【正文】 、樁數(shù)、樁基礎(chǔ)寬度與樁長的比值等）、成樁工藝、樁基施工與流程、土的類別與性質(zhì)、土層剖面的變化、荷載大小與持續(xù)時間以及承臺設(shè)置方式等眾多復(fù)雜因素，因此，目前尚未有較完整的樁基礎(chǔ)沉降計算方法?！督ㄖ鼗A(chǔ)設(shè)計規(guī)范》（GB 50007—2002）推薦的群樁沉降計算方法，不考慮樁間土的壓縮變形對沉降的影響，采用單層壓縮分層總和法按下式計算樁基礎(chǔ)的最終沉降： 式中 s——樁基礎(chǔ)最終沉降量，mm m——樁端平面以下壓縮土層范圍內(nèi)土層總數(shù)；——樁端平面下第j層土第i層分層在自重應(yīng)力至 自重應(yīng)力加附加應(yīng)力作用段的壓縮模量（MPa）；——樁端平面下第j層的計算分層數(shù)；——樁端平面下第j層土的第i個分層厚度（m）；——樁端平面下第j層土第i個分層的豎向附加應(yīng)力（KPa）；——樁基沉降計算經(jīng)驗系數(shù)，各地區(qū)應(yīng)根據(jù)當(dāng)?shù)氐墓こ處煖y資料統(tǒng)計對比分析確定。在樁頂豎向荷載作用下，當(dāng)樁相對于樁側(cè)土向下位移時，土對樁產(chǎn)生的向上作用的摩阻力，稱為正摩阻力(如圖3—2)；但是，當(dāng)樁側(cè)土體因某種原因而下沉，且其下沉量大于樁的沉降（及樁側(cè)土體相對于樁向下位移）時，土對樁產(chǎn)生的向下作用的摩阻力，成為負(fù)摩阻力（如圖3—3）。樁側(cè)負(fù)摩阻力問題，實質(zhì)上和正摩阻力一樣，只要得知土與樁之間的相對位移以及負(fù)摩阻力與相對位移之間的關(guān)系，就可以了解和樁側(cè)負(fù)摩阻力的分別和樁身軸力與界面位移了。由于樁側(cè)負(fù)摩阻力是由樁周土層的固結(jié)沉降引起的，因此負(fù)摩阻力的產(chǎn)生升和發(fā)展要經(jīng)歷一定的時間過程，這一時間過程的長短取決于樁自身沉降完成的時間和樁周土層固結(jié)完成的時間。中性點的位置取決于樁與樁側(cè)土的相對位移，原則上應(yīng)根據(jù)樁沉降與樁周土沉降相等的條件確定。工程實測表明，在可壓縮土層的范圍內(nèi)，中性點的穩(wěn)定深度是隨樁端持力層的剛度和強(qiáng)度的增大而增加的，其深度比可按下表經(jīng)驗取值。 表3—2 中性點深度 持力層性質(zhì)黏性土、粉土中密以上砂中密以上砂基巖中性點深度比精確計算負(fù)摩阻力是復(fù)雜而困難的。已有的一些有關(guān)的負(fù)摩阻力的計算方法與公式都是近似的和經(jīng)驗性的，使用較多的有以下兩種：（1） 對軟土和中等強(qiáng)度黏土，?。? 式中 ——土的無側(cè)限抗壓強(qiáng)度； ——土的不排水抗剪強(qiáng)度，可采用十字板現(xiàn)場測定。（2） 根據(jù)產(chǎn)生負(fù)摩阻力的土層中點的豎向有效覆蓋壓力，按下式計算： 對于砂類土，也可按下時估算負(fù)摩阻力強(qiáng)度： 式中 ——樁周第i層土經(jīng)鉆桿長度修正的平均標(biāo)準(zhǔn)貫入試驗錘擊數(shù)。 下拉荷載為中性點深度范圍內(nèi)負(fù)摩阻力的累計值，可按下式計算： 式中 ——樁截面周長； n——中性點以上土層數(shù)： ——中性點以上樁周第i層土的厚度。次此樁是預(yù)制混凝裝，采用涂以軟瀝青涂層的辦法來減小負(fù)摩阻力，涂層施工時應(yīng)注意不要將涂層擴(kuò)展到需利用樁周正摩阻力的樁身部分。在施工前，將樁表面清洗干凈；然后將瀝青加熱至150_180攝氏度，噴射在樁表面，噴澆厚度為6—10mm 圖3—2圖3—3參考文獻(xiàn) [1] 《建筑地基基礎(chǔ)涉及常用資料速查手冊》，地震出版社，2006年 [2] 東南大學(xué)、天津大學(xué)、同濟(jì)大學(xué) 合編，《混凝土結(jié)構(gòu)》，中國建筑工業(yè)出版社，2005年 [3] 東南大學(xué)、浙江大學(xué)等，《土力學(xué)》，中國建筑工業(yè)出版社，2005年 [4] 朱浮聲 主編，《地基基礎(chǔ)設(shè)計與計算》，人民交通出版社，2005年 [5] 益德清 主編，《深基坑支護(hù)工程案例》，中國建筑工業(yè)出版社，1996年 [6] 湯康民 主編，《巖土工程》，武漢理工出版社，2000年 [7] 張慶賀 朱合華編，《土木工程專業(yè)畢業(yè)設(shè)計指導(dǎo)》，中國水利水電出版社，2001年 [8] 北京土木建筑學(xué)會 編，《建筑地基基礎(chǔ)工程施工操作手冊》，經(jīng)濟(jì)科學(xué)出版社，2004年[9] 方惠清 主編，《土木工程施工》，同濟(jì)大學(xué)出版社，2009年 [10] Elias V，Juran Nailing for Stabilization of Highway Slopes and Exacavations,FHWA/RD89/198,June 1991[11] Juran I,et of Soil Nailed Retaining Structures,Geotechnical Special Publications ASCE,1990 致 謝隨著畢業(yè)設(shè)計和答辯的結(jié)束，大學(xué)的四年生活即將結(jié)束，在此向辛勤培育過我們的老師致以誠摯的謝意。在畢業(yè)設(shè)計過程中，李大勇老師、高盟老師和肖洪天老師給了我很大的幫助，給予了我悉心的指導(dǎo)。在此，向三位老師表示深深的感謝。在我們的實習(xí)過程中，青島海底隧道施工現(xiàn)場和前灣港碼頭給了我們很好的實習(xí)機(jī)會，并提供了豐富的資料，為我們的設(shè)計能夠順利完成提供了前提，向他們表示謝意。設(shè)計時同學(xué)們是在一起的，因此，同學(xué)之間相互幫助，共同完成了設(shè)計。在此，向幫助過我的同學(xué)表示深深的謝意。附錄Excavation of soil nailing Technical AnalysisAbstract: The soil nailing technique is a new type of foundation pit forms in China in recent years has been widely used in foundation engineering, and achieved good economic and social benefits. In this paper, soil nailing technology, has done a brief analysis of the characteristics and discusses the construction of soil nailing and construction. Key words: soil nailing。 