Combined excavation method for shaft in soft-over-hard composite strata

Abstract

A combined excavation method for a shaft in soft-over-hard composite strata, comprising the following steps: S1, performing a geological investigation on strata of a shaft excavation region to determine ranges of a soft stratum and a hard stratum; S2, determining whether the distance from the bottom of the hard stratum to the ground surface within a designed shaft depth is greater than 20 m, and if same is greater than 20 m, proceeding to S3, and if same is less than 20 m, proceeding to S4; S3, performing initial excavation on the soft stratum until the interface between the soft stratum and the hard stratum is exposed, and then proceeding to S4; and S4, directly blasting the hard stratum, and then performing main excavation on the blasted rock fragments and removing the waste; and repeating step S4 until the excavation reaches the designed shaft depth. The present application is an optimized combined excavation method based on a conventional shaft construction process, can realize efficient boring of a shaft in soft-over-hard composite strata, can reduce the impact of the excavation process on the surrounding environment, can reduce the blasting vibration, can reduce the wear of a cutter of a shaft boring machine during mechanical excavation, and can reduce the construction costs.

Description

Combined excavation method for shaft in upper-soft and lower-hard composite stratum TECHNICAL FIELD

[0001] The present application relates to the field of subway shaft construction, and particularly relates to a combined excavation method for shaft in upper-soft and lower-hard composite stratum. BACKGROUND

[0002] With the rapid development of rail transit construction in China, the densification of the traffic network makes the urban and underground engineering construction face the construction problems in complex environments such as large engineering depth, dense buildings or close to important traffic trunk lines, which increases the difficulty and risk of urban subway engineering construction. As an important structure and main passage of urban subway construction, the construction efficiency of the shaft affects the safe and efficient construction of the whole subway line. Due to the increase of the diameter and excavation depth of the shaft, the stratum conditions through which the shaft passes will be more complex. For example, there are upper-soft and lower-hard strata in some departments of China. Referring to FIG. 1, the upper-soft and lower-hard stratum is a composite stratum in the vertical direction, that is, the upper part of the composite stratum is a soft soil layer or a soft rock layer, and the lower part is a hard rock layer. In addition, the upper-soft and lower-hard stratum also includes a soft rock layer sandwiched in the hard rock layer, or a hard rock layer sandwiched in the soft rock layer, and the like. Among them, the hard rock generally refers to the rock with a saturated uniaxial compressive strength Rc greater than 30 MPa, the rock with Rc of 15-30 MPa is a relatively soft rock, and the rock with Rc less than 15 MPa is a soft rock or an extremely soft rock. Under the geological conditions of upper-soft and lower-hard, the shaft construction has higher requirements for the shaft excavation method, which not only needs to ensure the stability of the support structure of the upper soft rock or broken zone excavation, but also needs to meet the excavation requirements of the deep hard rock stratum. Therefore, it is of great significance for the subway shaft construction to carry out related research on the shaft excavation technology in the upper-soft and lower-hard composite stratum and to propose an efficient and low-disturbance excavation method for the shaft in the upper-soft and lower-hard composite stratum.

[0003] At present, the commonly used construction methods for shaft excavation mainly include drilling and blasting method and mechanical excavation method. Since the urban subway construction is in the environment-sensitive area with dense buildings, the construction disturbance and environmental protection requirements are high, and the traditional drilling and blasting method has complicated procedures and great difficulty in precise blasting, which easily brings great disturbance to the upper soft stratum, thereby leading to problems such as excessive deformation of surrounding rock and even surface subsidence and tunnel collapse. Therefore, the drilling and blasting method is limited in the excavation of subway shaft. Therefore, the mechanical method excavation mainly using shaft boring machine has developed rapidly in recent years and is widely used in the construction of different types of shaft engineering.

