【摘要】：吹填軟土是一種近些年才出現(xiàn)的人工成因軟土,其經(jīng)加固處理后次固結(jié)特性依舊存在,由次固結(jié)導致的工后沉降對建筑工程的正常使用及后期維護影響重大。目前對于加固處理后吹填軟土的次固結(jié)研究相對較少,且研究手段多通過單純的室內(nèi)人工模擬試驗來進行,難以較準確的反映實際狀況。本研究以天津港東疆港區(qū)某工程項目為依托,借助先進的全自動數(shù)據(jù)采集固結(jié)儀系統(tǒng),進行了一系列不同方案的一維固結(jié)試驗,對加固處理后吹填軟土的固結(jié)、次固結(jié)特性及各種影響因素進行了深入研究,并運用數(shù)理統(tǒng)計方法,以足量試驗數(shù)據(jù)的算術平均值作為研究依據(jù),減小誤差,提高可信度,使研究結(jié)果更貼實際,為減少及預防加固處理后吹填軟土的工后沉降提供依據(jù)及建議,亦為類似問題的研究思路及方法提供參考與借鑒。本研究通過對真空預壓加固處理后的吹填軟土與同區(qū)域下覆的成份基本相同的自然海相沉積軟土的工程特性比較,探討兩種土的物理、強度、固結(jié)特性的異同、產(chǎn)生的原因及可能帶來的后果,揭示了次固結(jié)系數(shù)隨荷載變化的特征,提出這種特征是原狀土的基本特征,具有普適性。并發(fā)現(xiàn)加固處理后吹填軟土在一維固結(jié)試驗中具有首級荷載下固結(jié)系數(shù)偏大,后隨著荷載的增加固結(jié)系數(shù)逐漸減小并趨于常值的現(xiàn)象,提出含水率大于40%的各類飽和原狀軟土亦有此種現(xiàn)象,并進行了解釋。分別采用0.5、1.0、3.0的不同加載比固結(jié)試驗,研究了加載速率的不同對加固處理后吹填軟土的固結(jié)系數(shù)、次固結(jié)系數(shù)的影響、影響程度及適用條件,提出在荷載總量一定的情況下,采用適當?shù)男≡隽慷嗯蔚募虞d方式進行軟基加固可改善加固效果,減少次固結(jié)沉降。并發(fā)現(xiàn)采用過小的加載比,會使其固結(jié)系數(shù)、次固結(jié)系數(shù)與荷載的關系曲線出現(xiàn)波浪起伏現(xiàn)象,表明其主、次固結(jié)沉降速率隨荷載的施加出現(xiàn)或大或小的不均勻現(xiàn)象,并解釋了原因。通過不同厚度的一維固結(jié)試驗探討了排水路徑對加固處理后吹填軟土的主、次固結(jié)的影響,及影響程度,并從理論公式角度進行了解釋。通過兩個回次的超載預壓及卸載回彈試驗,探討了超載預壓、重復超載預壓及卸荷回彈對加固處理后吹填軟土的主、次固結(jié)的影響,提出超載預壓、重復的超載預壓可有效降低次固結(jié)沉降。
[Abstract]:Filling soft soil is a kind of artificial soft soil that appeared only in recent years. The secondary consolidation characteristics still exist after reinforcement treatment. The post-construction settlement caused by secondary consolidation has a great impact on the normal use and later maintenance of building engineering. At present, there are few researches on secondary consolidation of dredged soft soil after reinforcement and treatment, and most of the research methods are carried out by simple indoor artificial simulation test, so it is difficult to accurately reflect the actual situation. Based on an engineering project in Dongjiang Port area of Tianjin Port, this study carried out a series of one-dimensional consolidation tests of different schemes with the help of advanced fully automatic data acquisition and consolidation instrument system, and the consolidation of soft soil after reinforcement and treatment was carried out. In this paper, the secondary consolidation characteristics and various influencing factors are studied in depth, and the arithmetic average of sufficient experimental data is used as the research basis by using mathematical statistics method. The error is reduced, the reliability is improved, and the research results are more practical. In order to reduce and prevent post-construction settlement of soft soil after reinforcement and treatment, it also provides reference and reference for the research ideas and methods of similar problems. Based on the comparison of the engineering characteristics of the soft soil filled by vacuum preloading and the natural marine sedimentary soft soil which has the same composition under the same area, the similarities and differences of the physical, strength and consolidation characteristics of the two soils are discussed. The causes and possible consequences reveal the variation of the secondary consolidation coefficient with the load. It is suggested that this characteristic is the basic feature of the undisturbed soil and has universal applicability. It is also found that the consolidation coefficient is larger under the first load and then decreases gradually with the increase of the load and tends to the constant value in the one-dimensional consolidation test. This phenomenon is also found in all kinds of saturated undisturbed soft soils with moisture content greater than 40%, and the explanation is given. The effects of different loading rates on the consolidation coefficient, secondary consolidation coefficient, influence degree and applicable conditions of soft soil after reinforcement are studied by using the different loading ratios of 0.5 and 1.0% 3.0 respectively. It is put forward that under the condition of constant load total amount, the effect of loading rate on the consolidation coefficient, secondary consolidation coefficient and application condition of soft soil after reinforcement treatment are studied. Using appropriate small increment multi-batch loading method to strengthen soft foundation can improve the reinforcement effect and reduce the secondary consolidation settlement. It is also found that if the loading ratio is too small, the wave fluctuation will occur in the curve of consolidation coefficient, secondary consolidation coefficient and load, indicating that the settlement rate of the main and secondary consolidation occurs with the application of the load or the phenomenon of large or small non-uniformity. And explained the reason. The influence of drainage path on the main and secondary consolidation of soft soil after consolidation and treatment is discussed through one-dimensional consolidation tests with different thickness, and the influence degree is explained from the point of view of theoretical formula. In this paper, the effects of overload preloading, repeated overload preloading and unloading rebound on the main and secondary consolidation of soft soil after reinforcement and treatment are discussed through the overloading preloading and unloading springback tests, and the overload preloading is put forward. Repeated overload preloading can effectively reduce the secondary consolidation settlement.
【學位授予單位】：天津大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU447

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