1、.畢業設計（論文）外文資料翻譯院（系） 建筑工程學院 專 業 土木工程 班 級 090702 姓 名 史 斌 學 號 090702120 2013年 6月 軟土質條件下管樁施工的技術措施摘 要：高強度預應力混凝土管樁（PHC）以其樁身混凝土的強度高，適應性強，具有較好的沖擊性能，穿透能力強，承載力高，抗彎抗裂性能好，施工方便快捷，質量穩定，可靠度高，耐久性好等優點，被廣泛應用到高層建筑基礎。本文討論了關于管樁施工中的技術措施。 關鍵詞：管樁施工 技術操作 樁基處理 1 引言目前，高強度預應力混凝土管樁已經被應用于房屋建筑和橋梁、碼頭和其他項目工程中。高強度的預應力混凝土管樁（PHC）以其樁身混

2、凝土的強度高，適應性廣，具有較好的沖擊性能，穿透力強，具有承載力高，抗彎抗裂性能好，施工快捷、方便，質量穩定可靠，耐久性好等優點，被廣泛應用于高層建筑基礎。管樁屬于擠土樁，施工速度快，軟土地區大量施工后，土體超孔隙水壓力較大，開挖時如果沒有很好的進行控制，將會引起偏樁、斷樁等的質量事故發生。因此，我們必須針對軟土的地質特點，在管樁施工、土方開挖方面采取有效的技術措施，保證樁基質量和挖土進度。 2 工藝原理 軟土具有天然含水量高、天然孔隙比大、壓縮性高、抗剪強度低、固結系數小、固結時間長、靈敏度高、擾動性大、透水性差、土層分布復雜、各層之間物理力學性質相差較大，縱向、橫向的擠壓均容易產生變形。同

3、時，由于其含水量大，透水性差，受到擠壓容易產生較大的超孔隙水壓力，而且很難在短時間內分散。其固結系數小、固結時間長的特點又使得土體受到擾動后很難迅速恢復。 高強度預應力混凝土管樁為擠土樁型，施工速度比較快，由此而造成施工區域內的擠土效應。管樁自身的抗壓強度較高，但是抗彎強度較低，不同土層間的水平力的作用容易引起樁身斷裂。因此，軟土地區管樁的施工對土方開挖有著極大的影響。挖土的部署和采取的技術措施，都要圍繞“避免土體應力釋放過快，避免土體施工荷載過大，合理控制土體的位移與應力釋放”這樣的原則進行。 3 操作要點 3.1挖土部署 1）軟土地區預應力管樁基礎置換率一般為4左右，土方開挖前應切實的了解

4、以下情況，根據它來編制挖土施工方案，明確挖土部署和技術措施：a場地地質情況，b周邊鄰近建（構）筑物及需保護管線情況，c圍護設計，d樁長、樁間距、置換率等樁基設計情況，e打樁順序、壓樁記錄等樁基施工情況。2）土方開挖宜分皮進行，每皮的厚度應該控制在2m左右（土釘墻圍護結構基坑根據土釘墻分層厚度控制），上皮挖除后再開挖下皮。坑內分級挖土留設臺階，臺階寬度與臺階下挖土深度的比值應在5以上。坑內土方坡道設置應該避開塘泥等軟弱區塊，坡道兩側土體的放坡系數不超過1:1.5時應考慮噴射砼護坡，土質特別差的應加設6.5200×200鋼筋網片。應盡量避免工程樁位于土方坡道兩側斜坡上，如果樁基較密無法避

5、免應考慮灌芯或噴錨加固，或改用鋼結構橋作為土方坡道。3）禁止邊壓樁邊開挖，開挖和樁基全部完成間隔時間應該超過15天（鉆打法10天以上）。4）承臺、地梁的位置如果土質仍較差，宜采用人工挖土，避免挖機荷載及震動對土體的影響。5）截樁安排應該要提前考慮。開挖前，要先對露出表面的樁進行截除；開挖過程中，應根據挖土流程分段截除。6）挖機、車輛選擇盡量避免采用大型設備。應盡量選擇小挖機，如PC100以下。坑內運土車輛避免使用10t大車。 3.2 挖土技術措施 1）挖土應逐層均勻進行，樁兩側土體高差不大于1m。2）禁止挖機碰撞樁身。機械開挖到樁頂30cm時樁兩側1m內土體采用人工開挖。3）挖機、土方車輛行走

