本文關(guān)鍵詞： 非飽和土 三軸壓縮試驗 儀器研制 數(shù)字圖像測量 水壓力控制器　出處：《大連理工大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：地球表層土有很大一部分處于地下水位以上,因此工程應(yīng)用中所遇到的土有很多為非飽和土,所以對非飽和土力學(xué)性質(zhì)的研究尤為重要。研究土壤力學(xué)性質(zhì)最重要的試驗為三軸壓縮試驗,即對土樣在軸對稱條件下施加應(yīng)力,通過測量其應(yīng)力應(yīng)變關(guān)系得到其力學(xué)性質(zhì)。飽和土三軸壓縮試驗儀發(fā)展比較成熟,應(yīng)用廣泛,但是非飽和土三軸壓縮試驗儀由于非飽和土理論體系不完善以及試驗測試技術(shù)較復(fù)雜等原因,目前仍沒有較為完善的儀器。 國內(nèi)外現(xiàn)有非飽和土三軸壓縮試驗儀存在很多可以改進之處,例如：應(yīng)變測量均采用傳統(tǒng)的接觸式測量,對試樣擾動較大,而且非飽和土試驗中試樣的體積變化無法精確測量；孔隙氣壓加載系統(tǒng)提供較高壓力時供氣量不足,需要先借助外部氣源提高初始壓力；由下至上的軸向應(yīng)力加載導(dǎo)致壓力室的隨動,容易對壓力室以及與其相連的管路內(nèi)的壓力的穩(wěn)定性造成影響；壓力室充水需要借助額外的儲水容器；儀器結(jié)構(gòu)不緊湊等。 結(jié)合本論文自主研發(fā)的非飽和土三軸壓縮試驗儀,基本上成功地解決了上述問題,并且在很大程度上提高了非飽和土三軸壓縮試驗的測量精度。該儀器主要特點有：應(yīng)變測量采用了具有自主知識產(chǎn)權(quán)的土樣全表面變形數(shù)字圖像測量系統(tǒng),該系統(tǒng)能夠?qū)ν翗拥臉硕c在整個實驗過程中的空間位置變化進行實時采集記錄,然后通過后處理程序?qū)Σ杉男畔⑦M行運算,得到試樣各種參數(shù)的變化；軸向應(yīng)力加載采用由上至下的加載方式,并內(nèi)置水下測力傳感器,并且在滿足常規(guī)的靜力加載的前提下增加了力反饋加載方式和位移反饋加載方式以及基于上述兩種加載方式的循環(huán)加卸載；試樣基質(zhì)吸力由電氣比例閥以及水壓力控制器進行實時控制,響應(yīng)快、精度高、壓力穩(wěn)定；對應(yīng)力加載系統(tǒng)、圍壓加載系統(tǒng)、吸力控制系統(tǒng)等進行了優(yōu)化設(shè)計,達到了布局合理、結(jié)構(gòu)優(yōu)化、操作簡便、一機多用等效果。 本文作者在綜合分析非飽和土三軸壓縮試驗的流程以及儀器應(yīng)具備的功能的基礎(chǔ)上,完成了以下工作：儀器各向應(yīng)力加載系統(tǒng)的設(shè)計和整機布局；試樣基質(zhì)吸力控制方案的設(shè)計實施；儀器控制流程設(shè)計、原件選型以及電控板的連接；全表面數(shù)字圖像測量系統(tǒng)的引入；儀器安裝、調(diào)試與試驗。
[Abstract]:A large part of the earth's surface soil is above the groundwater level, so many of the soils encountered in engineering applications are unsaturated soils. Therefore, it is particularly important to study the mechanical properties of unsaturated soils. The most important test to study soil mechanical properties is triaxial compression test, that is, applying stress to soil samples under axisymmetric conditions. The mechanical properties are obtained by measuring the stress-strain relationship. The saturated soil triaxial compression tester is developed and widely used. However, due to the imperfect theoretical system of unsaturated soil and the complexity of testing technology, there is still no perfect instrument for unsaturated soil triaxial compression test instrument. At home and abroad, there are many improvements in the existing unsaturated soil triaxial compression test instruments. For example, the strain measurement adopts the traditional contact measurement, which has a great disturbance to the sample. Moreover, the volume change of the sample can not be accurately measured in unsaturated soil test. When the pore pressure loading system provides the higher pressure, the gas supply is insufficient, so it is necessary to increase the initial pressure with the help of the external gas source. The axial stress loading from the bottom to the top leads to the follow-up of the pressure chamber, which can easily affect the stability of the pressure chamber and the pressure in the pipe connected to it. The pressure chamber needs to be filled with additional water storage vessels; The structure of the instrument is not compact, etc. Combined with the unsaturated soil triaxial compression tester developed in this paper, the above problems have been solved successfully. The measurement accuracy of unsaturated soil triaxial compression test is improved to a great extent. The main features of this instrument are as follows: the full surface deformation digital image measurement system with independent intellectual property rights is used for strain measurement. The system can collect and record the change of the space position of the standard spot of the soil sample in the whole experiment process in real time, then calculate the collected information through the post-processing program, and get the change of the sample's various parameters. Axial stress loading adopts top-down loading mode, and the underwater force sensor is built in. The loading mode of force feedback and displacement feedback and cyclic loading and unloading based on the above two loading modes are added under the premise of satisfying the conventional static loading. The suction of the sample matrix is controlled by electric proportional valve and water pressure controller in real time, which has the advantages of fast response, high precision and stable pressure. The stress loading system, the confining pressure loading system and the suction control system are optimized, and the results are as follows: reasonable layout, optimized structure, simple operation and multipurpose. On the basis of synthetically analyzing the flow chart of unsaturated soil triaxial compression test and the functions of the instrument, the author has accomplished the following work: the design of the stress loading system in each direction of the instrument and the layout of the whole machine; The design and implementation of the control scheme of sample matrix suction; Design of instrument control flow, selection of original parts and connection of electronic control board; The introduction of full surface digital image measurement system; Instrument installation, commissioning and testing.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU415

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