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 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, with the large number of high-rise building and the construction 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, the 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 in 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 points
1.孔的垂直度
1. The hole 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 not check perpendicularity, some units did not check or don't know how to detect equipment, time-consuming hole inclination for measuring some units don't want to reinvent the wheel. Be changed slope, the stress of pile, pile head deviation, affect the quality of the upper structure, seriously affect the 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钻都是有效的方法。 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 distribution 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 GuShi, 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 ending 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：
In malignant accident of pile foundation engineering, 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 lcm／lm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 or so of the error. Greater measurement error is caused by the measuring line is easy to broken, broken after don't 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 avoid 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.
(2)钻孔入岩深度达不到设计要求，更多的是由于地层分布不均匀，如岩层分布成倾斜状或起伏变化剧烈导致判断失误。因此入岩深度的控制应引起设计、施工和质检部门的共同重视。入岩深度的控制因钻孔工艺不同而有所区别。反循环工艺和冲击钻成孔的桩，可采用岩样鉴别法。此外，还需注意每个桩的入岩和终孔的岩样最好留样备案，直至工程使用正常，沉降稳定。正循环工艺成孔的桩由于取不到完整岩样确定嵌岩深度很困难。较可靠的办法是认真分析钻探资料，根据各钻孔土层分布情况综合评判场地地质概况，然后做出岩层分布的等高线图，按等高线图确定成孔深度。因本法有一定的随机性，应适当加大安全系数，有时尚需适当补充钻探孔，在某些缺少钻孔的控制区域，也可用钻机换取芯钻头直接取岩芯判定。正循环工艺采用的方法难度大。
(2) drilled into the rock depth can not meet the design requirements, the more is due to the uneven distribution of strata, 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 circulation 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 rock's best retention samples for the record, and until the project using normal, settlement and stability. Is cycle process 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 distribution 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 available 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 IL＞0.75呈软塑状态和流塑状态的粘性土而在 IL＞1.0 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 alluvial 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 model of cohesive soil and in IL > 1.0 in plastic flow state of silt soft soil pore forming shrinkage phenomenon is inevitable. 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 bending resistance capacity weakened or lost. To strengthen the detection of aperture 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 blades, 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孔。
(1) 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 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 weight is too large, makes 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 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 slurry 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 silting
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。沉渣的清除采用反循环成孔工艺能达到较好的效果速度能达到2~3m／s．是正循环的40倍以上，故携渣能力强。为此，可采用正循环成孔，气举反循环清孔的工艺。此法现场只需增加一台6m3的空压机即可，费用不大，简便易行，效果良好。采用该法，关键是控制好孔内泥浆面的落降，落降快、落差大则易塌孔，因此补浆要跟上，而且抽渣时间要短。实践证明，应用得当，桩的承载力能大幅度提高。
Usually confuse sediment and heavy silting, every hole bottom sediments are generally referred to as the sediment, actually 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 precipitation 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 time. 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 add a 6 m3 of air compressor, cost is 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. Practice 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, 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, 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 perfusion
砼灌注是最后一道也是最关键的一道工序。首先必须严格按设计强度配制砼。许多施工单位都是现场搅拌砼，其常见问题是：1)砂石的含泥量偏大；2)配料的计量不准确；3)水泥保管不善受潮。
Concrete pouring is the last one is also the most critical processes. First of all must 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.
