CN114320320A

CN114320320A - Supporting structure suitable for underground excavation section local expanding excavation and expanding excavation method

Info

Publication number: CN114320320A
Application number: CN202111680786.2A
Authority: CN
Inventors: 赵俊淞; 黄雪梅; 杨帆; 徐连盈; 林志达; 王昱
Original assignee: Beijing Uni Construction Group Co Ltd
Current assignee: Beijing Uni Construction Group Co Ltd
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-04-12

Abstract

The invention relates to a supporting structure suitable for partial expanding excavation of an underground excavation section and an expanding excavation method, which comprise the following steps: the method comprises the steps of setting an excavation process and a support system, obtaining surrounding rock grades of different sections of a tunnel to be excavated according to geological information obtained by advanced geological forecast, matching an excavation construction method and a support structure according to the surrounding rock grades of the different sections, and orderly arranging the excavation construction method and the support structure corresponding to the different sections to form the excavation process and the support system of the tunnel to be excavated through splicing; carrying out middle tunnel excavation, and carrying out advanced support, tunnel excavation construction and primary support on a middle tunnel area of the tunnel expanded excavation section according to the established excavation procedure and the support system; and (4) local expanding excavation of the section, namely establishing a support system of an expanding excavation area according to the grade of the surrounding rock and synchronously performing local expanding excavation by using a three-step method.

Description

Supporting structure suitable for underground excavation section local expanding excavation and expanding excavation method

Technical Field

The invention relates to the technical field of tunnel construction, in particular to a supporting structure and an expanding excavation method suitable for local expanding excavation of an underground excavation section.

Background

At present, underground traffic tunnels (such as roads or subways and the like) are constructed in large and medium-sized cities in large quantities. The variable cross-section of the underground traffic tunnel (the lane gradually becomes wider, such as the areas at the entrance and exit of a ramp or the entrance and exit of a subway vehicle section) is a difficult point and a key point for building the underground traffic tunnel, and the variable cross-section needs to be excavated and built on the basis of the built (mostly constructed by adopting the traditional shield tunneling machine) equal-diameter tunnel. The traditional expanding excavation construction method of the traffic tunnel variable section comprises an open excavation method, a cover excavation method, a mine method and the like. However, the above construction methods have a certain influence on ground traffic and buildings, and some (e.g. open cut methods) also need to occupy a large amount of ground space. With the economic development, in some areas with heavy ground traffic and dense population and buildings, the construction space adopting the construction method is not available, and the completely non-excavation construction method is almost the only choice to reduce the influence of tunnel construction on the stratum disturbance and the ground environment as far as possible. In addition, when the expanding excavation construction of the excavated middle hole is carried out, the space between the duct piece and the tunnel outline in the expanding excavation section is narrow, the temporary support stress conversion in the tunnel is frequent, the process is complex, and the potential risk is like shadow following; and the expanding excavation section is positioned on a silt layer, peripheral underground pipelines are complex, the building structure is dense, the requirement standard for the segment breaking reverse expanding excavation construction method is high, and the engineering has larger construction difficulty.

Chinese patent CN102865084 discloses an underground tunnel expanding excavation method from a double-line tunnel section to a three-line tunnel oversized section, which comprises excavating a middle hole in the double-line tunnel section and pouring a center pillar, excavating a single-line tunnel towards one side of the center pillar in the double-line tunnel section, and excavating a new double-line tunnel outwards from the double-line tunnel section on the other side of the center pillar; the single-line tunnel, the middle column and the new double-line tunnel form a three-line tunnel with a double-arch structure; the new double-line tunnel is excavated in a subsection mode through an I upper step, an II middle step, an III lower step, an IV upper step, a V middle step and a VI lower step which have the same height, and the I upper step, the II middle step and the III lower step are respectively and symmetrically distributed with the IV upper step, the V middle step and the VI lower step through the vertical center line of the new double-line tunnel. This patent can't verify and nimble adjustment to the supporting construction in the work progress, and can't monitor the wall rock after expanding to dig and supporting construction's deformation condition after accomplishing to expand to dig.

Therefore, it is necessary to provide an expanding excavation method capable of performing decomposed expanding excavation on a tunnel wall in a partitioned manner, so that the safety in the expanding excavation process is improved, the rock mass collapse of a large area of the whole body in the blasting expanding excavation process is avoided, and meanwhile, the deformation of tunnel surrounding rocks and a supporting structure is monitored, so that early warning is timely given under the condition of abnormal deformation, and the supporting structure is supplemented and reinforced.

Furthermore, on the one hand, due to the differences in understanding to the person skilled in the art; on the other hand, since the inventor has studied a lot of documents and patents when making the present invention, but the space is not limited to the details and contents listed in the above, however, the present invention is by no means free of the features of the prior art, but the present invention has been provided with all the features of the prior art, and the applicant reserves the right to increase the related prior art in the background.

Disclosure of Invention

Aiming at the defects of the prior art, the technical scheme of the invention provides an expanding excavation method suitable for the local expanding excavation of an underground excavation section, which comprises the following steps: the method comprises the steps of setting an excavation process and a support system, obtaining surrounding rock grades of different sections of a tunnel to be excavated according to geological information obtained by advanced geological forecast, matching an excavation construction method and a support structure according to the surrounding rock grades of the different sections, and orderly arranging the excavation construction method and the support structure corresponding to the different sections to form the excavation process and the support system of the tunnel to be excavated through splicing; carrying out middle tunnel excavation, and carrying out advanced support, tunnel excavation construction and primary support on a middle tunnel area of the tunnel expanded excavation section according to the established excavation procedure and the support system; and (4) local expanding excavation of the section, namely establishing a support system of an expanding excavation area according to the grade of the surrounding rock and synchronously performing local expanding excavation by using a three-step method. The method has the advantages that the linkage between rock walls can be reduced by expanding and digging the hole wall partition blocks on the basis of expanding and digging the middle hole of the area, and the integral collapse of the rock walls is avoided during blasting construction. The construction of the whole tunnel is divided into sections according to the pre-established excavation process and the support system, and the excavation methods of different sections are adjusted according to the actual surrounding rock grade, so that the tunneling efficiency of the tunnel is improved. In addition, the preset tunnel excavation process and the advanced support framework are verified or corrected in a mode of carrying out real-time surrounding rock grade testing on the section to be excavated before excavation, so that the tunnel excavation operation and the surrounding rock support operation can be carried out by using the optimal excavation construction method and the support structure all the time in the tunneling process, the controllability of the surrounding rock deformation in the tunneling process is ensured, the tunneling process is always within a controllable range, and safe and efficient tunneling is realized. Through the setting of joint supporting construction, can fully guarantee the stability of tunnel country rock, restrict the change degree of country rock deformation along with time to postpone or prevent the emergence of deformation destruction, ensure that the tunnel can keep good hole body structure in design service life or overhaul cycle.