6、路線及兩側工程樁應當視具體情況采取噴錨、鋪路基箱、填塘渣、換土等加固措施。4）坡區及坡頂內外側3米范圍內，管樁內放入6米長614的鋼筋籠，箍筋為6300，鋼筋籠頂標高位于樁頂以下1米處，在鋼筋籠范圍內灌入C20微膨脹混凝土。5）在場地軟硬土層交界的地方標高上下2m范圍內，也可采取管樁內加筋灌砼的措施。6）為了減少靜力壓樁的擠土效應對土方開挖的影響，選擇以下的措施：a設置袋裝砂井或塑料排水板，用來消除部分超孔隙水壓力，減少擠土現象。袋裝砂井的直徑一般為7080mm，間距l1.5m，深度1012m。塑料排水板的深度、間距與袋裝砂井相同。b應力釋放孔，直徑400，均勻布置，深度10m左右或為樁長的0

7、.8倍。 3.3 樁基問題的處理 1）開挖后如果發現樁偏差、傾斜問題，可根據動態測試情況判定樁身的質量，分別進行處理。如果樁身沒有斷裂，可以用千斤頂推（拉）和灌芯的方法進行處理。千斤頂推（拉）力不應大于單樁水平承載力。如果樁身有裂縫，可以用接樁、補錨樁的方法進行處理。如果樁身裂縫很深，而且樁傾斜較大，沉井接樁也不能實施。同時，錨樁長度25m承載力不夠。此時，可以考慮在底板相應位置留孔，等到底板完成后，在來打鉆孔樁。 2）打進管樁時的擠土作用會使附近已經打好的樁和原有建筑物或周圍其他設施產生破壞。擠土程度的大小除了和樁的截面積以及某處與樁間的距離有關外，還和樁長、樁型、打樁的速率以及打樁順序有較

8、大關系。 3）考慮到管樁施工產生的擠土效應對土方開挖情況的影響較大，為了做好預控制，提出一些關于管樁施工技術措施的建議： (1) 樁機自重與場地軟弱土層承載力以ZYJ500液壓靜力壓樁機作為例子，樁機重達506T，平面尺寸12m×8.4m，平均壓力為5T/m2。如果表層或者接近表層的土質物理力學性能較差，樁機行走和施工時容易沉陷，不僅不利于施工，而且，表層的深陷導致深層土體的位移、周邊土體的隆起，容易引起管樁偏差、傾斜，甚至樁身斷裂。因此，在樁機選型和確定打樁路線時，應考慮到表層土地基承載力和軟弱下臥層地基沉降問題。采用表層鋪設塘渣、枕木、路基箱等方式加固地基，分散樁機荷載。(2)

9、減小擠土效應的技術措施a根據工程的經驗，白天打樁引起的土體位移增加值會在夜晚停止的時候大約有25的下降，如果夜晚繼續打樁，擠土效應引起的土體水平、豎向位移會一直增加不下降。因此，我們應該避免24小時不停歇的打樁安排。b樁基置換率超過4時可以用預鉆孔沉樁，孔徑大約比樁徑小50100mm，深度根據樁距和土的密實度、滲透性來定，深度宜為樁長的1/31/2（不超過12m），施工時應隨鉆隨打。c工程周邊、分期施工的區塊周邊可以考慮應力釋放孔、隔震溝、砂井等措施。(3) 沉樁線路的選定 沉樁線路應盡量采取“走長蛇形線路”，在鄰近建筑物或者需要保護管線的區域應當考慮“由近及遠”的施工方向。由此，可以給超孔隙

10、水壓力分散提供盡量長的時間，避免其累積疊加，減小擠土影響。(4) 壓樁的速度控制沉樁的速度最好控制在lm/min左右，使得各層的土體能夠正確反映其抗剪能力。當地基表層中存在大塊石頭等障礙物時，要避免壓偏。 4) 施工現場應當準備有應急措施的砂袋、鋼管、鋼筋、水泥、注漿機、發電機等施工工具。地面出現裂縫采用灌漿修復，避免地表水滲入，并及時組織項目部和有關專家查明裂縫產生原因。當出現邊坡水平位移超過警戒值，要立即停止相應范圍內的土方開挖，必要時采用回填或者設置臨時支撐松木樁鋼板樁加固，控制變形的發展。 總之，在軟弱土的地質條件下，土方開挖過程中施工部署和技術措施的合理安排，以及管樁施工減小擠土效應

