The analysis of dates obtained from long-term creep tests to determine creep coefficients of rock salt

Bulletin of Engineering Geology and the Environment - Failure to properly characterize time-dependent behavior (i.e. creep) of rocks and the use of inappropriate behavior models when analyzing...     

构皮滩软岩流变模型原位载荷蠕变试验研究

针对构皮滩水电站破碎页岩进行2点原位刚性承压板载荷蠕变试验,采用1级循环加载方式,试验压力为工程应力水平,试验历时1686,2299 h。试验揭示了该软岩如下蠕变特性:在工程应力下,岩体经历起始阶段减速蠕变和682,910 h较长时间的等速蠕变后,蠕变速率趋于零,总体呈衰减蠕变,并不发生塑性流动;卸荷后,经历瞬时回弹、弹性后效,存在较大的残余变形,残余变形大于总变形的50%。提出一种加载呈弹性、卸载不回弹的单向弹簧元件[HI]描述残余变形,将其与广义Kelvin模型串联组成变异广义Kelvin模型,该模型结构简单,可综合描述软岩加载呈衰减蠕变、卸载存在较大残余变形的蠕变特性。视岩体体积变形为弹性、畸变遵循变异广义Kelvin模型,基于相应性原理推导了岩体表面蠕变方程,以岩体蠕变方程拟合试验蠕变曲线,得到了模型参数。     

土工布加筋土的三轴蠕变试验研究

 基于自行研发的大尺寸三轴蠕变试验仪,开展不同围压、加筋层数的素土和加筋土的三轴蠕变试验,得到不同偏应力、不同加筋层数下土体的蠕变特性和加筋对土体加固的机制,提出一种可以描述加筋土“应力–应变–时间”关系的PH经验模型,得到所获取的模型参数与加筋层数和偏应力的关系;并基于Burgers元件模型,建议一种加固效果系数来评价加筋前后对土体刚度的影响程度,结果表明：随着加筋层数的增加,其加筋效果呈线性增加,与高填方工程中以增加压实度的方法来减小工后变形相比,在填料中增加筋材具有更佳效果。     

软岩非线性蠕变模型研究

以工程实际中广泛应用的元件组合模型为基础,通过引入损伤变量和硬化变量,建立了一个软岩非线性蠕变模型。分析认为,Maxwell体等价于一个线性损伤的虎克弹性体,Kelvin体相当于一个线性硬化的牛顿黏性体,Burgers体则是一个能同时描述线性损伤、硬化的模型。软岩蠕变过程中,其微观结构会发生变化,并导致软岩形变行为产生相应的改变,引入非线性损伤、硬化变量代替Burgers模型中的线性损伤、硬化变量,可以反映这种改变对软岩蠕变的影响。所建立的非线性蠕变模型可以用一个统一的方程描述软岩蠕变过程三个阶段的变形特征。将该模型与试验曲线进行对比,两者吻合较好。     

Development of a transparent triaxial cell and observation of rock deformation in compression and creep tests

A transparent triaxial cell was designed and manufactured using acrylic resin. The cell was used to conduct strength and creep tests. Photographs were taken of the specimens at constant time intervals during the constant strain rate test. Photographs were also taken at constant intervals of strain during the creep test, but this rate was changed to one image per second when the specimens first showed tertiary creep. Comparison of the axial and lateral strains during the constant strain-rate and creep tests indicated no significant differences between the two tests. It is well known that the axial creep strain rate is inversely proportional to remaining life in tertiary creep. This study showed that the lateral creep strain rate is also inversely proportional to remaining life. The constant strain-rate tests were conducted with transparent end pieces attached firmly to the upper and lower ends of the specimens. Three holes were drilled into the end pieces, and water was expelled into the holes when the specimens were compressed. It was clearly observed that the water began flowing from the holes back into the specimen during the volumetric expansion of the specimen. The transparent triaxial cell permitted easy observation of water ejection and re-absorption into the specimens.     

岩石拉剪流变特性的试验研究

根据岩石受拉及拉剪流变试验结果 ,研究了岩石受拉、拉剪流变特性 ,以及岩石受拉及拉剪强度。给出了岩石流变破坏曲线、拉剪破坏强度曲线 ,研究了岩石受拉强度、岩石流变等效抗拉强度和等效变形模量等 ,得出了几点有意义的结论     

TBM卡机围岩蠕变机理分析

利用国际通用的Burgur蠕变模型,计算了卡机事故与围岩蠕变之间的定量关系,深化了对第三系砂岩中TBM掘进卡机机理的认识,指出在第三系砂岩地层中,由于岩石固结成岩差、岩石强度低、遇水易软化,因此易发生卡机事故。     

岩石直接拉伸与压缩变形的循环加载实验与双模量本构模型

采用一种可对同一岩石试样进行单轴压缩和直接拉伸试验的岩石试样试验装置,对5种岩石进行了压缩和拉伸循环加载试验。结果表明,对于其中压缩平均变形模量ECA较拉伸平均模量ETA大得多的3种岩石(ECA/ETA分别等于2,2.5和6),拉伸下的卸载平均模量ETAUN远大于ETA,且ETAUN约等于ECA。因此,虽然这几种岩石压缩下的变形可近似视为弹性的,拉伸下的变形却是非弹性或塑性的。一些研究者对ET<相似文献   