According to a preferred embodiment, the partial reaming comprises the following steps: firstly, constructing an advanced pipe shed, ensuring that the inner diameter of a shield tunnel is reinforced by grouting, backfilling a shield pipe slice to a temporary inverted arch position by using a sand bag before expanding and digging a tunnel body, and pre-embedding a temporary stand column according to an excavation footage before backfilling and firmly connecting the temporary stand column with the pipe slice; secondly, measuring and positioning the excavation size of the first excavation area, excavating soil on the outer side of the duct piece of the first excavation area, erecting a steel arch frame, erecting a temporary steel support between the arch frame and the duct piece, constructing a mortar anchor rod, positioning a tie bar, a small advanced conduit, a connecting bar, hanging a net, spraying and mixing, and spraying concrete to the designed thickness; and thirdly, the excavation construction of the residual area to be excavated is completed by repeating the second step.

According to a preferred embodiment, after the excavation and supporting operation of the set excavation area is completed, the pipe pieces in the circular pilot tunnel are cut off in blocks, and a temporary inverted arch and a steel upright post are erected, so that the corresponding excavation area is closed into a ring; the expanding excavation of the middle hole is at least divided into a first excavation area and a second excavation area which are positioned on the upper half section, and a third excavation area and a fourth excavation area which are positioned on the lower half section. The tunnel wall excavation construction method has the advantages that the maximum stress transferred in the excavation process can be reduced by excavating the tunnel wall in the divided areas, so that the maximum stress can be limited within the compressive stress range which can be borne by the duct piece, and the collapse of rock mass caused by construction is avoided.

According to a preferred embodiment, after the construction of the first excavation area is completed, a small grouting guide pipe advance support of the arch part of the tunnel is constructed at a position lagging behind a set distance of the first excavation area, soil on the outer side of a segment of the second excavation area is excavated, a reinforcing mesh is installed, a steel frame is erected, primary support around a guide pit of the second excavation area is constructed, and concrete is sprayed to a set thickness.

According to a preferred embodiment, after tunnel penetration is completed in pilot tunnel excavation of a first excavation area and a second excavation area, a sandbag in a pipe piece at an excavation section is transported backwards in the excavation direction, the size position of a left lower section is measured and positioned, and soil outside the pipe piece of a third excavation area is excavated; and finishing the construction and support of the fourth excavation area after the set distance lags behind the third excavation area.

According to a preferred embodiment, under the condition that the expanding excavation construction and the preliminary bracing of the first excavation area, the second excavation area, the fourth excavation area and the fourth excavation area are completed in sequence, the size and the position of an inverted arch are measured according to initial design data, residual earthwork is excavated, residual pipe pieces are dismantled, steel arch frames are erected, temporary steel sections are used for connecting the inverted arch and vertical braces, connecting ribs, a net is hung, and concrete is sprayed, so that the closure of a primary support whole ring is completed.

According to a preferred embodiment, when the excavation construction of the tunnel is carried out, the pre-established excavation process and a supporting system are verified by carrying out real-time surrounding rock grade measurement on a section to be excavated; when the construction method corresponding to the surrounding rock grade of the tunnel section to be excavated, which is acquired in real time, cannot be matched with the preset operation instruction in the pre-established tunnel excavation process, the adaptive excavation method is updated according to the actually measured surrounding rock grade, the pre-established tunnel excavation process is updated, so that the tunnel excavation process of the tunnel section which is not excavated is corrected, and the deformation of the section to be excavated in the subsequent excavation process is limited by selectively supplementing the established advance support for the second time.

The application also provides an expanding excavation method suitable for local expanding excavation of the underground excavation section, and the construction procedures of the expanding excavation method at least comprise inserting and beating the small upper-step conduit, grouting, drilling and blasting the upper step, erecting an arch frame, beating the anchor rod, hanging the net and spraying the anchor, inserting and beating the small middle-step conduit, grouting, drilling and blasting the middle step, erecting the arch frame, beating the anchor rod, hanging the net and spraying the anchor, drilling and blasting the lower step, erecting the arch frame, beating the anchor rod, hanging the net and spraying the anchor and lining.

The application still provides a supporting construction suitable for secretly dig local expanding of district section and dig, sets up preliminary bracing and secondary lining in the well tunnel that has excavated to arrange at least one horizontal support and vertical braces in the well tunnel, make horizontal support and vertical braces divide into a plurality of branch tunnel with the well tunnel, wherein, the well tunnel is divided into by horizontal support and vertical braces and is expanded excavation district, thereby accomplishes the rock mass hole wall expanding excavation of a plurality of branch tunnel in an orderly manner.

According to a preferred embodiment, the horizontal support and the vertical support are synchronously extended along with the expanding excavation construction of the rock mass hole wall of the branch tunnel, so that a support can be provided for an excavation area formed by expanding the branch tunnel hole wall

Drawings

Fig. 1 is a schematic flow chart of a supporting structure and an expanding excavation method suitable for partial expanding excavation of an underground excavation section according to a preferred embodiment of the invention.

Detailed Description

The following detailed description is made with reference to the accompanying drawings.

Example 1

The application relates to an expanding excavation method suitable for partial expanding excavation of an underground excavation section, which is characterized by comprising the following steps of:

(1) and (3) setting an excavation process and a support system, obtaining the surrounding rock grades of different sections of the tunnel to be excavated according to geological information obtained by advanced geological forecast, matching an excavation construction method and a support structure according to the surrounding rock grades of the different sections, and orderly arranging the excavation construction method and the support structure corresponding to the different sections to form the excavation process and the support system of the tunnel to be excavated through splicing.

(2) And (5) excavating the middle tunnel, and performing advanced support, tunnel excavation construction and primary support on the middle tunnel area of the tunnel expanded excavation section according to the established excavation procedure and the support system.

Preferably, when the tunnel excavation construction is performed, the pre-established excavation process and the support system are verified by performing real-time surrounding rock grade measurement on the section to be excavated;

when the construction method corresponding to the surrounding rock grade of the tunnel section to be excavated, which is acquired in real time, cannot be matched with the preset operation instruction in the pre-established tunnel excavation process, the adaptive excavation method is updated according to the actually measured surrounding rock grade, the pre-established tunnel excavation process is updated, so that the tunnel excavation process of the tunnel section which is not excavated is corrected, and the deformation of the section to be excavated in the subsequent excavation process is limited by selectively supplementing the established advance support for the second time.

(3) And (4) local expanding excavation of the section, namely establishing a support system of an expanding excavation area according to the grade of the surrounding rock and synchronously performing local expanding excavation by using a three-step method.