[0004] In order to improve the efficiency of shaft excavation, shaft mechanical method excavation has gradually developed from the traditional manual combined with engineering machinery excavation to more intelligent and mechanized shaft boring machine. Shaft boring machine excavation method is to realize the vertical mechanical excavation of shaft on the basis of traditional shaft construction technology, combined with tunnel boring machine technology (horizontal excavation) and material lifting technology. At present, shaft boring machine mainly includes SBM (Shaft Boring Machine) shaft boring machine, SBR (Shaft Boring Roadheader) cutting type shaft boring machine and full-face reaming type shaft boring machine. Among them, the SBR cutting type shaft boring machine can be applied to the upper soft and lower hard composite stratum. When the shaft boring machine excavates, the cutting type cutter head is used to excavate the soft stratum first, and stops at the boundary between soft rock and hard rock. Then the cutting type cutter head is replaced with a ring cutting roller cutter to excavate the hard rock layer. However, when the cutting type shaft boring machine changes the cutter, the main machine needs to be lifted, the cutter needs to be replaced and then fixed again, which makes the process more complicated. If the ring cutting roller cutter is used directly, the economic benefit of shaft excavation will be significantly reduced. In addition, the ring cutting roller cutter excavates only in the hard rock area at the bottom of the blade foot ring, and the excavation depth is relatively shallow, which is not suitable for large-area hard rock stratum excavation, especially when there are boulders or large hard rock layer in the middle of the shaft. If the lower hard rock layer of the composite stratum is thick and large in range, blasting or other methods still need to be used for excavation.

[0005] As can be seen from the above, the existing shaft tunneling technology mainly uses mechanical excavation, and through the optimization of shaft tunneling machine construction process and cutter, the vertical mechanical excavation of upper soft and lower hard stratum is realized. However, in practical application, the wear of rock to the excavation cutter of the tunneling machine is still inevitable, especially under the condition of large rock hardness, wide range and dense surrounding rock, the excavation efficiency of ordinary tunneling machine cutter is very low and the cutter wears greatly, so there are still many difficulties in excavation when there are boulders or large hard rock stratum range in the upper soft and lower hard stratum of the shaft. SUMMARY

[0006] In order to solve the technical problems of large cutter wear, low excavation efficiency and high cost in the process of shaft excavation in the upper soft and lower hard composite stratum of urban subway, a combined excavation method is proposed, which provides a new method for safe, efficient and low disturbance construction of urban subway shaft. The combined excavation method combines controlled blasting and cutting type shaft boring machine, and combines with the concept of assembly and intelligence, forming a set of shaft rapid and low disturbance tunneling system and method for upper soft and lower hard composite stratum, and successfully applied to engineering practice.

[0007] The present application is realized by the following technical solutions:

[0008] A shaft combined excavation method for upper soft and lower hard composite stratum, comprising the following steps:

[0009] S1: geological survey is performed on the stratum of the shaft excavation area to determine the range of soft stratum and hard stratum;

[0010] S2: it is judged whether the distance from the bottom of the hard stratum within the shaft design depth to the ground is greater than 20m; if greater than 20m, step S3 is performed; if less than 20m, step S4 is performed;

[0011] S3: initial excavation is performed on the soft stratum until the soft-hard stratum joint part is exposed; then step S4 is performed;

[0012] S4: direct blasting treatment is performed on the hard stratum; then main excavation is performed on the blasted rubble to remove waste;

[0013] Step S4 is repeated until the excavation depth reaches the shaft design depth to stop.

[0014] Compared with the prior art, the present application adopts a combined excavation method in the shaft construction process of the upper-soft-and-lower-hard stratum, utilizes the advantages of the two rock breaking methods of blasting method and shaft tunneling machine excavation, optimizes the tunneling method on the basis of the traditional shaft construction process, can realize efficient tunneling of the upper-soft-and-lower-hard composite stratum shaft, and reduces the influence on the surrounding environment in the excavation process, reduces blasting vibration, reduces the wear of the tunneling machine cutter during mechanical excavation, and reduces construction cost.

[0015] Further, the blasting treatment of step S4 further comprises the following steps: drilling a hollow hole from the center of the hard stratum to be blasted; arranging a circle of 6 interval undercut charging holes, a plurality of interval main charging holes and at least a circle of a plurality of interval peripheral charging holes outward along the hollow hole as blasting holes; in each circle of main charging holes, an empty hole is arranged between adjacent main charging holes.

[0016] Further, the blasting spacing D of the main charging hole and the peripheral charging hole is designed according to formula (1):

[0017] In the formula: D is the blasting spacing of the main charging hole or the peripheral charging hole, d b is the blasting hole diameter, mm; σ t is the tensile strength of the rock, MPa; α is the tensile stress wave attenuation coefficient, λ is the ratio of tangential stress and radial stress, μ is the Poisson's ratio; P is the initial stress peak value acting on the wall of the blasting hole, and p2 is the static pressure when the blast gas expands to fill the blast hole.

[0018] Further, the spacing between the undercut charging holes is 0.5m, and the depth of the undercut charging hole, the main charging hole and the peripheral charging hole is less than 20m.