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 pouring, 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)由于导管埋在泥浆和砼中，砼的灌入阻力是相当大的， 灌入阻力可按下式估算：
Under the premise of guarantee the quality of concrete qualified, catheter method of underwater pouring concrete quality is hard to control the main reason is that: 1) don't like the upper structure construction step by step a vibrating; 2) because the pipe is buried in the mud and concrete, concrete pumping resistance is quite big, pumping resistance can press type estimation:
R=π(D2—d2)(l1rw+l2rh)/4 (l)式中， D为桩直径；d为导管直径； rww为泥浆重度；rh为砼重度；
R = PI (D2 - D2) (l1rw + l2rh) / 4 (l), D as the pile diameter; D for pipe diameter; Accounts for the mud severe; Rh as heavy concrete;
要克服很大的灌入阻力保证砼桩身质量，必须有相当大的冲击力，冲击力越大，完成每一斗砼灌注的时间越短，砼桩身越均匀。由于砼是由水泥、砂、石子配制的混合料，不同材料、不同粒径则摩擦系数不一样，因此仅靠静力平衡产生的超压力缓慢流淌，则易造成砼粗骨料在桩芯堆积，随半径增大而递减。桩身不匀，则影响桩的抗压强度。
To overcome a lot of resistance to ensure the quality of concrete pile body, and must have a considerable impact, the impact force, the greater the shorter finish each bucket concrete perfusion time, concrete pile is more homogeneous. Because concrete is a mixture of cement, sand and gravel, different materials, different size, different coefficient of friction, so only on the super pressure caused by the static equilibrium flows slowly, the core accumulation, easy cause coarse aggregate in concrete pile increases with the radius decreasing. Then affects the pile of the pile body is uneven, the compressive strength.
目前最常见的水下砼灌注法的缺点是：
By far the most common method of underwater concrete perfusion defect is:
(l) 在向大斗投料过程中，砼的绝大多数势能在撞击大斗壁的碰撞中损耗掉，砼料落人导管中不连续，形不成较大的冲击能量，使砼没有足够的力量向四周挤压、扩散，桩的摩阻力严重降低。此外，还容易使桩身不均匀。
(l) in to the big feeding process, the vast majority of potential energy in the impact of large concrete pipe wall of the collision loss, discontinuous in concrete material fell into catheter and XingBuCheng larger impact energy, make the concrete does not have enough strength to squeeze, diffusion, pile friction resistance of severely reduced. In addition, the non-uniform pile body is easy to make.
(2) 砼料绝大多数要经过反弹再落入导管，容易造成砼离析和堵管。
(2) concrete material most to rally after falling into a catheter, easy to cause the concrete segregation and stuck pipe.
(3) 吊臂上下移动速度慢，产生不了大的加速度，因此砼料的下落没有足够的超压，造成砼料在导管附近堆积成钟形断面。 由于不能将隔浆层水平顶升，在钟形断面塌落时容易裹入泥浆，造成夹泥芯。
(3) the crane arm to move up and down slowly, produced no big acceleration, therefore the whereabouts of concrete material is not enough overpressure, caused concrete materials piled up near the catheter into bell shaped cross section. Due to the plasma level of jack-up, layer can not be easily incorporated into mud when bell shaped cross section morphology, sandwiched core.
(4) 由于导管上下移动次数过于频繁，使得泥浆不断沿导管壁渗入砼中，影响桩身砼质量。
(4) because the catheter is moved up and down too often, making the mud along the guide wall seep into concrete, influence the quality of pile body concrete.
鉴于以上缺点，监理应倡导施工单位使用大体积砼冲击灌注法，如桩的初斗砼灌注一样，每一斗灌注都是将2至3方砼在大斗中积蓄够量，出料口直接插入导管，然后打开活门一次连续冲击下去，其优点是：
Supervision should be advocated in view of the above shortcomings, the construction unit to use big volume concrete shock perfusion method, as the first bucket of concrete perfusion pile, each bucket perfusion is will be 2 to 3 square concrete volume enough savings in a big bucket, discharging mouth directly insert the catheter, then open valve a continuous impact, its advantage is:
(l) 功能大，冲击力强。物体的冲击能量与质量和速度有关，在速度相同的情况下就取决于质量。根据动量原理可得自由落体的平均冲力公式如—下：
(l) function is big, strong impact. Impact energy is associated with quality and speed of the object, under the condition of the same speed depends on the quality. According to the principle of momentum can get free fall in the average momentum formula such as: under -
F=mg[(2h/gt2)0.5+1] (2)式中， m为落体质量；t为作用时间；h为落体高度；g为重力加速度。
F = mg [0.5 (2 h/gt2) + 1) (2), m is fall quality; T is time; H height of fall; G is acceleration of gravity.
