1、discussion about the application of the anchor bar on the slope constructionfu ming fu , zhang tianabstract: there are some advantages in strengthening slope with the anchor bar, such as low project cost, convenient for construction and so on. it not only meets the requirement of the reliability of

2、the construction, but also is economic and reasonable for the construction.key words: anchor bar; slope; strengthening1. introduction anchor technique uses strata geotechnicals shear strength around bolt to deliver structures pulling force or keep strata of the excavation own stability. due to the u

3、se of the anchor rod, anchor strata produce compressive zone and have reinforcement effect to strata, can enhance the strength of strata, improve mechanical properties of strata, make structure and stratum together formed a kind of work together complex. anchor system can effectively sustain tension

4、 and shear, improve shear strength of the potential sliding surface, so it can effectively prevent slope to produce sliding damage. fig 1 after excavation of the slope2. project profile the length of a slope is about 60m, the most slope height is about 23m,the angle up to 50° 75°, a five-l

5、ayer frame structure buildings is far from about 1.5 to 4m at its base edge, its foundation is artificial bored pile and its bearing stratum is in weathered phyllite. due to the strong weathering of rocks, it was chunky, loosely structured, multi-muddy filling. it has residual slope deposits of silt

6、y clay overlying and local folder with a pulpy, low strength. slope had collapsed at various locations, it is vary dangerous to the building, so we need to reinforce the slope, and we use stone concrete retaining wall and bolt to support it.3. bolt retaining and protecting design3.1 bolt design（1）al

7、l formation of anchor use whole length bond-type, the binder materials are ordinary cement mortar, the mortar strength grade is m30, the anchor length l is 10 meters, the slope height h is 9 meters. anchoring section length is 5m.（2）according to the construction condition and the needs of the proces

8、s, the layout form of anchor use quincunx, and in order to make the anchoring force in the role of surface rock surface with uniform, the two adjacent line bolts should be staggered arrangement.（3）the anchors number according to h/3.24 per meter to calculation, the anchor length is l, a tolal of 252

9、. the diameter of drilling holes is 90,the number of drill according to (l-0.1)m per hole to calculation, m30 grout number according to average 0.052m3 per hole to calculation.（4）the two adjacent rows vertical spacing of anchor take 2.55m, horizontal spacing take 2.55m. the dip angle of anchor: with

10、 the angle of horizontal line is 20°, and drilling down with this angle.（5）anchor use the steel bar, which is hrb400 level, 28mm diameter.3.2 anchor calculation （1）the calculation of lateral geotechnical pressure12when the supporting structure to leave in rock and earth mass direction migration

11、 until to the limit equilibrium state, the geotechnical pressure which is role in supporting structure called active geotechnical pressure. its calculation method is as follows:for the slope which has no flare structure surface, generally speaking, failure is controled by rock mass strength, the cal

12、culation formula is same to the active soil pressure, but cohesive force c take zero, internal friction angle use (rock mass equivalent internal friction angle) instead of, according to the standard to selection; rupture angle is 45°+/2（is rock mass internal friction angle, is estimationed by h

13、aircut at the standard of rock mass internal friction angle, reduction factor according to the standard to selection).according to the engineering survey, active rock pressure can calculation as follows:（2）the calculation of anchor tension design value (1) (2)in the formula: is anchor tension design

14、 value; is anchor tension standard value; is partial load factor, take 1.3; is the horizontal tension standard value of anchor; is the dip angle of anchor.through the calculation, =112.3kn =145.99kn（3）the calculation of anchor steel section area (3)in the formula: is the steel section area of anchor

15、; is slope engineering importance coefficient(the slope engineering importance coefficient of this project is level 1, take 1.1); is the tensile working conditions coefficient of anchor bar ( permanent anchor take 0.69, temporary anchor take 0.92); is the tensile strength design value of anchor bar(

16、standard value=400, design value=360).according to the calculation, 0.588,choose level 3 steel of 128mm, =0.615.（4）the calculation of anchorage body and rock mass anchoring lengthanchoring length should not only meet the requirements which the bond force of formation on mortar and the bond stress of

17、 mortar on steel, but also meet the requirements that the structure design codes the minimum anchoring length. (4)in the formula: is the anchoring length; d is the diameter of anchorage body; is the bond strength eigenvalue of layer and anchorage body, through the experiment or local experience sure

18、, or according to the standard to selection ( this engineerings rock mass uniaxial compressive strength is 7.46, belong to soft rock, rock mass structural plane development, take 300);is the bond working conditions coefficient of anchorage body and layer (permanent anchor take 1.00). according to th

19、e calculation, 4.3m, take=5.0m.（5）the anchoring length between anchor steel and anchor mortar (5)in the formula: is the anchoring length between steel and mortar; d is the diameter of anchor bar; n is the number of steel; is the bond strength design value between steel and anchor mortar, through the

20、 experiment sure, or according to the standard take 2.40; is the working conditions coefficient of steel and mortar bond strength(permanent anchor take 0.60）. according to the calculation, 2.1m，take =5.0m.3.3 the construction technology and key points of anchor the anchors construction technology is

21、 as follows: build-up scaffoldexcavate and clear up the slope surfacemeasures to fix positiondrill holewashing holebolt put in a certain placegroutcolligation the end of the anchorflushing the slope surfacepouring frame spacespray seed（1）this slope belong to rocky slope, after excavate the slope 10

