1、浅论钻孔灌注桩的施工及监理摘要：本文从施工及监理的角度，较为详尽的阐述了钻孔灌注桩的施工技术及质量监理的要点，并对现阶段设计中存在的问题提出了个人意见。Abstract: this article from the perspective of the construction and supervision, more detailed expounds the main points of the bored piles construction technology and quality supervision, and the present problems existing in
2、 the design of individual opinions are put forward.关键词：桩基础 现场施工 施工管理Keywords: pile foundation construction construction management on site一引言A. The introduction近几年，随着大批高层建筑及高等级公路的建设，作为基础承力普遍采用的一种形式钻孔灌注桩，在现阶段的施工中得到了广泛应用。但在施工过程中因工艺落后、地下施工，情况不明确等原因仍存在较多问题，本文着重从工程实践及监理的角度，对钻孔灌注桩的主要问题进行探讨。In recent years
3、, with the large number of high-rise building and the http:/ http:/ of high-grade highway, as a form of basic load carrying generally used - bored piles, has been widely used in the present stage of construction. But due to backward technology, the underground construction in construction process, t
4、he situation is not clear because there are more problems, such as, in this paper, from the perspective of engineering practice and supervision for bored piles of the main problems are discussed.二施工监理与工程管理2. Construction supervision and project management按照国家现行有关规范施工并不存在什么困难，然而施工质量却常常达不到要求，如施工单位在施工中
5、能对最薄弱的环节予以关注，予以加强，就能收到事半功倍的效果。下面对钻孔灌注桩施工中影响承载力及的施工监理的要点作一剖析。In accordance with the relevant national current specification there is no difficulty in the construction, construction quality, however, often can not meet the requirements, such as the construction unit pay attention to the weakest link i
6、n the course of construction, to strengthen, can get twice the result with half the effort. In the face of bored piles construction under the influence bearing capacity and the main points of the construction supervision of profiling.（一）施工监理要点(a) construction supervision pointshttp:/ http:/ The hole
7、 of the vertical degree钻孔灌注桩的垂直度是保证承载能力的重要一环，目前绝大多数的施工现场不检查垂直度，有的单位没有检查设备或根本不知道如何检测，有的单位则因测孔斜费时费力不愿多此一举。斜率超标，桩的受力状态被改变，桩头偏位，影响上部结构质量，严重影响钢筋笼的安置；在砂土类地层中孔壁极易塌孔，沉渣不宜清除。Bored piles of verticality is one of the most important aspects of the bearing capacity, at present most of the construction site do no
8、t check perpendicularity, some units did not check or dont know how to detect equipment, time-consuming hole inclination for measuring some units dont want to reinvent the wheel. Be changed slope, the stress of pile, pile head deviation, affect the quality of the upper structure, seriously affect th
9、e placement of reinforcing cage; In sandy soil stratum of hole wall collapse hole extremely easily, sediment shoulds not be cleared.为避免钻孔倾斜，在钻机就位和钻孔过程中，要随时注意校核钻杆的垂直度，发现倾斜及时纠正。对于地基不均匀、土层呈斜状分布和土层中夹有大的孤石或其它硬物的情形，施工前必须作好准备。在不均匀地层中钻孔时，钻机自重大、钻杆刚度大较为有利。进入不均匀硬层、斜状岩层和碰到孤石时，钻速要打慢档。处理大孤石和坚硬岩石，采用自重大的复合式牙轮钻或换用冲击
10、钻都是有http:/ http:/ 导正装置经工程实践表明，也是防止孔斜的简单有效的方法。终孔后再发现孔斜纠正起来费时费力，且修孔常使桩的充盈系数增大，最大达1.6以上。To avoid borehole inclination, in the process of drilling and the drilling emplacement, always pay attention to the checking tool perpendicularity, found that tilt correcting in time. For uneven foundation, soil dis
11、tribution and soil layer with large helical shaped GuShi or other hard objects, construction must be prepared before. In inhomogeneous formation in the drilling, drilling rig from the big, big pipe stiffness is more favorable. Enter the uneven hardened layer, oblique rock formations and encounter Gu
12、Shi, drilling rate to a low gear. Processing large GuShi and hard rock, using the major composite cone or switch to impact drill are effective methods. Guide is device by the engineering practice shows that the hole inclination is to prevent the simple and effective method. Found again after the end
