本文選題：棱柱體混凝土　切入點(diǎn)：單軸壓縮　出處：《北京交通大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：不同材料、不同形狀尺寸的混凝土在不同的受力狀態(tài)下會(huì)表現(xiàn)出不同的變形破壞特征,破壞強(qiáng)度也會(huì)有不同的變化,而目前關(guān)于受力更符合實(shí)際情況的棱柱體的三軸試驗(yàn)極少。本文研究了使用棱柱體試塊(方形截面)在液壓三軸室內(nèi)開(kāi)展常規(guī)三軸壓縮試驗(yàn)的方式和技術(shù),利用常規(guī)三軸設(shè)備開(kāi)展棱柱體混凝土在不同側(cè)壓下的三軸壓縮試驗(yàn)以及不同長(zhǎng)寬比試塊的單軸壓縮試驗(yàn)。根據(jù)得到的單軸壓與三軸壓試驗(yàn)結(jié)果,分析了棱柱體混凝土強(qiáng)度特征、變形特性及試件的破壞形態(tài),擬合了棱柱體混凝土三軸壓下應(yīng)力-應(yīng)變?nèi)�,最后將同一試驗(yàn)機(jī)上開(kāi)展的不同長(zhǎng)寬比棱柱體混凝土單軸試驗(yàn)進(jìn)行總結(jié)和分析,形成系統(tǒng)的力學(xué)性能的研究,具體研究?jī)?nèi)容如下:(1)研究了使用常規(guī)三軸設(shè)備對(duì)(正方形截面的)棱柱體試塊進(jìn)行三軸試驗(yàn)的關(guān)鍵技術(shù)和方法,經(jīng)過(guò)試驗(yàn)檢驗(yàn),該方法方便可行。1)自制了與試塊形狀配套的橫向位移傳感器,在有限的壓力室空間便于使用,且經(jīng)驗(yàn)證量測(cè)設(shè)備滿(mǎn)足精度要求。2)設(shè)計(jì)加工了與棱柱體試塊和三軸設(shè)備匹配的上下壓頭和適用于不同尺寸試塊的底座壓頭。3)對(duì)三軸設(shè)備的測(cè)量系統(tǒng)進(jìn)行改造,通過(guò)加裝一套更為先進(jìn)的采集系統(tǒng),使外置系統(tǒng)與三軸設(shè)備的內(nèi)置測(cè)控系統(tǒng)能夠聯(lián)合使用,解決了三軸系統(tǒng)中的通道數(shù)量不足、采樣速率偏低、電位器數(shù)值波動(dòng)等問(wèn)題。(2)開(kāi)展了棱柱體混凝土常規(guī)三軸試驗(yàn),分析混凝土在三軸應(yīng)力下的強(qiáng)度及變形性能。1)分析了棱柱體混凝土單壓和三軸壓試驗(yàn)試件的破壞形態(tài),結(jié)果表明圍壓和減摩對(duì)其有顯著影響。2)對(duì)三軸定側(cè)壓試驗(yàn)數(shù)據(jù)進(jìn)行處理,分析棱柱體混凝土三軸抗壓強(qiáng)度及相應(yīng)變形、圍壓之間的關(guān)系。3)三軸試驗(yàn)選用減摩與不減摩兩種情況進(jìn)行應(yīng)力-應(yīng)變曲線和特征值等的對(duì)比,發(fā)現(xiàn)隨著圍壓的增大,端部效應(yīng)對(duì)棱柱體混凝土的三軸強(qiáng)度影響逐漸減小,在圍壓為30MPa時(shí),減摩與不減摩試塊的應(yīng)力-應(yīng)變曲線最為接近。4)對(duì)軸向應(yīng)力-應(yīng)變曲線擬合,并分別用D-P準(zhǔn)則、Rechart破壞準(zhǔn)則和Ansari常用的三種破壞準(zhǔn)則來(lái)描述棱柱體混凝土的強(qiáng)度,結(jié)果顯示Ansari破壞準(zhǔn)則及D-P修正準(zhǔn)則與實(shí)際破壞強(qiáng)度擬合程度較好。(3)采用4種尺寸的棱柱體試塊(分別為70.7mm×70.7mm×175mm、70.7mm×70.7mm×105mm、70.7mm×70.7mm×70.7mm 和 70.7mm×70.7mm×40mm)研究棱柱體混凝土的單軸力學(xué)性能。1)通過(guò)單軸試驗(yàn)分析棱柱體混凝土的尺寸效應(yīng),結(jié)果顯示立方體隨著幾何尺寸的增加,混凝土試件的單軸受壓峰值應(yīng)力和峰值點(diǎn)應(yīng)變均降低,當(dāng)幾何尺寸減小時(shí),試件的峰值應(yīng)力降低而峰值點(diǎn)應(yīng)變?cè)龃?顯示出尺寸效應(yīng)現(xiàn)象。
[Abstract]:Concrete with different materials and shapes and sizes will exhibit different deformation and failure characteristics under different loading conditions, and the failure strength will also vary. However, there are very few triaxial tests on prisms which are more in line with the actual conditions. In this paper, the methods and techniques of using prism test blocks (square sections) to carry out conventional triaxial compression tests in hydraulic triaxial chamber are studied. The uniaxial compression test of prismatic concrete under different lateral compression and the uniaxial compression test of different ratio of length to width are carried out by using conventional triaxial equipment. Based on the results of uniaxial and triaxial compression tests, the strength characteristics of prismatic concrete are analyzed. The deformation characteristics and the failure pattern of the specimen are fitted to the stress-strain curve of prismatic concrete under triaxial compression. Finally, the uniaxial tests of prismatic concrete with different aspect ratios are summarized and analyzed on the same testing machine. The study on the mechanical properties of the forming system is as follows: 1) the key techniques and methods of using conventional triaxial equipment to conduct triaxial tests on prisms (with square sections) have been studied and tested. This method is convenient and feasible. 