22、cm to the underside of the frame space, set bolt and pouring frame space, then spray grass or seeds after borrowed soil 20 cm in the frame space.（2）the slope should be payed attention to clean up, when construction. the anchor should be placed after wash hole, then put pressure (0.4mpa) and grout. a

23、fter the mortar fully solidification, colligation steel, cast-in-place reinforced concrete frame space, bend the end of the anchor and bind point by point with the skeleton steel.（3）before drilling, the hole should be measured to fix position and then do mark. pitch deviation is less than 150mm, hol

24、e depth error is less than 50mm. try not remold the surrounding rock, when drill. before put the anchor, it should be attentioned that blow wash clean the water of the hole and rock powder and so on, and rust removal the body of rod. when grouting, builders should attention the grouting pressure and

25、 mortar ratio. fig 2 anchor field construction drawing4. conclusionit is economical to reinforcement slope with bolt, and use the normal equipment, it is not only achieve safe and also economy and rational.(1) today bolt technology is widely used in the project. it is an effective reinforcement meas

26、ures to constraints sliding soil with the combining of bolt and concrete slope protection.(2) we must be sure to do geological exploration work of the slope to find out the nature of the rock and hydrogeological situation before reinforcing slope by grouting bolt. (3) due to the factors of engineeri

27、ng geological conditions, grouting pressure and construction technology, we should be given adequate attention to the quality of construction. reference1technical code for building slope engineering (jgj 120-99). the people's republic national standards. beijing: china architecture & buildin

28、g press.2 ying-ren zheng, zu-yu chen etc. engineering treatment of slope & landslide m. beijing：china communications press，20073 luozhenhai. talk shallowly the application of the anchor at the slope reinforcementj. fujian construction science & technology，2010,06:15-16淺談錨桿技術在邊坡工程中的應用 1.引言錨桿技

29、術是利用錨桿周圍地層巖土的抗剪強度來傳遞結構物的拉力或保持地層開挖面的自身穩定。由于錨桿的使用,使錨固地層產生壓應力區并對地層起到加筋作用,來增強地層的強度,改善地層的力學性能,使結構與地層一起形成一種共同工作的復合體。錨桿體系其能有效地承受拉力和剪力,能提高潛在滑移面上的抗剪強度,有效地阻止坡體產生滑動破壞。 2.工程概況某邊坡長約60m,最大坡高約23m,坡度達50°75°,為巖質邊坡。距坡底邊緣約1.54m處有1棟5層框架結構建筑物, 人工挖孔灌注樁基礎,建筑物以中風化千枚巖為持力層。因巖石風化強烈，呈碎塊狀，結構松散，多為泥質充填。上覆殘坡積粉質粘土，局部夾有泥狀，

30、強度較低。邊坡坡體多處位置曾發生崩塌，對建筑物存在威脅，所以需對邊坡進行加固，采用的是塊石混凝土擋墻+錨桿進行支護。3.錨桿支護設計3.1 錨桿的設計（1）采用全長黏結式錨桿，黏結材料為普通水泥砂漿，砂漿強度等級為m30，錨桿長度l為10米，防護邊坡高度h為9米。錨桿錨固段長度為5m。（2）錨桿的布置形式根據施工條件及工藝的需求采用梅花行布置，且為了使錨桿的錨固力均勻作用于巖體表面，應采用相鄰兩行的錨桿錯開布置。（3）錨桿數量按每延米h/3.24根計，錨桿長度為l，共計252根。鉆孔直徑為90，鉆孔數按(l-0.1)m/孔計， m30注漿數量平均按0.052m3/孔計。（4）錨桿的上、下排垂直

31、間距取2.55m，水平間距2.55m。錨桿傾角：與水平線成20°角度向下成孔。（5）錨桿桿體選用直徑為28mm的hrb400級鋼筋。3.2 錨桿計算（1）側向巖土壓力的計算12當支護結構向離開巖土體方向偏移至巖土體達到極限平衡狀態時，作用在支護結構上的巖土壓力稱為主動巖土壓力。其計算方法如下：對于無外傾結構面的邊坡，一般發生由巖體強度控制的破壞，計算公式按主動土壓力計算，但粘聚力c取零，內摩擦角用（巖體等效內摩擦角）代替，按表取值；破裂角按45°+/2（為巖體內摩擦角，由巖塊內摩擦角標準值折減確定，折減系數按表取值）確定。根據地勘報告可知，邊坡巖體類型為類，取等效內摩擦角為40，計算可得主動巖石壓力 （3-1）其中：為20kn/；h為9m；= =0.217通過計算可得=175.77 kn/m。（2）錨桿軸向拉力設計值的計算 （3-2） （3-3）其中：為錨桿軸向拉力設計值；為錨桿軸向拉力標準值；為荷載分項系數，取1.3；為錨桿所受水平拉力標準值；為錨桿傾角。通過計算可得=112.3kn =145.99kn（3）錨桿鋼筋截面面積的計算 （3-4）其中：為錨桿鋼筋截面面積；為邊坡工程重要性系數（本工程邊坡工程安全等級為一級，取1.1）；為錨筋抗拉工作條件系數（永久性錨桿取0.69，臨時性錨桿取0.92