多段擴(kuò)體錨桿拉拔受力性能的數(shù)值分析
發(fā)布時間：2018-11-12 07:51
【摘要】：隨著我國城市建設(shè)的迅速發(fā)展,高承載力錨桿在地下空間工程、邊坡支護(hù)、基坑支護(hù)等領(lǐng)域的需求不斷增加。與普通錨桿相比,擴(kuò)體錨桿的抗拔承載力高、支護(hù)效果好、并且施工便利。本文提出的多段擴(kuò)體錨桿是在端部擴(kuò)體錨桿的基礎(chǔ)上發(fā)展起來的一種新型錨桿。該類型錨桿在我國實(shí)際工程中應(yīng)用較少,而且理論研究滯后,因此有必要進(jìn)行深入研究。本文在西安理工大學(xué)結(jié)構(gòu)大廳進(jìn)行的多段擴(kuò)體錨桿模型試驗的基礎(chǔ)上進(jìn)行數(shù)值模擬,進(jìn)一步研究了多段擴(kuò)體錨桿的承載特性、破壞模式、群錨效應(yīng)等,本文主要研究內(nèi)容包括以下幾方面:(1)在模型試驗的基礎(chǔ)上,應(yīng)用ABAQUS軟件對多段擴(kuò)體的受拉性能進(jìn)行數(shù)值模擬分析,研究了不同擴(kuò)體個數(shù)和埋深對其破壞模式的影響。發(fā)現(xiàn)端部擴(kuò)體錨桿周圍土體的破壞模式為“倒立的燈泡形”,隨著擴(kuò)體的增加,其周圍土體的破壞形態(tài)由“燈泡形”逐漸發(fā)展為呈串“火苗形”。而且淺埋擴(kuò)體錨桿周圍土體的破壞模式屬于整體剪切破壞,破壞區(qū)一直與地表相連;深埋擴(kuò)體錨桿周圍土體的破壞模式屬于局部剪切破壞。(2)通過數(shù)值模擬研究了埋深、錨桿尺寸對其抗拔承載力的影響。依據(jù)結(jié)果分析發(fā)現(xiàn)隨著擴(kuò)體直徑、埋深的增加,其抗拔承載力也增大;當(dāng)埋深足夠大時隨著擴(kuò)體間距的增加其抗拔承載力也有所提高,只是效果不明顯;另外,埋深一定時,錨桿的抗拔承載力并不隨擴(kuò)體長度、擴(kuò)體個數(shù)的增加而增加,達(dá)到一定程度甚至?xí)S它們的增加而減小。通過多組試驗?zāi)M數(shù)據(jù)得出其最優(yōu)擴(kuò)體長度為100mm-150mm,而擴(kuò)體個數(shù)的最優(yōu)解與擴(kuò)體錨桿的埋深相關(guān),埋深越大,最優(yōu)擴(kuò)體個數(shù)就越大。(3)對土體參數(shù)進(jìn)行改變,研究了土體粘聚力、內(nèi)摩擦角、及變形模量對多段擴(kuò)體錨桿抗拔承載力的影響。通過數(shù)據(jù)分析發(fā)現(xiàn)隨著粘聚力、內(nèi)摩擦角、變形模量的增大,多段擴(kuò)體錨桿的抗拔承載力會提高,但是變形模量貢獻(xiàn)較小。(4)在實(shí)際工程中對群錨的應(yīng)用頗多,本文又進(jìn)一步研究了錨桿的水平間距、埋深、數(shù)量對群錨效應(yīng)的影響。研究發(fā)現(xiàn)同一埋深,水平間距越大,群錨效應(yīng)越小;埋深越大,為減小群錨效應(yīng)所需的水平間距就越小,但不得小于4D。而且單根錨桿的擴(kuò)體個數(shù)越多減少群錨效應(yīng)需要的水平間距越大。錨桿數(shù)量越多,群錨效應(yīng)越明顯。
[Abstract]:With the rapid development of urban construction in China, the demand of high bearing capacity anchor rod in underground space engineering, slope support, foundation pit support and other fields is increasing. Compared with the common bolt, the expanded bolt has higher pull-out bearing capacity, better supporting effect and more convenient construction. This paper presents a new type of anchor which is developed on the basis of the end extension anchor. The application of this type of bolt in practical engineering in our country is less, and the theoretical research is lagging behind, so it is necessary to carry on the thorough research. In this paper, based on the model test of the multi-segment expanded anchor bar carried out in the structural hall of Xi'an University of Technology, the bearing characteristics, failure mode and group anchor effect of the multi-segment expanded bolt are further studied. The main contents of this paper are as follows: (1) on the basis of model test, the tensile performance of multi-segment expander is simulated with ABAQUS software, and the influence of different number of extenders and depth of burying on its failure mode is studied. It is found that the failure mode of the soil around the end extension bolt is "inverted bulb shape", and with the increase of the expanding body, the failure pattern of the surrounding soil gradually develops from "bulb shape" to "flaming shape". Moreover, the failure mode of soil around the shallow-buried anchor bolt belongs to the whole shear failure, and the failure zone has always been connected with the surface of the earth. The failure mode of the soil around the deeply buried anchor is local shear failure. (2) the influence of buried depth and bolt size on the uplift bearing capacity is studied by numerical simulation. According to the analysis of the results, it is found that the uplift bearing capacity increases with the increase of the diameter of the expanding body and the depth of burying, and the pull-out bearing capacity increases with the increase of the distance between the expanded bodies when the buried depth is large enough, but the effect is not obvious. In addition, the uplift bearing capacity of the anchor does not increase with the length of the expanded body, but the number of the expanded body increases, and even decreases with the increase of the depth of burying. The optimum length of the expanded body is 100mm-150mm, and the optimal solution of the number of the expanded body is related to the buried depth of the anchor rod. The larger the burying depth, the larger the number of the optimal extender. (3) the parameters of the soil are changed. The effects of cohesive force, angle of internal friction and modulus of deformation on the pull-out bearing capacity of multi-segment expansion anchor are studied. Through the data analysis, it is found that with the increase of cohesion, angle of internal friction and modulus of deformation, the pull-out bearing capacity of multi-segment expanded anchor will be increased, but the contribution of deformation modulus is relatively small. (4) the application of group anchors in practical engineering is quite extensive. The effects of horizontal spacing, depth and number of anchors on the group anchor effect are further studied in this paper. It is found that the larger the horizontal spacing is, the smaller the group anchor effect is, and the smaller the horizontal spacing is to reduce the group anchor effect, but not less than 4D. Moreover, the more the number of expansion bodies of a single anchor rod is, the greater the horizontal spacing is required to reduce the group anchor effect. The more the number of bolts is, the more obvious the group anchor effect is.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU476