13、ing final hole of difficult and time-consuming to correct the hole inclination, and the holes often make filling coefficient of pile increases, maximum of more than 1.6.2.孔深2. The hole is deep在恶性工程事故的桩基工程中，孔深不到位的例子很多，对于孔深的量测应是监理工作的重点，实际操作中应注意的问题有：http:/ http:/ malignant accident of pile foundation e
14、ngineering, deep hole is not in place of many examples, for the measurement of deep hole should be the focus of the supervision work, some problems that should be paid attention to in practical operation are:(l)测量有误达不到设计深度。一般施工队常用的测绳一经水泡就会出现收缩现象，有的收缩量可达 lcmlm 左右，测50m 的孔就会产生0.5m 左右的误差。更大的测量误差是由于测绳易断引
15、起的，断了以后不知道的人仍以断处为起点继续使用，往往可差数米。采用细钢丝测绳要当心数标松动错位。彻底避免误测的办法是在施工现场或附近地面上设置长度标记作为准绳，每次终孔一定把测绳拿去核实。(l) measuring reach the design depth. General construction commonly used measuring line once the bubble contraction phenomenon will occur and some shrinkage of LCM/lm, 50 m measuring hole can produce 0.5 m
16、or so of the error. Greater measurement error is caused by the measuring line is easy to broken, broken after dont know still breaks as the starting point to continue use, often can be differential meters. Adopting fine steel wire rope should be careful for the loose dislocation. Way to completely a
17、void false-positive is set on the construction site or near the ground marking as the criterion, and each time the end hole must be take to verify the measuring line.http:/ http:/ drilled into the rock depth can not meet the design requirements, the more is due to the uneven distribution of strata,
18、such as rock distribution into sideways or resulting from severe ups and downs lapse in judgment. Therefore into rock depth control should be to the attention of the design, construction and quality inspection department. Into the depth of rock varies from one control for drilling process. Reverse c
19、irculation process and impact drill hole pile, sample identification method can be used. , moreover also must pay attention to each pile into the rock and the end hole of the rocks best retention samples for the record, and http:/ http:/ the project using normal, settlement and stability. Is cycle p
20、rocess into hole pile due to take less than complete sample to determine the rock-socketed depth is very difficult. A reliable method is to carefully analysis of drilling data, according to the drilling site geological condition, soil distribution of comprehensive evaluation and make the distributio
21、n of the strata contour map, contour map to determine the hole depth. Has a certain randomness, because of this law shall be the appropriate increase safety factor, and a fashion should be the appropriate supplement of drilling hole, in some lack of drilling control area, core drilling rig is also a
22、vailable for direct coring bit. Positive cycle process approach is difficult.3.孔径3. The pore size在湖、塘、沟、谷与河漫滩地段新近沉积的粘性土和粉士中钻孔容易出现缩孔现象。尤其要重视液性指数 IL0.75呈软塑状态和流塑状态的粘性土而在 IL1.0 呈流塑状态的淤泥质软土层成孔缩孔现象更不可避免。与孔径有关的质量问题有：In the valley of lakes, ponds and ditches, and newly deposition of cohesive soil and alluvi
23、al flat location hole easy to occur in the powder and the shrinkage phenomenon. Especially should attach importance to liquidity index IL 0.75 in RuanSu state and flow http:/ http:/ of cohesive soil and in IL 1.0 in plastic flow state of silt soft soil pore forming shrinkage phenomenon is inevitable
