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。     

自钻式旁压试验中邻近腔壁土的应力路径分析

 采用剑桥自钻式旁压仪对邻近膨胀腔壁土的应力–应变进行研究。根据自钻式旁压试验的特点和腔室膨胀理论,假设试验过程中土只发生小变形,土为弹性–完全塑性材料。基于以上假设,对试验过程的应力路径进行理论推导,并与试验得到的应力路径对比分析,结果表明：两者在弹性阶段差异较大,塑性阶段较为一致;非线性和线性两种理论分析方法相比,前者推导的应力路径理论曲线与试验确定的应力路径更为接近。此外,根据试验确定的应力路径曲线,可以分析土的应力变化,判定土的应力历史,推导土性参数。     

基于原位测试的土体参数研究

文中通过对某基坑工程回填土样开展室内试验和钻孔触探试验,系统研究了工程原位土体的力学相关参数随土体含水率和压实度变化的情况。结果表明,在含水率和压实度发生变化的情况下,土体的无侧限抗压强度、黏聚力和内摩擦角呈现特定变化趋势,钻进参数的变化趋势与土体的无侧限抗压强度、黏聚力的变化趋势基本一致;通过多元线性回归分析建立了扭矩、钻压与土体参数之间的关系模型,并在实际场地测试中验证了该模型的可靠性和准确性。本研究为回填土的力学参数提供了实用的测试和分析方法。     

玄武岩残积土综合原位测试与分析研究

受风化环境和成因的影响,未经水平运移的残积土结构性较强,扰动取样后的室内试验无法真实反映残积土的力学性能。在贵州玄武岩地区进行了原位旁压试验、动力触探和高密度电法试验,分析得到了残积土的原位力学参数的空间分布特征。试验结果表明:水平旁压模量EH与竖直旁压模量EV差值在15%左右,两方向的旁压模量相关性较好;该残积土边坡不同位置同一深度处力学参数差别较大;旁压试验所推算的旁压模量Em及地基承载力fk等参数在垂向上均随深度增加逐渐增大;通过高密度电法与旁压试验的对比,可在一定程度上了解残积土边坡力学参数的空间分布;将动力触探击数与旁压试验推算的地基承载力作对比,得出了该地区动力触探击数推算地基承载力的经验公式。     

岩体力学参数确定方法研究

结合理论及实践成果,研究探讨了岩体力学参数的确定方法,方法大致有：室内试验、现场试验、位移反分析、现场工程地质调查和室内计算等,从而准确确定岩体参数,保证模型计算结果的正确性。     

福州地区静力触探与旁压试验地基承载力计算对比研究

依托福州市在建轨道交通工程勘察项目进行静力触探试验、旁压试验现场比对,采用数理统计、相关分析,得到静力触探试验、旁压试验地基承载力计算的变异情况和相关程度。经过对比分析,提出福州地区静力触探试验地基承载力计算推荐公式,取得福州地区预钻式旁压试验地基承载力特征值修正系数经验值,供岩土工程从业人员参考。     

冻融循环作用下砂岩的力学特性及细观损伤本构模型研究

针对寒区岩体工程中岩石的冻融问题,选取砂岩为试样,通过进行室内冻融循环试验、扫描电子显微镜观测和三轴压缩试验对砂岩质量损失、微观结构和力学特性进行了分析。然后基于Lemaitre应变等效假设理论,通过引入能够反映岩石冻融破坏过程中的细观冻融损伤变量和力损伤变量来描述岩石材料的劣化程度及损伤演化规律,并采用连续损伤力学理论,建立了冻融与围压耦合作用下岩石的损伤演化方程及细观损伤本构模型。采用理论推导的方法得出所需的模型参数表达式,最后利用冻融岩石的三轴压缩试验数据对该模型的合理性和准确性进行了验证。将试验曲线的峰值点与模型理论曲线的峰值点进行对比,结果表明两者吻合度较好,该损伤本构模型能够较好地反映岩石三轴压缩过程的应力-应变峰值特性,验证了该模型及模型参数确定方法的合理性与可靠性。该模型拓展了岩石在冻融与围压耦合作用下的损伤模型,进一步的揭示了岩石在冻融与围压耦合作用下的损伤机制和破坏规律。     

钢钎静探在路基勘察中的试验研究

钢钎静探是近期出现的一种便携式新型勘探设备,具有地层划分及直接测试贯入地基反力等勘探功能,为验证地基贯入反力与静力触探比贯入阻力Ps之间的转换关系,以无为某公路项目为依托,将钢钎静探引入到路基勘察中,同时开展钢钎静探与静力触探、麻花钻及室内试验成果对比试验研究,对钢钎静探与单桥静力触探试验Ps～h曲线、地层划分及确定地...     

