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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浅谈锚杆技术在边坡工程中的应用 1.引言锚杆技

29、术是利用锚杆周围地层岩土的抗剪强度来传递结构物的拉力或保持地层开挖面的自身稳定。由于锚杆的使用,使锚固地层产生压应力区并对地层起到加筋作用,来增强地层的强度,改善地层的力学性能,使结构与地层一起形成一种共同工作的复合体。锚杆体系其能有效地承受拉力和剪力,能提高潜在滑移面上的抗剪强度,有效地阻止坡体产生滑动破坏。 2.工程概况某边坡长约60m,最大坡高约23m,坡度达50°75°,为岩质边坡。距坡底边缘约1.54m处有1栋5层框架结构建筑物, 人工挖孔灌注桩基础,建筑物以中风化千枚岩为持力层。因岩石风化强烈,呈碎块状,结构松散,多为泥质充填。上覆残坡积粉质粘土,局部夹有泥状,

30、强度较低。边坡坡体多处位置曾发生崩塌,对建筑物存在威胁,所以需对边坡进行加固,采用的是块石混凝土挡墙+锚杆进行支护。3.锚杆支护设计3.1 锚杆的设计(1)采用全长黏结式锚杆,黏结材料为普通水泥砂浆,砂浆强度等级为m30,锚杆长度l为10米,防护边坡高度h为9米。锚杆锚固段长度为5m。(2)锚杆的布置形式根据施工条件及工艺的需求采用梅花行布置,且为了使锚杆的锚固力均匀作用于岩体表面,应采用相邻两行的锚杆错开布置。(3)锚杆数量按每延米h/3.24根计,锚杆长度为l,共计252根。钻孔直径为90,钻孔数按(l-0.1)m/孔计, m30注浆数量平均按0.052m3/孔计。(4)锚杆的上、下排垂直

31、间距取2.55m,水平间距2.55m。锚杆倾角:与水平线成20°角度向下成孔。(5)锚杆杆体选用直径为28mm的hrb400级钢筋。3.2 锚杆计算(1)侧向岩土压力的计算12当支护结构向离开岩土体方向偏移至岩土体达到极限平衡状态时,作用在支护结构上的岩土压力称为主动岩土压力。其计算方法如下:对于无外倾结构面的边坡,一般发生由岩体强度控制的破坏,计算公式按主动土压力计算,但粘聚力c取零,内摩擦角用(岩体等效内摩擦角)代替,按表取值;破裂角按45°+/2(为岩体内摩擦角,由岩块内摩擦角标准值折减确定,折减系数按表取值)确定。根据地勘报告可知,边坡岩体类型为类,取等效内摩擦角为40,计算可得主动岩石压力 (3-1)其中:为20kn/;h为9m;= =0.217通过计算可得=175.77 kn/m。(2)锚杆轴向拉力设计值的计算 (3-2) (3-3)其中:为锚杆轴向拉力设计值;为锚杆轴向拉力标准值;为荷载分项系数,取1.3;为锚杆所受水平拉力标准值;为锚杆倾角。通过计算可得=112.3kn =145.99kn(3)锚杆钢筋截面面积的计算 (3-4)其中:为锚杆钢筋截面面积;为边坡工程重要性系数(本工程边坡工程安全等级为一级,取1.1);为锚筋抗拉工作条件系数(永久性锚杆取0.69,临时性锚杆取0.92

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