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振动扰动含细粒土砂强度特性试验研究
Alternative TitleExperimental study on the vibration strength of disturbed fine-grained sand characteristics
Language中文
刘文静
Thesis Advisor苏立君
2015
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name硕士
Degree Discipline建筑与土木工程
Keyword三轴试验 振动 正交设计 魏家沟 残余强度
Abstract地震诱发的地质灾害归因于地震波对土体造成的损伤,地震作用等效于地震波对土体施加了一种振动荷载,同时在与土体相互作用后,改变了土体的结构,降低了土体的强度,进而触发地质灾害。而且,土体受到地震波的损伤以后,在降雨、余震、边坡开挖等新的条件作用之下,相比结构完整的土体更易于发生破坏,形成滑坡。 本文以北川县魏家沟为例,借助野外现场调查、室内资料收集、室内试验与数据分析等手段,利用正交试验筛选出了对非饱和土体振动后残余饱和强度影响最大的一组振动参数:振幅2(mm)-周次8次-频率1.5(Hz)。然后以此为基础,分别从振幅、振动持时、振动频率三个方面来考察其影响程度。 通过以上的研究得到以下几点结论: (1)通过前期的资料收集和考察,确定了本次试验用土取土位置,完成了取土工作并测得了魏家沟取样点土样的基本原位指标:经过筛析以后获得实验用土的最大干密度为1.71 g/cm3,最优含水率为19%,液限 =43.4,塑限 =27.6,塑性指数 =15.8。根据《土的分类标准》(GBJ145-90),此土为粗粒土中的砂类土,进一步判断为含细粒土砂(代号:SF);细粒土部分为低液限粘土。 (2)介绍了正交试验的方法,确定了3个因素4个水平的正交试验,考察了不同振幅、不同持时以及不同振动频率下,非饱和土振动以后的饱和强度变化,发现这三个因素的影响强度为 ,并且确定了相应的振动参数来考察各自的影响变化情况,经过此轮的筛选工作,筛选了振幅2(mm)-周次8-频率1.5(Hz)这一组对土体残余饱和强度影响较大的参数,为下一步的研究工作奠定了基础。 (3)在振幅2(mm)-周次8-频率1.5(Hz)这一组基础上,分别考察了振幅、振动时长以及振动频率各自对非饱和土振动后残余饱和强度的变化规律,分别拟合了强度改变量与振幅、强度改变量与振动周次、强度改变量与频率的关系式。 (4)振幅、周次、频率3者试样破坏偏应力-轴应变曲线采用了邓肯-张的双曲线模型,并对此模型进行了修正,得到了50kpa下应力差表达式。 本文还根据偏应力拟合公式,对相应的偏应力-轴应变曲线进行了验证,结果显示计算值与实测值比较符合。 有了此公式,我们就可以估计一定振动条件下此围压下的应力差,运用本文所述方法,此公式可以推广到其他围压下对应的表达式,由此根据摩尔库伦准则我们可以获得此土体的抗剪强度指标,这对于野外快速评价震后滑坡体强度参数有重要的借鉴意义。 通过本文的研究,分析土体振动之后在静力作用下的应变破坏,得出土体在不同振幅、不同振动频率、持时的振动荷载作用下,土体损伤以后的强度变化规律,应力-应变关系,分析土体振动以后强度的敏感性因素。本研究所涉及的工作是研究地震对土体影响的基础工作,研究成果可为进一步研究地震诱发地质灾害的机理奠定基础。
Other AbstractGeohazards induced by earthquake attribute to the damage on the soil caused by the seismic waves, and the seismic action here is equivalent to the vibration load on the soil by seismic waves, which changes the structure of the soil, reduces the soil strength and thus triggers the geohazards. The soil damaged by the seismic waves is easier to be damaged and to cause landslides with the new disturbing conditions like rain, aftershocks and slope excavation. The present thesis takes North River County Weijiagou as an example by means of wild field investigation, laboratory data collection as well as laboratory experiments and data analysis, and screens out a set of vibrating parameters (amplitude 2 (mm) - cycles 8 - frequency 1.5 (Hz)) that exert the greatest impact on the residual saturated strength after the vibration of unsaturated soil by utilizing orthogonal test. Then, this paper attempts to investigate the influence factors of amplitude, the duration of vibration and vibrational frequency respectively. This present thesis finally concludes as the following 4 aspects according to the above study: (1)By the early data collection and investigation, this thesis confirms the soil-quarrying location, finishes the soil sampling and measures the basic situ indicators of soil sampling at Weijiagou. The test acquires the maximum dry density of experimental soil of 1.71 g/cm3, the optimum moisture content of 19% , liquid limit = 43.4, plastic limit = 27.6, plasticity index = 15.8. According to the Soil Classification Criteria (GBJ145-90), this soil belongs to coarse-grained sandy soil, further containing fine grit sandy soil with further judgment (Code: SF); and fine-grained soils belong to low liquid limit clay. (2)This thesis introduces the method of the orthogonal test, establishes the experiments with three variants and four level values of each variant, investigates the variation of saturated strength after the disturbance of unsaturated soil under the conditions of different amplitudes, durations and vibrational frequencies as well. Accordingly, this thesis finds out that the influence degree of the three factors ranks as amplitude, cycle and frequency, and determines the corresponding vibration parameters to examine the impact of changes in the respective cases. This round of test screens out a set of vibrating parameters (amplitude 2 (mm) - cycles 8 - frequency 1.5 (Hz)) that exert the greatest impact on the residual saturated strength, which lays the foundation for the further research. (3)On the basis of the screened vibrating parameters (amplitude 2 (mm) - cycles 8 - frequency 1.5 (Hz)) , this thesis respectively investigates the variation rule of the residual saturated strength after the vibration of unsaturated soil by the influence of amplitude, duration of vibration and vibration frequency, and fits the formula of strength variation and amplitude, strength variation and vibration cycle, and strength variation and frequency. (4)The deviator stress-strain relationship applied in the destruction of samples influenced by the three factors of amplitude, cycle and frequency adopts the Duncan-Chang hyperbolic model, which is also modified in the experiment of this present thesis. In addition, the thesis, according to the deviator stress fitting formula, verifies the corresponding deviator stress-strain relationship. The result proves that the calculated value comparatively conforms to the experimental value. Therefore, this thesis can figure out the differential stress in the confining pressure of 50kpa under a certain condition of vibration through this formula. Accordingly, this formula can be applied in the expressions under other confining pressures through the above modified model. According to the Mohr-coulomb Yield Criterion, this present thesis can acquire the shear strength index of the soil, which exerts a valuable reference on the field rapid assessment of landslide parameter strength after
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/14145
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
刘文静. 振动扰动含细粒土砂强度特性试验研究[D]. 北京. 中国科学院大学,2015.
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