Experiment Study On The Anchoring Mechanism And Bearing Characteristics Of The Capsule-type Expansion Bolt

Capsule-type expansion bolt is a new type expansion bolt body, is considering the clay, silt, sand, pebbles and other soil in the high pressure expanding cooperation lessens under the action of pouch easily designed has the characteristics of extrusion deformation.So capsule pressure grouting body expanding bolt using prefabricated rubber pouch set on the anchor end head, its rod body USES psb1080 reinforced bar, rubber pouch is chosen in stability, heat resistance and corrosion resistance performance stability of butyl rubber as the preferred material, prefabricated rubber pouch set with steel ring on the outside of reinforced ends on both ends fixed up and down.Capsule pressure grouting expansion bolt rod body with high bearing capacity, low cost, good effect of engineering etc, especially can be regulated according to the needs of engineering precast pouch geometry size and pressure grouting effectively to ensure that the expansion of the anchoring body space form and the ultimate bearing capacity.Capsule-type expansion bolt body to avoid the traditional expansion bolt on the pore forming process of technical defects, compared with blasting hole safer, more applicable than tool into the hole, the high pressure jet grouting is more efficient than, its load-bearing characteristics and mechanics mechanism of significant differences with the ordinary bolt.As soon as possible to press the capsule type expansion bolt applied to more and more geotechnical engineering, studying the characteristics of the anchor rod anchor and mechanics mechanism has important practical significance.This article USES the elastic mechanics analysis, engineering field test, the measured data contrast, methods such as computer simulation, studies the characteristics of new type expansion bolt body bearing and mechanical mechanism, discusses the changing law of its bearing capacity, and the results of the study was used to optimize the design method, completed the test for the performance improvement.This article related the test data for the promotion and application of expansion bolt body engineering significance.In this paper, the main work content can be summarized as the following:First, the theoretical research methods.Based on micro unit elastic equilibrium theory is a new type expansion bolt axial stress of anchor solid and anchor soil adhesive interface shear stress calculation formula, after get the axial distribution rule and characteristics of both, using a single variable principle of further analysis of new type expansion bolt anchorage segment size, mechanical parameters of soil and anchor head setting depth of anchor effect bonding interface shear stress distribution in the soil system.Research shows that main affect the anchoring effect of the diameter and soil physical parameters for the anchorage segment, embedment depth affects only free on the shear stress distribution in theory, the adoption of a variety of theoretical analysis hypothesis, quantitative analysis of the influence weight, only need to be done on Capsule-type expansion bolt more detailed field test.Second, the use of experimental research method.Considering capsule-type expansion engineering characteristics of the anchor rod body, designed a set of complete indoor and outdoor test plan, through indoor secrete water-borne test found the optimal material mixing ratio for pressure grouting concretion body and to determine the water reducing agent, water retention agent and other additive material, and through the outdoor experiment research methods to get the Capsule-type expansion of the main factors that influence the ultimate bearing capacity of anchor body, the conclusion is as follows:(1) through indoor secrete water-borne test found that the optimal mixture ratio for pressure grouting concretion body is cement, water, water reducing agent, water retention agent = 1000, 400:2.5:0.20 the cement by P0. 42.5;Water reducing agent with poly(carboxylic acid is a highly effective water reducing agent for liquor(solid content also called mother liquor 40%);Super absorbent polymers using hydroxyl methyl cellulose c when grouting slurry quick-setting and after curing strength performance is best.(2) through the turgor pressure and solid slurry water injection test, capsule type pressure expansion body when anchor grouting pressure in soft soil(sand soil and cohesive soil) in deformation structure presents the upside slants big gradually narrowed down the cylinder shape, general equivalent cylinders may be used for design and calculation.And found that pressure grouting pressure value after reaching a certain value, the pressure value can quickly reduce pouch expansion volume increased rapidly at the same time, shows that there is a certain pressure limit within the soil.(3) through field contrast test, the Capsule-type, expanding the ultimate bearing capacity of the anchor rod body is mainly composed of several under several factors are respectively expanding the anchoring body diameter, volume expansion bolt solid body, the soil parameters, the anchor head embedment depth, expanding anchorage length, pouch indicates that roughness, etc.The results show that the expansion and the diameter of the anchoring body anchor head soil compactness is the most important factor affecting bearing capacity of expansion bolt rod body, and the anchoring; and the relationship between bearing capacity with a certain ratio growth and the diameter ofThe anchoring length and the bearing capacity of a linear relationship between growth;Embedment depth different led to the stress pattern is different, the final pouch roughness, although also can affect the bearing capacity but limited to a certain degree.When end resistance fails to reach the limit state, expansion bolt body displacement depends mainly on the elastic-plastic