本文關(guān)鍵詞： 干濕循環(huán) 膨脹土 剪切蠕變 蠕變模型 長期強度　出處：《長沙理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：干濕循環(huán)作用對膨脹土的內(nèi)部結(jié)構(gòu)造成了一定程度的損傷,為了進一步研究干濕循環(huán)作用下膨脹土應(yīng)力-應(yīng)變狀態(tài)的規(guī)律、剪切蠕變模型及土體的長期強度參數(shù)衰減規(guī)律,建立符合工程實際并合理反映膨脹土蠕變性狀的本構(gòu)模型及確定模型參數(shù),使之能預(yù)測膨脹土的蠕變特性,本文進行了不同法向壓力下干濕循環(huán)作用第0次、2次、4次、6次后膨脹土的室內(nèi)剪切蠕變試驗,通過對剪切蠕變試驗曲線的數(shù)據(jù)分析與整理,對百色膨脹土的剪切蠕變機理進行了研究,構(gòu)建了半經(jīng)驗半理論的膨脹土剪切蠕變模型,該模型參數(shù)物理意義明確,不僅能描述土體的衰減蠕變和等速蠕變階段,也能對加速蠕變階段進行描述,能全面反映土體流變粘彈塑性特性且參數(shù)較易辨識,其準(zhǔn)確性得到了較好的驗證。主要得出了以下幾點結(jié)論:(1)在相同的應(yīng)力路徑下,經(jīng)干濕循環(huán)作用后的土樣瞬時變形及累積變形均大于未經(jīng)干濕循環(huán)作用的土樣,且變形隨干濕循環(huán)次數(shù)的增加而增大。干濕循環(huán)作用對土樣的蠕變特性產(chǎn)生了明顯影響,其瞬時強度和長期強度也較循環(huán)前大幅降低。(2)由剪應(yīng)變-時間曲線的分析可知,百色膨脹土的非線性蠕變呈現(xiàn)出彈性、黏彈性、黏塑性、黏彈塑性的特征。(3)膨脹土的剪切蠕變變形可分為三個階段:衰減蠕變階段、等速蠕變階段、加速蠕變階段。在蠕變過程中存在三個剪應(yīng)力特征值:τ_1、τ_2、τ_f,在低剪應(yīng)力水平τ_iτ_1時,土體僅發(fā)生瞬時變形,但蠕變速率不斷減小,最后收斂,無蠕變現(xiàn)象。剪應(yīng)力繼續(xù)增大至τ_2τ_i≥τ_1時,土體開始產(chǎn)生蠕變,為衰減蠕變階段;當(dāng)剪應(yīng)力水平τ_2≥τ_iτ_f時,土體開始以恒定的速度發(fā)生蠕變,為等速蠕變階段;當(dāng)剪應(yīng)力水平τ_i≥τ_f時,土體進入加速蠕變階段,迅速失穩(wěn)破壞。(4)建立了半經(jīng)驗半理論剪切蠕變模型,擬合了模型參數(shù)。經(jīng)驗證,該模型的擬合值與蠕變試驗得到的實測值較吻合,可為百色地區(qū)的工程建設(shè)提供了可靠的土體蠕變變形計算依據(jù)。(5)干濕循環(huán)作用將導(dǎo)致膨脹土的瞬時強度和長期強度大幅衰減,且長期強度的衰減幅度較瞬時強度更大。(6)瞬時強度與長期強度大小的排序依次為:干濕循環(huán)作用6次后土體長期強度干濕循環(huán)作用6次后土體瞬時強度未經(jīng)干濕循環(huán)作用的土體長期強度未經(jīng)干濕循環(huán)作用的土體瞬時強度。干濕循環(huán)作用導(dǎo)致土體瞬時強度和長期強度衰減,其衰減程度隨干濕循環(huán)作用次數(shù)的增加而增大。
[Abstract]:In order to study the stress-strain state of expansive soil under dry-wet cycle, shear creep model and attenuation law of long-term strength parameters of expansive soil are studied in order to further study the stress-strain state of expansive soil under dry-wet cycle. In order to predict the creep characteristics of expansive soil, a constitutive model and model parameters are established, which accord with the engineering practice and reflect the creep behavior of expansive soil reasonably. In this paper, the indoor shear creep tests of expansive soil under different normal pressures under dry and wet cycles were carried out, and the data of shear creep test curves were analyzed and sorted out. The shear creep mechanism of Baise expansive soil is studied, and a semi-empirical and semi-theoretical shear creep model of expansive soil is constructed. The physical meaning of the parameters of the model is clear, which can not only describe the stage of attenuation creep and constant velocity creep of soil. The accelerated creep stage can also be described, and the rheological viscoelastic-plastic properties of soil can be fully reflected, and the parameters can be easily identified, and its accuracy is well verified. The following conclusions are drawn: 1) under the same stress path, The instantaneous deformation and cumulative deformation of soil samples treated by dry and wet cycles are larger than those of soil samples without dry and wet cycles, and the deformation increases with the increase of dry and wet cycles. The creep characteristics of soil samples are obviously affected by dry and wet cycles. Its instantaneous strength and long-term strength are also significantly reduced compared with those before cycling. (2) from the analysis of the shear strain-time curve, it can be seen that the nonlinear creep of Baise expansive soil shows elasticity, viscoelasticity and viscoplasticity. The shear creep deformation of expansive soil can be divided into three stages: attenuated creep stage, isokinetic creep stage and accelerated creep stage. There are three eigenvalues of shear stress in the creep process: 蟿 _ 1, 蟿 _ 2, 蟿 _ f, and 蟿 _ I 蟿 _ 1:00 at low shear stress level. There is only instantaneous deformation in soil, but creep rate decreases continuously, and finally converges without creep phenomenon. The shear stress continues to increase to 蟿 _ 2 蟿 _ I 鈮，

本文編號：1494983