本文關(guān)鍵詞： 營口軟土 物理力學(xué)特性 真三軸試驗 各向異性特征　出處：《遼寧工程技術(shù)大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：受地質(zhì)構(gòu)造、應(yīng)力歷史、顆粒成分等因素影響,軟土具有顯著的區(qū)域性,不同地區(qū)的軟土物理力學(xué)性質(zhì)差異較大。營口地區(qū)軟土是遼寧濱海地區(qū)三角洲沖積平原形成的一種典型的粉質(zhì)粘土,隨著地鐵、隧道、基坑等工程中軟土變形與強(qiáng)度問題越來越突出,迫切需要對營口地區(qū)軟土的物理力學(xué)特性和土體變形及強(qiáng)度進(jìn)行深入研究,增強(qiáng)對營口地區(qū)軟土的認(rèn)識,為實際工程提供一定的理論參考和借鑒。文章通過搜集工程地質(zhì)資料,采用室內(nèi)試驗與理論分析相結(jié)合的方法,開展了營口軟土力學(xué)特性的試驗研究,具體成果如下：1)對比分析了營口地區(qū)與上海、天津等地區(qū)軟土的物理力學(xué)特性,發(fā)現(xiàn)營口地區(qū)軟土的孔隙比、液塑限指數(shù)、飽和度等普遍偏低；統(tǒng)計結(jié)果表明,營口地區(qū)軟土的粘聚力比上海、天津地區(qū)的軟土偏小,而內(nèi)摩擦角比天津地區(qū)軟土偏大,但略小于上海地區(qū)的軟土；無側(cè)限抗壓強(qiáng)度試驗測得土體的靈敏度在2-4之間,表明營口地區(qū)軟土屬于中靈敏度土；對含水量、密度等物理參數(shù)進(jìn)行線性回歸擬合,并得到了該區(qū)域的線性回歸方程；采用塑性圖分析表明營口地區(qū)軟土為中、高塑性粘土。2)開展了營口地區(qū)軟土的真三軸試驗研究,分析了營口軟土各向異性的特征以及其變形和強(qiáng)度,結(jié)果表明：當(dāng)載荷分別沿大主應(yīng)力方向、中主應(yīng)力方向和小主應(yīng)力方向單向加載時,大主應(yīng)變ε1、中主應(yīng)變ε2、小主應(yīng)變ε3呈現(xiàn)不同的變化趨勢；保持σ3不變時,土體的應(yīng)力應(yīng)變曲線隨b值的增加其變化趨勢變陡,變化幅度也隨之增大；隨著中主應(yīng)力比b增大,土體的粘聚力和內(nèi)摩擦角變化趨勢相反,前者呈先下降后上升的趨勢,后者呈先上升后出現(xiàn)略微下降的趨勢；在圍壓一定的條件下,隨著含水率越大,土體強(qiáng)度逐漸降低,從含水率為15%至25%的土體最大強(qiáng)度差值幅度接近35%；并通過試驗結(jié)果得到了試樣的在不同含水率下p-q平面上的臨界狀態(tài)線,都可以用直線進(jìn)行較好的擬合；此外根據(jù)土體破壞時的三維應(yīng)力狀態(tài)得到了在π平面上的屈服曲線,其在π平面上的屈服軌跡比較接近松崗-中井屈服準(zhǔn)則(SMP)。3)采用歸一化的方法對真三軸的試驗結(jié)果進(jìn)行了定量化分析,得到了營口地區(qū)軟土的應(yīng)力應(yīng)變歸一化方程,擬合結(jié)果能很好預(yù)測和評價對不同圍壓下軟土的應(yīng)力應(yīng)變關(guān)系；針對鄧肯-張模型不能考慮土體各向異性的不足,基于真三軸試驗結(jié)果對鄧肯-張本構(gòu)模型的參數(shù)提出修正,其可以充分考慮土體各向異性的特點,并通過真三軸試驗結(jié)果驗證了該模型的可靠性和實用性。
[Abstract]:Affected by geological structure, stress history, particle composition and other factors, soft soil has a significant regional. The soft soil in Yingkou area is a typical silty clay formed in the delta alluvial plain of coastal area of Liaoning Province, along with the subway and tunnel. The problem of deformation and strength of soft soil is more and more prominent in foundation pit and so on. It is urgent to study the physical and mechanical properties of soft soil and the deformation and strength of soil in Yingkou area to enhance the understanding of soft soil in Yingkou area. Through collecting engineering geological data and adopting the method of combination of laboratory test and theoretical analysis, the paper carried out the experimental research on the mechanical properties of Yingkou soft soil. The concrete results are as follows: (1) the physical and mechanical properties of soft soil in Yingkou area are compared with those in Shanghai and Tianjin. It is found that the porosity ratio, liquid-plastic limit index and saturation of soft soil in Yingkou area are generally low. The results show that the cohesion of soft soil in Yingkou area is smaller than that in Shanghai, and the angle of internal friction is larger than that in Tianjin area, but slightly smaller than that in Shanghai area. The sensitivity of soil measured by unconfined compressive strength test is between 2-4, indicating that the soft soil in Yingkou area belongs to medium sensitive soil. The physical parameters such as water content and density were fitted by linear regression, and the linear regression equation of the region was obtained. The plastic diagram analysis shows that the soft soil in Yingkou area is medium and high plastic clay. 2) the true triaxial test of the soft soil in Yingkou area is carried out, and the anisotropy characteristics, deformation and strength of the soft soil in Yingkou area are analyzed. The results show that the main strain 蔚 _ 1, the medium principal strain 蔚 _ 2 and the small principal strain 蔚 _ 3 show different trends when the load is loaded in the direction of large principal stress, middle principal stress and small principal stress respectively. When 蟽 _ 3 is kept constant, the stress-strain curve of soil becomes steeper with the increase of b value, and the range of variation also increases. With the increase of the mid-principal stress ratio b, the cohesive force and the angle of internal friction of the soil have the opposite trend, the former shows the tendency of decreasing first and then rising, the latter shows a tendency of rising first and then slightly decreasing. Under certain confining pressure, with the increase of water content, the soil strength decreases gradually, and the maximum strength difference range from 15% to 25% is close to 35. The critical state line on p-q plane with different moisture content is obtained by the test results, which can be fitted well by straight line. In addition, according to the three-dimensional stress state of soil failure, the yield curve on 蟺 plane is obtained. The yield trajectory on 蟺 plane is close to the yield criterion SMP.3) the true triaxial test results are quantitatively analyzed by the normalized method. The stress-strain normalization equation of soft soil in Yingkou area is obtained. The fitting results can well predict and evaluate the stress-strain relationship of soft soil under different confining pressures. In view of the deficiency that Duncan-Zhang model can not consider soil anisotropy, the parameters of Duncan-Zhang Ben model are modified based on true triaxial test results, which can fully consider the characteristics of soil anisotropy. The reliability and practicability of the model are verified by the true triaxial test results.
【學(xué)位授予單位】：遼寧工程技術(shù)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU447

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