deformation of rod body;When the end resistance exceeds limit state, anchor the whole deformation displacement is determined by the tensile deformation of the anchored body.Compared with the traditional expansion bolt and common bolt body, the new expansion body effectively improved the anchor rod anchor uplift bearing capacity limit.Third, through the field measured data.And emphatically analyzes the sac pressure expansion bolt body in the process of drawing mechanical characteristics and failure mode of new type expansion bolt body is studied through data contrast in detail the relationship between the load displacement and force transfer mechanism of the soil anchor system;Introducing the static field cavity expansion theory, put forward considering the turgor pressure and radius of plastic zone expansion bolt bearing capacity calculation formula, detailed conclusion is as follows:(1) based on the field test pressure type expansion bolt body according to the measured data found sac anchor head buried depth can be divided into different model of deep and shallow buried, in this paper experiment when buried depth less than or equal to 7 ~ 8 m expansion bolt in a shallow buried body mode, bearing capacity greatly reduced;When embedded mode bolt bearing capacity of local shear failure occurred after they will continue to increase slightly;And shallow buried body expanding bolt rapid decline after reaching the limit bearing capacity of bearing capacity, the overall shear failure.(2) considering the practical engineering problems, should not be expanding the anchoring body diameter increases indefinitely, put forward specific soil there is a reasonable load volume maximize the efficiency of bolt.Formation on the experiment, finishing the test data shows that when the expansion of the anchoring body diameter selection and its bearing capacity is 600 mm with anchor solid volume ratio of the highest, the best engineering economics.(3) Capsule-type expansion bolt body uplift bearing capacity is mainly composed of variable cross-section end resistance and side friction of two parts, the distribution is given on the basis of the principle of expansion expansion soil anchor in the main body(sandy soil and cohesive soil) is the ultimate bearing capacity calculation method.On the principle of expansion can be better to consider the expansion of the pouch process on soil elastic-plastic changes, introduces the pressure grouting pressure value in the process of the bearing capacity calculation, to starting from the formation mechanism of reaming estimate expansion bolt bearing capacity provides a new method.Fourth, the use of computer simulation software.Hard soil constitutive model based on new type expansion bolt anchor in different size of solid cases load-bearing characteristic and the mechanical model of the simulation, and the part and the third chapter experiment data from mutual authentication, the simulation analysis of the anchorage size and buried depth, different soil mechanics parameters of the ultimate bearing capacity of anchor bolt and the impact of growth, finally aimed at expanding bolt body buried deep shallow buried two main mode of anchor head soil elastic and plastic zone distribution, development and damage of qualitative analysis, the conclusion is as follows:(1) based on the numerical simulation of the two modes bolt stress research can be found that when the anchor rod anchor head in embedded mode often happen local shear failure, plastic damage in the whole process of stress range is always below the ground surface;In shallow buried mode, the plastic zone are extended and connectedtoGGthe surface with the increase of the displacement, the "glass".(2) can be found through the numerical simulation of physical and mechanical parameters of soil anchor head is fairly obvious to the promotion of the ultimate bearing capacity expansion bolt body, cohesive force and Angle of internal friction of two main parameters can make the expansion bolt bearing capacity increasing.Through the numerical simulation of single variable method is used to contrast more groups of data shows that the impact on the ultimate bearing capacity of a non-linear relationship, when the friction Angle increases, the expansion bolt rod body with the increase of cohesive force of ultimate bearing capacity of growth down gradually;And cohesive force increases, with the increase of friction, its contribution to ultimate bearing capacity increase amplitude is smaller.Five, the performance test method.Capsule-type expansion body compared to common anchor and traditional expansion bolt bolt has higher bearing capacity, but also the existence of displacement control of ascension is not significant, therefore in actual construction design of the first two enlarged pile side friction improved test, test effect of the conclusions are as follows:Will be a single capsule(1) the modified polycystic anchor can actually increase after solid anchor pile side friction, can be seen from the Q- S curve drawing test early bearing capacity increase rate increases obviously, improved the capsule type expansion bolt body early ascension obvious lack of enough bearing capacity, proved by polycystic continuous anchor solid transformation to further improve the comprehensive performance of Capsule-type expansion bolt body, improve the form of the ultimate bearing capacity.(2) the secondary splitting grouting technique can effectively control the sac pressure type expansion displacement of the anchor rod body, directly improve the ultimate bearing capacity, the secondary splitting grouting give full play to the structure characteristics of new type expansion bolt body, not only to strengthen the side resistance, and strengthened the end of play an important role on the soil strength, comprehensive improve loading efficiency, is the most widely applied reinforcement method in actual construction.