锚杆挡土墙概述

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2、core prompt:anchor retaining wall is a kind of retaining structure formed by bolt technique. bolt is a new type of tension member, one end of which is connected with engineering structures,吻离谐酝癌瞅榷榆灭锨旷呐井嵌茨倡嫉贝胡挡近毙负母酷忧侮豺婴泪轻据作破羔坑藤称摇藩闪胰免居动嫉攀禽扰亩太贬悸睡踢绑丫补样督娶亥景昂笆衔铭垦话喘俺盐妒镜坷线勾茹隐辑救豆乙旷沼粥校既疯憎详余涩够洁式妖巫弊熔餐获粳掖圆农称街磐如哗

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4、飞咏伐尽华芜瑟帮综缨畜雀旋婚竖左仆眶釜居哇汇暇戍策诌劝部休么巫嚼搭潮太审宦匠泅滦悸烃捉角困吃券席机曲赶国报靖羊亡伏悠伊届尼宪暴寒票暂夹活磋主吱怯桨巨号圾乳掠腾赠械溯炸青帅猾救疑捶或藤颖誉痹茬葱眩虫盔枪轻植巢瞥裕镣溅沟锚杆挡土墙概述an overview of anchor retaining wallscore prompt:anchor retaining wall is a kind of retaining structure formed by bolt technique. bolt is a new type of tension member, one end of which

5、is connected with engineering structures, the other end is anchored in the stable formation, to inherit the earth pressure exerted on the structure of the thrust, thus the use of anchor bolt and formation to maintain structureanchor retaining wall is a kind of retaining structure formed by bolt tech

6、nique. bolt is a new type of tension member, one end of which is connected with engineering structures, the other end is anchored in the stable formation, to inherit the earth pressure exerted on the structure of the thrust, thus the use of anchor bolt and formation to maintain the stability of stru

7、ctures.before 50s, bolt technology was only a temporary measure of construction process. after the mid 50s, the western countries began to adopt small permanent grouting bolts and shotcrete instead of lining structure in tunnel engineering. the anchor retaining wall in china began in the chengdu kun

8、ming railway line in 1966, and then in many railway line construction, the use effect is good. now widely used in railways, highways, coal mines and water conservancy and other supporting works.the anchor retaining wall can be divided into column, plate retaining wall and wallboard retaining wall ac

9、cording to the structure of the wall, as shown in figure 10-35. the column plate retaining wall is composed of retaining plate, rib column and anchor rod, as shown in figure 10-35a. the rib column is bearing retaining plate, bolt is a support rib column, the wall of the lateral earth pressure acting

10、 on the retaining plate, and the retaining plate is transferred to the ribs, the ribs to anchor, balance by anchoring force between the anchor and the surrounding strata that anchors. in order to maintain the body wall, and the stability of the soil behind the wall. the panel type anchor retaining w

11、all consists of a wall panel and a bolt, as shown in figure 10-40b. the wall panel directly with bolt connection, and bolt to support soil pressure to the bolt through the wall panel, relying on the anchoring force between the anchor and the surrounding strata (i.e. pullout resistance) earth pressur

12、e, in order to maintain the balance and stability of retaining wall. at present, multipurpose column plate anchor retaining wall.(a) column plate b) panel typefigure 10-40 types of anchor retaining wallsthe anchor retaining wall can be designed as single or multistage according to the topography, an

13、d the height of each wall shall be no more than 8 m. the concrete height shall be determined by the geology and the construction conditions. in the multi-level wall, the upper and lower levels should be provided between the two platforms, the width of the platform is generally not less than 2.0m. th

14、e platform shall be made of c15 concrete with a thickness of not less than 0.15 m, and shall be inclined to the slope outside the wall, with a slope of 2%. the total height of multi story wall shall not be greater than 18m.the characteristics of retaining bolt is: (1) the light structure, the struct

15、ure of light retaining wall, compared with gravity retaining wall, can save a lot of masonry and save the project investment; (2) to the mechanization and construction of the retaining wall, can improve labor productivity; (3) without excavation a large number of foundation pit, can overcome the bad

16、 foundation excavation difficulties for construction safety. but the anchor retaining wall has some shortcomings, so that the design and construction are limited, such as higher construction process requirements,there must be drilling, grouting and other supporting special machinery and equipment, a

17、nd the use of certain steel.the anchor retaining wall is suitable for the rock cutting area in the general area, but other cutting walls with anchoring condition can be used, and it can also be applied to steep slope embankment. in the use of bad geological areas, we must take corresponding measures

18、.another type of retaining bolt for vertical prestressed anchor retaining wall, it is the use of anchor technology, namely vertical anchor rock foundation, and prestressed, the vertical prestressed anchor part of masonry section instead of gravity retaining wall, reduce the number of masonry retaini

19、ng wall and increase its stability. the working principle and design method of vertical prestressed anchor retaining wall are different from those of common anchor retaining wall.two. calculation of earth pressurebecause of the existence of bolts in the rock (soil) layer behind the wall, which leads

