Research and Analysis on the Influence of Small Clear Distance Drilling and Blasting Method on the Existing Tunnel Structure

In order to study the vibration influence of tunnel drilling and blasting method on the built tunnel with small clear distance, taking the intersection of Zhuhai Dahengqinshan No. 1 tunnel and Zhuji urban rail tunnel as the engineering background, we used ABAQUS finite element software to conduct numerical simulation analysis on the influence of different blasting loads on existing tunnels with small clear distance in Zhuji tunnel construction. The following conclusions were drawn: the blasting construction of the tunnel under construction had the greatest impact on the vault of the existing tunnel; when the peak load was reduced by half, the stress value, vertical displacement, and resultant velocity of Mises were also reduced by half, which indicates that reducing the peak value of blasting load appropriately can ensure the safety of tunnel construction. When the peak load is 2.7 MPa, the measured and simulated values were less than the resultant velocity limit required by the specification. In addition, the relative error between the measured value and the simulated value was less than 5%, indicating the accuracy of the numerical simulation.

Increasing the productivity of water in takein water-containing crystalline rocks by increasing their fracture by an explosion

Global warming, which has been observed in the world and Ukraine in particular in recent decades, may lead to a decrease in surface and groundwater. In addition, the high level of groundwater pollution and the policy of water purification is a matter of concern. Thus, the question of finding additional and alternative sources of drinking water today is highly urgent. A significant percentage of prospecting works of the last century was devoted to discovering the groundwater fields in fractured crystalline rocks of the Ukrainian Shield. As a rule, the productivity of wells of these formations did not have high flow rates, so even now, mostly the aquifers in sedimentary deposits have been exploited. The low productivity of most wells in water-bearing fractured rocks is associated with the unknown degree of fracturing of the crystalline massif: it is difficult to determine the pathways of groundwater inflow into the fracture system and, accordingly, it is not easy to justify the exploitable groundwater reserves. In this paper, using the groundwater flow model of the Zhashkiv groundwater deposit, it is considered an increase of the productivity of water intake wells in the water-bearing crystalline rocks due to the increasing degree of their fracturing by an explosion. Thus, in hydrogeology, this technique is known when trying to increase the permeability in the near-borehole space, but as a method of artificial recharge of aquiferous crystalline rocks is used very rarely. The paper also examines typical water intakes conditions in fractured crystalline water-bearing rocks, which can be recommended for increasing their productivity by the blasting method. The results indicate that an artificial increase in fracturing degree can have a significant effect on increasing the productivity of water intakes. The basic methods of using explosives, as an example of an artificial increase in fracturing degree, in solving hydrogeological problems and the mechanisms of fractures’ formation during the action of blasting are considered.

Damage Analysis of Concrete Structure under Multidirectional Shaped Charge Blasting Using Model Experiment and Ultrasonic Testing

Quantitatively analyzing multidirectional shaped charge blasting energy distribution and improving the rock-fracturing efficiency have been a challenging problem in blasting and civil engineering. In this work, we carry out four groups of concrete model experiments using ultrasonic testing, comparing conventional blasting, and multidirectional shaped charge blasting. Then, the probability and statistics method is used to quantitatively analyze the blasting damage and the energy distribution. The test results show that ultrasonic testing and statistics model can quantitatively evaluate the damage law and energy distribution of blasting. By comparing with conventional blasting method, the multidirectional shaped charge blasting with V-shaped multidirectional shaped energy groove has achieved the effect of energy accumulation. It increases the distribution of energy in the rock crack district, increases the blasting damage range, and improves the rock-fracturing efficiency of blasting. The V-shaped multidirectional shaped energy groove can be used as a new approach for rock fracturing in similar projects.

Methodology for calculating the technological parameters of preventive deformation of the hardened parts of the "wall" type

The article aims to establish the effect of preventive deformation on the accuracy of aircraft parts made from the thermally hardened aluminium alloy 1933T2, after blasting hardening. Determination of the impact of preventive deformation was carried out by analysing structural parts of the "wall" type produced using various technological sequences. Sample 1 was produced using a standard manufacturing sequence: milling – blasting hardening – blasting correction. Sample 2 was produced as follows: milling – preventive deformation – hardening – blasting correction. The deformation of the samples was determined at checkpoints by deviations from flatness based on bending deflections. In sample 2, preventive deformation was performed on its ridges by a rolling device. The calculation of the technological parameters of the rolling device was conducted following the principle of superposition of individual operations, such as rolling and blasting hardening. The definition of the parameters of preventive deformation of sample 2 was based on the results ob tained for sample 1. It was established that, for both samples, the deviation from flatness after milling comprised 2.5 mm. The maximum deviation of sample 1 (without preventive deformation) after blasting hardening was 2.6 mm under a high degree of surface saturation. The maximum deviation of sample 2 (with preventive deformation) after blasting hardening did not exceed 0.4 mm, which corresponds to the acceptable deviation of such structural parts. Thus, the inclusion of the preventive deformation stage in the manufacturing process, with consideration of the deviations resulting from the milling stage, allows minimisation of deviations from the required form after blasting hardening. An analysis of the obtained re[1]sults confirmed that preventive deformation of structural parts reduces distortions after blasting hardening. Therefore, it is advisable to use the following manufacturing sequence: preventive deformation → hardening by a blasting method → correction by a blasting method.

