Estimation of Penetration Rate in Percussive Drilling by Means of Coarseness Index and Mean Particle Size     

R. Altındağ 《Rock Mechanics and Rock Engineering》2003,36(4):323-332

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The mechanics of spall fracture in rock and concrete     

H. P. Rossmanith  K. Uenishi 《Fragblast: International Journal for Blasting and Fragmentation》2006,10(3):111-162

Spalling is a wave-induced dynamic fracture phenomenon. The waves can be either one: elastic, elasto-plastic, or shock waves. From a continuum mechanics point of view, fracture mechanics and wave propagation form the main ingredients in the formation of spalls. Recently, however, micro-structural effects have become important in the initial stages of spall formation in a variety of engineering materials ranging from metals to rock and concrete. From a structural geology point of view, the rock mass cannot be modelled as a continuum. In this case, a discontinuum approach has to be taken where the individual features of the rock mass such as joints and faults need to be taken into account. From an application point of view, spallation is important where rapid loading by explosives, impact, or energy deposition, occurs. The range of applications stretches from blasting in mining engineering to damage prevention to structures under explosive excitation.

This contribution offers a multi-faceted and multi-disciplinary approach to the study of spalling with special attention to analytical and experimental work. The reader is assumed to be somewhat familiar with the basics of continuum mechanics, fracture mechanics, and propagation of elastic, plastic and shock waves. The application to rock and concrete will show the effects of structural geological discontinuities such as open and closed joints - and to some degree also faulting - in rock, as well as the micro-structure of concrete on the (shock) wave field.

Extensive use will be made of time-space diagrams which proved very useful in practical applications to blasting problems [Rossmanith, H.P., 2002, The use of Lagrange diagrams in precise initiation blasting. Part I: two interacting blastholes, Fragblast 6, 104-136].  相似文献   

Determination of undrained strength of fine-grained soils by means of SPT and its application in Turkey   总被引：1，自引：0，他引：1  

O. Sivrikaya  E. To?rol 《Engineering Geology》2006,86(1):52-69

The Standard Penetration Test (SPT) is one of the oldest and the most common in situ test used in soil explorations. In the recent years with the advent of new technology and techniques in determining the drawbacks in SPT, several researchers have attempted to correlate corrected field measured values with several soil properties. In this context, corrections applied to field values have become critical. In this study a questionnaire including the performance of the standard penetration test and equipment used in practice in Turkey is circulated in order to determine the relevant correction factors. Thus the appropriate corrections are used in acquiring corrected SPT-N values. The relationships between SPT-N and the undrained shear strength (S_u) are examined from the statistical point of view by taking the test types and SPT corrections into consideration, and comparison is made with previous studies. It is observed that SPT corrections play an important role on the obtained correlation equations. In addition, the importance of the effects of test types on the correlations is also emphasized. The Standard Penetration Test is found to be sufficient for reliable assessment of S_u.  相似文献   

An ALE method for penetration into sand utilizing optimization-based mesh motion     

《Computers and Geotechnics》2015

The numerical simulation of penetration into sand is one of the most challenging problems in computational geomechanics. The paper presents an arbitrary Lagrangian–Eulerian (ALE) finite element method for plane and axisymmetric quasi-static penetration into sand which overcomes the problems associated with the classical approaches. An operator-split is applied which breaks up solution of the governing equations over a time step into a Lagrangian step, a mesh motion step, and a transport step. A unique feature of the ALE method is an advanced hypoplastic rate constitutive equation to realistically predict stress and density changes within the material even at large deformations. In addition, an efficient optimization-based algorithm has been implemented to smooth out the non-convexly distorted mesh regions that occur below a penetrator. Applications to shallow penetration and pile penetration are given which make use of the developments.  相似文献   

Resistant performance of perforation in protective structures using a semi-empirical method with marine applications     

C. -C. Liang  C. -Y. Jen  M. -F. Yang  P. -W. Wu   《Ocean Engineering》2003,30(9):1137-1162

To predict the performance of protective structures, in a preliminary design for weapons effects analysis processes considering the ship vulnerability evaluation, it is important to choose a method which is simple, quick and feasible. This paper presents a semi-empirical method to study the resistant performance of perforation in protective structures for fragment effects, such as residual velocity after penetration of structures between source of explosion and the target. In the calculation procedure, the mass distribution of fragments is obtained by expressing Mott’s equation, the initial and striking velocities are calculated using Gurney’s formulas and the residual velocity is estimated using Baker et al.’s equation. Using experimental results from the literature, Woodward’s test data (1978) and Edwards and Mathewson’s experimental data (1997) are employed to verify the ballistic limit velocity, and Rupert et al’s test data (1997), Sorensen et al’s test data (1999) and Yarin et al’s test data (2000) are adopted to check the residual velocity. An example of a 500-ton patrol-boat’s hull and bulkhead is also discussed. The results of the verification are good in terms of agreement, and impact velocities of this study varies from 1500 m/s to 2000 m/s, the ratio of L/D ranges from 6 to 10 and the ratio (h/D) varies from 2.0 to 11.0, may serve as a useful reference for designers.  相似文献   

Analysis of spatial variability of SPT penetration resistance in collapsible soils considering water table depth     

