Classified arrangement technology of freezing holes in deep and thick alluvium and its influence on freezing control

Abstrat;The arangement of freezing holes not only determines whether the effective thickness and average temperature of the freezingwallrequired by the design can be formerd on schetule , but also directly affects the speed, safety and construction cost of the freezing shaftsinking.Improper arrangement will even become the hidden danger.'Therelore , the amrangement of freezing holes and formation characteris-tics of freezing wall are always the hot and difficult points in theory and techmology research. The design and arrangement of freezing holesin deep and thick allwvium can be classified into three types ; main freezing hole , auxiliary freezing hole and spalling-prevention freezinghole， which can solve the problems of safety and stability of main structure of main freezing hole and frezing wall.Arranging auxiliaryholes evenly accordling to the thickness of fromen wall and freezing time can obviously retduce the number of atuxiliary holes and improve theuniformity and stability of the frezing wall.The flexibility and effect of freezing contol can be improved by arranging muliple circles ofspalling-prevention freezing holes accordling to the change of excavation diameter. The enginering practice shows that the holes arrangement method with outer ring as the main frezing hole is beneficial to the sadety and stability of the main freezing hole and the overallfreez-ing wall, which can reruce the mumber of freezing holes , the work amount of drilling holes and the cooling capacity required, improve theadjustability and control effect of freezing, and is recommended as the first choice for the arrangement of freezing holes in deep and thickalluwvium.The reasonable arrangement of freezing holes can lay a good founmdation for the safety and stability of the freezing wall and thecontrol of freezing. In the constuction process, through the establishment of the mechanism of the actual measurenent and analysis of thefomation charactristis of the frezing wall , engineering predliction and frezing control , the development trend of the effective thickness ,average temperalure and the temperature of the frzen wall are analyzel and predlicted on a regular lasis , and the flow and temperature ofsalt water in the spalling-prevention hole and atuxiliary hole are regulated in advance , or even the freezing and freezing cycles are stopped,which can effectively control the temperatur of the shat sidewall and the amount of frozen soil expanding into the excavation section , andcreate good conditions for the excavation.Through the practice and application of the outer ring as the main freezing hole in the West Ven-tilating Shaft of Zhaogu No.2Coal Mine，which passes through one of the deepest alluwvium thickness , the total number of freezing holes ,the work amount of dilling holes and the cooling capacity requiredl are decreased by 10.7%，12.1% and 9.7% respectively , and the uni-fomity of temperature and strength inside the frezing wall is better.Combined with the observation of the stability of the shaft sidewal inthe cohesive soil ayer, through active control , the tempenature of the shaft sidewall below 400 m can be slightly higher than the designedcontrol target.'The temperature of the shaft sidewall below 635 m is close to the designed control target.T'he thickness and average temper-ature of the freezing wall always meet the design requirements.'Tlhe temperature of the shaft sidewall in the deep ohesive soil layer in theallwvium is controlled above -ll ℃ , and the temperature of the shat sidewall in the sandy soil layer is above -13 ℃. The stability of thefrzing wall of the alluvium is god , and the cooperation between freezing and excavation is good. The excavation speed of the deep outerwall of the allwvim is basically maintained at 75 ~80 m per mouth , the average excavation speed of the outer wall of the alluvium sectionis 87.1m per month，and the aveage excavation speed of the outer wall of the freezing section is 82.1 m per month.