11、的有效控制，能有效地避免造成土體的位移引起樁的偏移、斷樁、周邊道路、建筑物沉降等問題，社會效益明顯。同時，減少了樁基問題的處理也降低了費用。Soft soil conditions of the technical measures pipe constructionAbstract The high-strength prestressed concrete pile (PHC) with its high strength concrete pile, wide adaptability and good impact resistance, penetration, with high

12、capacity, flexural cracking performance, construction of fast, convenient stable and reliable quality, durability, etc., and is widely used in high-rise building foundation. This paper discusses the technical measures in the pipe construction. Key words: pile construction; technical operations; pile

13、 treatment.1 Introduction Currently, high-strength prestressed concrete pipe has been applied to housing construction and bridges, piers and other projects. High-strength prestressed concrete pipe (PHC) with its high strength concrete pile, wide adaptability, good impact resistance, penetration, wit

14、h high capacity, flexural cracking good performance, construction speed, convenience, quality reliability, durability and good, and is widely used in high-rise building foundation. Pipe is soil compaction piles, construction speed, a large number of injections in soft soil area, the soil pore water

15、pressure, excavation without effective control, will cause partial piles, such as the quality of the broken pile accident . Therefore, we must for the quality characteristics of soft soil in the pipe construction, earth excavation techniques and adopt effective measures to guarantee the progress of

16、pile foundation and excavation.2 Process Principle High water content soft soil has a natural, natural void ratio, high compressibility, low shear strength, coefficient of consolidation, consolidation for a long time, high sensitivity, disturbance of the large, poor permeability, complex distributio

17、n of soil layer, the physical and mechanical properties between the layers of difference between the larger, vertical, horizontal squeeze all prone to deformation.Also, because of its large water content, poor permeability, squeezed easily have a greater excess pore water pressure, and difficult to

18、disperse in a short time. The coefficient of consolidation, consolidation characteristics of a long time and disturbed the soil after it difficult to quickly recover.High-strength prestressed concrete pipe pile to soil compaction, construction, faster, and the resulting soil compaction within the co

19、nstruction area effect. Pile itself high compressive strength, flexural strength but low levels of power between the different role of soil prone to pile fracture. Therefore, the construction of soft soil on the earth excavation pipe has a great impact. Excavation of the deployment and technical mea

20、sures, should be around "to avoid excessive soil stress release, to avoid excessive construction load of soil, reasonable control of soil displacement and stress release," such principles.3 Operating Points3.1 Excavators deployed 1) The basis of soft soil prestressed concrete pipe replacem

21、ent rate is generally around 4%, before excavation practical understanding of the following circumstances under which the preparation of excavation construction plan, deploy, and technical measures clearly digging: a site geological conditions, b around adjacent building (structure) and the need to

22、protect the pipeline case, c enclosure design, d pile length, pile spacing, pile foundation design exchange rate situation, e piling order, piling records and other foundation construction situation. 2) Excavation should be carried out sub-skin, skin thickness should be controlled in each of about 2

23、m (soil nailing pit envelope layer under the soil nail wall thickness control), after the excavation of excavation under the skin epithelium. Pit excavation leaving in graded steps, step width and the depth of excavation over the next steps should be 5 or more. Earth pit should be set to avoid the p

24、ond scum ramp so weak block, put the soil on both sides of the ramp slope coefficient of less than 1:1.5 should be considered in the sprayed concrete slope protection, soil particularly bad should be added 6.5 200 × 200 steel mesh. Should be avoided in the earth piles on both sides of the ramp

25、slope, such as dense pile can not be avoided should be considered or gunite reinforced grouted, or switch to steel bridge as the earthwork ramp. 3) Edge against edge piling excavation, excavation and pile interval should be completed in 15 days or more (more than 10 days drilling play). 4) Caps, gro

26、und beam position if the soil is still poor, the appropriate use of artificial excavation, avoid digging machine loading and vibration effects on the soil. 5) Cut pile arrangement should think ahead. Excavation before exposing the surface of the pile should be cut first; excavation process, the proc