[Abstract]:With the rapid development of urban construction in China, the demand of high bearing capacity anchor rod in underground space engineering, slope support, foundation pit support and other fields is increasing. Compared with the common bolt, the expanded bolt has higher pull-out bearing capacity, better supporting effect and more convenient construction. This paper presents a new type of anchor which is developed on the basis of the end extension anchor. The application of this type of bolt in practical engineering in our country is less, and the theoretical research is lagging behind, so it is necessary to carry on the thorough research. In this paper, based on the model test of the multi-segment expanded anchor bar carried out in the structural hall of Xi'an University of Technology, the bearing characteristics, failure mode and group anchor effect of the multi-segment expanded bolt are further studied. The main contents of this paper are as follows: (1) on the basis of model test, the tensile performance of multi-segment expander is simulated with ABAQUS software, and the influence of different number of extenders and depth of burying on its failure mode is studied. It is found that the failure mode of the soil around the end extension bolt is "inverted bulb shape", and with the increase of the expanding body, the failure pattern of the surrounding soil gradually develops from "bulb shape" to "flaming shape". Moreover, the failure mode of soil around the shallow-buried anchor bolt belongs to the whole shear failure, and the failure zone has always been connected with the surface of the earth. The failure mode of the soil around the deeply buried anchor is local shear failure. (2) the influence of buried depth and bolt size on the uplift bearing capacity is studied by numerical simulation. According to the analysis of the results, it is found that the uplift bearing capacity increases with the increase of the diameter of the expanding body and the depth of burying, and the pull-out bearing capacity increases with the increase of the distance between the expanded bodies when the buried depth is large enough, but the effect is not obvious. In addition, the uplift bearing capacity of the anchor does not increase with the length of the expanded body, but the number of the expanded body increases, and even decreases with the increase of the depth of burying. The optimum length of the expanded body is 100mm-150mm, and the optimal solution of the number of the expanded body is related to the buried depth of the anchor rod. The larger the burying depth, the larger the number of the optimal extender. (3) the parameters of the soil are changed. The effects of cohesive force, angle of internal friction and modulus of deformation on the pull-out bearing capacity of multi-segment expansion anchor are studied. Through the data analysis, it is found that with the increase of cohesion, angle of internal friction and modulus of deformation, the pull-out bearing capacity of multi-segment expanded anchor will be increased, but the contribution of deformation modulus is relatively small. (4) the application of group anchors in practical engineering is quite extensive. The effects of horizontal spacing, depth and number of anchors on the group anchor effect are further studied in this paper. It is found that the larger the horizontal spacing is, the smaller the group anchor effect is, and the smaller the horizontal spacing is to reduce the group anchor effect, but not less than 4D. Moreover, the more the number of expansion bodies of a single anchor rod is, the greater the horizontal spacing is required to reduce the group anchor effect. The more the number of bolts is, the more obvious the group anchor effect is.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU476
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