高压喷射灌浆和深层搅拌法加 固技术（Reinforcement technique of high pressure jet grouting and deep mixing method）

1、高压喷射灌浆和深层搅拌法加 固技术（Reinforcement technique of high pressure jet grouting and deep mixing method）Reinforcement technique of high pressure jet grouting and deep mixing methodDate: 2009-02-07 source: Author: anonymous font: medium-Abstract: the technology of high pressure jet grouting and deep mixing is

2、 similar. The main difference is that different feeding and mixing methods are adopted.Key words: high pressure jet grouting; deep mixing; strengtheningFirst, high pressure jet grouting technologyHigh pressure injection method is the use of engineering drilling to design processing depth, high press

3、ure mud pump, through the installation of the drill pipe (spray rod rod) special nozzle arranged at the end of the bottom of the hole, jet cement slurry to surrounding soil pressure (general use cement), and the drill pipe (boom) rotate at a certain speed the soil structure upgrade, high pressure je

4、t within a certain range of damage, and forced mixing and curing slurry solidification after the formation of a solid with certain properties and shape in soil.The shape of the consolidated body is related to the direction of the jet flow. Generally divided into rotary jet (referred to as rotary jet

5、), directional jet (referred to as fixed jet) and oscillating jet (referred to as pendulum spray). The jet grouting pile is mainly used to reinforce the foundation, improve the shear strength of the foundation, and improve the deformation property of the foundation soil, so that it can not destroy o

6、r produce too big deformation under the action of the upper structure. Jet consolidation body is wall shaped, fan-shaped jet formation consolidation thick body. Constant injection and pendulum spraying are usually used to prevent seepage of foundation and improve hydraulic condition and slope stabil

7、ity of foundation soil.(1) reinforcement mechanismHigh pressure compressed air parcel damage with high impact jet flow stirring soil spray method such as three high and low pressure spray method, grouting slurry is poured into the slurry pump, high pressure water and air entrainment into, and distur

8、bed soil mixed consolidated. The mechanism of reinforcing the foundation to form piles, plates and walls can be explained by five functions:1. high pressure jet cutting destroys the soil, and the dynamic pressure of the jet impacts the soil in pulse form, and the structure of the soil is destroyed a

9、nd the cavity appears.2. mixing effect in the process of rotation and lifting the drill pipe, the formation of voids in the jet back in the injection pressure, forcing the soil particles and nozzle moving in opposite directions (i.e. small resistance direction) mobile, consolidated and mixed slurry.

10、3. replacement three pipe high pressure jet method called displacement method, high speed water jet cutting soil at the same time, due to pass into the compressed air and the part of cutting soil particles from the grouting hole, the soil particles discharged by the air volume by pouring slurry feed

11、ing.4. filling and consolidation effect of the high pressure grout filling open and original soil void, condensate water consolidation, but also penetrate into the sand thickness and the formation of consolidation.5. the compacting effect of high pressure jet flow in the process of cutting soil, in

12、the edge and the residual pressure is broken, and the pressure can have a certain effect on soil compaction, the high compressive strength of pile body is higher than the edge portion of the central part.(two) basic speciesAccording to the injection medium and its piping number, it can be divided in

13、to single tube method, two tube method, three tube method, etc.1. single tube jet grouting through a single pipeline, the use of high-pressure slurry (20 30MPa), jet punching cut soil destruction, the pile diameter of 40 50cm. The reinforcement is of good quality,The construction speed is fast and t

14、he cost is low, but the diameter of the concretion body is smaller.2., two tube spinning method, in the single tube method on the basis of compressed air, and the use of double channel double grouting pipe. There is a coaxial double nozzle at the bottom side of the tube. The high-pressure slurry is

15、ejected at a pressure of about 20MPa from the inner nozzle at high speed, and the compressed air around 0.7MPa is ejected at the periphery of the jet. In the soil, a column shaped consolidation body with obvious diameter increases, ranging from 80 to 150cm.3., three tube jet grouting using three kin

