基于静力触探的不同压力段土体压缩模量确定方法研究

静力触探技术具有测试资料连续、重复性好、测试速度快、劳动强度低及经济效益高等优点,已在许多国家广泛应用,并在工程勘察中占有重要地位,然而在应用静力触探成果确定土体压缩模量工程化应用方面尚待进一步完善。本文通过开展深层双桥静力触探及其相应点位的土体固结试验,将所得静力触探试验结果与相应点位的不同压力段土体压缩模量进行综合对比分析,归纳总结出适用于天津地区的基于静力触探确定各土性不同压力段土体压缩模量的经验公式,所得研究成果可为相关工程提供参考,并推动静力触探技术工程化应用进程。     

标准贯入试验和双桥静力触探试验在饱和吹填砂液化判别中的对比分析

通过标准贯入试验和双桥静力触探试验,对某工程场地饱和吹填砂进行液化判别,结果表明双桥静力触探试验液化判别计算所得液化指数与锥尖阻力基准值取值有关,且总体高于标准贯入试验计算所得液化指数,双桥静力触探试验液化判别结果更偏于安全;结合吹填砂的特点,建议饱和吹填砂液化判别采用标准贯入试验与静力触探试验相结合的综合评价方法。     

基于扁铲侧胀和静力触探参数的桩基数值模拟

桩基础的承载力和变形性状与周围土体的岩土力学参数直接相关,扁铲侧胀试验和静力触探试验提供大量可靠的土体原位测试参数。分析桩径为0.4 m、桩长为12 m的长螺旋桩的工程性状,对桩基进行静力载荷试验,并与扁铲侧胀试验参数和静力触探试验参数进行三维有限元数值对比分析,结果表明两者具有一定的差异性,无论是极限桩基承载力还是沉降量,以扁铲侧胀试验所得参数进行的数值模拟与静力载荷试验结果较为接近,而以静力触探试验所得参数进行的数值模拟与静力载荷试验结果相比略大。     

旋进式触探机制研究

 通过切削机制的引入,对角片式探头切削刃的受力进行分析,除建立轴向负荷与扭矩之间的数学模型外,还建立作用在探头上轴向负荷、扭矩与探头的运行参数(探入速度和旋转速度)及岩土体物理力学参数间的数学模型,并通过室内试验验证数学模型的存在性。根据数学模型分析轴向负荷、扭矩的影响因素,明确旋进式触探技术的理论依据：当机械运行参数,探头直径、材料及型式都相同时,轴向负荷和扭矩只与岩土体物理力学性质有关。将静力触探的轴向负荷与旋进式触探进行比较,从根本上解释旋进式触探技术能在岩体中得到应用的原因。     

静力触探在软土砂性岩土工程中的勘察优势

静力触探作为一种用于工程勘察的原位测试方法,由于具有快速、精确、经济和节省人力等优势,在软砂性岩土工程勘察工程中得到了有效而广泛的应用。本文通过静力触探在松江区某老镇改造项目岩土工程勘察中的应用,对静力触探测试特点、主要研究理论进行了初步介绍,并通过对比静力触探测试与钻探取样室内试验,显示了静力触探勘察的明显优势。     

轻便动探在检验粉喷桩质量中的应用

通过轻便动力触探试验和现场静载荷试验所得数据的对比初步得出通过N10击数判断粉喷桩体强度和搅拌均匀程度的标准。     

静力触探试验的离散元数值模拟研究

由于静力触探试验的可重复性及可靠性,它在现场试验中被广泛应用。对静力触探试验进行颗粒流模拟,有助于从细观上了解静力触探试验机理,使之更好地服务于工程实际。颗粒流方法在模拟土体大变形方面具有一定的优势,本文利用颗粒流理论及其程序,首先在双轴试验的基础上确定了土样细观参数,然后建立静力触探的数值模型,模拟研究了贯入过程及锥尖土体的细观力学特征,重点分析了静力触探过程中砂土的位移运动规律,砂土的水平和垂直应力场及主应力的偏转。通过施加不同的应力边界条件,分析了模型不同的应力条件及超固结比(OCR)对锥尖贯入阻力的影响。同时,分析了锥尖尺寸效应对锥尖贯入阻力的影响规律。数值模拟结果与已有的试验规律具有较好的一致性,从而验证了颗粒流方法模拟静力触探试验的可行性,所得结论具有一定的理论价值和工程意义。     