Preferably, the partial reaming comprises the steps of:

firstly, constructing an advanced pipe shed, ensuring that the inner diameter of a shield tunnel is reinforced by grouting, backfilling the shield pipe segment to a temporary inverted arch position by using a sand bag before expanding and digging the tunnel body, and pre-embedding a temporary stand column according to an excavation footage before backfilling and firmly connecting the temporary stand column with the pipe segment.

And secondly, measuring and positioning the excavation size of the first excavation area, excavating a soil body on the outer side of a segment of the first excavation area, erecting a steel arch frame, erecting a temporary steel support between the arch frame and the segment, constructing a mortar anchor rod, positioning a tie bar, a small advanced conduit, a connecting bar and a hanging net, spraying concrete to the designed thickness (300 mm). And cutting off the pipe piece in the circular pilot tunnel in blocks, and erecting a temporary inverted arch and a steel upright post so as to close the corresponding excavation area into a ring.

And thirdly, after the construction of the first excavation area is completed, constructing a tunnel arch grouting small guide pipe advance support at a position 1m behind the first excavation area, excavating a soil body on the outer side of a segment of the second excavation area, installing a reinforcing steel bar net and erecting a steel frame, constructing a primary support at the periphery of a guide pit of the second excavation area, and spraying concrete to a set thickness (300 mm). And cutting off the pipe piece in the circular pilot tunnel in blocks, and erecting a temporary inverted arch and a steel upright post so as to close the corresponding excavation area and the extended transverse support and vertical support into a ring.

And fourthly, after the tunnel penetration of the pilot tunnel excavation of the first excavation area and the second excavation area is completed, transporting the left part of sandbags in the pipe piece at the excavation section back to the excavation direction, measuring and positioning the size position of the left lower section, and excavating the soil body outside the pipe piece of the third excavation area. Erecting a left lower part steel arch frame, constructing a foot locking anchor rod, connecting ribs, installing a reinforcing steel bar net piece, spraying concrete to a set thickness (300mm), and cutting off the pipe piece in the circular pilot tunnel in blocks.

And fifthly, after the distance lags behind the third excavation area by 1m, transporting the residual sandbags in the pipe piece at the section towards the tunneling direction, measuring and positioning the position of a steel arch frame of the fourth excavation area, excavating soil on the outer side of the pipe piece of the fourth excavation area, installing a reinforcing steel bar net piece, erecting a steel frame, constructing primary support on the periphery of a guide pit of the second excavation area, spraying concrete to a set thickness (300mm), and cutting the pipe piece in the circular guide tunnel in blocks.

Preferably, the expanding excavation of the middle hole is at least divided into a first excavation area and a second excavation area which are positioned on the upper half section, and a third excavation area and a fourth excavation area which are positioned on the lower half section. Preferably, the first excavated area, the second excavated area, the third excavated area, and the fourth excavated area may be, in turn, an upper left portion, an upper right portion, a lower left portion, and a lower right portion of the middle hole that are laterally supported and vertically supported. Preferably, under the condition that the expanding excavation construction and the preliminary bracing of the first excavation area, the second excavation area, the fourth excavation area and the fourth excavation area are completed in sequence, the size and the position of an inverted arch are measured according to initial design data, residual earthwork is excavated, residual pipe pieces are removed, a steel arch frame is erected, temporary section steel is used for connecting the inverted arch and a vertical support, connecting ribs are applied, a net is hung, and concrete is sprayed, so that the closing of a primary support whole ring is completed.

Preferably, a support monitoring system is built while the support is built in the tunnel after excavation and support building are completed, the support monitoring system can monitor and analyze the change situation of the built support structure and the tunnel rock mass along with time, a tunnel and a support model can be built according to the acquired deformation data of the support structure in the tunnel and the omnibearing space structure data of the tunnel, and the support structure and the tunnel surrounding rock deformation analysis are carried out by utilizing a plurality of models built in a time period. Preferably, the deformation and stress data of the supporting structure in the tunnel and the omnibearing space structure data of the tunnel, which are collected by the supporting monitoring system and related to time, are recorded by taking the preset deformation of the surrounding rock of the tunnel as the driving time. The preset deformation for sampling of the support monitoring system is adjustable and set according to the intensity of deformation of the tunnel surrounding rock. Preferably, when the support monitoring system monitors that the time period of the tunnel surrounding rock with the preset deformation is shortened, the support monitoring system adjusts the data acquisition frequency representing the surrounding rock deformation condition according to the mode of reducing the preset deformation and shortening the sampling period, and can send out early warning information according to the acquired abnormal deformation data.

Example 2

The application also relates to an expanding excavation method suitable for local expanding excavation of the underground excavation section. The surrounding rock self-stability of IV-grade and V-grade surrounding rocks is poor, and a full-section expanding excavation method is adopted, so that the blocks can fall off in the construction process, and even large-area collapse can be realized. And for IV-grade and V-grade surrounding rocks, adopting a small duct advanced support, and carrying out expanding excavation under a small duct support system by a three-step method. The construction process of the expanding excavation method at least comprises the steps of inserting and beating small conduits on the upper step, grouting, drilling and blasting on the upper step, erecting an arch frame, beating an anchor rod, hanging a net and spraying anchors, inserting and beating small conduits on the middle step, grouting, drilling and blasting on the middle step, erecting the arch frame, beating the anchor rod, hanging the net and spraying anchors, drilling and blasting on the lower step, erecting the arch frame, beating the anchor rod, hanging the net and spraying anchors and lining.

Preferably, the lead small pipe is a hot rolled seamless steel flower pipe with a diameter of 42mm and a wall thickness of 3.5 mm. And (4) inserting and drilling the small advanced guide pipe and grouting to ensure that the small guide pipe and the rock mass solidified by the grout form an advanced support system and provide conditions for expanding and excavating. The advanced small guide pipes are divided into single-row advanced small guide pipes and double-row advanced small guide pipes. When the surrounding rock is broken, cracks develop and water seepage is more multi-stage, double rows of advanced small guide pipes are adopted; and a single-row advanced small guide pipe is adopted for the relatively complete section of the surrounding rock.

The single-row advanced small guide pipe is generally applied to IV-grade surrounding rocks of the tunnel, and the length of a single pipe is 3.5 m. The circumferential distance is 50cm, the longitudinal distance is consistent with the single-cycle footage, namely, a row of small advanced catheters are inserted and punched in each cycle, the distance is 2m, the lap joint length is 1.1m, and the external insertion angle is controlled to be 10-15 degrees during insertion and punching.

The double rows of small advanced guide pipes are generally used for tunnel V-level surrounding rock, the length of each single pipe is 3.5-4 m, the distance between the two rows is 15cm, the circumferential distance is 50cm, and the pipes are arranged in a quincunx manner; when the surrounding rock is broken and the water seepage is more, the advanced small conduit is properly encrypted. The double rows of advanced small guide pipes are matched with a steel frame for use, the longitudinal distance is consistent with the single-cycle footage, the distance is 1.5m, the lap joint length is 1.5m, the external insertion angle of the 1 st row of small guide pipes is controlled to be 5-10 degrees, and the external insertion angle of the 2 nd row of small guide pipes is controlled to be 10-15 degrees.