用简单原位试验确定切线模量法的参数及 其在砂土地基非线性沉降分析中的验证

地基沉降计算一直是岩土工程研究中的热点和难点问题,其困难在于室内试验与原位岩土参数差异较大,尤其是砂土地基和结构性强的硬黏土地基,基于室内试验参数的沉降计算与实际的误差较大。基于原位压板载荷试验来确定计算参数的切线模量法能克服这个缺点,并能计算地基的非线性沉降,是地基沉降计算的一个新进步。但原位压板载荷试验相对其他试验难度大、费用高,尤其对于深层土体,难度更大。为此,利用位于美国Texas A&M University大学河滨校区砂土地基上进行的系统的岩土试验资料,通过其不同压板尺寸的载荷试验,对切线模量法应用于砂土地基非线性沉降计算的适用性进行了验证,然后进一步研究由旁压试验、静力触探等简单的原位试验确定切线模量法所需的计算参数的可行性。结果表明：切线模量法所需的计算参数由旁压试验、静力触探等简单的原位试验确定是可行的,从而为切线模量法的推广应用确定提供了更简单的方法。对推动地基设计理论的发展有较好的意义。     

四川某水电站坝基不均匀持力层承载力研究

四川某电站坝基位于厚层含漂(块)卵(碎)石层之上,存在结构及颗粒组成不均匀的特点,采用单一原位测试手段难于全面反映其力学特性,本工程通过超重型动力触探试验、预钻式旁压试验、浅层平板载荷试验的对比分析,综合选定了持力层承载力参数,对类似工程有一定的参考作用。     

An analytical drilling model of drag bits for evaluation of rock strength

To evaluate the unconfined compressive strength (UCS) of rocks from drilling data is a promising in-situ method and has been studied by many researchers. In most studies, experimental methods have been used to determine the relationship between UCS and drilling data. In this paper, an analytical model is proposed to describe rock drilling processes using drag bits and rotary drills, and to deduce the relations among rock properties, bit shapes, and drilling parameters (rotary speed, thrust, torque, and stroke). In this model, a drilling process is divided into cycles, each of which includes two motions: feeding and cutting. Feeding is treated as an indentation motion. There is a linear relation between indentation pressure (thrust) and the indentation depth (penetration rate). The cutting forces and friction forces of both the rake surface and the flank surface are examined. Also, a virtual base is set to the model to simulate the contact surface between the flank surface of the bit and the rock.According to this model, drilling torque consists of four parts respectively generated from cutting, friction, feeding, and idle running. Torque caused by friction and idle running is ineffective for drilling, whereas that caused by cutting and indentation is effective. Similar to torque, specific energy also has four parts respectively from cutting, friction, feeding, and idle running. For the purposes of this study, effective specific energy is defined as the sum of specific energy consumed by cutting and feeding. Effective specific energy is independent of the penetration rate. Since it is proportional to the UCS of the rocks, it is not influenced by the penetration rate, and is more useful in the evaluation of UCS than other parameters. Some laboratory and field tests were conducted, and the results verified the usefulness and effectiveness of the proposed model.     

应用旋转触探试验划分地层及确定土类定名方法研究

旋转触探作为一种新型原位测试技术已通过生产实践检验并在岩土工程勘察中逐步推广,然而有关其工程化应用问题尚有待完善。本文通过在京津城际线、京沪高铁线桩基试验点、邯郸至黄骅铁路线等地开展现场旋转试验,并将所得旋转触探试验结果与相应点位的静力触探及钻孔化验资料进行对比分析,初步总结出应用旋转触探试验结果划分地层、确定土的定名方法的一些规律,所得结果为推动旋转触探工程化应用提供了重要依据。     

Investigation of active vibration drilling using acoustic emission and cutting size analysis