structure。 construction A soil nailing technology, concept and characteristics of Soil nail wall, also known as soil nailing technology, which is installed in situ soil with a relatively dense soil nails, and soil slope surface of sprayed concrete to build a steel mesh surface layer, through the soil nails, the surface layer and insitu soil the role of the three mon slope or retaining wall side. Soil nail walls but also poses a similar gravity in situ reinforced earth retaining structures. And supporting a variety of methods have been pared, it has the construction easy, simple equipment, require little space, excavation and supporting jobs can be parallel, the overall progress of the fast, low cost, as well as pollution, low noise, stable and reliable, social and economic good, and many other advantages, and therefore at home and abroad with the foundation pit slope reinforcement has been widely applied rapidly. Soil nail wall construction technology is a topdown step by step build process, according to the following order: According to design requirements for excavation face, trimmed slope, planted sprayed concrete thickness control signs。 jet first layer of concrete。 erection of drilling soil nails, grouting, erection of connectors。 banding steel net, spray a second layer of concrete。 set top of the hill, slope and the foot of the slope of the drainage system. Soilnailed lawenforcement: keep as much as possible, significantly higher maximum use of pit wall side of inherent mechanical strength of soil, changing soil structure and system load as part of the bracing. Sprayed concrete under the effect of high pressure gas flow, wherein highspeed soil surface layer and the soil in the spray created between 39。embedded solideffect39。, and gradually form a pletely closed with the excavation shoring systems, spray layer and mounted with a protective layer of and reinforcement of topsoil, so that to avoid exposure to wind and rain erosion, shallow collapse, local spalling, as well as the role of impermeable impermeable. Soil nailing a special control pressure grouting can be reinforced medium greatly improved physical and mechanical properties make it bee a new geological body, its solidsolid in the slip plane the deep section of the soil outside the house, its external fixed terminal Spray the surface layer in conjunction with the network as a whole may be a tendency to instability in the side wall transferred to the solidsection and its vicinity and to eliminate. Reinforced Mesh sprayed layer can have a better integrity and flexibility, can effectively adjust the spray layer and the stress distribution within the soil nail. Active soil nail retaining soil and with soil together with construction of simple, rapid and timely, flexible applicability, with the digging with sticks, safe and economic characteristics. Its duration is generally poorer than the traditional method to save more than 3060d, engineering