The advanced small conduit grouting is the key for forming a small conduit advanced pre-support system, the water-cement ratio of grouting slurry is 0.5-1.0, the grouting pressure is 0.5-1.0 MPa, and targeted grouting materials can be adopted for loose broken zones with large water inflow. After the small guide pipe is grouted, the grouted and consolidated rock mass and the small guide pipe replace the existing lining together, and safety guarantee is provided for expanding and digging.

Preferably, the expanding and digging operation under the support of the advanced small guide pipe adopts controlled blasting, more holes are punched, the powder is filled less, and the damage to the small guide pipe support system caused by the blasting operation is avoided. And the excavation single-cycle progress is strictly controlled, the IV-grade surrounding rock is controlled within 2.0m, and the V-grade surrounding rock is controlled within 1.5 m. When the lower step is excavated, the excavation method of separately expanding and excavating the left half and the right half is implemented, and the influence of single expanding and excavating on the surrounding rock is reduced to the maximum extent. After the expanding excavation is finished, an arch center is erected in time, a system anchor rod is inserted and driven, and the anchor rod is supported by a net, so that the exposure time of an excavated surface is reduced, the excavated anchor-jet system is deformed and settled, and the risk of collapse is reduced.

The application relates to a supporting construction suitable for partial expanding excavation of an underground excavation section. The method comprises the steps of arranging primary support and secondary lining in an excavated middle tunnel, and arranging at least one transverse support and one vertical support in the middle tunnel, so that the middle tunnel is divided into a plurality of branch tunnels by the transverse supports and the vertical supports. The middle tunnel is divided into expanding excavation areas by the transverse supports and the vertical supports, so that rock mass tunnel wall expanding excavation of a plurality of branch tunnels is orderly completed. Preferably, the expanding excavation construction of the rock mass cave wall of the lateral support and the vertical support following the branch tunnel is synchronously extended, so that support can be provided for an excavation area formed by expanding the branch tunnel cave wall.

Example 3

The application also provides a region underground excavation method based on the surrounding rock grades, which comprises the steps of conducting advanced geological forecast on a tunnel region with standardized measurement and marking completed, obtaining geological surrounding rock grade information of the tunnel region according to the obtained advanced geological forecast, establishing a tunnel excavation procedure for reference of subsequent construction according to the distribution condition of the surrounding rock grades, and establishing an advanced support in a tunnel to be excavated according to the established tunnel excavation procedure and the surrounding rock grades. And adopting different excavation methods to carry out tunneling operation on different sections of the tunnel according to the constructed tunnel excavation procedure, and increasing active supports which can be combined with advanced supports to adapt to dynamic changes of surrounding rock stress and continuous attenuation of strong rigidity for different surrounding rock grades in the tunneling process. When the tunnel is tunneled in the preset excavation method along the set direction, the geological information acquisition equipment can detect the geology of the tunnel to be excavated, acquire the grade of surrounding rocks of the tunnel according to the detected geological information, and output the excavation method and the supporting structure which are matched with the tunnel according to the grade of the surrounding rocks. And when the real-time output excavation construction method cannot be matched with the excavation construction method of the corresponding tunnel section in the tunnel excavation process, updating the established tunnel excavation process according to the surrounding rock data acquired by the geological information acquisition equipment. And two constructors carry out tunneling on the section of tunnel according to the updated tunnel excavation procedure or the excavation construction method of the interval tunnel output in real time, and the constructors control the deformation of the tunnel surrounding rock in an increased active supporting mode in the excavation area according to the surrounding rock grade information acquired by the geological information acquisition equipment. The method for verifying whether the tunnel surrounding rock grade output according to the advanced geological forecast is accurate or not is verified through the construction area real-time tunnel surrounding rock grade acquired by geological information acquisition equipment, and the preset tunnel excavation process and the advanced support framework are verified or corrected, so that the tunnel excavation operation and the surrounding rock support operation can be performed by using the optimal excavation construction method and the support structure all the time in the tunnel excavation process, the controllability of surrounding rock deformation in the excavation process is ensured, the tunnel excavation process is always within a controllable range, and safe and efficient excavation is realized. In the process of tunnel excavation, constructors can selectively adjust an excavation construction method and a corresponding support framework according to surrounding rock grades, so that tunnels with different geological conditions and surrounding rock grades are excavated by adopting different construction methods, a matched support system is constructed, active support can be effectively added particularly under the condition of advanced support, the stability of the surrounding rock of the tunnel can be fully ensured through the arrangement of a combined support structure, the change degree of the deformation of the surrounding rock along with time is limited, the occurrence of deformation damage is delayed or prevented, and the tunnel can be ensured to keep a good tunnel body structure within the design service life or the overhaul period.

Preferably, under the condition that the tunnel excavation process constructed by the geological information acquisition equipment is updated according to geological data acquired by the geological information acquisition equipment, the updated tunnel excavation process is verified in a mode of secondary advanced geological prediction on an unearthed tunnel region, and secondary advanced support is carried out on a tunnel section, needing to be reinforced and supported, of the region to be excavated according to the verified tunnel excavation process. The initial detection surrounding rock grade is verified and corrected according to the geological data and the surrounding rock grade acquired in real time in the construction process, so that the preset tunnel excavation process and the advance support framework can be accurately adjusted, and the tunnel excavation project can be quickly and stably constructed. Preferably, the tunnel excavation procedure is to select an excavation method adapted to the tunnel section according to the surrounding rock grades of different sections of the tunnel to be excavated, and arrange the plurality of excavation methods in order to form an operation set. Namely, the tunnel excavation process at least comprises the operation steps of orderly performing excavation construction on at least part of the tunnel region according to a plurality of excavation methods selected according to the surrounding rock grades of different sections of the tunnel. Preferably, the plurality of excavation methods associated with the grade of the surrounding rock of the section tunnel sequentially splice the plurality of excavation methods corresponding to the grade of the surrounding rock of the section tunnel in a manner that the section tunnels are butted to form a tunnel model, and only segment marking is performed on the constructed tunnel model. Preferably, the non-matching means that the excavation method of a section of the tunnel set according to the advanced geological forecast is inconsistent with the excavation method output by acquiring the real-time field surrounding rock data before the same section is tunneled, and if the two excavation methods are different, the excavation method output in real time cannot be matched with the excavation process. Preferably, the matching operation is that in the construction process, the real-time surrounding rock grade of the section to be excavated is calculated according to surrounding rock data acquisition of the section to be excavated, the excavation construction method is output according to the calculated surrounding rock grade, the output excavation construction method is matched with the preset excavation construction method of the corresponding section in the excavation procedure, if two excavation construction methods in different periods of the same tunnel section are consistent, the construction operation can be directly performed, if the two excavation construction methods are inconsistent, tunneling construction along with the tunnel is indicated, and if the surrounding rock of the same section changes or data of early advance geological forecast has errors, the tunneling operation is continued after the supporting and protecting geology of the section of the tunnel is pertinently supplemented according to the surrounding rock data and the advance geological data detected in real time.