Rodolfo M. Mendes  Reinaldo Lorandi 《Engineering Geology》2008,101(3-4):218-225

Geostatistical kriging approach was used for mapping of water table depth and for checking its influence on penetration resistance observed in standard penetration test (SPT). Geostatistical mapping was based on a compartmentalisation of 204 SPT records in two main groups using monthly and yearly rainfall marks as a segregation criterion. Six maps produced at 1:10,000 scale were achieved as follows: water table depth variation and penetration resistance variation at the depths of 1.5, 6.0, 8.5, 11.0, 13.5 m. Greater variations of the penetration resistance, in terms of increase and reduction of resistance, were observed at the depths of 6.0 and 8.5 m.  相似文献   

Three-dimensional RITSS large displacement finite element method for penetration of foundations into soil     

L. Yu  J. Liu  X.J. Kong  Y. Hu 《Computers and Geotechnics》2008,35(3):372-382

The Remeshing and Interpolation Technique with Small Strain (RITSS) approach has been developed to deal with 3-D geotechnical problems in this paper. Unstructured 20-node hexahedral element is found to work well for predicting collapse loads accurately for 3-D undrained geotechnical problems involving material incompressibility. Remeshing is automatically accomplished by ANSYS program. With remeshing and interpolation, small fluctuations appear in the load–deformation results. In order to minimize these fluctuations, different increment sizes and remeshing frequencies are explored. Meanwhile, various 3-D interpolation methods are compared, and the unique element division method is found to work best. The results of two numerical applications are presented for a 3-D strip footing penetrating deeply into uniform clay and a square foundation into normally consolidated clay. The computed bearing capacity responses are compared with other numerical or conventional results. The results show that the present method is accurate and efficient for 3-D large displacement foundation penetration problems.  相似文献   

Centrifuge modelling of SCR vertical motion at touchdown zone     

H.J.E. Hu  Y.K. Chow  A.C. Palmer 《Ocean Engineering》2011,38(7):888-899

Steel catenary risers (SCR) connect seabed pipelines and flow lines to floating structures used for oil and gas production in deep waters. Waves and currents induce motions of the structure and the risers. The repeated motions of the risers at the touchdown zone in turn induce loads on the seabed soil and might eventually cause fatigue damage to the risers. The analysis of riser fatigue damage is heavily dependent on the soil model. Soil behaviour at touchdown zone such as soil remoulding, stiffness degradation and deformation of the seabed at the touchdown zone further complicate the accurate assessment of riser fatigue damage, which is currently not appropriately quantified in existing design methods. This paper presents centrifuge model tests simulating the repeated vertical movement of a length of riser on clay seabed with increasing undrained shear strength with depth. During the tests, the pipe was subject to cyclic motion over fixed vertical displacement amplitude from an invert embedment of 0.5-3.5 pipe diameters into the soil. The test results show a significant progressive degradation of soil strength and diminution of excess pore water pressure with increasing number of riser penetration/uplift cycle. In view of the different types of environment loadings experienced by floating platforms and various soil conditions, tests were also conducted to investigate the effect of soil strength, riser displacement rate and loading mode on riser-soil interaction during repetitive penetration/uplift motion of the riser.  相似文献   

Penetration depth of the dynamic response of seabed induced by internal solitary waves     

《Applied Ocean Research》2019

We use flume experiments and numerical modeling to examine the penetration depth of internal solitary waves (ISWs) on partially saturated porous sandy silt and clayey silt seabed. The results of the experiment and model showed that the instantaneous excess pore water pressure in both the sandy silt and clayey silt seabed followed the same trend of decreasing with the seabed depth. In general, the excess pore water pressure generated by the sandy silt was bigger than that by clayey silt at the same depth. The ISW-induced excess pore water pressure greatly influenced the surface seabed and showed a linear relationship. The penetration depth was approximately one order of magnitude smaller than the half-wavelength of the ISWs, which might be larger than the penetration depth induced by surface waves. Our study results are helpful for understanding the damage that ISWs inflict upon the seabed and for informing future field experiments designed to directly measure the interaction between ISWs and seabed sediments.  相似文献   

海床式静力触探在黄河口海底土工程特性研究中的应用          下载免费PDF全文

楚立鹏  孙永福  宋玉鹏  董立峰  周其坤  马彬彬  张伟朋 《海岸工程》2017,36(1)

海床式静力触探设备工作效率高,能够实现从垂向上对地层的连续探测,数据分辨率较好。通过对黄河口海域3个静力触探孔和1个地质钻孔的分析,将研究区20m以浅地层自上而下划分为粉土、粉质黏土、粉土夹粉砂或粉砂、粉质黏土、粉土五层,静力触探曲线对粉土层中的硬壳层和粉质黏土层中的贝壳夹层等特殊地质现象有很好的反映。对粉质黏土的静力触探参数与物理力学参数进行相关性分析,得到适合该区域的回归方程。采用基于CPT数据的液化判别法,对研究区表层粉土液化可能性进行评判,通过Seed简化法计算的周期应力比(CSR)与Olsen法计算的周期阻力比(CRR)的大小比较,得出当抗震设防烈度为7度时,研究区表层粉土不会液化,当抗震设防烈度为8度时,粉土层将发生液化,计算最大液化深度3.7m。  相似文献