1、Discussion about the application of the anchor bar on the slope construction Fu Ming Fu , Zhang Tian Abstract: 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 o
2、f the construction, but also is economic and reasonable for the construction. Key words: anchor bar； slope； strengthening 1. 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 t
3、he use 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 ten
4、sion 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 slope 2. 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-layer f
5、rame 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 silty clay
6、 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 design 3.1 Bolt design （ 1） all
7、 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 proc
8、ess, 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 21 h /3.24 per meter to calculation, the anchor length is L, a t
9、olal of 252. 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 o
10、f anchor: with 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 pressure12 When the supporting structure to leave in rock and earth mass dir
11、ection migration 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
12、strength, the calculation formula is same to the active soil pressure, but cohesive force C take zero, internal friction angle use e (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 e
13、stimationed by haircut 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 a Q akNN (1) (2) In the for
14、mula: aN is anchor tension design value； akN is anchor tension standard value； Qis partial load factor, take 1.3； tkH is the horizontal tension standard value of anchor； is the dip angle of anchor. Through the calculation, akN =112.3kN aN =145.99kN （ 3） the calculation of anchor steel section area (
15、3) In the formula: SA is the steel section area of anchor； is slope engineering importance coefficient(the slope engineering importance coefficient of this project is level 1, take 1.1)； 2 is the tensile working conditions coefficient of anchor bar ( permanent anchor take 0.69, temporary anchor take
16、 0.92)； yfis the tensile strength design value of anchor bar(standard valuekyf=400 aMP , design valueyf=360 aMP ). According to the calculation, SA 0.588 3210m ,choose level 3 steel of 1 28mm, SA =0.615 3210m . （ 4） The calculation of anchorage body and rock mass anchoring length anchoring length sh
17、ould not only meet the requirements which the bond force of formation on mortar and the bond stress of mortar on steel, but also meet the requirements that the Structure design codes the Minimum anchoring length. (4) In the formula: al is the anchoring length； D is the diameter of anchorage body； rb
18、f is the bond strength eigenvalue of layer and anchorage body, through the experiment or local experience sure, or according to the standard to selection ( this engineerings rock mass uniaxial compressive 2 2 2 21 1 12 0 9 t a n ( 4 5 ) 2 0 9 0 . 2 1 7 1 7 5 . 7 7 /2 2 2 2eaaE H K k N m costkak HN 2aSyNA f1akarbNl Df
