本文選題：軟土 + 一維壓縮��； 參考：《暨南大學(xué)》2015年碩士論文

【摘要】：軟土具有含水率高、孔隙比大、壓縮性高、滲透性差、抗剪強(qiáng)度低等特性,其長(zhǎng)期變形量一般較大。在軟土地基上修筑建筑物時(shí),變形問題和長(zhǎng)期沉降問題是工程面臨的主要難題。軟土的變形與時(shí)間密切相關(guān),這既包括超靜孔隙水壓力消散的固結(jié)壓密過程,也包括由土體粘滯性所引起的蠕變變形,兩者相互影響,共同決定著土體的長(zhǎng)期沉降。因此,開展反映軟土變形與時(shí)間相關(guān)的性狀研究以及建立能夠考慮時(shí)間效應(yīng)的固結(jié)模型,對(duì)軟土地基固結(jié)沉降過程和固結(jié)沉降量的預(yù)測(cè)是具有理論和實(shí)際意義的。本文針對(duì)汕頭東部吹填軟土,在掌握試樣基本物理力學(xué)性質(zhì)的基礎(chǔ)上,通過室內(nèi)一維壓縮試驗(yàn)系統(tǒng)研究了軟土在不同固結(jié)條件下的壓縮特性及壓縮性指標(biāo)。主要研究?jī)?nèi)容及成果如下:(1)針對(duì)試樣進(jìn)行了K0側(cè)限固結(jié)試驗(yàn),對(duì)比分析了試樣在不同初始狀態(tài)、排水距離和固結(jié)時(shí)間等條件下的等時(shí)壓縮曲線特性、基本變形規(guī)律和各項(xiàng)壓縮性指標(biāo)的發(fā)展規(guī)律。結(jié)果表明,不同固結(jié)因素影響下,試樣的等時(shí)壓縮曲線特性、基本變形規(guī)律和各項(xiàng)指標(biāo)的發(fā)展規(guī)律是一致的,只是指標(biāo)的量值會(huì)因固結(jié)影響因素改變而發(fā)生變化,說明elgp等時(shí)壓縮曲線規(guī)律具有普遍適用性,能夠直觀地反映固結(jié)變形與時(shí)間相關(guān)的性狀,但是指標(biāo)的取值需要考慮固結(jié)影響因素。(2)作為對(duì)比,進(jìn)行了等K柔性側(cè)限固結(jié)試驗(yàn),將試驗(yàn)結(jié)果與K0側(cè)限條件下的成果進(jìn)行了對(duì)比分析。結(jié)果表明,等K柔性側(cè)限條件下,除了在正常固結(jié)階段0~0.1min時(shí)段內(nèi)產(chǎn)生了明顯的瞬時(shí)變形外,之后的壓縮變形特性及壓縮性指標(biāo)的發(fā)展規(guī)律與K0側(cè)限條件下的相同。等K柔性側(cè)限條件下允許發(fā)生一定側(cè)向變形,導(dǎo)致壓縮性指標(biāo)發(fā)生相應(yīng)變化,其壓縮指數(shù)CK0側(cè)限條件下的1.8~2.6倍,次固結(jié)系數(shù)Ca約為K0側(cè)限條件下的2.3~2.4 倍。(3)為進(jìn)一步了解軟土的回彈再壓縮特性,還進(jìn)行了K0側(cè)限回彈-再壓縮試驗(yàn),分析了回彈再壓縮變形特性及各階段應(yīng)力應(yīng)變關(guān)系。試驗(yàn)結(jié)果表明,壓縮曲線具有明顯的分段特性,不同固結(jié)壓力回彈起點(diǎn)下的回彈-再壓縮等效直線可視為近似平行的,再壓縮超固結(jié)階段變形以彈性變形為主,可用彈性理論計(jì)算該過程的應(yīng)力應(yīng)變關(guān)系;回彈再壓縮之后的正常固結(jié)壓縮線可視為回彈前正常固結(jié)壓縮線的延續(xù),正常固結(jié)階段變形以粘塑性變形為主,彈性變形量很小,可采用粘塑性理論給出該過程的變形計(jì)算。(4)在上述試驗(yàn)及成果整理的基礎(chǔ)上,基于等時(shí)壓縮曲線理論和等效時(shí)間概念,建立了分段式的一維彈-粘塑性固結(jié)模型,并明確了參數(shù)的物理意義和確定方法。該模型還給出了結(jié)構(gòu)屈服應(yīng)力點(diǎn)的確定方法,考慮了時(shí)間效應(yīng)對(duì)變形及土體結(jié)構(gòu)屈服應(yīng)力的影響,能夠較好地描述軟土的壓縮變形特性,反映固結(jié)過程中準(zhǔn)先期固結(jié)壓力增加的現(xiàn)象。該模型也被推廣到等K柔性側(cè)限條件,使之可以考慮側(cè)向變形對(duì)模型參數(shù)的影響。
[Abstract]:Soft soil is characterized by high moisture content, high porosity ratio, high compressibility, poor permeability and low shear strength. Deformation and long-term settlement are the main problems in building on soft foundation. The deformation of soft soil is closely related to time, which includes both consolidation and compaction process of excess pore water pressure dissipation and creep deformation caused by soil viscosity. Therefore, it is of theoretical and practical significance to study the characteristics of soft soil deformation related to time and to establish a consolidation model which can take account of time effect to predict the consolidation settlement process and consolidation settlement of soft soil foundation. Based on the basic physical and mechanical properties of the soft soil in the east of Shantou, the compression characteristics and compressibility indexes of the soft soil under different consolidation conditions were studied by one-dimensional compression test system in laboratory. The main research contents and results are as follows: (1) the K0 side limit consolidation test is carried out for the specimen, and the characteristics of isochronous compression curves under different initial state, drainage distance and consolidation time are compared and analyzed. Basic deformation law and the development law of each compressibility