Weak rock tunnel design of blasting technology
Abstract: This paper mainly introduces the new forest economy highway tunnel Cheng Shao geological and hydro-geological conditions of the tunnel
sections in the soft rock blasting techniques, analysis of smooth blasting
design and construction safety measures, and the design of drilling and blasting method Construction of the organization provide a reference for similar projects.
Key words: weak rock; tunnel blasting; design; construction technology
1 Project Overview
The new tunnel is located WANGWU forest mountains, tunnels, split tunnel, length 670m. The tunnel is located in the new forest Wangwu Township Primary School near the end of an erosion of denuded mountain
hilly area (?). The tunnel axis through the Department, the maximum altitude of about 578 m, the maximum relative height difference of about 55m. Mountains to the north-south direction. Xin-Lin JOINTED rock tunnel
area general development, the tunnel area surrounding rock mainly
developed occurrence of 90 ? ? 88 ?, 60 ? ? 85 ?, 200 ? ? 28 ?,
183 ? ? 40 ? of the four sets of joints, joint-ping Straight-based,
multi-closed, joint density of 2 ~ 5 / m, local density of up to 7 / m. Rocks inside the tunnel section of sandstone, silty mudstone, less wind resistance capabilities. Into the east portal of the natural slope tilt, terrain slope from 200 to 400, in order to slope topography, surface Qel thinner, some missing, lithology for the sub-clay, is a V-class rock, the
underlying bedrock of the Triassic 2 Horse Camp Group sandstone, silty mudstone, strong weathering thickness of about 1.5m, poor stability of surrounding rock, BQ <250, belonging to grade ? rock.
The tunnel through the sandstone weathered, weak weathered layer,
buried shallow groundwater is not developed, mainly bedrock fissure water, water than the poor
Two weak rock tunnel blasting excavation plan was finalized
In the excavation process should be based on rock type (or level)
to adopt a reasonable form of blasting parameters and undercutting, blasting materials, detonating mode, charging structure and the plug material to minimize blasting of rock and neighboring cavern of the disturbance and destruction, and strictly control the under-excavation and
blasting vibration speed, the full protection of the self-supporting
ability of surrounding rock. The previous chamber blasting on adjacent chamber blasting vibration velocity should be controlled at 5cm / s within.
Three drill and blast design
3.1 Drilling and Blasting Design
The overall design idea is to use smooth blasting arch, side-wall
use of pre-split blasting, the core use of controlled blasting, undercutting the integrated use of throw blasting controlled blasting.
According to excavation methods were used two kinds of half-sections and
full-face blasting methods, using non-electric millisecond detonator
blasting network. Grade ? ? level and right semi-section of rock
blasting step approach, in order to reduce the disturbance of surrounding rock blasting, excavation cross-section multi-Dan non-electric blasting
caps to network design.
Characteristics of rock under this project, ? grade rock for the
weak siltstone, with parallel hole cut slot, strabismus undercutting mix. Used is less than 2m deep eyes askance undercutting.
In the weathered, broken more serious geological conditions, the appropriate use of smooth blasting or drilling eye contour method, or set aside smooth layer of smooth blasting excavation trimming.
3.2 Bottom eyes drilling and blasting requirements
? the floor is divided into paragraphs, separated from eye-
detonation, which can reduce the floor eye-detonation in the same
paragraph, the amount of explosives together and changed the bottom line of eye-resistance direction, would actually narrow the eye bottom line of resistance, which can be reduce the floor eye-bursting intensity generated
by an earthquake.
? initiation sequence: undercutting the inner eye ? boring eyes
? eyes ? eyes ? bottom peripheral eye.
? Select the paragraphs when the detonators are three: First, a reasonable interval between paragraphs; second, with a porthole of the loading dose should be less than the maximum permitted single-stage
loading dose; third, the bursting of the preceding paragraph as far as possible for the post-blasting to create a good overhead surfaces.
3.3 The selection of blasting parameters
By testing to determine if blasting blasting parameters, smooth blasting parameters
Blasting parameters on the selected Note:
? Soft Rock Tunnel smooth blasting the relative distance (E / W) should adopt the table minimum.
? Charge concentration (q) in accordance with No. 2 rock ammonium nitrate explosives to consider, when the change should be carried out using other explosives, filling, conversion targets mainly Brisance and burst strength (average). Reposted elsewhere in the paper for free
? The smooth blasting, the blasting vibration velocity should be controlled in: the hard rock 15 cm / s, soft rock 5 cm / s. Require blasting vibration velocity is based on face to leave the dug-