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锚杆是一种新型的受拉杆件,它一端与工程建(构)筑物连接,另一端锚固在土层中承受土压力和水压力所产生的拉力。国内外在修建各种地下建(构)筑物及大跨度厂房时,已大量地采用锚杆代替横撑作为基坑侧壁支撑,简化了支撑工作,使基坑开挖和基础工程做到文明施工。由于各种水平钻机及高效钻机的出现,推动了锚杆技术的发展,现锚杆除用作基坑支护外,还可用于保持路堑、边坡的稳定、地基的加固、基础的托换,以及建(构)筑物的抗浮、抗倾覆等方面。近年来,锚杆技术的应用日趋广泛,它不仅可用于岩层,而且还可用于砂卵石、砂土及粘性土;并从临时性支挡发展到永久性锚杆支挡。由于钻孔及灌浆机具的改进,促进了二次高压灌浆预应力锚杆的成功。锚杆经二次高压分段灌浆,形成形状各异的矿体,增加了锚杆的摩阻力,同时对土体产生的挤压和渗透提高了土的力学性能,使它具有常压灌浆无法比拟的优点,其承载力可成倍提高,因而解决了锚杆在饱和软粘土中的应用问题,进一步扩大了锚杆的应用范围。在土层中锚杆的极限承载力受土的性质、锚固长度、地下水、锚杆类型和灌浆工艺等多种复杂因素的影响,其可靠性及经济效益也因之而异。因此,现阶段在土层中应用锚杆技术,一定要重视和严格执行现场检测工作,在饱和软粘土中应用更应慎重对待,对永久性锚杆的长期强度、抗拔机理、局部强度和整体稳定,以及钢筋(或钢绞线)的防腐问题,均有待进一步深入研究。
The bolt is a new type of tension member, one end of which is connected with an engineering building (structure), and the other end is anchored in the soil layer to withstand the pulling force generated by earth pressure and water pressure. At home and abroad, when constructing underground structures (buildings) and large-span plants, a large number of anchor rods have been used instead of cross brace as sidewall pit support, which simplifies the support work and enables excavation and foundation engineering to be completed. Civilization Construction. Due to the emergence of various horizontal drilling rigs and high-efficiency drilling rigs, the development of bolt technology has been promoted. In addition to the use of foundation pit support, anchor bolts can also be used to maintain the stability of roads, slopes, reinforcement of foundations, and underpinning of foundations. , as well as anti-floating and anti-overturning aspects of buildings (structures). In recent years, the application of bolt technology has become increasingly widespread. It can be used not only in rock formations, but also in sand and gravel, sand and cohesive soils; and it can develop from temporary support to permanent bolt support. Due to improvements in drilling and grouting equipment, the success of secondary high pressure grouting prestressed anchors was promoted. The anchor rods are grouted by secondary high pressure to form ore bodies of various shapes, which increase the friction resistance of the anchor rods. At the same time, the extrusion and infiltration produced by the soil body improve the mechanical properties of the soil, making it unable to grout with atmospheric pressure. Compared with the advantages, the bearing capacity can be increased exponentially, thus solving the application problem of the anchor rod in the saturated soft clay, and further expanding the application range of the anchor rod. The ultimate bearing capacity of anchors in soil layers is affected by many complex factors such as the nature of the soil, the length of the anchorage, the groundwater, the type of anchor rods, and the grouting process. The reliability and economic benefits vary accordingly. Therefore, the application of anchor rod technology in the soil layer at the present stage must pay attention to and strictly implement the on-site inspection work. The application in the saturated soft clay should be treated with more care. The long-term strength, pull-out mechanism, and local strength of the permanent anchor rod are The overall stability, as well as the anti-corrosion problems of rebar (or steel strands), have yet to be further studied.