[0019] Further, the blasting treatment of step S4 further comprises calculating the single-hole explosive quantity Q of the cut charging hole, the main charging hole and the peripheral charging hole according to formula (4):

[0020] In the formula, R is the safety allowable distance of blasting vibration, m; Q is the single-hole explosive quantity, kg; v is the safety allowable particle velocity of the location of the protected object, cm / s; K and a are the coefficient and attenuation index related to the topography and geological conditions from the blasting point to the protected object.

[0021] Further, the blasting treatment of step S4 further comprises placing the shaped charge structure filled with emulsion explosive into the blasting hole; when the height of the hard stratum to be blasted is less than 1 m, the blasting hole adopts continuous charging, and the charging quantity of each blasting hole is not higher than Q; when the height of the hard stratum to be blasted is greater than 1 m, the blasting hole adopts interval charging, and the charging quantity of each section of the explosive column is not higher than Q.

[0022] Further, when the hard stratum to be blasted is located in the middle of the shaft, the shaped charge structure has six shaped grooves; when the hard stratum to be blasted is located at the periphery of the shaft, the shaped charge structure has two shaped grooves.

[0023] Further, the blasting treatment of step S4 further comprises controlling the sequential delay initiation of the blasting hole from the cut charging hole to the peripheral charging hole, and the segmented delay initiation of the explosive column in the interval charging blasting hole.

[0024] Further, the initial excavation of step S3 comprises the following steps:

[0025] S31: A lock ring beam is constructed, and the base of the shaft lining system is pre-buried; a blade foot ring is constructed, and a steel strand holder anchor box is pre-buried for installing the steel strand; the soil is excavated, and the assembly of the equipment installation ring segment is simultaneously completed; the shaft boring machine is fixed on the equipment installation ring segment;

[0026] S33: Balanced mud is poured into the shaft lining, the shaft boring machine is used to cut the soil layer and soft rock underwater in layers, and the sinking ring segment is assembled synchronously until the excavation depth reaches the soft rock and hard rock boundary line.

[0027] Further, the main excavation of step S4 comprises the following steps: balanced mud is poured into the shaft lining, the shaft boring machine is used to cut the soil layer and soft rock underwater in layers, and the sinking ring segment is assembled synchronously until the hard rock stratum without blasting treatment is exposed. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 is a schematic view of the upper-soft-and-lower-hard composite stratum.

[0029] Figure 2 is a construction process flow chart of the upper-soft and lower-hard composite stratum shaft combined excavation method of the present application.

[0030] Figure 3 is a plum blossom arrangement drilling hole edge detection schematic diagram of the boulder encryption survey of the present application.

[0031] Figure 4 is an assembly schematic diagram of the shaft heading machine 100 of the present application.

[0032] Figure 5 is a blasting hole arrangement schematic diagram of the shaft middle hard rock fracturing of the present application.

[0033] Figure 6 is a vertical arrangement schematic diagram of the drilling hole measurement point of the present application.

[0034] Figure 7 is a multi-directional shaped charge structure plan view of the present application.

[0035] Figure 8 is a slotting area shaped jet schematic diagram of the present application, wherein the arrow indicates the shaped jet direction.

[0036] Figure 9 is a conventional area shaped jet schematic diagram of the present application, wherein the arrow indicates the shaped jet direction.

[0037] Figure 10 is a bidirectional shaped charge structure plan view of the present application.

[0038] Figure 11 is a blasting hole arrangement schematic diagram of the shaft peripheral hard rock fracturing of the present application.

[0039] Figure 12 is a vertical arrangement schematic diagram of the charge structure of the present application; wherein (a) is a single continuous charge structure used when the hard rock area height is less than 1m; (b) is an interval charge structure used when the hard rock area height is greater than 1m.

[0040] Wherein, 1, ground; 2, blasting hole; 3, hard rock or boulder area; 4, soft rock or ordinary area; 5, shaft; 10, original hole site (boulder survey hole); 12, edge detection hole; 20, central empty hole; 22, slotting charge hole; 24, main charge hole; 26, empty hole; 28, peripheral charge hole; 100, shaft heading machine; 101, shaft peripheral soil; 102, locking ring beam; 104, blade foot ring; 106, ring pipe piece; 108, cutting type cutter head. DETAILED DESCRIPTION

