High stress in the surrounding rock mass causes serious stability problems. The applied support system used in this conduction should be able to carry high loads and also accommodate large deformations without experiencing serious damage. In this paper, a brief overview of the history of yielding/energy-absorbing rock bolts is provided. And then, a new yielding bolt invented by the author is introduced in detail, including its layout and principle. Theoretical analysis shows that the bolt has large load-bearing and deformation capacities, thereby absorbing a large amount of energy to maintain the stability of surrounding rock.

Original scientific paper To analyse the influence of joint angle, number and spacing on the strength and acoustic emission (AE) characteristics of rock mass, the uniaxial compression model of rock specimens was established using the micro particle flow PFC2D software platform. The intact rock parameters were determined via trial and error, joints with different angles, numbers and spacing were prefabricated in the model, and a compression test was performed using the displacement control method. The compressive strength, elastic modulus, and AE time characteristics of the rock specimens increased, decreased, and then increased again along with increasing joint angle. The AE characteristics at joint angles 0°, 15°, 30° and 90° were consistent with those of the intact rock specimens, while the 45° ÷ 75° joint angle showed relatively discrete AE characteristics. A larger number of joints corresponded to lower uniaxial compressive strength, elastic modulus, and AE intensity. However, the time and strain range of the obvious AE were not significant. The compressive strength and AE signal intensity of the rock specimens increased along with joint spacing, but the AE triggering time did not show obvious changes. Uniaxial compression tests were performed via numerical simulation to avoid the non-homogeneous and discrete effects from the indoor test and to reflect accurately the influence of joint angle, number, and spacing on the strength and AE characteristics of rock mass. The results can help in generating reliable criteria for predicting the instability of engineering rock mass. Keywords: acoustic emission; intensity; joint angle; joint number; joint spacing; jointed rock mass Simulacijska analiza čvrstoće i karakteristika akustičke emisije raspucale stijenske maseIzvorni znanstveni članak Kako bi se analizirao utjecaj kuta, broja i raspona raspukline na čvrstoću i karakteristike akustičke emisije (AE) stijenske mase, postavljen je jednoosni kompresijski model uzoraka stijene uz primjenu PFC2D računalne platforme za protok mikro čestica. Metodom pokusa i pogreške određeni su originalni parametri stijene, u modelu su unaprijed izvedene raspukline različitih kutova, brojeva i razmaka, te je provedeno ispitivanje na pritisak metodom praćenja pomaka. Tlačna čvrstoća, modul elastičnosti i vremenske karakteristike AE uzoraka stijene su se povećali, smanjili te ponovo povećali kako se povećavao kut raspukline. Karakteristike AE kod raspukline kutova 0°, 15°, 30° i 90° bile su u skladu s onima kod originalnih uzoraka stijene, dok su se kod kuta raspukline od 45° ÷ 75° pojavile relativno diskretne karakteristike AE. Veći broj raspuklina podudarao se u nižoj jednoosnoj tlačnoj čvrstoći, modulu elastičnosti i intenzitetu AE. Međutim, nije došlo do značajne promjene u vremenu i veličini deformacije. Tlačna čvrstoća i intenzitet signala AE uzoraka stijene porasli su s povećanjem razmaka raspukline, ali se to nije pokazalo na pokazivaču vremena AE. Jednoosna ispitivanja kompresije provedena su numeričkom simulacijom kako bi se i...

Mechanical behaviors of pile-soil effect and anchor-soil effect are significantly important in supporting engineering activities of foundation pit. In this paper, finite difference method (FDM) was utilized to perform the numerical simulation of pile-anchor system, composed of supporting piles and pre-stressed anchor cables. Numerical simulations were on the basis of the foundation pit of Jinan's West Railway Station, and 3D simulation analysis of foundation pit has been prepared during the whole processes of excavation, supporting and construction. The paper also analyzed the changes of bending moments of piles and axial forces of cables, and discussed mechanical behaviors of pile-anchor system, through comparisons with field monitoring. The results show that the parameters concluding vertical gridding's number, cohesion of pile and soil, and pile stiffness have robust influences on supporting elements' behaviors. Mechanical behaviors of supporting pile and axial forces of anchor cable changed dramatically, indicating that the potential failure form was converted from toppling failure to sliding failure.

The reinforcement in both directions of a square tower crane foundation is obtained by ANSYS three-dimensional analysis and VB reinforcement program and VB optimization program to meet the requirements such as foundation bearing capacity, bending, overturning and punching under the general combination of various loads.

The nuclear waste storage projects, hydropower and etc are often installed in the hard crystalline rocks. The creep phenomenon of the hard rocks appears in virtue of the complex geological conditions, especially when the excavation brings about damage and cracks to the rockmass, and they largely weaken the hydraulic performances of surrounding rock. Once the excavation-caused cracks are well connected with the native ones together, the engineering safety will be brought great harm to. By dint of newly developed shear-flow-creep coupled experiment system, on condition of the constant normal stiffness boundary conditions, the coupled shear-flow-creep tests are conducted. Not only the tests testify that the equipments is reasonable and effective and the creep largely influences the seepage performance of the rock crack, but also the coupling characters are primarily proved up.