This paper presents an experimental study in which molded gypsum specimens with different crack geometries (T-shaped and X-shaped cross crack) were tested biaxial compression. Crack propagation failure behaviors investigated nine types detected, namely, wing crack, antiwing secondary horizontal quasi-coplanar far-field surface spalling, lateral split crack. Moreover, first observed the rocklike specimens, was caused by added confining pressure. Besides, cracks modes under uniaxial...

The mechanical parameters of surrounding rock are an essential basis for roadway excavation and support design. Aiming at the difficulty in obtaining large experimental errors, optimized BP neural network model is proposed this paper. mind evolutionary algorithm can adequately search optimal initial weights thresholds, while has advantage strong nonlinear prediction ability. So, (MEA-BP model) takes two models. It not only avoid local extreme value problem but also improve accuracy...

There is a high risk of ground collapse during the construction closely spaced overlapping metro tunnels in sensitive environments. When pass beneath important structures such as high-speed railway (HSR) bridges whose deformation controlling standard extremely strict, special reinforcement measures should be implemented. This paper investigated stability control for and passing HSR bridge based on engineering project Jinan R1 Metro line China. The sources difficulties were analyzed. Further,...

In order to study the mechanism and control technique of deep roadways in faulted zones, 11-2 transport roadway Guqiao coal mine Huainan was taken as a case. The research encountered two faults named F97 F98 suffered severe large deformation disaster (including floor heaving, side cracking, steel arch bending, section shrinkage) after excavation. Then, laboratory tests, situ stress measurement, numerical simulation results indicate that lower strength easy soften property surrounding rock is...

A novel in situ stress monitoring method, based on rheological recovery (RSR) theory, was proposed to monitor the of rock mass deep underground engineering. The RSR theory indicates that tiny hole can close gradually after it drilled due rheology characteristic, during which process existed be monitored real-time. Then, a three-dimensional sensor, vibrating wire technique, developed for field measurement. Furthermore, in-field procedures technique are introduced, including drilling, sensor...

Commonly used methods of measuring rock stress, including hydraulic and borehole relief methods, are difficult to apply in deep soft masses. This study proposes a new method measure stress by taking advantage the strong rheological behavior Rock stresses can be gradually measured over time embedding pressure transducers into masses; this accomplished with newly developed vibrating-wire transducer that monitor three orthogonal normal stresses. Based on elastic theory, derives relationship...

The time-temperature-stress equivalent (TTSE) principle refers to the phenomenon that time-dependent mechanical properties of materials rely on variations temperature and stress level. Thus, it is reasonable predict long time material based their relationships with rising temperatures levels. According single-integral nonlinear constitutive equation proposed by Schapery, a general expression TTSE for viscoelastic creep property deduced. specific shift factor presented assuming quadratic...

In situ stress is one of the most important parameters in underground engineering. Due to difficulty and weakness current measurement methods deep soft rock, a new one, rheological recovery (RSR) method, determine three-dimensional tensor developed. It supposed that rock stresses will recover gradually with time can be measured by embedding transducers into borehole. order explore relationship between initial stress, analytical solutions are developed for process RSR method viscoelastic...

In tunnel construction in western China, a vast amount of carbonaceous slate is encountered. High situ stress and foliation structures cause the rock mass to exhibit pronounced anisotropic creep, readily inducing series engineering disasters like collapses lining cracks. Investigating time-dependent characteristics beneficial long-term stability operation. view this, specimens with different angles, β, between plane loading direction were studied using graded method through uniaxial...

The rheological stress recovery (RSR) method was proposed to obtain measurements of in-situ stress. Rock can be evaluated by monitoring the process sensors embedded in rock mass. In order achieve this application, a novel sensor employing fiber Bragg grating (FBG) technique designed and manufactured. This consisted three parts: A sensing spherical head, connecting rod, coupler box. six independent pressure units were assembled together with temperature compensation unit. addition, wavelength...

Objective To improve the safety and reliability in high intensity focused ultrasound(HIFU)therapy, effects of tissue acoustic properties on ultrasound temperature field were investigated. Methods Based measured data sound velocity attenuation coefficient at different temperature, variation coefficient, distribution during HIFU therapy was simulated using FDTD method. Moreover, two variable parameters therapeutic region above 60 ℃ evaluated. Results Tissue raise, speed decreased increased...

Objective In the treatment of tumor with high intensity focused ultrasound (HIFU),the acoustic pressure distribution determines safety and reliability HIFU.It is necessary to predict field produced by HIFU transducer.Methods To analyze generated different excitation frequency variable incentive power,comparison was made between simulated finite difference time domain (FDTD) method ones measured experiments.Results The resultsshowed that pressureat focalpoint increasedwiththe increasing...

Objective To improve the safety and reliability in HIFU therapy, effects of vessel locations on high intensity focused ultrasound temperature field were investigated. Methods The distribution was obtained by combining nonlinear acoustic propagation formula Pennes bio-heat transfer equation, as well finite difference time domain method. Results fields almost unchangeable whether vessels had perfusion or not. However, there a significant reduction center rise, while located axis. If distance...

Abstract To address the challenge of achieving precise real-time monitoring significant deformation in deep roadway surrounding rock, a quasi-distributed strain-sensing cable (SSC), which has spatial resolution 1 m, was developed based on principle Identical Weak Fiber Bragg Gratings. The performance SSC been evaluated through series calibration tests, revealing range 0%–3%, an accuracy level 0.5%, strain sensitivity measuring at 1.23 pm/με, and temperature recorded as 10.78 pm/℃....

A 3-D numerical model is presented to study the effect of blood vessel locations on high intensity focused ultrasound (HIFU) temperature field. The based Westervelt formula and Pennes bio-heat transfer equation. finite difference time domain (FDTD) method used obtain distribution induced by HIFU procedures. Temperature rise focal area are then shown for different vessel. Results show that when located beam, significant reduction in observed due flow. If there a gap between beam axis vessel,...