本文選題：歷史風(fēng)貌建筑　切入點(diǎn)：基坑　出處：《天津大學(xué)》2013年博士論文

【摘要】：大規(guī)模的地鐵建設(shè)使盾構(gòu)法得到了廣泛的應(yīng)用，同時(shí)也促進(jìn)了地下工程的發(fā)展。軟土地區(qū)進(jìn)行深基坑和區(qū)間隧道的施工存在多種風(fēng)險(xiǎn)，特別是對(duì)鄰近基坑的歷史風(fēng)貌建筑物的影響，不同的保護(hù)措施存在較大差別，研究不同施工階段對(duì)建筑物的影響、注漿加固地層機(jī)理、盾構(gòu)推力引起地層中的附加應(yīng)力等非常必要。 首先，基于對(duì)歷史風(fēng)貌建筑物的實(shí)測(cè)數(shù)據(jù)分析，考察了基坑開(kāi)挖、降水、端頭注漿與凍結(jié)加固、盾構(gòu)掘進(jìn)等方面對(duì)建筑物的影響，并在此基礎(chǔ)上對(duì)注漿抬升過(guò)程進(jìn)行有限元模擬，得到了與實(shí)測(cè)擬合較好的計(jì)算結(jié)果。結(jié)果表明，合理的盾構(gòu)掘進(jìn)參數(shù)可將建筑物的沉降控制在較小范圍內(nèi)，地下水通過(guò)凍結(jié)區(qū)盾尾間隙進(jìn)入刀盤(pán)前方可引起建筑物的顯著沉降；建筑物基礎(chǔ)與隧道之間存在淤泥質(zhì)土層時(shí)，在淤泥質(zhì)土層下方進(jìn)行注漿不能對(duì)自重較大的建筑物進(jìn)行有效抬升，注漿在淤泥質(zhì)土層中引起孔壓的消散可導(dǎo)致建筑物在后期產(chǎn)生沉降。 進(jìn)而，采用通過(guò)實(shí)測(cè)驗(yàn)證的有限元參數(shù)計(jì)算盾構(gòu)正面推力和盾殼摩擦在地層中產(chǎn)生的附加應(yīng)力，研究了盾構(gòu)正前方、側(cè)方、上方和下方平面上不同方向附加應(yīng)力的分布，并分析了附加應(yīng)力對(duì)地下管線及構(gòu)筑物等的影響。結(jié)果表明，盾構(gòu)正面推力在正前方平面上產(chǎn)生的x向正應(yīng)力隨著距掌子面距離的增加影響范圍逐漸增大，但附加應(yīng)力值迅速減小。盾構(gòu)摩擦力在地層中引起的附加應(yīng)力分布與正面推力導(dǎo)致的附加應(yīng)力分布規(guī)律相似，但整體影響范圍更大，附加應(yīng)力值相應(yīng)衰減較慢。盾構(gòu)推力在地層中產(chǎn)生的附加應(yīng)力以土壓力的形式作用在地下管線和構(gòu)筑物上，過(guò)大的變形可能導(dǎo)致管線滲漏或者構(gòu)筑物開(kāi)裂，工程中需引起足夠重視。 基于實(shí)測(cè)驗(yàn)證的有限元模型，分析了不同土層中注漿和注漿位置相鄰?fù)翆訌椥阅Ａ繉?duì)注漿效果的影響。結(jié)果表明，本工程中實(shí)際產(chǎn)生的注漿效果為注漿量的70%，注漿會(huì)導(dǎo)致注漿體周?chē)馏w中產(chǎn)生超靜孔隙水壓力，在注漿結(jié)束后超靜孔隙水壓力逐漸消散，建筑物會(huì)發(fā)生小幅度的下沉，注漿體上部土層彈性模量太大會(huì)對(duì)注漿體的膨脹有一定的約束作用，導(dǎo)致抬升效果不明顯，而注漿體下部土層，彈性模量越大注漿對(duì)自重荷載較大的建筑物的抬升效果越明顯，而對(duì)自重荷載較小的建筑物抬升效果越不明顯。 對(duì)天津地區(qū)的土層進(jìn)行凍土實(shí)驗(yàn)，研究天津地區(qū)的凍土的物理力學(xué)特性，凍土的三軸試驗(yàn)結(jié)果表明，凍土在零下5度時(shí)，應(yīng)力應(yīng)變曲線體現(xiàn)出應(yīng)變軟化的特性，而溫度為零下10度和零下15度時(shí)，凍土應(yīng)力應(yīng)變特性為應(yīng)變硬化型。 最后，對(duì)凍結(jié)法盾構(gòu)進(jìn)出洞進(jìn)行研究，將盾構(gòu)進(jìn)出洞人工凍結(jié)簡(jiǎn)化為厚壁筒受內(nèi)壓，利用凍土彈性-線性強(qiáng)化模型推導(dǎo)出塑性狀態(tài)下凍土凍結(jié)壁厚度。并結(jié)合工程實(shí)例，，對(duì)凍結(jié)法施工進(jìn)行了實(shí)測(cè)分析，結(jié)果表明，凍結(jié)帷幕在早期的發(fā)展會(huì)很快，交圈后所形成的凍結(jié)壁為不均勻體，后期凍結(jié)壁趨于均勻。目前的凍結(jié)設(shè)計(jì)參數(shù)選擇偏于保守，應(yīng)結(jié)合凍土試驗(yàn)參數(shù)對(duì)凍結(jié)設(shè)計(jì)進(jìn)行優(yōu)化。
[Abstract]:Large - scale subway construction has made the shield method widely used , and also promoted the development of underground engineering . There are many kinds of risks in the construction of deep foundation pit and interval tunnel in soft soil area , especially the influence of different construction stage on buildings , the mechanism of grouting reinforcement formation , and the additional stress in the formation caused by shield thrust .

