外文翻译软土质条件下管桩施工的技术措施

1、毕业设计（论文）外文资料翻译院（系） 建筑工程学院 专 业 土木工程 班 级 090702 姓 名 史 斌 学 号 090702120 2013年 6月 软土质条件下管桩施工的技术措施摘 要：高强度预应力混凝土管桩（PHC）以其桩身混凝土的强度高，适应性强，具有较好的冲击性能，穿透能力强，承载力高，抗弯抗裂性能好，施工方便快捷，质量稳定，可靠度高，耐久性好等优点，被广泛应用到高层建筑基础。本文讨论了关于管桩施工中的技术措施。关键词：管桩施工 技术操作 桩基处理 1 引言目前，高强度预应力混凝土管桩已经被应用于房屋建筑和桥梁、码头和其他项目工程中。高强度的预应力混凝土管桩（PHC）以其桩身混凝土

2、的强度高，适应性广，具有较好的冲击性能，穿透力强，具有承载力高，抗弯抗裂性能好，施工快捷、方便，质量稳定可靠，耐久性好等优点，被广泛应用于高层建筑基础。管桩属于挤土桩，施工速度快，软土地区大量施工后，土体超孔隙水压力较大，开挖时如果没有很好的进行控制，将会引起偏桩、断桩等的质量事故发生。因此，我们必须针对软土的地质特点，在管桩施工、土方开挖方面采取有效的技术措施，保证桩基质量和挖土进度。 2 工艺原理 软土具有天然含水量高、天然孔隙比大、压缩性高、抗剪强度低、固结系数小、固结时间长、灵敏度高、扰动性大、透水性差、土层分布复杂、各层之间物理力学性质相差较大，纵向、横向的挤压均容易产生变形。同时，

3、由于其含水量大，透水性差，受到挤压容易产生较大的超孔隙水压力，而且很难在短时间内分散。其固结系数小、固结时间长的特点又使得土体受到扰动后很难迅速恢复。 高强度预应力混凝土管桩为挤土桩型，施工速度比较快，由此而造成施工区域内的挤土效应。管桩自身的抗压强度较高，但是抗弯强度较低，不同土层间的水平力的作用容易引起桩身断裂。因此，软土地区管桩的施工对土方开挖有着极大的影响。挖土的部署和采取的技术措施，都要围绕“避免土体应力释放过快，避免土体施工荷载过大，合理控制土体的位移与应力释放”这样的原则进行。 3 操作要点3.1挖土部署1）软土地区预应力管桩基础置换率一般为4左右，土方开挖前应切实的了解以下情况

4、，根据它来编制挖土施工方案，明确挖土部署和技术措施：a场地地质情况，b周边邻近建（构）筑物及需保护管线情况，c围护设计，d桩长、桩间距、置换率等桩基设计情况，e打桩顺序、压桩记录等桩基施工情况。2）土方开挖宜分皮进行，每皮的厚度应该控制在2m左右（土钉墙围护结构基坑根据土钉墙分层厚度控制），上皮挖除后再开挖下皮。坑内分级挖土留设台阶，台阶宽度与台阶下挖土深度的比值应在5以上。坑内土方坡道设置应该避开塘泥等软弱区块，坡道两侧土体的放坡系数不超过1:1.5时应考虑喷射砼护坡，土质特别差的应加设6.5200×200钢筋网片。应尽量避免工程桩位于土方坡道两侧斜坡上，如果桩基较密无法避免应考虑

5、灌芯或喷锚加固，或改用钢结构桥作为土方坡道。3）禁止边压桩边开挖，开挖和桩基全部完成间隔时间应该超过15天（钻打法10天以上）。4）承台、地梁的位置如果土质仍较差，宜采用人工挖土，避免挖机荷载及震动对土体的影响。5）截桩安排应该要提前考虑。开挖前，要先对露出表面的桩进行截除；开挖过程中，应根据挖土流程分段截除。6）挖机、车辆选择尽量避免采用大型设备。应尽量选择小挖机，如PC100以下。坑内运土车辆避免使用10t大车。 3.2 挖土技术措施1）挖土应逐层均匀进行，桩两侧土体高差不大于1m。2）禁止挖机碰撞桩身。机械开挖到桩顶30cm时桩两侧1m内土体采用人工开挖。3）挖机、土方车辆行走路线及两侧

6、工程桩应当视具体情况采取喷锚、铺路基箱、填塘渣、换土等加固措施。4）坡区及坡顶内外侧3米范围内，管桩内放入6米长614的钢筋笼，箍筋为6300，钢筋笼顶标高位于桩顶以下1米处，在钢筋笼范围内灌入C20微膨胀混凝土。5）在场地软硬土层交界的地方标高上下2m范围内，也可采取管桩内加筋灌砼的措施。6）为了减少静力压桩的挤土效应对土方开挖的影响，选择以下的措施：a设置袋装砂井或塑料排水板，用来消除部分超孔隙水压力，减少挤土现象。袋装砂井的直径一般为7080mm，间距l1.5m，深度1012m。塑料排水板的深度、间距与袋装砂井相同。b应力释放孔，直径400，均匀布置，深度10m左右或为桩长的0.8倍。