假设大斗方量为2.5m3；，砼容重为22KN／m3 则m约为5.5t，假设h=30m， t=1.0s，由式(2)求得F=1872.679kN。 平均冲力是砼自重的34倍，与前面根据式(l)计算的砼灌入阻力相比大6倍。 实际瞬时冲力的峰值比平均冲力高达一倍以上。在巨大冲力的作用下，砼的向上顶升力和侧向挤压力就有了保证，桩的摩阻力和桩身砼密实性都得以提高。
Assume DouFang volume of 2.5 m3; Of 22 kN/m3, concrete density, m is about 5.5 t, assuming that h = 30 m, t = 1.0 s, F (2) obtained by the type = 1872.679 kN. Average momentum is 34 times the weight of concrete, and calculated according to the type (l) in front of the concrete pumping is six times greater than resistance. Peak value of the actual instantaneous impulse momentum up to more than double than average. In the huge momentum, under the action of concrete lift up head and lateral extrusion is the guarantee, the friction resistance and density of pile body concrete have been improved.
(2) 首斗砼灌注冲力大，沉渣、沉淤被溅开，桩端与持力层能较好地结合，确保了端承力的发挥。
(2) the first bucket of concrete pouring large momentum, sediment, heavy silt is splash, subsoil can well combine with the pile end, to ensure the play of the bearing.
(3) 灌注时间短，桩身段骨料分布均匀，桩身段强度能得到保证。但用大体积砼冲击灌入法应注意以下几个问题：
(3) infusion time is short, the pile body uniform aggregate distribution, intensity of the pile body can be guaranteed. But with big volume concrete impact penetration method should be paid attention to the following questions:
(l) 必须注意排气技术，防止形成气堵，使砼料灌不下去。大斗出料口与导管不可用螺扣联接成一体，会形成气堵。应改为插入式联接方式，大斗出料口外径比导管内径小2至3cm。另外，还要在出料管活门的下方焊上比导管外径大2~3cm的法兰盘。
(l) must pay attention to exhaust technology, prevent the formation of gas, make the concrete material to fill. Big bucket discharge port and catheter, not with screw connection into an organic whole, will form the air lock. Should be changed to plug-in connection way, the big bucket discharging mouth diameter smaller than the tube diameter 2 to 3 cm. In addition, but also on the discharge tube to the bottom of the valve welding flange than big duct diameter 2 ~ 3 cm.
(2) 砼料最好通过网筛(网眼8~10cm左右)进入料斗，防止夹杂大直径块石、水泥块等造成卡管。
(2) concrete material via "screen (mesh 8 ~ 10 cm) into the hopper, prevent the inclusion of large diameter stone, concrete, etc. Causing stuck pipe.
(3) 砼和易性要好，如砼离析，则容易在料斗下部和出料口处形成堆积，导致出料困难，同时也容易堵塞导管.
(3) concrete workability is better, such as concrete segregation, is easily formed at the bottom of the hopper and the discharging mouth accumulation, result in difficulties of discharge, and also easily clogged catheters.
(4) 砼灌注时，吊车司机的配合也至关重要。当打开活门砼料下落时，必须随砼料的下落不断向上提动导管，提动量要小，注意掌握时机。实践证明，有经验的吊车司机对缩短砼的灌注时间，防止卡管、堵管事故，起相当大的作用。
(4) concrete perfusion, with the crane operator is also crucial. When open the valve material falling concrete, must the whereabouts of concrete material is continuously upward with catheter, carry momentum is smaller, pay attention to grasp the opportunity. Practice has proved that experienced crane driver to shorten the perfusion time of concrete, to prevent the card tube, the tube jam accidents, play a considerable role.
(5) 当砼灌注到桩顶部位时，为了保持足够的冲力，必须注意导管要留有一定的长度，一般为10m左右，灌注时及时上拨，保证高度产生冲力，使桩头部分的砼质量不至降低。此外，不可忽视大斗和导管的保养，内壁光滑可大大减小摩擦阻力，同时也减少堵管的发生率。
(5) when the concrete perfusion to the pile top, in order to keep enough momentum, must pay attention to the length of tube must be reserved, to 10 m or so commonly, when filled in a timely manner on the dial, ensure high momentum, makes the concrete quality of pile head part not be reduce. In addition, the measurement can not be ignored, and catheter care, wall smooth can greatly reduce the frictional resistance, but also reduce the incidence of blocking pipe.
