本文選題：石灰改良黃土 + 平面應(yīng)變　； 參考：《西北農(nóng)林科技大學(xué)》2015年碩士論文

【摘要】：黃土作為一種特殊土體,廣泛分布在我國中西部地區(qū)。隨著經(jīng)濟(jì)的快速發(fā)展,不可避免的在黃土地區(qū)進(jìn)行工程建設(shè),因黃土具有高壓縮性、濕陷性和遇水敏感性等天然缺陷,黃土填料很難滿足現(xiàn)代工程對地基的強(qiáng)度、變形和耐久性等高標(biāo)準(zhǔn)要求。合理對黃土進(jìn)行改良使其技術(shù)和經(jīng)濟(jì)上滿足工程要求是很有必要的,為類似的工程設(shè)計提供有效的參數(shù),對我國經(jīng)濟(jì)發(fā)展有重要的現(xiàn)實意義。本文在前人研究改良黃土的力學(xué)特性及測試手段的基礎(chǔ)上,利用PY-10型平面應(yīng)變儀來研究石灰改良黃土在不同影響因素下的變形、強(qiáng)度及局部化變形特性,即不同石灰摻入量、不同含水率、不同養(yǎng)護(hù)齡期、不同固結(jié)圍壓和不同固結(jié)應(yīng)力比。整理、分析土體在不同影響因素其變形和強(qiáng)度的變化規(guī)律,進(jìn)而得出影響石灰改良剪切強(qiáng)度原因,最后嘗試探討影響土體局部化變形的原因,主要的研究結(jié)論如下:(1)石灰改良涇陽黃土的擊實特性涇陽黃土在不同石灰摻入量下?lián)魧嵲囼灳憩F(xiàn)為干密度隨著含水率增加先增大后顯著減小;隨著黃土中石灰摻入量的增加,石灰土的最優(yōu)含水率增大,最大干密度減小,且摻入石灰后的黃土,擊實曲線較素土為平緩;在實際工程中石灰與黃土拌和后應(yīng)及時壓實,否則會引起最大干密度的下降而影響壓實效果。(2)石灰改良涇陽黃土的應(yīng)力-應(yīng)變關(guān)系石灰改良黃土在平面應(yīng)變下應(yīng)力-應(yīng)變曲線隨影響因素的不同有硬化型和軟化型兩種,在養(yǎng)護(hù)齡期較長時基本呈軟化曲線,土體表現(xiàn)為脆性破壞;而在養(yǎng)護(hù)齡期較短時基本呈硬化曲線,土體表現(xiàn)為延性破壞。應(yīng)力-應(yīng)變曲線受圍壓、石灰摻入量、含水率、養(yǎng)護(hù)齡期、固結(jié)應(yīng)力比影響明顯,隨著初始含水率減小、固結(jié)圍壓增大和石灰摻入量的增大其應(yīng)力-應(yīng)變曲線有不同程度的增高;養(yǎng)護(hù)齡期、固結(jié)應(yīng)力比的不同,土體應(yīng)力-應(yīng)變曲線表現(xiàn)為不同的形態(tài)。(3)石灰改良涇陽黃土的抗剪強(qiáng)度在平面應(yīng)變下固結(jié)應(yīng)力比、石灰摻入量和含水率對土體抗剪強(qiáng)度有明顯的影響;無論是等壓固結(jié)或不等壓固結(jié),隨著土體含水率的增大凝聚力呈明顯降低,內(nèi)摩擦角隨著含水率的增大降低幅度較小。土體的凝聚力隨摻灰量增加先增大后減小;等壓固結(jié)下,土體的內(nèi)摩擦角隨摻灰量增大基本呈增大趨勢;而在不等壓固結(jié)下,當(dāng)土體的初始含水率較小時內(nèi)摩擦角隨摻灰量增大而減小,當(dāng)土體的初始含水率較大時內(nèi)摩擦角隨摻灰量增大而增大。(4)石灰改良涇陽黃土主應(yīng)力之間的關(guān)系中主應(yīng)力隨著剪切的時間的變化大致分為三個階段。剪切初期中主應(yīng)力隨軸向應(yīng)變迅速增加,曲線初始斜率較大;剪切后期中主應(yīng)力緩慢增長,曲線斜率也逐漸減小。在土體剪切過程中,剪切初期σ1、σ2隨軸向應(yīng)變的增大而增加;隨著剪切的進(jìn)一步增大,應(yīng)力-應(yīng)變曲線σ1~ε1和σ2~ε1出現(xiàn)較為明顯的拐點,兩條曲線的拐點基本同時出現(xiàn),且拐點大概在軸向應(yīng)變ε1=3%。(5)石灰改良涇陽黃土的剪切帶特性平面應(yīng)變下土體的剪切帶性狀主要有三種類型:“X”型剪切帶形狀、“V”型剪切帶形狀和單一型剪切帶形狀;采用Mohr-Columb理論計算土體剪切帶的傾角值為64°~68°范圍之內(nèi),而實際測量剪切的帶傾角值為62°~70°范圍之內(nèi),實測傾角值十分接近于理論計算傾角值。
[Abstract]:As a special soil, loess is widely distributed in the central and western regions of China. With the rapid development of the economy, it is inevitable to carry out engineering construction in the loess region. Because of the natural defects such as high pressure shrinkage, collapsibility and water sensitivity, the Loess filler is difficult to meet the high standard of the foundation, such as the strength, deformation and durability of the foundation. It is necessary to make rational improvement of the Loess so that it is necessary to meet the engineering requirements technically and economically. It is of great practical significance for the economic development of our country to provide effective parameters for similar engineering design. On the basis of previous studies on the mechanical properties of loess and the test hand section, the PY-10 plane strain gauge is used in this paper. The deformation, strength and local deformation characteristics of lime modified loess are studied under different influence factors, that is, different lime content, different water content, different curing age, different consolidation confining pressure and different consolidation stress ratio. The change law of deformation and strength of soil in different influence factors is analyzed, and then the influence of lime modified shear is obtained. The causes of shear strength are discussed at last. The main research results are as follows: (1) the main results are as follows: (1) the compaction characteristic of Jingyang loess with lime improvement, the dry density of Jingyang loess under different lime content shows that dry density increases significantly with the increase of water