Preferably, the advanced geological forecast is to find out information such as unfavorable engineering, hydrogeology and the like in front of the tunnel face of the tunnel through comprehensive means such as geological survey, physical detection, advanced geological drilling and hole exploration and the like, and early warn in advance so as to take targeted engineering technical measures, reduce the harm of the unfavorable geology to the construction of the rail traffic engineering and ensure the safety quality of the construction of the tunnel engineering. The method comprises the steps of detecting the condition grade and the surrounding environment of the whole surrounding rock of the engineering by adopting a geological radar forecasting means, matching with advanced geological drilling, and timely mastering the scale, the property, the stability and the underground water condition of a rock stratum and a broken zone, so that the obtained geological information of the area of the tunnel to be excavated establishes a targeted and reasonable tunnel excavation process. Preferably, the advanced geological drilling aims at detecting the lithology, the structure and the water-leaking condition in front of the surrounding rock, and the front geological condition is judged through the change of the lithology, the stuck drill, the blunt drill and the water-leaking condition. And in the drilling process, observing the hole forming speed, hole slag, water flow in the hole and the like to judge whether the front stratum is suddenly changed. In the construction process, geological sketch and geological record are required after each blasting is finished, the geological condition is analyzed and compared with the geological survey report and the advanced geological forecast, so that the support parameters are optimally adjusted, the cyclic footage is accelerated, and the construction progress is improved.

Preferably, the constructor can carry out tunneling construction and tunnel surrounding rock supporting on different tunnel sections by adopting different excavation methods in sequence according to a pre-established tunnel excavation procedure. Specifically, the excavation operation of the constructor is performed according to a predetermined construction scheme, and the constructor can perform excavation construction on tunnel sections with different surrounding rock grades by using different excavation methods according to a predetermined tunnel excavation procedure in the construction operation process. Preferably, the excavation method for selecting a tunnel in a specific section by a constructor is to verify the tunnel excavation process established in advance by adopting the excavation method according to the surrounding rock grade information of the section to be excavated of the tunnel acquired by geological information acquisition equipment and the output. Preferably, the constructor may be the assembled tunnelling equipment and tunnelling process. Preferably, when the excavation construction method of the tunnel in the section output by the geological information acquired by the geological information acquisition equipment is inconsistent with the excavation construction method of the same section in the tunnel excavation process established in advance, the built advance support in the tunnel in the section is supplemented according to the actual surrounding rock grade of the tunnel in the section acquired by the geological information acquisition equipment, so that the surrounding rock of the tunnel in the section can be always kept in a relatively stable state in the excavation process, sufficient construction time is provided for building an active support in the subsequent tunneling process, the deformation in the initial deformation stage can be timely inhibited, and the tunnel is prevented from generating larger deformation when an effective support structure is not built in the initial stage; secondly, the rapid deformation stage is effectively controlled and pushed to be rapidly completed, so that the deformation enters the deformation slowing stage as soon as possible.

Preferably, the constructor can selectively perform the tunneling construction operation of the tunnels in different sections by adopting a three-step method, a CD method or a CRD method according to the verified tunnel excavation procedure, and can perform the conversion of the excavation construction method according to the corrected tunnel excavation procedure after collecting and confirming the actual grade of the surrounding rock of the tunnel in the next section to be excavated at the junction of the tunnel sections with the changed grade of the surrounding rock by using geological information collecting equipment, thereby completing the tunneling operation of the tunnels in a plurality of continuous sections.

Preferably, when the tunneling operation of the tunnel in the section is performed, different support systems are constructed in the tunnel according to the excavation method and the grade of the surrounding rock adopted in the area of the tunnel, and a support monitoring system capable of monitoring the deformation condition of the surrounding rock is arranged in the tunnel. The supporting monitoring system monitors the omnibearing space structure of the tunnel and generates space structure data, so that surrounding rock deformation and supporting deformation of the whole tunnel space are monitored, a tunnel model along time is constructed by utilizing the collected space structure data, tunnel deformation analysis is completed by utilizing a mode of comparing a plurality of orderly arranged tunnel models established along a time axis, and accordingly section tunnels with abnormal deformation of the surrounding rock and the supporting structure can be monitored more frequently and accurately, and construction maintainers are prompted to make targeted supplementary supporting for the abnormal deformation area. Namely, under the condition that a plurality of tunnel models established along the time axis have differences, the deformed region of the tunnel is selectively and additionally supported to control the deformation amount of the surrounding rock of the tunnel. Preferably, the spatial structure data related to time collected by the support monitoring system is recorded by taking a preset deformation amount of the tunnel surrounding rock as driving time, and the preset deformation amount for sampling is adjustable and set according to the intensity of deformation of the tunnel surrounding rock. Preferably, when the support monitoring system monitors that the time period of the preset deformation of the tunnel surrounding rock is shortened, the support monitoring system acquires dense space structure data representing the deformation condition of the surrounding rock in a mode of reducing the preset deformation and shortening the sampling period. Further preferably, when the support monitoring system detects that the tunnel surrounding rock is abnormally deformed and/or excessively deformed, the support monitoring system can send early warning information to at least one display terminal while adjusting the preset deformation of the sampling.

Preferably, the support monitoring system may include a three-dimensional laser scanner and an infrared thermal imager. The three-dimensional laser scanner can scan the inside of the tunnel. The spatial structure data are accurately and comprehensively acquired in real time, the tunnel deformation analysis is carried out, and the tunnel information construction is guided, so that the risk early warning and forecasting can be timely carried out on the tunnel construction. The inside of the tunnel is scanned in a segmented mode in the scanning process, and a wireless transmission device carried by the three-dimensional laser scanner transmits a real-time scanning picture to a main control module to remotely acquire point cloud data; and after the cloud data are obtained, the main control module processes the data and automatically generates a tunnel structure diagram. In addition, the measured point cloud data are respectively in mutually independent coordinate systems with the measuring stations as the origin, so that the point cloud data of the measuring stations need to be spliced when the tunnel deformation analysis is carried out. And comparing the generated tunnel section diagram with a design specification, observing whether displacement such as peripheral displacement and vault subsidence of the tunnel is in a normal state, and when abnormal conditions such as a recurved point and the like occur in the measured data convergence rate, indicating that abnormal deformation occurs in the surrounding rock and needing to take a reinforcing support measure. And the infrared thermal imager and the three-dimensional laser scanner are used for monitoring the interior of the tunnel simultaneously. The thermal infrared imager is composed of an infrared detector, an optical imaging objective lens and an optical machine scanning system and is mainly used for receiving infrared radiation energy distribution maps of all positions in a tunnel, the infrared radiation energy is converted into electric signals by the detector, and the electric signals are amplified, converted or standard video signals are displayed on an infrared thermal image through a display module. The display module can be a television screen or a monitor; the infrared thermal imager also utilizes the equipped wireless transmission device to construct the environment for the transmission tunnel. This facilitates monitoring of abnormal infrared radiation (e.g. water inrush) within the tunnel. The real-time scanning picture and the infrared radiation energy distribution map are matched and analyzed to perform form and energy complementary analysis, so that the detection capability is improved, and real-time and omnibearing detection can be realized.

