Solid Lifting Socket Cross Pin
Taboo 5.
Reasons and consequences of not protecting the freezing facilities in the hole excavation.
If you do not know the exact position of the freezing tube, there is no strict and scientific drilling and blasting design, and the driller’s accuracy is low, it can not form a stable and complete frozen body, but it is easy to thaw the frozen body quickly and return to the original state, and the initial support can not be closed into a ring in time, There are potential safety hazards of collapse or even large collapse.
Secondary lining without thawing is very easy to deform or even damage the secondary lining structure due to thawing settlement, and the section size can not meet the clearance requirements, resulting in certain potential safety hazards.
At the same time, appropriate drilling rig, drill bit and drilling tool assembly and mud circulation system suitable for construction requirements shall be selected to ensure the effect of mud wall protection.
Portal excavation is very important.
(source: tunnel, micro soil wooden person recommended) [copyright notice] at present, “micro soil wood man” is the public welfare official account, aiming to provide an online communication platform for the vast number of civil servants.
Reasons and consequences: if the length of one-time excavation is too long and the exposure time of surrounding rock is too long, the frozen stratum will thaw quickly and return to the original state.
Correct practice: the key of freezing technology lies in freezing hole drilling and freezer laying.
The diameter and spacing of freezing holes shall be arranged in strict accordance with the freezing design requirements, and appropriate drilling rig, bit and BHA shall be selected to ensure the driller’s accuracy, so that there is no gap in the freezing body and form a complete support.
The initial support cannot be followed up in time and closed into a ring, which is very easy to cause collapse or even major collapse accidents.
Correct practice: pipe exceeding front, short excavation, multi circulation, frequent measurement, tight sealing and strong support.
After the hole excavation, the expected effect cannot be achieved.
After the freezing facilities are damaged, the freezing reinforcement cannot be carried out in time, which affects the smooth entry into the hole and causes economic losses.
Taboo 2.
Correct practice: for freezing construction, holes shall be arranged according to the diameter and spacing of freezing holes required by freezing design.
After the frozen body is formed, the excavation construction shall be carried out.
If the freezing facilities are not effectively protected during the hole excavation, the shape and expansion range of the frozen structure cannot be artificially controlled at any time.
Taboo 4 ， construction reasons and consequences of frozen and unfrozen transition sections in case of unknown geology ， risky construction of frozen and unfrozen transition sections in case of unknown geology may cause water inrush, mud inrush, peeling, collapse and even major collapse accidents.
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Taboo 1.
Reasons and consequences of secondary lining without thawing.
Taboo 3: do not know the exact position of the freezing tube, there is no strict and scientific drilling and blasting design, and the reasons and consequences of the low driller’s accuracy.
Correct approach: carry out advance geological prediction, make accurate judgment on the surrounding rock condition of the tunnel face, carry out strict and scientific freezing technology and drilling and blasting design, play steadily and do not rush in.
The secondary lining shall be carried out when the uneven deformation caused by thawing settlement after the thawing of frozen soil, that is, the vault settlement and clearance convergence value measured by surrounding rock monitoring tend to be stable.
Then lay the freezer and conduct the pressure and leakage test to ensure that the design requirements are met.
Correct practice: when the frozen body is used for tunnel excavation, the section size shall meet the clearance requirements, and appropriate frost heave deformation shall be reserved.
During the initial excavation, it is strictly prohibited to freeze or disturb the tunnel into a ring, and it is strictly prohibited to drill or blast the support in time to ensure the safety of the tunnel.
Ensure the safe construction of tunnel excavation under the cover of frozen body.