孔压静力触探试验的应用

本文简要地介绍了孔压静力触探试验在国内的应用现状。文中包括５项内容：①探头的性能及操作；②土分类图的检验及由此所得土层柱状图的可靠性；③固结系数的确定及其与室内试验、现场原位观测推求值的比较；④利用孔压静力触探试验指标进行沉降量的计算；⑤判定土结构性的可能性。上述内容以三个工程实例加以说明     

振动辅助式静力触探可行性试验研究

振动辅助式静力触探是我院提出的一种新型静力触探原位测试方法,是在现有传统静力触探基础上,通过增加振动力穿越深层密实粉土、砂土层的触探方法。为验证该技术的可行性,我院课题组针对性地设计了不同的试验装置,采用两类四种能量不同的振动源进行了场地试验,选取了典型分布的不同深度、不同密实度的三层粉土、粉砂土层进行试验,在试验过程中记录了每贯入10cm对应的锤击数,对振动贯入效果进行了定量与定性分析,得出了振动辅助式静力触探技术的可行性结论,推荐了后续改装应用的有效振动源类型,为后续集成式仪器的研发提供了试验依据,通过本次试验,为静力触探技术向更深的土层应用提出了一个新方向。     

含裂隙岩体点触探破坏机制研究

岩石点触探试验是间接评估岩体力学特性的重要方法，在其原位应用过程中，岩体的触探特性会受到原位裂隙的重要影响。为了明确岩体裂隙对点触探试验的影响范围，揭示含裂隙岩体点触探的破坏机制，量化不同裂隙对点触探指标的影响，进行一系列含裂隙岩体的室内点触探试验，并通过数值模拟对其破裂机制进行了研究。试验结果表明：点触探加载点下方的影响区域内存在裂隙时会改变点触探破坏模式和强度特性。当裂隙延伸至加载压头附近时，点触探加载下岩体会发生从加载点向该裂隙端部的剪切破坏，裂隙内端的位置决定了点触探的强度及裂纹扩展路径，基于剪切破坏的极限平衡原理可建立点触探强度与剪切路径的对应关系。为了进一步阐明含裂隙点触探破裂规律，通过数值模拟分析了裂隙内端延伸至压头附近不同区域条件时点触探特性，根据破坏模式界定了触探加载点下方的裂隙影响范围，通过定义弱化系数量化了影响区域内不同裂隙对点触探强度的影响程度。同时基于岩体裂隙扩展路径耗能规律，对多裂隙条件下的点触探破裂特性进行了探讨。     

砂桩处理高速铁路软基质量检验研究

通过砂桩处理高速铁路软土地基的现场试验,采用静力触探、重型动力触探、复合地基载荷试验、标准贯入试验检验方法,对砂桩质量检验进行了系统的研究,提出了满足高速铁路软土地基处理质量要求的质量检测手段和频度。     

花岗岩残积土基床系数的求取——以深圳华润、地铁2号线等工程为例

基床系数是隧道、基坑设计的重要参数,一般要求采用K_(30)载荷板试验求取,但受场地、安全等因素制约,K_(30)载荷板试验往往很难进行,本文通过取土室内试验、标准贯入试验、重型动力触探试验、旁压试验、螺旋板载荷试验等较易实现的手段求取基床系数,并与现场K_(30)试验值进行对比,验证了各种原位测试求取基床系数的有效性,对花岗岩残积土基床系数的求取有一定借鉴作用。     

Evaluation of Undrained Shear Strength of Soils from Field Penetration Tests

The evaluation of undrained shear strength of soils is necessary in determining the possibility of occurrence of flow deformation during earthquakes. The present study is aimed at examining the evaluation of undrained shear strength of silty sands from field with Swedish weight sounding tests and cone penetration tests. Based on the outcome of the previous studies on laboratory triaxial tests, the undrained shear strength ratio is defined as the undrained shear strength divided by the initial effective major principal stress. The undrained shear strength ratio is then formulated with respect to the relative density. The penetration resistances of Swedish weight sounding and cone penetration tests are then formulated with respect to the effective overburden stress and relative density, based on laboratory calibration chamber tests. By combining these formulations, the correlations of the undrained shear strength with Swedish penetration resistance and cone tip resistance are established. The range of values of penetration resistances indicative of soil layers susceptible to flow deformation is discussed. The correlations of the undrained shear strength with field penetration resistances thus derived are then examined from case history studies. Two case history studies are carried out with Swedish weight sounding tests at the sites of flow failures induced during the recent earthquakes. A series of case history studies are reexamined, which were carried out with Dutch cone penetration tests in the past studies.     