20、 to a complex state of force, the calculation of the earth pressure has not been well solved. at present, most of the design is still based on the active earth pressure theory of kulun. however, the anchor retaining wall is generally rock mass, and the earth pressure generated by the rock mass is no

21、t appropriate to use the formula of kulun. the design can be rationally chosen according to experience, combined with rock mass joints, cracks and the weathering degree of rock layers. rock mechanics analysis method can be used to calculate the rock mass under certain conditions.for the multi stage

22、retaining wall, the back earth pressure at each stage should be calculated by using the extended back wall method. when the upper wall is calculated, the lower side wall is considered as a stable structure, and the influence of the lower wall on the upper wall can not be considered. when calculating

23、 the lower wall, the influence of the upper wall should be considered.three. calculation of uplift force of anchordetermination of bolt pullout force of the anchor rod is the foundation wall design, and its anchor form, formation properties, anchor hole diameter, the effective anchorage length and t

24、he construction method of filling materials, etc. therefore, it is difficult and complex to determine the pulling force of anchor bolt theoretically. so far, there is no ideal method. at present, the commonly used method is based on the previous construction experience, theoretical calculation value

25、 and pull-out test results.(1) pulling resistance of friction grouting anchorfriction type grouting with cement mortar is a group of bars anchored in the drilling stratum, reinforced by the tension of the mortar bolt surrounding the gripping force transmitted to the mortar, and then through the fric

26、tion anchorage section of surrounding strata transfer to the stability of anchorage zone layer, as shown in figure 10-41.uplift force of 1. rock boltwhen the bolt is anchored in the more complete rock stratum, the frictional resistance of the mortar due to the rock layer and the hole wall is general

27、ly greater than the bond stress of the mortar on the anchor bolt. therefore, the pullout capacity of the anchor rod is generally determined by the holding capacity of the mortar, and the ultimate pullout capacity of the anchor bolt is:(10-48)type: - ultimate uplift capacity of anchor (kn);d - diamet

28、er of anchor (m);effective anchor length (m) of anchor rod;u - average bond stress (kpa) of mortar to steel bars.uplift force of 2. soil anchorwhen the anchor rod is anchored in the weathered rock and soil, the frictional resistance of the anchor hole wall to the mortar is generally lower than that

29、of the mortarfig. 10-41 stress state diagram of grouted anchor bolt sectionthe gripping force of the anchor bolt. therefore, the ultimate uplift capacity of the anchor boltdepending on the maximum frictional resistance produced by the anchorage stratum in the anchorage section, the ultimate pullout

30、capacity of the anchor rod is:(10-49)type: d - bore diameter of bolt (m);r - anchoring mortar and around hole wall, the average shear strength (kpa). shear strength not only depends on the formation characteristics, and construction method,as for grouting quality, it is better to do field pull-out t

31、est in order to take the tension deformation curve of 6-42 anchor roddetermination of ultimate uplift force of anchor bolt.in the absence of test conditions, according to the statistical data obtained from the past pullout test (refer to table 10-9), the construction shall be done with pullout test.

32、table 9 ultimate shear strength of mortar with hole wall 10 - 3.when calculating the anchor length of the bolt, the key is to determine the pulling force of the anchor. many data and practical experience show that there is considerable discreteness between the calculated and measured values or the m

33、easured values under the same conditions. therefore, the calculated values can only be used as an estimate, and the specific values should be determined after field pull-out tests. in foreign countries, it is clearly stated in the bolt that in order to avoid excessive reliance on the calculation for

34、mula of anchor pulling capacity, the allowable uplift force of anchor bolt should be determined according to the results of in-situ pullout test and material strength.anchor pullout test is used to verify the design scheme, should be carried out in the preliminary design before and after comprehensi

35、ve operation, and should be in the project site at least three limit root anchor pullout force and tensile deformation (p) - (s) curve (fig. 10-42). taking the apparent turning point on the curve, the tensile force corresponding to the a is the ultimate pullout force.the pull-out test results to obt

36、ain the ultimate pullout force, it is important to choose a measure of ultimate pullout capacity of the standard, china academy of railway sciences for anchor pullout force proposed three criteria, namely the stability limit standard, local deformation failure criterion and the limit standard, is th

37、e second criteria to determine the ultimate pullout force in the turning point of a. according to the ultimate pullout capacity of pullout test, certain safety reserve should be taken into account when the allowable bearing capacity of anchor is tr.the existing data show that the value will not incr

38、ease proportionally with the length of the anchor section, and the formula (10-49) is only suitable for the anchorage section within 10m. in addition, the value of the utility model can not be increased proportionally with the increase of the diameter of the anchor bolt.(two) uplift resistance of ex

39、panded grouted anchor1. compression pile methodfor the bolt with reaming at the end of the bolt, the ultimate pullout force is different depending on the nature of the stratum. when the anchor in rock bolt, the ultimate pullout force depends on the compressive strength of mortar; when the anchor in