滨海软黏土加速蠕变特性试验研究

为了研究滨海软黏土加速蠕变特性,采用典型的滨海相软黏土进行室内蠕变和加速蠕变试验,研究不同围压、加荷比、振动频率、动应力比对软黏土蠕变特性的影响,并通过对比得出了不同试验条件下滨海软黏土的加速蠕变的变化规律。试验结果表明:滨海软黏土具有非线性应力–应变关系的流变特性,其蠕变试验曲线呈衰减型,蠕变变形大部分应变量发生在蠕变前期,变形随时间增长趋于一个定值;静载作用下,围压越大初始蠕变速率越大。初始加荷压力一致,加荷比越大破坏应力越小。循环动荷载作用下,应变在动荷载阶段变化缓慢,而动荷载结束后进入稳定阶段后应变发生突变,急剧变大最后趋于稳定;此外在不同振动频率和动应力比下试样承受荷载等级不同,均存在一个临界安全荷载,超过这个临界值试样会发生蠕变破坏现象。     

平面变形超固结软黏土蠕变特征

通过对原状软土进行平面变形蠕变试验,研究超固结软土平面变形条件下的蠕变特征。研究表明,正常固结软土平面变形蠕变的体变过程,和一维变形条件下正常固结软土的次固结过程具有相同的规律,在主应力比与K₀状态相同时,相对于一维变形平面变形情况具有较小的轴向变形;平面变形条件下,采用土体受到的不同时期的体积球应力定义超固结比,能够全面地反映超固结软土的超固结特征;平面变形条件下,超固结软土蠕变的体积变形较正常固结状态明显减小,超固结比越大减小程度越明显,由超固结比确定体积蠕变系数具有合理性;平面变形在主应力比为K₀的状态下,超固结软土蠕变的轴向蠕变系数与超固结比负相关,由超固结比直接确定轴向蠕变系数是可行的;平面变形条件下土体的超固结应力历史,使超固结软土相对于正常固结状态具有较大的泊松比,在限制水平变形方向具有较大的主应力。     

Proposing a new model to approximate the elasticity modulus of granite rock samples based on laboratory tests results

Bulletin of Engineering Geology and the Environment - An accurate examination of deformability of rock samples in response to any change in stresses is deeply dependent on the reliable...     

蠕变围岩隧道的二衬支护时间研究

采用粘弹性方法对隧道施工过程中的力学动态进行了时间效应分析,探讨了二衬支护时间对围岩位移、初衬应力、二衬应力的影响,得出了Ⅴ级围岩隧道的二衬在开挖完60 d内施作较为合理的结论。     

Frictional sliding tests on combined coal-rock samples

A test system was developed to understand the sliding mechanism of coal-rock structure. The test system was composed by a double-shear testing model and an acousto-optic monitoring system in association with a digital camera and an acoustic emission （AE） instrument. The tests can simulate the movement of activated faults and the sliding in coal-rock structure. In this regard, instable sliding conditions of coal- rock samples, sliding types under different conditions, displacement evolution law, and AE character- istics during sliding process were investigated. Several sliding types were monitored in the tests, including unstable continuous sliding, unstable discontinuous sliding, and stable sliding. The sliding types have close relation with the axial loads and loading rates. Larger axial load and smaller loading rate mean that unstable sliding is less likely to occur. The peak shear stress was positively correlated with the axial load when sliding occurred, whereas the displacement induced by unstable sliding was uncorre- lated with the axial load. A large number of AE events occurred before sliding, and the AE rate decreased after stable sliding. The results show that the tests can well simulate the process of structural instability in a coal bump, and are helpful in the understanding of fault activation and the physical processes during squeezing process of roof and floor.     

饱和盐渍土的一维蠕变试验与模型研究

饱和盐渍土中土颗粒和孔隙盐溶液间相互的物理化学作用对土体的力学行为有较强的影响,使得盐渍土表现出不同的变形特性。为了能够准确地描述饱和盐渍土的这种相互作用,首先采用常规固结试验和恒载蠕变试验对通过蒸馏水、硫酸钠溶液和氯化钠溶液饱和后的重塑土样进行了试验研究。试验结果显示：盐渍土和非盐渍土的固结蠕变存在明显差异,此类现象会随着含盐量的增加而更加明显;而同含盐量的硫酸盐渍土和氯盐渍土的固结蠕变效应也不尽相同。其次,基于Yin-Graham一维蠕变方程,利用Pitzer离子相互作用模型和Van't Hoff渗透吸力方程,通过引入有效渗透应力,建立了饱和盐渍土的一维蠕变理论模型。最后,将改进的理论模型与试验数据进行了对比分析。结果表明,所提出的理论模型不仅能够描述饱和盐渍土中化学力学耦合,而且可以有效地预测一维蠕变行为。     

基于蠕变试验的橡胶沥青混凝土粘弹性分析

采用橡胶沥青混凝土小梁,在MTS810材料试验机上进行弯曲蠕变试验。通过对弯曲蠕变试验及其粘弹性进行分析可知,橡胶沥青混凝土的蠕变柔量较低,随着应力水平的增加,蠕变应变速率增长缓慢,具有较好的抵抗荷载变形能力。