27、ess should be based on sub-excavation cut off. 6) Digging machines, vehicles should be chosen to avoid using large equipment. Should try to choose a small digging machines, such as PC100 below. Vehicles to avoid the use of earth pit 10t cart.3.2 Technical measures digging 1) Excavation should be car

28、ried out layer by layer evenly, on both sides of the soil pile height shall not exceed 1m. 2) Collision against digging machine shaft. Mechanical excavation to the top of the pile 1m 30cm on both sides of the pile with the soil excavated. 3) Digging machines, moving vehicles, routes and both sides o

29、f the pile, as the case should be taken to spray anchor, paving the way for the base box, pond residue, such as for soil reinforcement. 4) Top of the hill slope areas and within 3 meters inside and outside, into the 6-meter long pipe 614 within the reinforcement cage, stirrup to 6 300, top elevation

30、 of the reinforcement cage is located at 1 m below top of the pile, the reinforcement cage within the irrigation C20 micro-expansion into the concrete. 5) Soft and hard layer at the junction of the venue up and down elevation range of 2m, but also take concrete irrigation pipe within the reinforceme

31、nt measures. 6) To reduce static piling of the squeezing effect on the impact of excavation, the choice of the following measures: a set of sand bags or plastic drain well to remove part of the excess pore water pressure, reduce soil compaction phenomenon. Sand Wick diameter is generally 70 80mm, sp

32、acing l 1.5m, the depth of 10 12m. Plastic drain depth, spacing and the same Sand Wick. b stress release holes, diameter of 400, uniformly arranged around the depth of 10m or 0.8 times the pile length.3.3 Handling of pile 1) Pile after excavation, such as face deviation, skew problems, according to

33、pile dynamic testing conditions to determine the quality of, respectively, to be addressed. If the pile without breaking, jack can be used to push (pull) and the core of the method of irrigation treatment. Jack push (pull) force shall not be greater than the horizontal bearing capacity of single pil

34、e. If there are cracks in the pile, can be connected piles, anchor piles make way for processing. If deep cracks in the pile, and pile inclination larger caisson pile can not be implemented then. Meanwhile, the length of 25m anchor pile bearing capacity is not enough. At this point, consider the cor

35、responding bottom hole location to stay until the floor is completed, set to play bored piles. 2) Pile into the soil compaction when the role will have to play well near the original building or the surrounding piles and other facilities have destroyed. In addition to the size of soil compaction and

36、 the degree of cross-sectional area and somewhere in the pile and the distance between piles, but also with the pile length, pile, piling rate and more related to the piling sequence. 3) Taking into account the pipe construction squeezing effect generated by the situation on the impact of large eart

37、h excavation, in order to make pre-control, to make a few suggestions on technical measures pipe construction: (1) Pile weight bearing capacity of soft soil with the site to ZYJ-500 as an example of hydraulic static pile driver, pile driver weight 506T, plane size 12m × 8.4m, the average pressu

38、re of about 5T/m2. Surface or near the surface, such as physical and mechanical properties of soil is poor, when the pile driver is easy walking and injections of settlement, is not conducive to construction, and that led to the deep surface of the deep soil displacement, uplift of the surrounding s

39、oil, easily lead pipe pile offset, tilt, or pile fracture. Therefore, in the pile driver, route selection and determine the piling should take into account the land surface of the base load capacity and weak underlying layer of foundation settlement problems. Pond by laying the surface residue, ties

40、, roadbed foundation reinforcement boxes, etc., scattered pile driver load. (2) Effect of technical measures to reduce soil compaction, according to engineering experience a day and piling soil displacement caused by the added value will stop at night when about 25% of the decline, such as the night

41、 continued piling, compacting effect of soil caused by the level of vertical will always increase in displacement does not come down. Therefore, we should avoid the 24-hour non-stop piling arrangements. b pile replacement rate of more than 4% can be pre-bored piling, pile diameter smaller than the p

42、ore size of about 50 100mm, depth of soil as the pile spacing and density, permeability, depending on the depth of the pile length of 1 should be / 3 to 1 / 2 (less than 12m), construction should be drilling with the fight. c projects around, stage construction of the blocks around the hole could be

43、 considered stress release, isolation trenches, sand wells and other measures. (3) Pile pile selected line route should be taken to "take the long snake-like lines" in the adjacent building or area should consider the need to protect the pipeline, "from near and far," the construction of direction. As a result, can dissipate ex