16、ds of medium, respectively, conveying water, gas and slurry three grouting pipes. Coaxial flow of high pressure water jet and jet surrounded by punching failure in the surrounding soil, a high-pressure water jet nozzle and the cylindrical air jet, water, gas coaxial jet, can reduce the friction of w

17、ater jet and the surrounding medium, avoid water flowing through early atomization, enhanced water jet cutting ability. The nozzle side rotary jet, lifting, negative pressure area is formed larger in the foundation, carrying the slurry filling gap at the same time pressed, it will form a large diame

18、ter, high strength consolidation in the foundation, the foundation reinforcement effect.(three) slurry materialCement is the basic material of jet grouting, and cement grout can be divided into the following types.1. ordinary portland cement slurry is generally used, without any admixture, the water

19、 cement ratio is generally 0.8:1 1.5:1, the compressive strength of solidified body (28d) up to 1 20MPa, suitable for no special requirements of the project.2. - speed - early - strength type is suitable for the project with higher water level or early load. The compressive strength of cement soil c

20、onsolidated with 2% calcium chloride is 1.6MPa, and after adding 4% CaCl2, the compressive strength is 2.4MPa.3. the average compressive strength of high strength jet consolidated body is above 20MPa. High grade cement can be selected, or a composite formulation consisting of highly effective diffus

21、ion agents and inorganic salts can be selected.2 - 4% water glass is added to cement slurry, and its impermeability is improved obviously. If the project is impervious, it is better to use flexible materials. The cement slurry can be filled with 10 50% bentonite (the proportion of the cement weight)

22、. This is the use of slag cement, such as the only anti permeability requirements without freezing all can use the volcano ash cement.(four) high pressure jet grouting process;The range of injection shall be determined by field test. There is a close relationship between the size of the high jet con

23、solidated body and the type of soil and its compactness. The size of the consolidated body formed by different injection types and injection modes is also different. The injection energy of fixed injection is concentrated, and the range of injection is larger. See table 5-6.Table 5-6 characteristics

24、 of high pressure jet grouting consolidation bodyCharacteristics of consolidation bodySprinkling irrigation methodSingle tube methodTwo tube methodThree tube methodEffective diameter of consolidation body (m)cohesive soil0N101.2 + 0.21.4 + 0.32 + 0.310N200.8 + 0.21.1 + 0.31.5 + 0.320N300.6 + 0.20.8

25、+ 0.31 + 0.3Sand soil0N101 + 0.21.6 + 0.32.5 + 0.310 n 200.80.21.30.31.80.320 n 300.60.21.00.31.20.3砾 砂20 n 300.60.21.00.31.20.3单向定喷有效长度 (m)1.02.5单桩垂直极限荷载 (cn)500600100012002000单桩水平极限荷载 (cn)3040最大抗压强度 (mpa)砂土 1020, 粘性土26, 砾砂820平均抗折强度 / 平均抗压强度51 / 10 / 1干土容重 (kn / m 3)砂土 1620, 粘性土1415, 黄土135渗透系数 (cm

26、/ s)砂土、砂砾 10 - 5 10 - 7, 10 - 7 - 6 粘性土10粘聚力 (mpa)砂土 0.40.5, 粘性土0.71.0内摩擦角 (o).砂土 3040, 粘性土2030标准贯入锤击数 n砂土 3050, 粘性土2030弹性波 (km / s)p波砂土 23, 粘性土1.52.0s波砂土 1.01.5, 粘性土0.81.0旋喷粘性土固结强度为 0.36.0mpa, 无粘性土固结强度为415mpa.对于防渗工程多采用定喷、摆喷, 地层含的粒径较粗时多采用摆喷或旋喷.对处理深度大于 20m的复杂地层最好按双排或三排布孔, 使高喷桩形成堵水帷幕.孔距应为 1.73r (r为旋喷固