Research on Construction Control Technology of Large-Span and Small Clear Distance Underpass High-Voltage Line Tunnel

Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project. It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance, which requires high construction requirements. In view of the difficulties such as shallow buried depth of tunnel and small clear distance between tunnel and tower of high-voltage line, multiple excavation blasting method is adopted, and smooth blasting, charge quantity control and damping hole setting are comprehensively used to reduce the impact on the tower and structure of high-voltage line. In order to ensure the smooth progress of the project, the large-scale finite element analysis software is used to simulate the whole excavation project. The influence of the full-section method and the middle partition wall method (CD method) on the surrounding rock and the high-voltage electric tower is compared. It is found that the CD method can effectively control the displacement of the surrounding rock and the tower on it and the uneven settlement.

The Efficiency of Large Hole Boring (MSP) Method in the Reduction of Blast-Induced Vibration

Drill and blast is the most cost-effective excavation method for underground construction, however, vibration and noise, induced by blasting, have been consistently reported as problems. Cut blasting has been widely employed to reduce the blast-induced problems during underground excavation. We propose that the large hole boring method using the state-of-the-art MSP (Multi-setting smart-investigation of the ground and pre-large hole boring) machine (“MSP method”) can efficiently improve vibration reduction. The MSP machine will be used to create 382 mm diameter empty holes at the tunnel cut area for this purpose. This study assessed the efficiency of the MSP method in reducing blast-induced vibration in five blasting patterns using a cylinder-cut, which is a traditional cut blasting method. The controlled blasting patterns using the MSP method demonstrated up to 72% reduction in blast-induced vibration, compared to the base case, Pattern B, where only cylinder-cut and smooth blasting method were applied. Therefore, the MSP method proves to be a promising alternative for blasting in sensitive urban areas where non-vibration excavation techniques were initially considered. Geological characteristics of 50 m beyond the excavation face can be acquired through the proposed real-time boring data monitoring system together with a borehole alignment tracking and ground exploration system. The obtained geological information will be a great help in preparing alternative designs, and scheduling of construction equipment and labour during the tunnel construction.

Field Investigation of Blasting-Induced Vibration in Concrete Linings during Expansion of Old Highway Tunnel

Numerous mountain highway tunnels in China do not satisfy the current traffic design standards and therefore need to be rebuilt or expanded. The drilling-blasting method is the primary method employed in China for expanding mountain highway tunnels, and it is crucial to monitor the vibrations caused by blasting. This study conducted a field investigation of the vibrations caused by blasting during the expansion of Yujiaya tunnel, which was built in 1999. The blasting-induced vibrations in the new and old concrete linings were monitored and analyzed during the expansion. The measured values of the peak particle velocity (PPV) varied within the range of 0.097–8.246 cm/s. The attenuation law of the PPV was determined via a regression analysis using Sadovsky’s empirical formula. The relationship between the main vibration frequency and the distance from the blasting source was expressed as a power function. Finally, the safety distances of the concrete linings subject to blasting vibrations were analyzed and discussed.

Effectiveness of Surface Treatment With Blasted Bioceramic Materials on Implants Surfaces

Hydroxyapatite (HA) and other forms of bioceramics coatings had been reported to stimulate bone healing, which helps in initial implant integration. This study was to evaluate the effectiveness of air blasting with two combinations of bioceramic powders (hydroxyapatite and calcium oxide) on the selected implant surfaces for surface deposition. Five different types of implant disks were tested, namely Commercially pure (Cp), Sandblasted (SB), Sandblasted and etched(SBE), SLActive®, Roxolid®. The studied samples were blasted with apatite abrasive bioceramic powders, 95% Hydroxyapatite (HA)/5% Calcium Oxide (CaO) and 90% Hydroxyapatite (HA)/10% Calcium Oxide (CaO). The surface and elemental differences between the blasted samples were compared using a Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). Results after surface treatment had demonstrated changes in surface morphologies; most evidently on the Cp implant discs. All treated surfaces revealed a non-uniform distribution of the treatment on the surface layer, with dispersed patches of bioceramic powders over the surfaces. The experimental blasting method used in this study has demonstrated the ability to deposit bioceramic materials on different implant surfaces.