Example 2

This embodiment is a further improvement of embodiment 1, and repeated contents are not described again.

When the subway tunnel construction of the metal starting section is carried out, the hidden beam and the embedded part are synchronously embedded in the construction of the transverse channel, and the horsehead door reinforcing frame is constructed after the construction. And then, opening a south side ingate, and carrying out front line excavation supporting construction. After the full section is sealed into a ring of 15m, opening the side ingate to carry out front line excavation supporting construction.

And synchronously pre-burying the hidden beam and the pre-buried part in the construction of the vertical shaft, and constructing a horse head door reinforcing frame after the construction is finished. And then opening a north side ingate, and performing main line excavation supporting construction. After the full section is sealed into a ring of 15m, opening the side ingate to carry out front line excavation supporting construction.

And excavating the main line by adopting a drilling and blasting method, and mechanically finishing to break the excavation matching.

Excavating II and III-grade surrounding rock sections by adopting a three-step method, and adopting a support system of a reinforcing mesh, sprayed concrete and an anchor rod, wherein the step offset is 3-5 m;

excavating the IV-level surrounding rock section by adopting a three-step method, and adopting a supporting system of a steel grating, sprayed concrete, a reinforcing mesh and an anchor rod, wherein the step offset is 3-5 m;

and excavating the V-level surrounding rock section by adopting a CD method, adopting a combined supporting system of a steel grating, sprayed concrete, a reinforcing mesh and an anchor rod, and excavating each pilot tunnel by adopting a step method, wherein the step offset is 3-5 m, and the offset distance between the left pilot tunnel and the right pilot tunnel is more than 10 m.

And (3) excavating in the range of 5m on two sides of the vertical shaft wall by adopting a CRD method, namely adding temporary cross braces at the upper step and the lower step excavated by the original CD method.

The underground excavation operation needs to be carried out strictly according to the designed construction step sequence, and 1-3 advanced exploration holes are drilled under the guidance of advanced geological forecast before the underground excavation operation is determined to be implemented so as to find the development condition of underground water. The probe hole is arranged at a position 1m below the vault.

Preferably, the transverse passage ingate is firstly constructed towards the south side area and then constructed towards the north side area.

In the construction stage of the transverse channel, arch crown advanced small guide pipes and grouting are drilled at the part of the ingate in the alignment line section, hidden beam steel bars are pre-buried, a ingate reinforcing frame is constructed after the early support of the transverse channel is finished, early support of an upper step of a left pilot tunnel is broken → three reinforcing steel grids in front of an arch part of the erecting tunnel and concrete is sprayed → soil mass of the arch part is excavated, a fourth steel grid of the arch part is erected and concrete is sprayed → hollow anchor rods are drilled along the arch part for grouting → next construction is carried out → excavation is carried out for 3-5 meters → the lower step of the left pilot tunnel is broken → three reinforcing steel grids in front of the erecting tunnel are sprayed → soil mass is excavated, the fourth steel grid is erected and concrete is sprayed → construction of the next steel grid is carried out → circular construction of an upper step and a lower step is carried out after ring is closed.

And after the left pilot tunnel is excavated to be not less than 10m, constructing a ingate of the right pilot tunnel according to the same method.

And after the full sections of the left and right pilot tunnels are closed to form a ring of not less than 15m, opening the side ingates according to the same construction sequence.

The highly weathered basalt in the ingate range is preferentially broken mechanically, and is constructed by adopting a drilling and blasting method when the strong weathered basalt is difficult to break. And constructing the other stroke-induced rock layers by adopting a drilling and blasting method.

Preferably, the two sides of the vertical shaft wall are excavated within 5m by adopting a CRD method. The vertical shaft ingate is firstly constructed towards the north side interval and then constructed towards the south side interval.

In the construction stage of the vertical shaft, a small arch crown advance guide pipe and grouting are arranged at the position of the horsehead door in the alignment line section, hidden beam steel bars are pre-buried, a horsehead door reinforcing frame is applied after the early support of the vertical shaft is finished, a horsehead door reinforcing frame is firstly supported on the left side pilot tunnel on the north side of the broken section, three reinforcing steel grids in front of the arch part of the erection tunnel door are sprayed with concrete → the soil mass of the arch part is excavated, a fourth steel grid of the arch part is erected and sprayed with concrete → a hollow anchor rod is arranged along the arch part for grouting → the next construction is carried out → the excavation is carried out for 10m → the first support of the upper step of the broken right side pilot tunnel → three reinforcing steel grids in front of the erection tunnel door are sprayed with concrete → the soil mass is excavated, the fourth steel grid is erected and sprayed with concrete → the next construction is carried out → the upper step of the left side pilot tunnel is circularly constructed according to the CRD closed ring of not less than 10 m.

And (3) closing the ingate on the left and right pilot tunnels on the opposite side (south side) of the construction interval into a ring of not less than 5 meters according to CRD (cross-linking detection).

And then constructing the ingate of the lower step of the left and right guide tunnels on the north side according to the same method, and opening the ingate of the lower step of the left and right guide tunnels on the opposite side (south side) according to the same construction sequence after the full section of the left and right guide tunnels is closed into a ring of not less than 15 m.

Preferably, in order to ensure construction safety, the temporary bottom sealing of the shaft bottom is carried out when the shaft is constructed to 2m below the arch crown of the passage from top to bottom. Then, a single row of small ducts are arranged, wherein the advanced small ducts are made of DN25 multiplied by 2.75mm steel pipes, the small ducts are 4m long, the ducts are arranged horizontally, single-liquid cement slurry is injected, the annular distance is 0.3m, the distance from an excavation line is 0.3m, and the ducts are arranged along the range of the arch part.

After the pilot tunnel on the transverse channel is finished, immediately drilling a single-row small guide pipe, wherein the advanced small guide pipe is a DN32 multiplied by 2.75mm steel pipe, the length of the small guide pipe is 4m, the horizontal drilling is carried out, single-liquid cement slurry is injected, the annular interval is 0.3m, the distance from an excavation line is 0.3m, and the drilling is carried out along the range of the arch part.