当施工单位机械化程度低时，现场搅拌砼可采用卧式大斗，在地面装满料，再用吊车吊起与导管连接进行灌注。在保证上述砼材料质量合格的前提下，如每一斗砼灌注下去孔口返浆激如泉涌，则灌注质量一定好，如孔口返浆弱如渗流，甚至反复升降导管不见泥浆返流，则灌注质量必定欠佳。
When the low degree of mechanization of construction unit, the mixing of concrete can be used horizontal measurement, in the ground filled with material, then use the crane to lift perfusion with conduit connections. On the premise of guarantee the quality of the concrete material qualified, as every bucket of concrete pouring down orifice FanJiang spout, the infusion must be good quality, such as orifice FanJiang weak such as seepage, even repeated lifting pipe mud reflux, the perfusion quality will be poor.
(二)工程管理
(2) project management
钻孔灌注桩质量控制按地面作业和隐蔽作业两部分划分。 隐蔽作业的质量控制关键是检测的准确性和检测与施工作业配合的适时性。可编制由成桩过程的不同时段表示的动态控制表，无论对进度还是质量的动态控制都十分有效。
Drill hole filling pile quality control according to the homework assignments and hidden divided into two parts. Hidden job quality control is the key of detection accuracy and cooperate with construction work of the timing. Can be prepared by the process of pile at different times said the dynamic control of the table, regardless of the dynamic control of the progress and quality are very effective.
必须指出的是：在市场经济的冲击下，施工中各种弄虚作假、偷工减料现象造成工程隐患时有发生，这应引起监理的高度重视。
It must be noted that: under the impact of the market economy, the construction of all kinds of fraud, jerry phenomenon caused by engineering hidden danger, the supervision should attach great importance to.
三．技术问题
3. Technical problems
(一)嵌岩深度
(a) rock-socketed depth
1.岩石力学性状
1. The rock mechanics properties
在确定嵌岩深度之前，应对岩石的力学性状有所了解，尤其是抗压强度。微风化软质岩如粘土岩，其饱和单轴极限抗压强度一般在10~12MPa之间， 当于 C15~C20砼。硬质岩如微风化砂岩，其饱和单轴极限抗压强度一般在50~60Mpa之间。高于C60砼。这是根据钻探取芯试验的结果得来的，实际上未扰动岩层的抗压强度比这还要高。事实上，当嵌岩深度设计的很深时，把强度高于或相当于砼强度的岩层钻空，然后灌入砼显然是不值得的。
Before determine the rock-socketed depth, rock mechanical properties, especially the compressive strength. Breeze soft rock such as clay, the saturated uniaxial compressive strength limit, generally between 10 ~ 12 mpa, when in C15 to C20 concrete. Hard rock such as the breeze sandstone, the saturated uniaxial compressive strength limit is in commonly 50 ~ 60 between mpa. Above C60 concrete. This is according to the result of drilling for core tests, and, in fact, the compressive strength of undisturbed strata higher than this. In fact, when the design of deep rock-socketed depth, the strength is higher than or equal to the concrete strength of rock drilling and empty, and then is pumped concrete is obviously not worth it.
工程中还常把强风化岩层视为软弱下卧层，即使在强风化上有很厚的卵石层也不敢将桩端置于其上；此外，不论强风化层有多厚也非得钻穿，直到中微风化为止。实际上强风化岩层本身就是低压缩坚硬层，其承载力q能达1000~1500kPa，侧摩阻力qs能达40~ 50kPa，不亚于较硬的卵石层.只要桩的施工水平达到要求，其承载力相当可观，我个人意见设计时应具体情况具体分析。
Strong weathering rock engineering is often regarded as weak layer, even in the strong weathering on has very thick gravel layer also dare not to pile end under it; In addition, no matter how thick is strongly weathered layer also have to drill through, until the breeze in. Strong weathering rock itself is actually low compression is hard layer, the bearing capacity of q can reach 1000 ~ 1500 kpa, side friction of qs can reach 40 ~ 50 kpa, pebble bed as hard. As long as the level meet the requirements of construction, and its bearing capacity is considerable, I personal opinion when the design should be particular case is particular analysis.
