A model to determine hole spacing in the rock fracture process by non-explosive expansion material

The application of the non-explosive expansion material （NEEM） is widely used as the controlled fracture method in quarry min- ing, especially in hard rocks. The pressure of NEEM is an important parameter in causing rock fracture. An empirical model based on hole spacing was developed to determine the pressure of NEEM in the rock fracture process. Primarily, the empirical model was developed by the mathematical method, utilizing dimensional analysis. Then, the Phase2 code, which is based on the finite element method, was utilized to predict crack growth in rocks. The results of numerical analysis show slight deviations from the empirical model. Hence, the polynomial re- gression analysis was used to modify the model. Finally, the modified model shows a good agreement with the results gained from numerical modeling.

Investigation of a non-explosive directional roof cutting technology for self-formed roadway

Traditional explosives have characteristics of high risk,large vibration,and poor directional fracturing.Consequently,an instantaneous expander with a single crack surface(IESCS),which is a novel nonexplosive directional rock-breaking technique,has been developed.The directional roof-cutting mechanism of the IESCS method,driven by high-pressure gas,was theoretically analyzed.Laboratory experiments and numerical simulations proved the directional slitting effect of the IESCS method to be excellent.Compared with shaped-charge blasting,the charge of IESCS was reduced by 8.9%,but the crack rate increased by 9%in field tests.After IESCS pre-splitting,the roof directionally collapsed along the cutting line,and the gangue filled the goaf.Moreover,the directional roof cutting by the IESCS could decrease roadway stress.The average pressure of hydraulic supports on the cutting side of the roof was 31%lower than that on the non-cutting side of the roof after pre-splitting.After the self-formed roadway constructed by the IESCS was stabilized,the final relative displacement of the roof and floor was 157.3 mm,meeting the required standard of the next working face.Thus,the IESCS was effectively applied to directional roof pre-splitting.The results demonstrate the promising potential of IESCS in the mining and geotechnical fields.

Experimental and numerical investigation into the non-explosive excavation of tunnels

The use of explosives is restricted on some important holidays,and the handling of unexploded charge is very dangerous.Therefore,an innovative non-explosive technology called instantaneous expansion(IE)was developed for tunneling.IE,whose components are derived from solid wastes such as coal gangue and straw conduces to realizing the reuse of waste.Moreover,its cost is lower than explosives.Blind guns of IE are easy to treat with water.The IE tunneling method is classified into two categories,i.e.IE with a single fracture(IESF)and IE with multiple fractures(IEMF),which are used to form the tunnel crosssection directionally cross-section and to fragment the rocks inside the cross-section,respectively.In this study,the principle of IE tunneling was elaborated first.Then,tunneling experiments and numerical simulations were performed on IE,conventional blasting(CB)and shaped charge blasting(SCB)in comparison.The experimental and numerical results show that IE achieved the best performance of directional rock breaking and corresponded to the most minor excavation-induced damage zone of the surrounding rock.Besides,the tunnel cross-section created by IE was flat and smooth.Comparing IE with CB and SCB,the over/under-excavation area decreased by 64%and 17%,and the excavation-induced damage zone fell by 26%and 11%,respectively.The range of the loose circle is reduced,which is conducive to improving the long-term stability of the roadway.The research provides a safe and economical tunneling method with excellent application prospects.

Audiological characteristics of the contralateral ear in patients with unilateral physical non-explosive ear trauma

Objectives:To document the frequency of occurrence and types of symptoms experienced in the contralateral ear in patients with unilateral physical non-explosive(UPN)ear trauma and to compare the audio metric and tympano metric parameters between asymptomatic and symptomatic contralateral ears.Design:Prospective analytical clinical study Setting:Specialized(Ear,Nose,and Throat)clinic of a tertiary health institution.Participants:Patients with UPN ear trauma who presented within the first week of the incident.Main outcome measures:Otologic symptoms in the contralateral ear in UPN ear trauma Results:Eighteen out of 53 patients(34.0%)experienced symptoms in the contralateral ear.The symptoms were tinnitus in 77.8%(14/18),hearing loss in 66.7%(12/18),and ear blockage in 27.8%(5/18).There was hearing loss in 38/53(71.7%)of contralateral ears.Hearing loss type and PTAv at the low frequencies were not significantly different(p=0.142),but other audiometric parameters were significantly different between asymptomatic and symptomatic contralateral ears(p<0.05 in all).Type C tympanogram was more prominent in the symptomatic contralateral ear.There was a statistically-significant difference in the type of tympanogram between the two categories of patients(p=0.018).There was no difference in acoustic reflex between the two categories of patients(p=0.095).Conclusions:The contralateral ear may be affected in up to one-third of patients with UPN ear trauma,and experience otologic symptoms similar to those of the traumatized ears.Audiologic and audiometric parameters were abnormal in most of the contralateral ears.The two ears must be assessed thoroughly in cases of UPN ear trauma.

A reusable SMA actuated non-explosive lockrelease mechanism for space application

After the satellite is launched with the carrier rocket,it is necessary to separate the satellite from the rocket at an appropriate time to ensure that the satellite enters the intended orbit.In this process,it is vital to ensure a reliable connection and accurate separation.With the increasing use of microsatellite in orbit,the contradiction between the shock of separation and the requirement of the platform’s dynamic environment is becoming increasingly prominent.Therefore,the traditional pyrotechnic separation device can no longer meet the requirements.This paper presents a reusable non-explosive release actuator using shape memory alloy(SMA)wire for high load and low shock.The system is based on the Fast Acting Shock-less Separation Nut(FASSN)technology.Using the shape memory effect of SMA,a biased SMA wire trigger has been developed,which is used as the driver source of the actuator.At the moment of receiving the electrical signal,the SMA wire generates stress and deformation.The trigger set free the constraints on the mechanical components,and the target is released.Experimental results indicate that the trigger device can unlock successfully and well meet the technical objectives.