Grouting pressure: 0.2 to 0.5 MPa. Grouting diffusion radius: 250 mm. The grouting speed is less than or equal to 30L/min.

Example 3

Preferably, in the construction process of the three-step method, the distance between every two steps is staggered by 3-5 m; core soil does not need to be reserved on each step, and the steps are set to be on the slope according to the soil layer stability condition 1 (0.7-1.0). During construction, the working surface is ensured to be operated without water, and water accumulation on the tunnel surface and in the tunnel is strictly forbidden. And (5) performing back grouting in time after the primary support is finished. Monitoring and measurement should be enhanced during construction, and support parameters are adjusted according to feedback information of the monitoring and measurement. Further preferably, the construction step of the interval standard end face three-step method comprises the following steps:

step 1: and excavating an upper step with the height of 2.5 m. Setting hollow anchor rod in arch part, hanging net and spraying concrete.

Step 2: and excavating middle steps with the height of 3.165 m. And (4) arranging a hollow anchor rod, hanging a net and spraying concrete.

And 3, step 3: the lower step was excavated, height 3.165 m. And hanging a net and spraying concrete.

The three-step method construction step sequence of the section cross crossover section comprises the following steps:

Step 2: and excavating middle steps with the height of 3.735 m. And (4) arranging a hollow anchor rod and a local mortar anchor rod, hanging a net and spraying concrete.

And 3, step 3: the lower step was excavated, height 3.735 m. And (4) arranging local mortar anchor rods, hanging nets and spraying concrete.

Preferably, in the CD method construction process, each pilot tunnel is excavated by a step method, the distance between an upper step and a lower step is staggered by 3-5 m, and the longitudinal excavation surface of each pilot tunnel is staggered by more than 10 m; and each step adopts 1 (0.7-1.0) slope relief according to the soil layer stability condition. During construction, the working surface is ensured to be operated without water, and water accumulation on the tunnel surface and in the tunnel is strictly forbidden. Grouting in time after primary backing. Monitoring and measurement should be enhanced during construction, and support parameters are adjusted according to feedback information of the monitoring and measurement. In order to reduce the stress concentration of the bottom corner of the grating, the deficient slag under the ground must be removed before the steel frame is installed, the over-digging part is preferably filled with sprayed concrete, so that the base of the steel frame is dropped on the sprayed concrete cushion layer to prevent the whole sinking or uneven sinking of two sides of the steel frame.

Further preferably, the interval standard section CD method construction step comprises:

step 1: and excavating an upper step of the left pilot tunnel, wherein the height is 4.75m and the width is 6.5 m. And (3) arranging a hollow anchor rod of the arch part, hanging a net, erecting a steel grating, arranging a locking anchor pipe, and arranging a small arch crown advanced guide pipe. And (5) spraying concrete. Excavating for 3-5 m.

Step 2: and excavating a lower step of the left pilot tunnel, wherein the height is 4.38m and the width is 6.5 m. Hanging a net, erecting a steel grid and spraying concrete. Excavating for more than 10 m.

And 3, step 3: and excavating an upper step of the right pilot tunnel, wherein the height is 4.74m and the width is 5.6 m. And (3) arranging a hollow anchor rod of the arch part, hanging a net, erecting a steel grating, arranging a locking anchor pipe, and arranging a small arch crown advanced guide pipe. And (5) spraying concrete. Excavating for 3-5 m.

And 4, step 4: and excavating a lower step of the right pilot tunnel, wherein the height is 4.37m and the width is 5.6 m. Hanging a net, erecting a steel grid and spraying concrete.

The CD method construction step sequence of the section cross crossover line comprises the following steps:

step 1: and excavating an upper step of the left pilot tunnel, wherein the height is 5.48m and the width is 6.75 m. And (3) arranging a hollow anchor rod of the arch part, hanging a net, erecting a steel grating, arranging a locking anchor pipe, and arranging a small arch crown advanced guide pipe. And (5) spraying concrete. Excavating for 3-5 m.

Step 2: and excavating a lower step of the left pilot tunnel, wherein the height is 4.78m and the width is 6.75 m. And (4) arranging local mortar anchor rods, hanging nets, erecting steel grids and spraying concrete. Excavating for more than 10 m.

And 3, step 3: and excavating an upper step of the right pilot tunnel, wherein the height is 5.47m and the width is 5.85 m. And (3) arranging a hollow anchor rod of the arch part, hanging a net, erecting a steel grating, arranging a locking anchor pipe, and arranging a small arch crown advanced guide pipe. And (5) spraying concrete. Excavating for 3-5 m.

And 4, step 4: and excavating a lower step of the right pilot tunnel, wherein the height is 4.78m and the width is 5.85 m. And (4) arranging local mortar anchor rods, hanging nets, erecting steel grids and spraying concrete.

Preferably, in the tunnel excavation process, different excavation methods are adopted for tunnels in different sections according to different requirements of surrounding rock grades of a tunnel passing area, so that when the surrounding rock grades of the tunnels are changed and the excavation methods are adjusted correspondingly, the following excavation method conversion operations can be included according to different actual front and back excavation methods:

method for converting CD method into three steps

1. And when the upper step of the pilot tunnel on one side of the CD method reaches the construction method conversion section, stopping construction. 2. And when the upper step of the pilot tunnel on the other side reaches the construction method conversion section, starting the three-step construction. 3. The remainder of the CD method was performed in the order of the CD method steps.

Method for converting three-step method into CD method

1. And when the step method is adopted for step construction to the construction method for converting the section, left and right pilot tunnels are respectively constructed according to the CD method excavation step sequence. 2. And excavating the rest part by a three-step method, and gradually transitioning to the CD method for excavating the section.

CRD to CD conversion

In the construction process, the excavation steps of the CRD method and the CD method are consistent, and the difference is whether a temporary cross brace is erected after the upper step of the pilot tunnel at one side is excavated. Therefore, when the CRD method is converted into the CD method, only the temporary cross brace needs to be cancelled, and construction can be carried out according to the requirements of the CD method.

Preferably, for the selected specific subway tunnel, the interval tunnel is excavated by a drilling and blasting method and is mechanically or manually matched and renovated. The slag soil is horizontally transported to a vertical shaft, then lifted to a ground slag yard through lifting equipment, and transported out of the yard through a slag transport vehicle.

Blasting construction is detailed in blasting design and construction. After the grid spacing and the surrounding environment risks are considered in the CD method excavation circulation footage, the upper step is temporarily set to be 0.75m, and the lower step is temporarily set to be 1.5 m. The three-step construction circulation footage temporarily sets an upper step 1m, a middle step and a lower step 2 m. In the construction, the circulation footage is dynamically adjusted according to the vibration monitoring condition and the protection of the risk source, so that safe, economical and efficient excavation is facilitated.

