盾构渣土固化处理及静动荷载作用下变形特性研究

【作者】 陈军；

【导师】 徐志洪； 顾琳琳； 薛丹璇；

【作者基本信息】 南京理工大学 ， 土木工程（专业学位）， 2023， 硕士

【摘要】 我国每年因城市地铁工程建设而产生大量的盾构渣土,传统的堆放抛填处理方式,不仅土地占用量大,而且易造成环境污染、地质破坏等问题。盾构渣土作为工程渣土的一种,具有潜在的回收利用价值,但是由于其具有含水率高、孔隙比大、强度低、力学性能差等特点,使得无法直接满足工程建设的要求。前人研究证明,利用土体固化技术对工程渣土进行改良处理是一种切实可行的方法,固化后的工程渣土可以作为土木工程材料,得到合理的利用,有着巨大的环境效益和经济价值。然而现有的工程渣土固化研究主要集中在固化剂研制和固化机理分析方面,较少涉及到固化土的工程性能研究,对盾构渣土的固化研究更是少之又少。本文以南京地铁五号线盾构渣土作为主要研究对象,通过对其进行物理化学性质分析,从绿色环保、成本节约的角度,选择适宜的固化材料研制高效、适用的盾构渣土固化剂,并分析其作用机理。在此基础上,从路基工程实际出发,通过系列室内试验研究固化盾构渣土在各种工况下的变形特性,以验证其路用性能。主要研究成果如下:(1)通过正交试验,研制出能显著改善盾构渣土力学性能的复合高分子固化剂,固化剂的最优配合比为水泥:电石渣:粉煤灰:高分子材料=25:30:40:5。并利用扫描电镜对固化土的微观结构进行分析,发现固化剂的加入可以促进土颗粒的积聚成团,减小土体的孔隙率和含水率,增强盾构渣土的整体性,大幅提高其强度。(2)通过无侧限压缩试验研究固化剂掺量和养护龄期对固化土强度的影响,发现随着固化剂掺量的增加,固化土的无侧限抗压强度有大幅的提高,但当固化剂的掺量大于10%时,试样的无侧限抗压强度增长幅度随着固化剂掺量的增加开始减缓。此外,试样的无侧限抗压强度随着养护龄期的增大而不断增长,当养护龄期为28 d时,试样的无侧限抗压强度提升最大。在此基础上,通过回归分析,建立了固化盾构渣土无侧限抗压强度与固化剂掺量和养护龄期之间的预测公式。(3)通过蠕变试验研究固化盾构渣土在恒定荷载作用下的长期变形特性,发现固化盾构渣土的蠕变类型主要为衰减蠕变和等速蠕变两种,当荷载等级较低时,试样的蠕变曲线主要由衰减阶段和稳定阶段构成,当荷载等级较高时,试样的蠕变曲线主要由衰减阶段和等速阶段构成。在各荷载等级下,试样总体变形量的95%以上主要发生在加载后的96 h内,固化盾构渣土的屈服应力大约在200 kPa左右,试样的蠕变变形主要发生在加载的48 h之后。(4)通过常规三轴压缩试验研究固化盾构渣土在三维应力状态下的变形特性,发现在围压的作用下,固化土的应力-应变曲线与无侧限压缩试验所得到的应力-应变曲线相类似,都属于脆性破坏的曲线类型。试样的破坏偏差应力随着围压的增大而增大,破坏应变随着围压的变化很小,大约在2%左右。(5)通过动三轴试验研究固化盾构渣土的动力特性。发现当动应力幅值小于临界动应力时,试样的累积变形随着加载次数的增加而缓慢增大,累积变形曲线近乎线性发展,动应力的幅值越小,曲线的线性越强,累积变形增长的越慢。当动应力幅值大于试样的临界动应力时,试样的累积变形随着加载次数的增大而大幅增加,增长速率逐渐增大,试样很快就会发生结构破坏。此外,试样的动弹性模量随着动应力的增大而增大,随着加载次数的增大而减小,相同加载次数条件下,盾构渣土的动弹性模量随着围压的增加而先增大再减小,在围压为60 kPa时,试样的动弹性模量达到最大。更多还原