24、. Related to aperture quality problems are:(l)由于孔径小于规范要求，桩的截面缩小，承载能力降低，实际上降低了桩的安全系数。(l) due to the pore size is less than specification requirements, pile cross section shrinking, carrying capacity is reduced, actually reduced the safety factor of the pile.(2)软弱土层一般都在地层上部，缩颈现象也发生在此段，而桩的内力也是上段大，容易造成桩
25、身抗压强度不够而破坏。(2) soft soil layer in the upper strata commonly, necking phenomenon also occurred in this section, the section on pile internal force is also big, easy to cause damage pile compressive strength is not enough.(3)由于孔径达不到要求，导致钢筋笼无保护层，桩的抗压弯能力削弱或丧失。防治的主要措施是加强对孔径的检测与控制，提高泥浆质量，增大泥浆比重和粘性及稠度。钻头直径
26、应适当加大，也可采用处理孔斜的导正器法，在导正器上焊一定数量的合金刀片，在钻进或起钻的过程中起扫孔作用。此外在易于产生缩孔的土层中施工，减少空孔时间也是非常重要和有效的措施。(3) due to the pore size can not meet the requirements, which leads to the reinforcing cage without a protective layer, the pile http:/ http:/ resistance capacity weakened or lost. To strengthen the detection of a
27、perture is the main measures of prevention and cure and control, improve the mud quality, increase the mud weight and viscosity and consistency. Bit diameter should be increased appropriately, also can use handle hole inclination is guide method, welding on is guide to a certain number of alloy blad
28、es, drill in drilling or in the process of scavenging hole effect. In addition construction in easy to produce porosity of soil, reduce the empty hole time is also very important and effective measures.4. 泥浆4. The mud在钻孔灌注桩的施工中，无论对于成孔质量还是最终对桩的承载能力的发挥，泥浆质量都是相当重要的因素。目前桩基施工队伍绝大多数缺乏对泥浆质量和泥浆管理的重视，泥浆质量差，其
29、后果是：In construction of bored piles, both pore forming quality and ultimately bearing capacity of pile, the mud quality are very important factors. The pile foundation construction team most of the lack of recognition of mud and mud quality management, poor quality of mud, the consequences are:(1)形成不
30、了护壁泥膜或形成的泥皮粘附力差，易于脱落，导致孔壁稳定性差，在砂性土地层易于塌壁，在流塑状粘土层则易于缩http:/ http:/ forming the breast wall of mud membrane or form the poor adhesion of mud cake, is easy to fall off, lead to poor stability of hole wall, in the sandy soil layer is easy to collapse, the flow of plastic clay layer is easy to shrinkage
31、cavity.(2)泥浆稠度大、比重大，含砂率高，形成的泥皮质量差、厚度大，大大降低桩的侧摩阻力。(2) large mud consistency, than major, high sand ratio, formation of mud skin of poor quality, large thickness, greatly reduce the pile side friction.(3)稠浆在钢筋笼钢筋上沉积粘附，导数钢筋与砼握裹力降低。泥浆比重过大，使得砼水下灌注阻力增大，降低砼的流动半径，使砼骨料大部分堆积在桩芯部位，而钢筋笼外几乎无骨料，不仅桩身质量不好而且桩的侧摩阻力也难
32、以发挥。有的工程计算承载力为14000kN 以上，而静载试验不到5000kN 就破坏，其中就有泥浆的影响。在空气中坍落度为21cm 、扩散直径为38cm 的砼，在水中坍落度下降为16.5cm、扩散直径为30.5cm，而在比重为1.2的泥浆中，坍落度则为14cm，扩散直径只有 27cm。因此，对泥浆质量的管理决不是个小问题，监理一定要严格要求施工单位按规范要求严格控制。(3) thick deposit adhesion on reinforcing cage bars, steel rebar and concrete derivative grip of reduced. Mud weigh
33、t is too large, http:/ http:/ underwater concrete perfusion resistance increase, reduce the radius of the flow of the concrete, concrete aggregate of accumulation in the pile core area, and almost no aggregate reinforced some freedom, not only the pile body quality is bad and pile side friction also
34、 play hard. Some engineering calculation capacity is above 14000 kn, and static load test in less than 5000 kn damage, including the influence of the mud. Slump in the air for 21 cm, spreading 38 cm diameter concrete, slump in the water reduced to 16.5 cm, spreading diameter is 30.5 cm, and in the s
35、lurry specific gravity of 1.2, the slump is 14 cm, spreading only have 27 cm in diameter. Therefore, the management of mud quality never is a small problem, supervision must be strict with construction units strict control according to the requirements of specification.5.沉渣与沉淤5. Sediment and heavy s