In order to ensure the construction safety, the water stopping is carried out on the rock stratum fracture, and the water stopping method is cement-water-glass double-liquid grouting water stopping to reduce the permeability of bedrock. If water seepage occurs, a temporary water collecting pit is arranged in the middle, and the submerged pump can timely pump out the accumulated water.

And the arch top of the plane excavation contour line is expanded by 8cm, the side wall is expanded by 6cm, the requirement of surrounding rock deformation convergence and the clearance of construction errors is met, and the external expansion amount is adjusted according to the monitoring and measuring conditions.

When the distance between the two opposite excavation working surfaces is 13m, one end stops construction, personnel and machinery are removed to a safe area, and the other end is constructed until the tunnel is communicated.

Preferably, in order to meet equipment installation and space planning requirements, local locations need to be enlarged. The specific mounting positions (center lines) are YK10+036.003 and ZK10+ 044.006. The longitudinal length of excavation is 3.8m, the height is 6.573m, and the depth is 0.6-2.137 m from the tunnel excavation profile. Support parameters: 4.0m vault R25 hollow slip casting anchor @1.2 mx1.2m. L is 4.0m side wall diameter 22 mortar anchor rod @1.2 mx1.2m. C25 shotcrete 150mm thick. Single layer Φ 8 rebar mesh @150 × 150. Preferably, the main line of the section is excavated by a three-step method, and the primary support is an anchor-shotcrete support. And after the interval tunnel passes through the expanding excavation section, expanding excavation is carried out. During expanding excavation, after the primary support of the existing tunnel is chiseled in parts, drilling explosion is adopted and mechanical chiseling is combined for carrying out.

It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not limiting upon the claims. The scope of the invention is defined by the claims and their equivalents. Throughout this document, the features referred to as "preferably" are only an optional feature and should not be understood as necessarily requiring that such applicant reserves the right to disclaim or delete the associated preferred feature at any time.

Claims

1. An expanding excavation method suitable for partial expanding excavation of an underground excavation section is characterized by comprising the following steps of:

(1) the method comprises the steps of setting an excavation process and a support system, obtaining surrounding rock grades of different sections of a tunnel to be excavated according to geological information obtained by advanced geological forecast, matching an excavation construction method and a support structure according to the surrounding rock grades of the different sections, and orderly arranging the excavation construction method and the support structure corresponding to the different sections to form the excavation process and the support system of the tunnel to be excavated through splicing;

(2) carrying out middle tunnel excavation, and carrying out advanced support, tunnel excavation construction and primary support on a middle tunnel area of the tunnel expanded excavation section according to the established excavation procedure and the support system;

2. The method of claim 1, wherein the partial ream comprises the steps of:

firstly, constructing an advanced pipe shed, ensuring that the inner diameter of a shield tunnel is reinforced by grouting, backfilling a shield pipe slice to a temporary inverted arch position by using a sand bag before expanding and digging a tunnel body, and pre-embedding a temporary stand column according to an excavation footage before backfilling and firmly connecting the temporary stand column with the pipe slice;

secondly, measuring and positioning the excavation size of the first excavation area, excavating soil on the outer side of the duct piece of the first excavation area, erecting a steel arch frame, erecting a temporary steel support between the arch frame and the duct piece, constructing a mortar anchor rod, positioning a tie bar, a small advanced conduit, a connecting bar, hanging a net, spraying and mixing, and spraying concrete to the designed thickness;

and thirdly, the excavation construction of the residual area to be excavated is completed by repeating the second step.

3. The expanding excavation method suitable for the partial expanding excavation of the underground excavation section as claimed in claim 2, wherein after the excavation and supporting operation of the set excavation area is completed, the pipe pieces in the circular pilot tunnel are cut off in blocks, and a temporary inverted arch and steel columns are erected so that the corresponding excavation area is closed into a ring;

the expanding excavation of the middle hole is at least divided into a first excavation area and a second excavation area which are positioned on the upper half section, and a third excavation area and a fourth excavation area which are positioned on the lower half section.

4. The method of claim 2, wherein after the first excavation is completed, a tunnel arch grouting small conduit advance support is constructed at a position lagging behind the first excavation by a set distance, soil outside the segment of the second excavation is excavated, a reinforcing mesh is installed, a steel frame is erected, primary support around a pilot tunnel of the second excavation is constructed, and concrete is sprayed to a set thickness.

5. The enlarging excavation method suitable for partial enlarging excavation of the underground excavation section as claimed in claim 2, wherein after the tunnel penetration of the pilot tunnel excavation of the first excavation area and the second excavation area is completed, the sandbags in the pipe pieces at the excavation section are transported backwards in the excavation direction, the position of the size of the left lower section is measured and positioned, and the soil body outside the pipe pieces of the third excavation area is excavated;

and finishing the construction and support of the fourth excavation area after the set distance lags behind the third excavation area.

6. The expanding excavation method suitable for partial expanding excavation of the underground excavation section according to claim 5, wherein in the case of sequentially completing expanding excavation construction and preliminary bracing of the first excavation region, the second excavation region, the fourth excavation region and the fourth excavation region, the size and position of the inverted arch are measured according to the initial design data, the remaining earthwork is excavated and the remaining segments are removed, and the steel arch is erected and the inverted arch and the vertical braces are connected with temporary section steel, and the connecting bar, the net and the shotcrete are applied, thereby completing the closing of the primary support whole ring.

7. An excavation expanding method suitable for partial excavation expanding of an underground excavation section according to any one of the preceding claims, wherein during the excavation construction of the underground excavation, the pre-established excavation procedure and support system are verified by performing real-time surrounding rock grade measurement on the section to be excavated;

8. The expanding excavation method suitable for the local expanding excavation of the underground excavation section is characterized by comprising the construction procedures of inserting and beating small upper-step conduits, grouting, upper-step drilling blasting, erecting an arch frame, beating anchor rods, hanging and anchoring, inserting and beating small middle-step conduits, grouting, middle-step drilling blasting, erecting the arch frame, beating anchor rods, hanging and anchoring, lower-step drilling blasting, erecting the arch frame, beating anchor rods, hanging and anchoring and lining.

9. A supporting structure suitable for partial excavation of an underground excavation section is characterized in that primary supports and a secondary lining are arranged in an excavated middle tunnel, and at least one transverse support and a vertical support are arranged in the middle tunnel, so that the transverse support and the vertical support divide the middle tunnel into a plurality of branch tunnels, wherein,

the middle tunnel is divided into expanding excavation areas by the transverse supports and the vertical supports, so that rock mass tunnel wall expanding excavation of a plurality of branch tunnels is orderly completed.

10. A support structure adapted for use in partial excavation of an undercut section according to any one of the preceding claims, wherein the lateral and vertical supports are extended simultaneously with the excavation of the rock mass wall of the spur to provide support for the excavated area formed by the extension of the spur wall.