2.施工工艺水平
2. The level of construction technology
加大桩的嵌岩深度，主要目的是增加侧摩阻力。要使入岩段桩的侧摩阻力能充分发挥，必须使砼与岩石孔壁很密实地结合为一体，这就需要清除泥皮，目前国内施工水平还解决不了这个问题（日本在导管端部外周围安装一环状管，可喷射高压水，喷射力能达2000N／cm2以上，在比重1.2左右的泥浆中，射程达1.5m以上，此法可用来清渣、清淤和清洗孔壁），因此片面强调增加嵌岩深度有时效果适得其反。
Increasing pile rock-socketed depth, the main purpose is to increase the pile side friction. To make into the rock section of pile side friction can give full play to, must be made of concrete and rock hole walls is for providing a compact body, it will need to remove mud cake, the current domestic construction level also can't solve the problem (outside Japan at the end of catheter placed around a circular tube, can jet high pressure water, jet force can reach more than 2000 n/cm2, in mud weight around 1.2, the range of 1.5 m above, this method can be used to clear slag, dredging and cleaning hole wall), so the one-sided emphasis on increasing rock-socketed depth and sometimes counterproductive.
3.上覆土层力学性状
3. The overlaying soil mechanics properties
上覆土层能提供的侧摩阻力qs越大，桩尾段承载力发挥的比例就越小，增加入岩深度也就更无意义。总之，增加嵌岩深度并不能保证承载力提高，有时适得其反。桩的承载力与成桩用时关系极大，空孔时间长，孔壁浸泡时间就长，不但泥皮增厚，孔壁一定范围的土质也会泡得松软，无疑降低了摩阻力，使质量事故的发生率提高。
Overlaying soil pile side friction qs can provide, the greater the bearing capacity of pile late play a greater proportion of small, increase the depth into rock are more meaningless. All in all, increase the bearing capacity of rock-socketed depth does not guarantee increased, sometimes backfire. Pile bearing capacity and pile when relationship is great, long empty hole, hole wall soak time is long, not only mud skin thickening, a range of hole wall also covered in soft soil, there is no doubt that reduces the friction resistance, increase the incidence of quality accident.
随嵌岩深度的增加，桩的造价也增加。粗略统计表明，入岩深度占桩长比例增加10%，每米桩长平均造价约增40%。
With the increase of the depth of rock-socketed, the pile of cost also increased. Rough statistics show that in the depth of the rock pile length ratio increased by 10%, the average cost of pile length per meter is increased about 40%.
(二)极限承载力
(2) the ultimate bearing capacity
确定桩的极限承载力主要是依据规范GBJ7~89和 JGJ94~94，由于这个问题至今还未圆满解决，所以在规范中都未作严格的规定。在实际工程中，对于 Q-s曲线在s≤40mm时即出现陡降的情况，以上两规范结果一致；而对于s＞40mm的缓变形曲线，则因设计人员对规范的不同理解，有的取s=40mm，有的取s=60mm，所对应的荷载作为极限承载力，这20mm之差，其经济效益可达数百万元的差距。如某高层建筑，设计桩数600多根，φ1000mm，60多 m长嵌岩桩，单桩造价5万元左右。 当s=40mm时， Q：13500kN；当 s=60mm时， Q=16250kN。这是根据五组试桩结果的较保守取值，如取 Q=16250kN作极限荷载，可减少100多根桩，节省造价500多万元，工期也可缩短几个月。
Determine the ultimate bearing capacity of the pile is mainly based on code JGJ94-94 and GBJ7-89, due to this problem has not yet settled satisfactorily, so in the specification are not strict rules. In actual engineering, for Q -s curve appeared in the s 40 mm or less steep fall in the situation, the above two specifications consistent; For s > 40 mm slow deformation curve of the different understanding for the designers to the specification, some take s = 40 mm, some take s = 60 mm, and the corresponding load as the ultimate bearing capacity, the 20 mm, the economic benefits of hundreds of millions of yuan. Such as high-rise building, design of pile number more than 600 root, phi is 1000 mm, more than 60 m long rock-socketed pile, single pile construction cost 50000 yuan. Q: when s = 40 mm 13500 kn; When s = 60 mm, Q = 16250 kn. This is according to the result of five groups of test pile more conservative values, such as take Q = 16250 kn for ultimate load, can reduce more than 100 root pile, saves the cost of more than 500 ten thousand yuan, the construction period can be shorten a few months.