7、3.3 桩基问题的处理1）开挖后如果发现桩偏差、倾斜问题，可根据动态测试情况判定桩身的质量，分别进行处理。如果桩身没有断裂，可以用千斤顶推（拉）和灌芯的方法进行处理。千斤顶推（拉）力不应大于单桩水平承载力。如果桩身有裂缝，可以用接桩、补锚桩的方法进行处理。如果桩身裂缝很深，而且桩倾斜较大，沉井接桩也不能实施。同时，锚桩长度25m承载力不够。此时，可以考虑在底板相应位置留孔，等到底板完成后，在来打钻孔桩。 2）打进管桩时的挤土作用会使附近已经打好的桩和原有建筑物或周围其他设施产生破坏。挤土程度的大小除了和桩的截面积以及某处与桩间的距离有关外，还和桩长、桩型、打桩的速率以及打桩顺序有较大关系。 3

8、）考虑到管桩施工产生的挤土效应对土方开挖情况的影响较大，为了做好预控制，提出一些关于管桩施工技术措施的建议： (1) 桩机自重与场地软弱土层承载力以ZYJ500液压静力压桩机作为例子，桩机重达506T，平面尺寸12m×8.4m，平均压力为5T/m2。如果表层或者接近表层的土质物理力学性能较差，桩机行走和施工时容易沉陷，不仅不利于施工，而且，表层的深陷导致深层土体的位移、周边土体的隆起，容易引起管桩偏差、倾斜，甚至桩身断裂。因此，在桩机选型和确定打桩路线时，应考虑到表层土地基承载力和软弱下卧层地基沉降问题。采用表层铺设塘渣、枕木、路基箱等方式加固地基，分散桩机荷载。(2) 减小挤土效应

9、的技术措施a根据工程的经验，白天打桩引起的土体位移增加值会在夜晚停止的时候大约有25的下降，如果夜晚继续打桩，挤土效应引起的土体水平、竖向位移会一直增加不下降。因此，我们应该避免24小时不停歇的打桩安排。b桩基置换率超过4时可以用预钻孔沉桩，孔径大约比桩径小50100mm，深度根据桩距和土的密实度、渗透性来定，深度宜为桩长的1/31/2（不超过12m），施工时应随钻随打。c工程周边、分期施工的区块周边可以考虑应力释放孔、隔震沟、砂井等措施。(3) 沉桩线路的选定 沉桩线路应尽量采取“走长蛇形线路”，在邻近建筑物或者需要保护管线的区域应当考虑“由近及远”的施工方向。由此，可以给超孔隙水压力分散提

10、供尽量长的时间，避免其累积叠加，减小挤土影响。(4) 压桩的速度控制沉桩的速度最好控制在lm/min左右，使得各层的土体能够正确反映其抗剪能力。当地基表层中存在大块石头等障碍物时，要避免压偏。 4) 施工现场应当准备有应急措施的砂袋、钢管、钢筋、水泥、注浆机、发电机等施工工具。地面出现裂缝采用灌浆修复，避免地表水渗入，并及时组织项目部和有关专家查明裂缝产生原因。当出现边坡水平位移超过警戒值，要立即停止相应范围内的土方开挖，必要时采用回填或者设置临时支撑松木桩钢板桩加固，控制变形的发展。 总之，在软弱土的地质条件下，土方开挖过程中施工部署和技术措施的合理安排，以及管桩施工减小挤土效应的有效控制，

11、能有效地避免造成土体的位移引起桩的偏移、断桩、周边道路、建筑物沉降等问题，社会效益明显。同时，减少了桩基问题的处理也降低了费用。Soft soil conditions of the technical measures pipe constructionAbstractThe high-strength prestressed concrete pile (PHC) with its high strength concrete pile, wide adaptability and good impact resistance, penetration, with high capacit

12、y, 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 treatmen

13、t.1 IntroductionCurrently, 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, with high cap

14、acity, 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 pressure,

15、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 pile found

16、ation 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 distribution of soil

17、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 disperse i

18、n 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 construction

19、 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 measures, sho

20、uld 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 replacement rate i

21、s 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 protect th

22、e 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 2m (soil na

23、iling 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 pond scum r

24、amp 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 slope, suc

25、h 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, ground beam p

26、osition 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 process should

27、 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 carried out l

28、ayer 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 of the pile

29、, 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 of the re

30、inforcement 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 reinforcement measure

31、s. 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, spacing l 1.

32、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 pile dynam

33、ic 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 pile. If ther

34、e 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 corresponding

35、 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 the degre

36、e 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 earth excavati

37、on, 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 pressure of abou

38、t 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 soil, easil

39、y 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, roadbed

40、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 continued

41、 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 pore size o

42、f 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 considere

43、d 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