27、结体半径), 排距为1.5r时最 经济.一般定喷、摆喷孔距为1.22.5m 旋喷为0.81.2m.高喷防渗效果一般可达10 - 5, 10 - 6 cm / s .高喷桩桩距应根据上部结构荷载、单桩承载力及土质情况而定.一般取桩距为 (34) and d (d, 桩的布置方式可选用矩形或梅花形布置 为旋喷桩直径).高喷灌浆施工钻孔的目的是将灌浆管插入预定的土层中, 由下而上进行喷射作业.近来也有用振冲方式成孔直接进行喷射作业的方法.喷射时应注意以下事项:(1) 灌浆深度大时, 易造成上粗下细的固结体, 影响 固结体的承载能力或抗渗作用, 因而需采用增大压力和流量或降低旋转和提升速度等措施补救;

28、(2) 当发现喷浆量不足而影响工程质量时, 可采用复喷技术;(3) 当冒浆量大于灌浆量的20% 时, 可采用提高喷射压力、缩小喷嘴直径、加快提升速度和旋转速度等措施, 对冒出的浆液, 可回收利用;(4) 根据工程需要调节喷射压力和灌浆量, 改变喷嘴移动方向和速度, 控制喷射固结体的形状, 即圆盘状、圆柱状、大底状、糖糊芦状、大帽状和墙壁状.(5) 喷灌后的浆液有析水现象, 可造成固结体顶部出现凹穴,Unfavorable for foundation reinforcement and seepage control. Therefore, static pressure grouting o

29、r adding expansion material in slurry can be adopted to prevent it.High pressure pump is the key equipment in high pressure jet grouting, and the pressure and flow rate can be adjusted in a certain range. Rated flow is 85 150L/min; rated pressure is 20 50MPa.Table 5-7 jet grouting parameter listType

30、s of high injection groutingSingle tube methodTwo tube methodThree tube methodApplicable soil qualitySandy soil, cohesive soil, loess, miscellaneous fill soil, small diameter gravelSlurry material and formulationUsing cement as the main material, adding different additives with rapid hardening, earl

31、y strength, anti corrosion, anti freeze properties, common water cement ratio is 1:1, can also be used in chemical materials.High injection grouting parameterwaterPressure (MPa)-TwentyFlow rate (L/min)-80120Nozzle bore diameter (mm) and number-23 (12)atmospherePressure (MPa)-Zero point sevenZero poi

32、nt sevenFlow rate (m 3 /h)From 1 to 2From 1 to 2Nozzle clearance (mm) and number12 (12)12 (12)SlurryPressure (MPa)TwentyTwenty0.2 to 3Flow rate (L/min)801208012080150Nozzle bore diameter (mm) and number23 (2)23 (12)102 (1 or 2)Outside diameter of grouting pipe (mm)Phi 42 or Phi 45Phi 42, Phi 50, Phi

33、 75Phi 75 or Phi 90Lifting speed (cm/min)20251030From 5 to 20Rotational speed (r/min)About 201030From 5 to 20(five) quality inspection of high jet consolidated body1) excavation test: after the grout has a certain strength, it can be excavated to check the verticality, shape and quality of the conso

34、lidated body;2) drilling inspection: drilling core from the consolidated body for laboratory physical and mechanical performance test. Water pressure or pumping test is carried out in the borehole to determine its impermeability;3) standard penetration test: standard penetration test can be carried

35、out in the middle of rotary jet consolidation body.4) load test: static load test is divided into two kinds of vertical and horizontal static load tests. During test, concrete layer of 0.2 0.3m should be poured in the stress part;5) enclosure well test: increase the spray hole in the side wall, form

36、ing a closed enclosure and wall, water pressure and pumping test in two wells, or observation wells inside and outside the water level, for anti-seepage effect inspection.The technology of grouting with high pressure jet grouting is mainly applicable to Quaternary alluvium, residual layer and artifi

37、cial earth fill. For sand soil, clay soil, loess and silt can be reinforced. But the gravel diameter is too large, too much content and there are a large number of fibers, humus injection quality is a bit poor, sometimes even better effect of static pressure grouting.Because of the excessive velocit

