CN103628886A - Method for excavating weak surrounding rock tunnel under water-rich high-ground-stress conditions - Google Patents

Abstract

The invention discloses a method for excavating a weak surrounding rock tunnel under water-rich high-ground-stress conditions. The method includes the following steps that firstly, advanced small pipe grouting and pre-supporting are carried out in advance before tunnel excavation; secondly, excavation is carried out according to a three-step seven-excavation-surface method; thirdly, C35 reinforced concrete is adopted in the secondary lining process, wherein the C35 reinforced concrete is 65cm in inverted arch thickness and 55cm in arch wall thickness and comprises phi22@20cm annular main ribs, phi14@20cm longitudinal steel ribs and phi8 stirrups. The method can effectively avoid the steel frame torsion and cracking phenomenon, thereby guaranteeing normal tunnel construction, accelerating construction and improving construction safety and engineering quality.

Description

The excavation method of Support System in Soft Rock Tunnels under rich water high-ground stress condition

Technical field:

The invention belongs to a kind of construction of tunnel construction method, the particularly excavation method of Support System in Soft Rock Tunnels under a kind of rich water high-ground stress condition.

Background technology:

For the weak surrounding rock under rich water, high-ground stress condition, due to complicated geological, country rock excavation easily collapses, rock crushing, reduction compressive strength, so rock mass very easily collapses, and threatens constructor's safety.After preliminary bracing completes, country rock does not almost have self-stable ability, and preliminary bracing body holding capacity is huge, easily causes steelframe distortion, distortion, fracture, invades the phenomenons such as two linings, has had a strong impact on construction safety, construction quality, construction speed.

Home and abroad soft rock tunnel is comparatively common, but also slightly inadequate to the aspects such as versatility of the practicality of soft rock Deformation control construction method, complete set technology, the directiveness of construction technology file and referential are greater than experience and the more aobvious shortcoming of technical basis of large Section in Soft Rock constructing tunnel under the practice in engineering, particularly high-ground stress, rich water condition.

For the reason of Support System in Soft Rock Tunnels distortion, without guiding manufacture bases, the soft rock Deformation control construction method that large section Weak Surrounding Rock Construction forms a set of perfect systematization, maturing is very urgent.

Summary of the invention:

The object of this invention is to provide the excavation method of Support System in Soft Rock Tunnels under a kind of rich water high-ground stress condition, the method can be controlled the distortion of this type of country rock.

As above design, technical scheme of the present invention is: the excavation method of Support System in Soft Rock Tunnels under a kind of rich water high-ground stress condition, is characterized in that: comprise the steps:

(1) before tunnel excavation, perform in advance the pre-supporting of advanced tubule slip casting;

(2) while excavating, adopt three step seven footworks excavations, wherein top bar at 3-4 rice, excavation will be reserved the deflection of 30-40cm; In the preliminary bracing of each step, steel arch frame loopful adopts H175 steelframe, spacing 0.6～0.8m, and paving is hung double-deck φ 8 steel mesh reinforcements, Mesh distance 20 * 20cm; The self-feeding anchor pile abutment wall system of φ 22, the long 6.0m combination hollow bolt that arch adopts, φ 22, long 6.0m, spacing 1.0 * 0.8m grouting rock bolt and the long 8m that abutment wall adopts forms system anchor bolt; Lock foot anchoring stock adopts long φ 42 ductules of the 6.0m of 16,4 place;

(3) secondary lining employing C35 steel bar concrete, the thick 65cm of inverted arch, the thick 55cm of arch wall, the main muscle of hoop are that φ 22@20cm, longitudinal reinforcement are φ 14@20cm, and stirrup is φ 8.

The pre-supporting of above-mentioned steps (1) advanced tubule slip casting adopts individual layer φ 42 pre-grouting with micropipes, long 4m.

The present invention, for the excavation of the Support System in Soft Rock Tunnels under rich water, high-ground stress condition, can effectively solve the phenomenon of steelframe distortion, fracture, avoids steelframe bending resistance, antitorquely can not meet construction needs phenomenon.And can solve that preliminary bracing distortion is large, supporting and protection structure unstability, invade headroom, need the phenomenons such as displacement bow member, thereby guaranteed the normal construction in tunnel, accelerate construction speed, improve safety and the workmanship of construction.

