters are all from reference)第39页/共54页第三十九页，共55页。Then, the form of the Equation is determined as 40 The Powell Optimize Method is used to obtain the parameters, then a=0.9692b=30.4862c=-0.03179第40页/共54页第四十页，共55页。41The formula

22、is derived from masonry structures around construction pit第41页/共54页第四十一页，共55页。4.7 Building Direct loss PredictionThe direct loss of damaged building caused by ground water pumping may be obtained as V-current value of building, andVN _rebuild cost of buildingV _depreciation of building42第42页/共54页第四十

23、二页，共55页。5 Practical ApplicationA case project is chosen to verify the algorithm 43第43页/共54页第四十三页，共55页。 If a certain building is located in one donut, then G is set as the gradient of the donut. If a certain building is cross-over several donuts, then G is taken as the maximum gradient of the donuts.

24、Assumptions44第44页/共54页第四十四页，共55页。45第45页/共54页第四十五页，共55页。46第46页/共54页第四十六页，共55页。47第47页/共54页第四十七页，共55页。48第48页/共54页第四十八页，共55页。49第49页/共54页第四十九页，共55页。50DiscussionTake it for granted, the buildings loss will increase with the increasing of water table falling. However, the analysis results show that althoug

25、h the general tendency of loss increase with water table falling, at some certain spot , the curve turns to the reverse direction.More detail analysis shows that the building loss is in proportion to the ground settlement gradient, rather than settlement itself, and G is affected by the soil distrib

26、ution and water table of a certain area.第50页/共54页第五十页，共55页。6 Conclusions511 The Dupuits equation is verified to be adequate to determine the water table after pumping in construction pit2 For the convenience of engineers, the algorithm stipulated in Chinese National Code (soil compression accumulati

27、on) may be used to determine the ground settlement. For the north-east part of Zhengzhou, the modification factor 第51页/共54页第五十一页，共55页。3 The formula for building direst loss vs. ground settlement gradient is set up as 524 The adjacent building loss is proportion to the ground settlement gradient, rat

28、her than settlement itself, and G is affected by the soil distribution and water table falling as a certain area.第52页/共54页第五十二页，共55页。Thanks for your attention第53页/共54页第五十三页，共55页。54谢谢您的观看(gunkn)！第54页/共54页第五十四页，共55页。NoImage内容(nirng)总结1。1 Study background。Ground settlement gradient。(2-D stable flow)。monitored water table(m)。modification factor :。Monitored settlement (mm)。Monitored settlement (mm)。Thanks for your。谢谢您的观看(gunkn)第五十五页，共55页。