1) A transversal displacement sensor matched with the shape of the specimen is made, which is easy to use in the limited pressure chamber space. The measuring equipment has been verified to meet the precision requirement. (2) the measuring system of the triaxial equipment has been modified by the design and machining of the upper and lower pressure head matching with the prism test block and the triaxial equipment and the pedestal head. 3) suitable for different size test blocks. By installing a more advanced collection system, the external system and the built-in measurement and control system of the three-axis equipment can be jointly used, which solves the shortage of channels in the three-axis system and the low sampling rate. The conventional triaxial test of prism concrete is carried out, and the strength and deformation performance of concrete under triaxial stress are analyzed. 1) the failure modes of concrete specimen under uniaxial and triaxial compression are analyzed. The results show that confining pressure and reducing friction have significant influence on the triaxial constant lateral compression test data, and the triaxial compressive strength and corresponding deformation of prism concrete are analyzed. The relationship between confining pressure. 3) triaxial test is used to compare the stress-strain curves and eigenvalues between friction-reducing and non-friction-reducing conditions. It is found that with the increase of confining pressure, the effect of end effect on triaxial strength of prismatic concrete decreases gradually. When the confining pressure is 30MPa, the stress-strain curve of friction-reducing and non-friction-reducing specimen is the closest. 4) fitting the axial stress-strain curve. The strength of prismatic concrete is described by D-P criterion and three failure criteria commonly used by Ansari. The results show that Ansari failure criterion and D-P correction criterion fit well with the actual failure strength.) the uniaxial mechanical properties of prismatic concrete are studied by uniaxial test with four kinds of prisms (70.7mm 脳 70.7mm 脳 175mm, 70.7mm 脳 70.7mm 脳 105mm, 70.7mm 脳 70.7mm 脳 70.7mm and 70.7mm 脳 70.7mm 脳 40mm). The size effect of prismatic concrete is analyzed. The results show that the peak stress and peak strain of concrete specimen under uniaxial compression decrease with the increase of geometric size. When the geometric dimension decreases, the peak stress decreases and the peak strain increases. The size effect is shown.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TU528

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