38、y of groundwater, the spray slurry can not condense around the grouting pipe, there is no filling in the karst area, and the permafrost and the foundation where the cement is seriously corroded should not use high-pressure jet grouting method.(six) characteristics of high pressure jet grouting;Compa

39、red with common grouting method, high jet method has the following characteristics: low cost, fast construction speed, strong consolidation strength and high reliability:High speed flow spray method is the use of mandatory destruction of the soil forming concretion body, irrigation problems generall

40、y exist in the overburden layer; at the same time because of the high-speed jet is limited in the range of soil broken, so the grout loss is not easy, can guarantee the expected reinforcement scope and control of consolidation body shape; construction of any period in the process of drilling, also c

41、an be in the bottom of the hole or the central jet, in addition, can also be horizontal and the inclined direction of jet jet construction; high spraying method usually adopts cement slurry, it will not cause environmental pollution and groundwater, and better durability; the construction noise is s

42、mall, single and two pipe construction method is simple.Two 、 deep mixing method (cement soil consolidation method)Deep mixing method is to use cement as curing agent, through the special deep mixing machine in deep foundation in soft soil and cement (slurry or powder) stirred, cement and soft soil

43、will produce a series of physical and chemical reaction, soft soil hardening modification. The strength of the modified soft soil is much higher than the natural strength, and its compressibility and water permeability are much lower than that of the natural soft soil.(1) reinforcement mechanismThe

44、basic principle of mechanical mixing strengthening of soft soil and cement is based on the physical and chemical reaction process of cement stabilized soil. The water content in the soft soil is reduced, the cohesive force between the particles is increased, and the strength of the cement soil and t

45、he stability of the water are increased. In cement stabilized soil, due to the small amount of cement, it usually accounts for 10 - 15% of the weight of the reinforced soil. The hydration reaction of cement is completely carried out around the soil with a certain active medium, so the hardening spee

46、d is slow and the action is complicated.(two) the main characteristics of cement soil;1., the physical properties of cement soil bulk density is similar to the bulk density of natural soil, but the proportion of cement soil is slightly larger than that of natural soil.2. the unconfined compressive s

47、trength of cement soil unconfined compressive strength is 300 400kPa, dozens of times to hundreds of times larger than the natural soft soil, but the influence factors of cement soil unconfined compressive strength of many, such as cement, curing time, cement grade, soil moisture content and organic

48、 matter content and additive etc.In order to reduce the cost of the project, the measures of adding fly ash can be adopted. The strength of cement soil mixed with fly ash is generally higher than that without fly ash. The different cement ratio of cement soil, when the incorporation of fly ash and c

49、ement quantity, strength ratio of fly ash increased by 10%, so the use of deep mixing method in soft soil reinforcement when mixed with fly ash, not only the consumption of industrial waste, but also can improve the strength of cement soil.(three) construction technology1. reinforcement typeAccordin

50、g to the current construction technology of deep mixing method, mixing pile can be arranged in a column, wall and block three types for foundation reinforcement in the dike, mainly adopts pile type, used for seepage control and reinforcement, the wall shaped type, wall type is adjacent pile part ove

51、rlapping is a wall shaped reinforcement the type, composition of cement soil retaining wall, the wall has high impermeability, can form a good waterproof curtain.2. construction process(1) wet constructionThe main construction machinery is deep mixing machine. The construction of deep mixing method

52、can be divided into several steps, such as positioning, pre stirring, sinking, preparing cement slurry, lifting shotcrete mixing, repeating up and down mixing, cleaning and so on.(2) dry constructionDry powder is made of cement, by air, by blowing voids produced by the rotation of the mixing blades,

53、 and with the rotation of the stirring blades are uniformly distributed in the whole space orbit plane, and then in situ soil mixing and mixed together. Construction machinery mainly drilling machine, powder transmitter, air compressor, stirring drill bit, etc.The construction process includes 1) column para 2) 3) 4) the end of drill dri