Firstly , based on the measured data analysis of historic buildings , the influence of foundation pit excavation , precipitation , end grouting , freezing and strengthening , shield tunneling and so on are studied , and the calculation results are obtained . The results show that the reasonable shield tunneling parameters can control the settlement of the building in a small range .
When the silt soil layer exists between the foundation of the building and the tunnel , the grouting in the bottom of the muddy soil layer can not effectively uplift the building with large dead weight , and the dissipation of the pore pressure caused by the grouting in the muddy soil layer can cause the building to generate settlement in the later stage .

In addition , the influence of the additional stress on the underground pipelines and structures is studied by using the finite element parameters verified by the measured finite element parameters , and the influence of the additional stress on the underground pipelines and structures is studied . The results show that the additional stress generated in the forward plane of the shield is similar to the distribution of the additional stress caused by the front thrust . However , the additional stress caused by the shield thrust in the formation is relatively slow . The additional stress generated in the shield is applied to the underground pipelines and structures in the form of earth pressure .

Based on the finite element model , the influence of the elastic modulus of the adjacent soil layers in different soil layers on the grouting effect is analyzed . The results show that the grouting effect in the project is 70 % of the grouting amount , and the pressure of the super - static pore water is gradually dissipated in the surrounding soil of the grouting body . The higher the elastic modulus of the upper soil layer of the grouting body , the higher the lifting effect is , the more obvious the lifting effect of the grouting body under the weight load is more obvious , and the less obvious the lifting effect of the building with smaller dead load .

The physical and mechanical properties of frozen soil in Tianjin area were studied . The results of triaxial tests of frozen soil showed that the stress - strain curve showed strain - softening characteristic when frozen soil was 5 degrees below zero , while the stress - strain characteristic of frozen soil was strain - hardening when the temperature was 10 degrees and 15 degrees below zero .

The frozen wall thickness of frozen soil under plastic condition is deduced by using the frozen soil elastic - linear reinforcement model . The results show that the frozen wall is not uniform in the early development , and the frozen wall in the later stage tends to be uniform . The current frozen design parameters are conservative , and the frozen design should be optimized in combination with the frozen soil test parameters .

【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類(lèi)號(hào)】：TU43;U231.3

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