content; with the increase of lime content in the loess, The optimum water cut rate of lime soil increases and the maximum dry density decreases, and the compaction curve of loess after adding lime is more gentle than that of plain soil. In actual engineering, lime and loess should be compacted in time, otherwise the maximum dry density will be caused by the decrease of maximum dry density. (2) the stress strain of the lime modified Jingyang loess is related to the lime improvement yellow. The stress-strain curves of soil under plane strain are two kinds of hardened and softening types with different influence factors. When the curing age is long, the softening curve is basically presented, and the soil is brittle failure, while the soil is basically hardening curve when the curing age is short, and the soil is ductile. The stress strain curve is subjected to confining pressure, lime content and water content. Rate, curing age, consolidation stress ratio is obviously affected. With the decrease of initial water content, the stress strain curve of the consolidation confining pressure and the amount of lime content increase in different degrees; the curing age, the consolidation stress ratio is different, the soil stress strain curve is different form. (3) the shear strength of the lime improved Jingyang loess is in the shear strength. The consolidation stress ratio under plane strain, lime content and water content have an obvious influence on the shear strength of soil. No matter isobaric consolidation or unequal pressure consolidation, the cohesive force decreases with the increase of soil moisture content, and the internal friction angle decreases with the increase of water content. The cohesiveness of soil mass increases first and then decreases with the increase of the amount of cement. Under the constant pressure consolidation, the internal friction angle of the soil increases basically with the increase of the amount of cement. While under the unequal pressure, the friction angle of the soil decreases with the increase of the amount of cement. When the initial water content is larger, the internal friction angle increases with the increase of the amount of cement. (4) lime improved the main stress of Jingyang loess The main stress in the inter relationship is roughly divided into three stages with the change of the shear time. In the early shear, the main stress increases rapidly with the axial strain, the initial slope of the curve is larger, and the main stress increases slowly in the late shear, and the slope of the curve decreases gradually. During the shear process, the initial shear stress is increased with the increase of the axial strain. With the further increase of shearing, the stress strain curve Sigma 1~ epsilon 1 and sigma 2~ epsilon 1 appear more obvious inflection point, and the turning point of the two curves appears at the same time, and the turning point is about three types of shear zone of soil under the characteristic plane strain of the shear zone of the modified Jingyang loess with the axial strain of 1=3%. (5) lime: "X" shear zone Shape, the shape of "V" shear band and the shape of a single shear band, and the angle value of the shear zone of soil is within the range of 64 degrees ~68 degrees with the Mohr-Columb theory, while the actual measured shear zone angle is within the range of 62 ~70 degrees, and the measured dip value is very close to the theoretical calculation angle value.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU411

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本文編號：2006233