This paper describes an investigation of active bit vibration on the penetration mechanisms and bit-rock interaction for drilling with a diamond impregnated coring bit. A series of drill-off tests (DOTs) were conducted where the drilling rate-of-penetration (ROP) was measured at a series of step-wise increasing static bit thrusts or weight-on-bits (WOBs). Two active DOTs were conducted by applying 60 Hz axial vibration at the bit-rock interface using an electromagnetic vibrating table mounted underneath the drilling samples, and a passive DOT was conducted where the bit was allowed to vibrate naturally with lower amplitude due to the compliance of the drilling sample mountings. During drilling, an acoustic emission (AE) system was used to record the AE signals generated by the diamond cutter penetration and the cuttings were collected for grain size analysis. The instrumented drilling system recorded the dynamic motions of the bit-rock interface using a laser displacement sensor, a load cell, and an LVDT (linear variable differential transformer) recorded the dynamic WOB and the ROP, respectively. Calibration with the drilling system showed that rotary speed was approximately the same at any given WOB, facilitating comparison of the results at the same WOB. Analysis of the experimental results shows that the ROP of the bit at any given WOB increased with higher amplitude of axial bit-rock vibration, and the drill cuttings increased in size with a higher ROP. Spectral analysis of the AEs indicated that the higher ROP and larger cutting size were correlated with a higher AE energy and a lower AE frequency. This indicated that larger fractures were being created to generate larger cutting size. Overall, these results indicate that a greater magnitude of axial bit-rock vibration produces larger fractures and generates larger cuttings which, at the same rotary speed, results in a higher ROP.     

基于旋挖桩随钻参数的地层识别方法

旋挖钻机钻进参数是在钻进过程中分析钻进情况的基础数据。地层结构的变化必然使钻进参数发生变化,进而使旋挖钻机显示出与不同埋置深度地层相适应的动态特征。采用旋挖钻机随钻检测与控制系统,对钻进过程中的直测参数和派生参数进行采样和分析,根据钻机工作参数和地层岩土体物理力学参数的固有特性、统计特性、结构特性,建立单一指标到多指标的地层识别模型,把地质条件和钻机的工况参数联系起来,利用钻机的转速、扭矩、钻进压力预估岩石抗压强度和土质地基承载力,并与一桩一孔勘察结果进行对比,证明基于随钻参数的持力层判定方法的有效性。     

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.     

取土引孔在静力压桩工程中的应用

在静力压桩工程中,由于静压桩对坚硬土层和厚砂层中穿透能力差,经常遇到桩长达不到理想持力层的状态,对桩基础工程的质量有一定的影响。通过采用介绍取土引孔厂房静力压桩的实践中取得成功,对同类工程有一定的借鉴和参考作用。     

旋挖法在铁路特大桥钻孔灌注桩施工中的运用

随着铁路客运专线施工的迅速发展,旋挖法施工钻孔灌注桩在铁路特大桥梁工程中得到广泛运用。该施工方法主要特点是施工效率高、质量好、环境污染少、噪音低,是一种较先进的钻孔桩施工方法。文章结合具体工程介绍旋挖法在铁路特大桥钻孔灌注桩施工中的运用。     

硬岩地层旋挖钻进组合工艺的研究与应用

根据旋挖钻进施工存在的主要问题,将旋挖工法依据岩石硬度进行量化钻进分类,提出硬岩钻进概念,并对当前硬岩钻进组合工艺进行分类、比较。同时介绍新型取芯筒钻的结构特点和操作规程。结果表明,新型取芯筒钻不仅解决了旋挖钻进硬岩组合工艺取芯的技术难题,而且丰富了旋挖硬岩钻进组合工艺。     

深杂填土区钻孔灌注桩后压浆施工技术

针对深杂填土区存在成孔困难、桩基承载力不足的问题,提出旋挖钻机配合潜水钻机的成孔方法,并采用钻孔灌注桩后压浆施工技术提高桩基承载力。详细阐述了后压浆灌注桩的技术参数、施工工艺和异常问题的处理,并对其施工效果进行了分析和总结。结果表明,旋挖钻机配合潜水钻机能够解决深杂填土区成孔困难的问题;该技术极大地提高了桩基承载力,确保了结构的整体沉降安全,可有效提高经济效益。