index. The results show that under the influence of different consolidation factors, the characteristics of isochronous compression curve, the basic deformation law and the development law of each index are consistent, but the value of the index will change with the change of consolidation factors. The results show that the law of elgp isochronous compression curve is universal and can directly reflect the properties of consolidation deformation related to time, but the value of the index needs to consider the influence factor of consolidation. The experimental results are compared with those under K _ 0 side limit. The results show that under the condition of equal K flexible lateral limit, except for the obvious instantaneous deformation during the 0~0.1min period of normal consolidation stage, the development law of compression deformation and compressibility index is the same as that under K0 lateral limit condition. A certain lateral deformation is allowed under the condition of equal K flexible lateral limit, which results in the corresponding change of compressibility index, and its compression index CK0 is 1.82.6times higher than that under the lateral limit condition. In order to further understand the springback and recompression characteristics of soft soil, K0 side limited springback and recompression tests were carried out, and the deformation characteristics of springback recompression and the stress-strain relationships in each stage were analyzed. The experimental results show that the compression curve has obvious piecewise characteristics, and the springback-recompression equivalent straight line at different springback starting points of consolidation pressure can be regarded as approximately parallel, and elastic deformation is the main deformation in the recompression overconsolidation stage. The stress-strain relationship of the process can be calculated by elastic theory, and the normal consolidation compression line after springback and recompression can be regarded as a continuation of the normal consolidation compression line before springback. The deformation in normal consolidation stage is mainly viscoplastic deformation, and the elastic deformation is very small. The deformation calculation of the process can be given by using the viscoplastic theory. (4) based on the above experiments and the arrangement of the results, based on the theory of isochronous compression curve and the concept of equivalent time, a segmented one-dimensional elastic-viscoplastic consolidation model is established. The physical meaning and determination method of the parameters are clarified. The model also gives a method to determine the yield stress point of the structure, considering the influence of time effect on the deformation and the yield stress of the soil structure, which can better describe the compressive deformation characteristics of the soft soil. It reflects the increase of quasi-preconsolidation pressure in the consolidation process. The model is also extended to the equivalent K flexible lateral limit condition, so that the influence of lateral deformation on the model parameters can be considered.
【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU447;TU411

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