本文選題：膨脹土 + 干濕循環(huán)�。� 參考：《廣西大學》2014年碩士論文

【摘要】：膨脹土對在其分布區(qū)域內(nèi)的工程建設(shè)產(chǎn)生不利影響。例如,在濕熱交替頻繁氣候條件下膨脹土路基的不均勻沉陷、隆起和開裂,膨脹土邊坡的滑溜、坍塌及滑坡,膨脹土地基上房屋的開裂等工程地質(zhì)災害。因此,研究膨脹土在干濕循環(huán)條件下的壓縮特性和建立能夠反映膨脹土力學特性的本構(gòu)模型對膨脹土區(qū)域的工程建設(shè)有著重要的理論和實際意義。為此,本文以南寧膨脹土的原狀樣、重塑樣、干濕循環(huán)樣為試驗對象,對其做了相關(guān)的基本物理力學試驗和一維固結(jié)試驗研究,然后建立了反映膨脹土超固結(jié)性的本構(gòu)模型和反映膨脹土超固結(jié)性、結(jié)構(gòu)性的本構(gòu)模型。隨后利用有限元分析軟件的子程序接口編制了對應于上述模型的材料子程序,建立了適用于超固結(jié)土、結(jié)構(gòu)性土的數(shù)值模擬平臺�；跀�(shù)值模擬平臺進行了系列數(shù)值模擬試驗,驗證了上述模型以及對應子程序的精度與穩(wěn)定性。最后,對比本文模型和其他模型模關(guān)于Fujinomori黏土與Boom黏土的模擬結(jié)果及試驗數(shù)據(jù)。 上述試驗研究表明,干濕循環(huán)效應使得膨脹土產(chǎn)生了一種特殊的結(jié)構(gòu)性,該結(jié)構(gòu)性對膨脹土壓縮特性的影響與結(jié)構(gòu)性對土壓縮特性的影響相反,故此在本文中被稱為“負結(jié)構(gòu)性”,具體表現(xiàn)為：膨脹土循環(huán)樣在固結(jié)壓力小于“負結(jié)構(gòu)性”屈服應力之前,壓縮性不受干濕循環(huán)效應的影響；當固結(jié)壓力大于該應力時,壓縮性隨“負結(jié)構(gòu)性”的衰減而增強；在“負結(jié)構(gòu)性,,隨固結(jié)壓力的增加被完全破壞后,壓縮性不再受干濕循環(huán)效應的影響。 在本構(gòu)模型研究方面,針對膨脹土的超固結(jié)性本文建立了改進超固結(jié)狀態(tài)參量下負荷面模型。該模型能夠準確描述超固結(jié)土在三軸壓縮試驗過程中的孔隙比與有效應力變化規(guī)律、變形特征、應力-應變關(guān)系等特性,且能更為連續(xù)平滑地模擬實際超固結(jié)七的彈塑性應力-應變關(guān)系。同時,該模型相對UH模型能夠更準確地刻畫重超固結(jié)Fujinomori黏土的應力-應變關(guān)系、應變軟化以及峰值強度與殘余強度等特征。 為反映超固結(jié)性與結(jié)構(gòu)性對膨脹土的影響,本文建立了改進狀態(tài)變量上下負荷面模型。該模型模擬的應力路徑、超孔隙水壓力變化、應力-應變關(guān)系等完全符合超固結(jié)土及結(jié)構(gòu)性土力學行為的一般規(guī)律。同時,該模型能準確描述Boom原狀黏土與Fujinomori黏土的應力-應變的非線性、應變軟化以及峰值強度與殘余強度等特征。此外,該模型相對Nakai和Hinokio模型能更準確地反映主應力旋轉(zhuǎn)效應的影響。 本文通過建立考慮超固結(jié)性、結(jié)構(gòu)性影響的本構(gòu)模型,擴充了有限元軟件的材料子程序庫,為文中的兩個本構(gòu)模型在實際工程中的應用奠定了基礎(chǔ),隨著對膨脹土超固結(jié)性、結(jié)構(gòu)性的進一步科學的定性定量研究,上述兩個本構(gòu)模型的實際應用指日可待。
[Abstract]:Expansive soil has an adverse effect on engineering construction in its distribution area. For example, engineering geological disasters such as uneven subsidence, uplift and cracking of expansive soil subgrade, slippage, collapse and landslide of expansive soil slope, cracking of house on expansive soil foundation, etc. Therefore, it is of great theoretical and practical significance to study the compression characteristics of expansive soil under dry-wet cycle and to establish a constitutive model which can reflect the mechanical properties of expansive soil. Therefore, in this paper, the basic physical and mechanical tests and one-dimensional consolidation tests of the expansive soil in Nanning were carried out, including the undisturbed sample, the remolded sample and the dry wet cycle sample. Then a constitutive model reflecting the overconsolidation of expansive soil and a constitutive model reflecting the overconsolidation and structure of expansive soil are established. Then the material subroutine corresponding to the above model is compiled by using the subroutine interface of the finite element analysis software, and a numerical simulation platform for the overconsolidated and structural soils is established. A series of numerical simulation experiments are carried out based on the numerical simulation platform to verify the accuracy and stability of the above model and the corresponding subroutine. Finally, the simulation results and experimental data of Fujinomori clay and Boom clay are compared with other models. The experimental results show that the dry and wet cycle effect makes expansive soil produce a special structure. The influence of this structure on the compression characteristics of expansive soil is opposite to that of the structural effect on soil compression characteristics. Therefore, it is called "negative structure" in this paper, which shows that the compressibility of expansive soil cyclic sample is not affected by dry-wet cycle effect before the consolidation pressure is less than "negative structural" yield stress, and when the consolidation pressure is greater than this stress, the compressibility of the expansive soil is not affected by the dry and wet cycle effect before the consolidation pressure is less than the negative structural yield stress. The compressibility increases with the attenuation of "negative structure", and when the "negative structure" is completely destroyed with the increase of consolidation pressure, the compressibility is no longer affected by the effect of dry-wet cycle. In terms of constitutive model, an improved load surface model for the overconsolidation of expansive soils is established in this paper. The model can accurately describe the variation law of void ratio and effective stress, deformation characteristics and stress-strain relationship of overconsolidated soil during triaxial compression test. Furthermore, the elastoplastic stress-strain relationship of the actual over-consolidated seven can be simulated more smoothly and continuously. Compared with UH model, the model can describe the stress-strain relationship, strain softening, peak strength and residual strength of heavily overconsolidated Fujinomori clay more accurately. In order to reflect the influence of overconsolidation and structure on expansive soil, an improved upper and lower load surface model of state variables is established in this paper. The stress path, excess pore water pressure and stress-strain relationship simulated by this model fully accord with the general law of mechanical behavior of overconsolidated soil and structural soil. At the same time, the model can accurately describe the stress-strain nonlinearity, strain softening, peak strength and residual strength of Boom and Fujinomori clay. In addition, the model can reflect the effect of principal stress rotation more accurately than Nakai and Hinokio models. In this paper, the material subprogram library of the finite element software is expanded by establishing a constitutive model considering the overconsolidation and structural effects, which lays a foundation for the application of the two constitutive models in the practical engineering. Further scientific qualitative and quantitative studies on the structure of the above two constitutive models can be applied in the near future.
【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU443;TU411

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