【Abstract】 In China,a large amount of shield muck is generated every year due to the construction of urban subway projects.The traditional method of stacking,dumping,and filling not only takes up a large amount of land,but also easily causes environmental pollution,geological damage,and other issues.As a kind of engineering muck,shield muck has potential recycling value.However,due to its high water content,large void ratio,low strength,and poor mechanical properties,it cannot directly meet the requirements of engineering construction.Previous studies have proven that using soil solidification technology to improve engineering waste soil is a feasible method.The solidified engineering waste soil can be used as a civil engineering material and has significant environmental benefits and economic value.However,the existing research on the solidification of engineering waste soil mainly focuses on the development of solidification agents and the analysis of solidification mechanism,and rarely involves the research on the engineering performance of solidified soil.The research on the solidification of shield waste soil is even less.In this paper,the main research object is the shield muck of Nanjing Metro Line 5.Through analyzing its physical and chemical properties,from the perspective of green environmental protection and cost saving,select suitable solidification materials to develop efficient and suitable shield muck solidification agent,and analyze its mechanism.On this basis,based on the actual situation of subgrade engineering,a series of indoor tests were conducted to study the deformation characteristics of solidified shield muck under various working conditions to verify its road performance.The main research results are as follows:(1)Through orthogonal tests,a composite polymer curing agent that can significantly improve the mechanical properties of shield slag has been developed.The optimal mix ratio of the curing agent is cement: carbide slag: fly ash: polymer materials=25:30:40:5.Using scanning electron microscopy to analyze the microstructure of solidified soil,it was found that the addition of solidification agents can promote the accumulation of soil particles into clusters,reduce the porosity and moisture content of soil,enhance the integrity of shield slag,and significantly improve its strength.(2)Through unconfined compression tests,it was found that the unconfined compressive strength of solidified soil increased significantly with the increase of the amount of solidified agent,but when the amount of solidified agent was greater than 10%,the increase in the unconfined compressive strength of the sample began to slow down as the amount of solidified agent increased.In addition,the unconfined compressive strength of the sample continuously increases with the increase of the curing age.When the curing age is 28 days,the unconfined compressive strength of the sample increases maximum.On this basis,through regression analysis,a prediction formula between the unconfined compressive strength of solidified shield slag and the amount of curing agent and curing age is established.(3)Through creep tests to study the long-term deformation characteristics of solidified shield muck under constant load,it is found that the creep types of solidified shield muck are mainly attenuation creep and constant velocity creep.When the load level is low,the creep curve of the sample mainly consists of attenuation stage and stable stage.When the load level is high,the creep curve of the sample mainly consists of attenuation stage and constant velocity stage.Under various load levels,more than 95% of the total deformation of the sample mainly occurs within 96 hours after loading,the yield stress of solidified shield slag is about 200 kPa,and the creep deformation of the sample mainly occurs after 48 hours of loading.(4)The deformation characteristics of solidified shield muck under three-dimensional stress state were studied through conventional triaxial compression tests.It was found that the stress-strain curves of solidified soil under confining pressure were similar to those obtained from unconfined compression tests,and both belonged to the type of brittle failure curve.The failure deviation stress of the sample increases with the increase of the confining pressure,while the failure strain changes slightly with the confining pressure,about 2%.(5)The dynamic characteristics of solidified shield muck were studied through dynamic triaxial tests.It is found that when the dynamic stress amplitude is less than the critical dynamic stress,the cumulative deformation of the sample slowly increases with the increase of the loading times,and the cumulative deformation curve develops almost linearly.The smaller the dynamic stress amplitude,the stronger the linearity of the curve,and the slower the cumulative deformation growth.When the dynamic stress amplitude is greater than the critical dynamic stress of the specimen,the cumulative deformation of the specimen increases significantly with the increase in the number of loading times,and the growth rate gradually increases,resulting in rapid structural failure of the specimen.In addition,the dynamic elastic modulus of the sample increases with the increase of dynamic stress,and decreases with the increase of loading times.Under the same loading times,the dynamic elastic modulus of the shield muck first increases and then decreases with the increase of confining pressure.When the confining pressure is 60 kPa,the dynamic elastic modulus of the sample reaches the maximum.更多还原