36、ilting一般把沉渣与沉淤混为一谈，凡是孔底的沉积物统称沉渣，实际上是有区别的。沉渣是钻孔过程中钻机切削和孔壁塌落的岩士，主要是砂、砾石和碎岩硝等，而沉淤则是比重大、稠度大的劣质泥浆由于空孔时间过长沉淀而成的流塑状混合物，沉淤的厚度往往大于沉渣，沉渣与沉淤均在桩底形成软弱隔层，能导致端承力丧失殆尽。沉淤的控制主要是提高泥浆质量和减少空孔时间。沉渣的清除http:/ http:/ confuse sediment and heavy silting, every hole bottom sediments are generally referred to as the sediment, a
37、ctually there is a difference between. Sediment that is in the process of drilling rig YanShi for cutting and wall of hole collapsing, mainly is the sand, gravel, crushed rock, nitrate, etc., and heavy silting is bigger than big, consistency of inferior mud because time is too long empty holes preci
38、pitation and flow model of the mixture, heavy sediment often greater than the thickness of the sediment, sediment and heavy silting form weak interlayer in the pile bottom, can cause the bearing no. Heavy sedimentation control mainly is to improve the quality of the mud and reduce the empty hole tim
39、e. Sediment removal by reverse circulation pore forming process can achieve good effect speed can reach 2 3 m/s is positive cycle of more than 40 times, so the slag with ability. For this, can be used is recycled into hole, gas lift reverse circulation hole cleaning process. This site only need to a
40、dd a 6 m3 of air compressor, cost http:/ http:/ not big, easy, the effect is good. Using this method, the key is to control the hole on the surface of the mud falling down, falling down fast, is easy to fall down hole, so the filling slurry to keep up with, and slag extraction time is shorter. Pract
41、ice proves that the application is proper, the pile bearing capacity can be increased significantly.无论采用反循环还是正循环成孔工艺，都应重视砼灌注前的清孔。灌注前抽吸二分钟左右，一方面抽出一定的沉渣，另一方面泥浆的抽吸作用导致一部分沉渣、沉淤上浮，而且短时间内不会沉淀。此时灌注砼，砼坠落的巨大冲击力还能溅除最后残余的部分沉渣与沉淤，可基本上将孔底沉渣清除干净。Whether using reverse circulation or are cyclic pore forming process
42、, should pay attention to before concrete pouring hole cleaning. About 2 minutes before infusion pump, on the one hand, pull out sediment, mud suction effect lead to part of the sediment on the other hand, the heavy silting, and in a short period of time will not precipitate. When pouring concrete,
43、concrete the tremendous impact of the falling can splash except the last remaining part of the sediment with heavy silting, can basically clear out sediment at the bottom of the bore.6.砼灌注6. Concrete perfusionhttp:/ http:/ pouring is the last one is also the most critical processes. First of all mus
44、t be designed in accordance with the strength of concrete. Many construction units are on-site mixing concrete, its common problems are: 1) silt content of sand and gravel is big; 2) the ingredients of the measurement is not accurate; 3) the cement storage be affected with damp be affected with damp
45、.水下砼灌注由于阻力大不易流畅灌入，于是施工单位常随意加大水灰比，增大塌落度便于砼灌注，结果砼的强度等级严重降低。质检和设计人员应加强现场质量监理，决不能轻易相信试块的试验结果。Underwater concrete perfusion is not smooth because of the large resistance down, and the construction units often optional increasing water-cement ratio, increasing the slump is advantageous for the concrete po
46、uring, the concrete strength grade of severely reduced. Quality control and design personnel should strengthen the quality supervision, block test results must not be believed.在保证砼质量合格的前提下，导管法水下灌注砼质量难以控制的主要原因是：1)不能象上部结构施工那样逐层振捣；2)由于导管http:/ http:/ 灌入阻力可按下式估算：Under the premise of guarantee the quality of concr