按规范无论取s=40mm还是s=60mm，都是很笼统的，不分长桩、短桩，不分预制桩还是现场灌注桩，不分摩擦桩还是摩擦端承桩，也不考虑施工工艺、地基土层和荷载量级，这反映了至今对桩的承载力的研究还不够深入，应尽早研究和解决这个问题。
According to the specification whether take s = 40 mm or s = 60 mm, and is very general, regardless of long pile and short pile, regardless of precast pile or pile, both or frictional end bearing pile, friction pile, also does not consider construction technology, the foundation soil and load magnitude, reflecting the so far the study of the bearing capacity of pile is not enough in-depth, should study and solve this problem as soon as possible.
按目前的取值标准，对承载力量级大的大直径中长桩偏于保守且不够经济。 如对 φ1000mm，长55m的桩。当 Q=15000kN时，砼桩身的弹性压缩就达20mm以上；如按s=40mm或s=60mm取值则桩土之间的相对位移就更加微小，桩的承载力尤其是桩下部和端部的承载力就得不到充分发挥，结果是安全系数增大，经济效益降低。在确定桩的极限承载力时，大直径中长桩Q-s曲线常常是缓变形，这时的取值以变形控制为主。
According to the standard values, the order of magnitude larger bearing capacity of large diameter long pile tilt conservative and not economic. Such as the phi 1000 mm, 55 m long pile. When Q = 15000 kn, concrete elastic compression of pile body reached more than 20 mm; S = 40 mm or as s = 60 mm value the relative displacement between pile soil is more small, the bearing capacity of the pile especially the pile bottom and end bearing capacity won't get into full play, as a result increase safety factor, economic benefit is lower. In determining the ultimate bearing capacity of pile, large diameter long pile Q -s curve is often slow deformation, then the value is given priority to with deformation control.
四、结语
Four, conclusion
综上所述，为了不断提高建设工程钻孔灌注桩的质量，监理单位应从以下几个方面进行严格控制并不断进行研究、改进和提高：
To sum up, in order to constantly improve the construction quality of bored piles, supervision units from the following several aspects to strictly control and constantly study and improve and improve:
(l)对施工单位钻孔设备钻头的切削性能、泥浆的处理设备等与施工效率和质量有关的机具、仪器等都应进行检查。
(l) on the cutting performance of the construction units drilling equipment, drill bits, mud treatment equipment related to the construction efficiency and quality of machines, instruments and so on should be checked.
(2)不同的施工方法其效率和质量有很大差异，监理应从施工方法着手进行预先控制。
(2) the different construction methods there is a big difference between the efficiency and quality, the supervision should be construction methods to control in advance.
(3)认真研究质量检测设备的准确性和可靠性，如大小应变动测的适用范围等。检测结果不准确易引起纠纷，处理不当会降低安全度，留下工程隐患。
(3) seriously study the veracity and reliability of quality testing equipment, such as size should be dynamic test scope. Test results inaccurate easy cause dispute, improper handling can reduce safety to spend, engineering hidden danger.
(4)提高和完善管理水平，应以工序控制和事前控制为主，建立系统化的动态管理制度和方法。
(4) improve and perfect the management level, should give priority to in order to process control and advance control, establishing a systematic dynamic management system and method.
(5)桩的施工过程中既要做到严格监理、关键工序进行旁站，又要热情服务，把质量隐患消除在萌芽中
(5) pile construction process should be strict supervision side, key process, and enthusiastic service, to eliminate the quality hidden danger in the bud