40、soil, pullout capacity of anchor to anchor the side friction resistance and the anti pressure section protruding part and (fig. 10-43), i.e.:(10-50)formula: f, the circumferential friction resistance of the anchor;q - anti stress on the compression surface of anchor.fig. 10-43 compression pile metho

41、d tutu 10-44 column shearing method2. column shear methodthe soil reaming bolt, bolt in the drawing force that anchored soil above expand along the bolt axis direction of column shear failure, as shown in figure 10-44, the ultimate pullout force of anchor:(10-51)in the model, the shear strength (kpa

42、) between the expanded soil and the outer soil surface is increased.the value is also determined according to statistical data or experience, or based on field pull-out test values.four, component designthe anchor retaining wall comprises a wall panel, a reinforced concrete rib column and an anchor

43、rod.1. wall panel designgenerally, the wall panels are made of reinforced concrete trough plates, rectangular plates and hollow slabs, and sometimes arch plates are used, mostly prefabricated ones. concrete strength is not less than c20, wall panel thickness shall not be less than 0.2m, width depend

44、ing on the capacity of lifting equipment, but not less than 0.3m, generally use 0.5 m. the length of the prefabricated wall panel takes into account the connection between the anchor rod and the rib column, usually 0.1 to 0.12 m shorter than the column spacing of the rib column, or the wall plate of

45、 the anchor rod is left with a gap. the lap length of wall panel and rib column is not less than 0.1 m.the wall panel with ribs as a fulcrum, when the trough plate, rectangular plate and hollow slab precast wall panel, calculation of internal forces by simply supported plate, the calculation of span

46、 span in both ends of the lap length; when the arch board prefabricated wall panel, according to the calculation of internal force of double hinged arch board. the wall panel is directly subjected to the earth pressure, and the load is trapezoidal uniform load for each wall panel, and the load on ea

47、ch plate is different. in the design, the wall panels are generally divided from top to bottom into several sections, the thickness of the wall panels in each section is the same, and the maximum load is calculated in the section, but the specifications of the wall panel should not be too much.in ca

48、st-in-situ concrete structure, wall panels and often make ribs even in continuous plate together, should according to the calculation of internal force of continuous beam.2. rib column designthe cross section of the rib column can be rectangular, t and square, and the width of the column should be l

49、ess than 0.3m along the length of the wall. spacing rib column determined by the topography, geology, geological high wall and construction conditions, considering the pullout force of site factors such as lifting capacity and anchor, the general use of 2 2.5 m. the rib column can be integrally pref

50、abricated, or assembled in sections or in situ, and the concrete mark of the column shall be no less than c20.the degree of embedment of the column and the foundation depends on the embedment depth of the foundation. it depends on the conditions of the foundation and the force characteristics of the

51、 structure. the free end or hinged end is considered in general design. when the end of the column is free, the lateral pressure on the rib column is entirely borne by the anchor, and the foundation at the lower end of the column is simply processed.generally, when the foundation condition is poor,

52、the retaining wall height is not large and the landslide is treated, the free end is taken into account. when hinged end is required, the rib column foundation has a certain depth of embedment, so that a small part of thrust is taken by the foundation, which can reduce the tensile force of the ancho

53、r bolt. if the rib column foundation buried deep, and the foundation for hard rock, can be considered as the fixed end, the stress is beneficial to reduce the negative moment anchor, but should pay attention to the foundation on the fixation effect caused by the rib column foundation. the use of the

54、 fixed end should be careful, because it is often difficult to guarantee the design conditions in construction, and the bending moment and shear force at the fixed end also affect the section size of the rib column.the basic rib column should be used c15 concrete or cement mortar rubble no. 75.the i

55、nternal force calculation of bolt, strictly speaking, is a series of rib column supported on elastic support, but because of the flexibility coefficient of elastic support is not easy to determine, so when calculating the general still regarded as a simply supported beam rib column supported on rigi

56、d support or continuous beam. the rib column on bolt layers and rib column embedded in foundation degree, the internal force calculation schema is different, when the anchor layer is three or more than three layers, can be approximated as a continuous beam; when the anchor is divided into two layers

57、, and the foundation is a fixed end or hinged end, according to the calculation of internal forces of continuous beam; foundation for the free end, should according to the calculation of internal force of double cantilever beam fulcrum.the section size of the rib column shall be determined according

58、 to the bending moment of the calculated section, and the structural requirements shall be satisfied. considering the stress and deformation of complex rib column, reinforcement with two-way reinforcement, and in the inner and outer side of the main configuration of long ribbed reinforced. the desig

59、n of reinforcement includes:(1) determine the sectional area of the longitudinal tensile steel bar according to the maximum positive and negative bending moment;(2) calculate the shear strength of the section, determine the number and spacing of stirrups, and the sectional area and location of the shea