Numerical investigation of thermal spallation drilling using an uncoupled quasi-static thermoelastic finite element formulation

Tan

European Journal of Remote Sensing

2020

Thermal-jet for water Measurement spallation is a rock removal process that utilizes induced thermal stress to fracture the rock into small fragments before melting of the rock occurs. Because of the low conductivity, thermal stress will be created on the rock surface. When the thermal stress exceeds the strength of the rock, cracks will form and expand. Eventually, rocks disintegrating into small fragments. The simulation result obtained by the Crank-Nicolson method of the temperature field and the distribution of thermal stress has been analyzed. The result indicates that during thermal spallation drilling, the temperature of the surface exposed to the thermal-jet for water Measurement rises rapidly and create temperature gradients in both radial and axial directions. Because of volume expansion, the heated part is subjected to compressive stress in radial direction and shear stress in axial direction, respectively. The result is very helpful to the field application. ARTICLE HISTORY

Section: Establishment and Solution Of Thermal Cracking Drilling Modelmentioning

confidence: 99%

Section: Establishment and Solution Of Thermal Cracking Drilling Modelmentioning

confidence: 99%

RETRACTED ARTICLE: Numerical simulation of temperature field and temperature stress of thermal jet for water measurement

Tan

European Journal of Remote Sensing

2020

“…Therewith, it is possible to spatially and temporally resolve the spallation process [ Kant and Rudolf von Rohr , ]. A uniaxial pressure p orthogonally to the front surface was applied to the rock cores during the spallation experiments with the confining system proposed by Hoeser et al [ Hoeser , ; Meier et al , ]. In this system, the rock core is placed between two metal flanges.…”

Section: Preliminary Validation With Central Aare Granitementioning

confidence: 99%

A theory on thermal spalling of rocks with a focus on thermal spallation drilling

et al. 2017

Thermal cracking of rocks is an intensively studied topic in different research areas and for various engineering problems. In this context, we present a modeling approach which describes thermal spalling of rocks with a focus on thermal spallation drilling. This drilling technology uses high thermal loads to locally destruct the surface of the rock formation. With the presented model, the operating conditions which are required to initiate spalling of rocks can be estimated. Additionally, a Spallability number is introduced allowing a categorization of rocks according to their ability to spall. The presented model is based on linear fracture mechanics and the stress intensity concept. It evaluates if a crack with a certain geometry embedded in a rock with specific properties propagates during exposure to different heat loads and external pressures. Thereby, rapid heat transfer processes are coupled with induced thermal stresses and fracture mechanics in rocks.

“…At present time problems related to the spallation and destruction of materials are of most interest [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Experimental study for the process of the borehole thermal reaming by means of the angular plasmatron

et al. 2019

Full-scale experimental study of the rock spallation by means of plasma jets is carried out. The aim of the experimental study was the measurement of the thermal power of plasma, weight of the rock spalls and duration of the plasma jets influence on the borehole surface. For the weight measurement of the rock spalls VT-200 analytical balance was used. In experimental study plasma jets flow out directly into the borehole of the granite block. The borehole and nozzles parameters of the plasmatron are complied with geometrical similarity. Experimental data are processed in the form of the energy consumption dependence of the thermal reaming of the borehole from the duration of the thermal treatment of the borehole surface. The results of the study could be applied to the borehole drilling processes.