Field study on swelling-shrinkage response of an expansive soil foundation under high-speed railway embankment loads

This paper presents a comprehensive field investigation of the swelling-shrinkage behavior of an expansive soil ground under high-speed railway embankment loads. In this study, a test site close to the Kunming-Nanning high-speed railway (KNHR) was chosen for the construction of four full-scale field test facilities for artificially soaking the expansive soil ground. Three of the facilities consist of embankments of three different heights, while the fourth facility is for a series of plate load swelling tests. All the test embankments were fully instrumented to monitor the ground deformation and the changes in volumetric water content profiles of the foundations. The full-scale field tests were complemented by a detailed site investigation comprised of cone penetration tests (CPTs), standard penetration tests (SPTs) and a comprehensive laboratory characterization of intact expansive soil samples retrieved from the test site. The results obtained from the laboratory and field tests show that the swelling behavior of the expansive soil ground mainly depends on the embankment load. By properly designing the embankment height and considering the maximum swelling pressure the expansive ground could induce, the heave of the embankment could be controlled efficiently. The measured displacements at the ground surface are well correlated with the evolution of measured volumetric water contents within a ground depth of around 4.5?m. The majority of these displacements occurred when the ground was approaching saturation along both wetting and drying paths. Finally, a simple method based on one-dimensional test results was proposed, and a good performance was shown in predicting the heave or settlement of embankments over an expansive soil ground upon wetting and drying.     

振冲碎石桩在软弱液化地层中应用试验研究

某拟建电厂工程通过采用振冲碎石桩复合地基的处理方法,开展了软弱液化地基治理的现场试验研究,试桩施工结束后,采用载荷试验、标准贯入试验、土工试验、超重型动力触探试验等原位测试方法,对桩间土、桩体及复合地基的承载性能、变形参数及液化处理效果进行了评价和分析,取得了大量可靠的试验数据,对类似工程具有一定的参考价值。     

砂性土地基中静压PHC管桩施工

密实砂层中的静力触探和标准贯入试验表明,将PHC管桩静力压入砂层地基中极为困难。郑州市某住宅工程中,经方案比选采用大密度泥浆护壁预引孔静压沉桩技术,经检测管桩各项技术指标满足设计要求。     

基于回转切削的岩石力学参数获取新思路

 基于回转钻探和静力触探试验的综合优势,开发并进行系统地旋进式触探试验,在室内试验和理论推导的基础上进一步验证。从旋进式触探机制入手,根据切削、静压及钻压作用过程建立旋进式触探试验参数钻压、扭矩与每转进给量之间的关系曲线,结合室内试验成果进而以曲线斜率和钻削理论为依托推导出岩石的抗压强度、弹性模量、内摩擦角及黏聚力的计算公式。以粉煤灰砌块旋进式触探试验成果为例,按上述方法计算试样4大基本力学参数,与试验实测值进行验证。结果表明计算值与室内实测的基本力学参数值比较接近,论证了该方法的可行性和后续研究的可期待性。     

Prediction of the penetration rate of rotary blast hole drills using a new drillability index

Rotary blast hole drills were observed in several formations at different open pit mines and quarries. Rock samples were collected as near as possible to drilling locations and mechanical and physical properties of the total 22 rock samples were determined. Indentation tests were carried out on the block samples from the same formations. A new drillability index for the prediction of the penetration rates of rotary blast hole drills and the mechanical and physical properties of the rock formations was defined from force-indentation curves of indentation tests. A penetration rate model for rotary for blast hole drills was developed using this drillability index. It was seen that the model was valid for the formations having uniaxial compressive strength over 40 MPa and especially for carbonaceous rocks.The drillability index exhibits a significant correlation with the proportionality constant k defined in the model. It is also seen that significant correlations exist between the drillability index and rock properties suggesting that the proposed model may be used universally to estimate the penetration rate of rotary blast hole drills.     

高压旋喷桩处理铁路软弱地基施工技术

结合广珠铁路SG5标段软基处理工程,介绍了采用高压旋喷桩处理铁路软弱地基的施工工艺,具体阐述了施工过程中的安全控制以及质量检查方法,积累了施工经验,为类似工程提供了技术参考。