Accompanying drawing explanation:

Fig. 1 is section excavation schematic diagram of the present invention;

Wherein: 1 for topping bar, 2 and 3 for middle step, 4 and 5 for getting out of a predicament or an embarrassing situation, 6 for Core Soil, 7 be tunnel bottom.

The specific embodiment:

As shown in Figure 1: excavation method of the present invention is, before tunnel excavation, perform in advance long 4 meters of φ 42 pre-grouting with micropipes of individual layer, carry out advance support.During excavation, adopt three step seven footwork excavations, can reduce like this disturbance of explosion to country rock, first excavate 1 part shown in Fig. 1, excavation excavates 2 parts after just having propped up again, according to 3,4,5,6,7 orders successively excavation supporting.The definite of crucial importance of excavation height of topping bar, has increased the headroom of topping bar to a certain extent although increase the excavation height of topping bar, and is conducive to like this operation of construction, can increase the stressed of the distortion of country rock and increase supporting and protection structure.Through theory analysis and field practice, top bar and be advisable between 3-4 rice, and excavate the deflection that will reserve 30-40, for preventing tunnel subsidence distortion intrusion two lining headroom.

Preliminary bracing adopts H175 steelframe, and H175 steelframe can effectively be controlled distortion, and it bears larger pressure than the I20 steelframe of using in common engineering.Paving is hung double-deck φ 8 steel mesh reinforcements, Mesh distance 20 * 20cm, and the soft rock under heavily stressed, rich water condition loses self-stable ability completely, becomes mud shape, and quicksand like is pressed on prop, and the individual layer steel mesh reinforcement of conventionally using in engineering easily lost efficacy, and steel mesh reinforcement fracture is dropped.Arch φ 22 combination hollow bolts, long 6.0m, abutment wall φ 22 grouting rock bolts, long 6.0m, spacing 1.0 * 0.8m, and by each 5 self-feeding anchor piles that are adjusted into long 8m of abutment wall system anchor bolt left and right sides, lock foot anchoring stock adopts long φ 42 ductules of the 6.0m of 16,4 place.Adopt the problems such as a this just prop can more effectively prevent steelframe distortion, and tunnel just props up distortion, supporting and protection structure unstability.

Two linings adopt 35 steel bar concretes, the thick 65cm of inverted arch, and the thick 55cm of arch wall, the main muscle of hoop is φ 22@20cm, and longitudinal reinforcement is φ 14@20cm, and stirrup is φ 8.Mainly prevent tunnel double-lining distortion, particularly inverted arch protuberance phenomenon.

The present invention adopts seven excavation methods of three steps, particularly the height of topping bar has been done to careful deep experimental study.Supporting parameter has been done to detailed experimental study, shown that supporting parameter is as follows

Claims (2)

1. an excavation method for Support System in Soft Rock Tunnels under rich water high-ground stress condition, is characterized in that: comprise the steps:

(1) before tunnel excavation, perform in advance the pre-supporting of advanced tubule slip casting;

(2) while excavating, adopt three step seven footworks excavations, wherein top bar at 3-4 rice, excavation will be reserved the deflection of 30-40cm; In the preliminary bracing of each step, steel arch frame loopful adopts H175 steelframe, spacing 0.6～0.8m, and paving is hung double-deck φ 8 steel mesh reinforcements, Mesh distance 20 * 20cm; The self-feeding anchor pile abutment wall system of φ 22, the long 6.0m combination hollow bolt that arch adopts, φ 22, long 6.0m, spacing 1.0 * 0.8m grouting rock bolt and the long 8m that abutment wall adopts forms system anchor bolt; Lock foot anchoring stock adopts long φ 42 ductules of the 6.0m of 16,4 place;

(3) secondary lining employing C35 steel bar concrete, the thick 65cm of inverted arch, the thick 55cm of arch wall, the main muscle of hoop are that φ 22@20cm, longitudinal reinforcement are φ 14@20cm, and stirrup is φ 8.

2. the excavation method of Support System in Soft Rock Tunnels under rich water high-ground stress condition according to claim 1, is characterized in that: the pre-supporting of above-mentioned steps (1) advanced tubule slip casting adopts individual layer φ 42 pre-grouting with micropipes, long 4m.

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