[0041] At present, the vertical shaft tunneling machine is mainly used for vertical shaft excavation in the prior art, but the vertical shaft tunneling machine is mainly suitable for soft rock or soft soil layer excavation, and a small amount of vertical shaft tunneling machine can be used for vertical shaft excavation in soft and hard rock composite stratum, but its efficiency and effect limit its application in soft and hard rock composite stratum excavation. For example, the cutting type vertical shaft tunneling machine realizes the excavation of soft and hard rock composite stratum by replacing the cutter head, the cutting type cutter head excavation has high economic benefit, and the ring cutting roller cutter disc excavation can adapt to different geological conditions and has good excavation performance. However, when the cutting type vertical shaft tunneling machine replaces the cutter disc, the main body needs to be lifted out of the vertical shaft, and the cutter disc replacement, re-fixing of the main machine and other processes are needed, the process is relatively complex, and in the construction process, the ring cutting roller cutter disc excavation only excavates a ring groove in the hard rock area at the bottom of the blade foot ring to ensure that the blade foot ring can be embedded in the hard rock layer, and the excavation depth is relatively shallow, which is not suitable for large-area hard rock stratum excavation, especially when there are boulders or large hard rock layers in the middle of the vertical shaft. If the thickness and range of the hard rock layer are large, other methods still need to be used for excavation. In addition, the structure of the ring cutting roller cutter disc is complex, the cost is high, maintenance is difficult, and the skill requirement for the operator is high, so it is necessary to improve the vertical shaft excavation method.

[0042] In addition, in the process of tunnel excavation construction in China, the drill and blast method is usually used to handle hard rock or boulders in the stratum, which has the advantages of low construction cost, high tunneling efficiency, easy operation, and the ability to break hard rock to facilitate excavation, etc., so it can replace the vertical shaft tunneling machine and be used to handle hard rock or boulders. However, in the process of drill and blast construction, the explosion of explosives will produce negative effects such as blasting vibration and shock wave, and when the construction is close to an existing line or building at a very close distance, the influence of the generated blasting vibration on the surrounding environment is more prominent, which is easy to bring great disturbance to the relatively soft upper stratum, thereby causing problems such as excessive deformation of surrounding rock and even surface subsidence and tunnel collapse. Therefore, at present, the drill and blast method is mainly used for tunnel excavation in simple environment, and when it is used in complex environment, shallow holes are drilled, less explosive is used, and vibration blasting is used to reduce the influence on the surrounding environment. This blasting method increases the number of blasting, and after each blasting, slag removal and re-drilling and blasting are needed, which significantly limits the vertical shaft excavation efficiency and affects the economic benefit. In addition, in the process of drill and blast construction, the construction personnel need to drill holes and remove slag in the pilot shaft, and after the drill and blast, a large amount of harmful gas and dust is generated in the vertical shaft, which has great safety hazards.

[0043] For the complex geological conditions of the upper soft and lower hard composite stratum, the shaft boring machine has low excavation efficiency and low economic benefit, and the traditional drilling and blasting method has a greater impact on the surrounding environment. The present application proposes to use controlled blasting method instead of traditional drilling and blasting method, and combines shaft boring machine excavation with controlled blasting excavation. The soft stratum is excavated by shaft boring machine, and the hard rock stratum is excavated by controlled blasting, so as to avoid the problems of low efficiency and serious tool wear when the shaft boring machine excavates hard rock stratum, and to avoid the problems of great impact on the surrounding environment and low efficiency of traditional drilling and blasting method, thereby improving the shaft excavation efficiency and economic benefit.

[0044] Further, in order to determine the specific combined excavation scheme, the present application first carries out geological survey on the stratum of the shaft excavation area before excavation, so as to determine the range of soft stratum and hard stratum, and then determines the specific excavation scheme according to the range and hardness of hard stratum, so as to optimize the shaft excavation procedure and reduce the impact of blasting excavation on the surrounding environment.

[0045] When the distance from the bottom of the hard stratum or boulder area to the ground in the range of the designed depth of the shaft is less than 20m, the hard stratum or boulder area can be directly controlled to blast, at this time, the depth of the blasting hole is less than 20m (i.e. the depth of the blasting hole), and the controlled blasting has a smaller impact on the surrounding environment. After blasting, the shaft boring machine is used to excavate the unblasted soft stratum and the blasted hard stratum, and directly excavate to the designed depth of the shaft, so as to avoid the complex construction process of hoisting the shaft boring machine out of the shaft and re-installing it many times.

[0046] When the distance from the bottom of the hard stratum or boulder area to the ground is greater than 20 m in the vertical shaft design depth range, the soft stratum is excavated by the vertical shaft boring machine first until the hard stratum or boulder area is exposed, at this time, if the depth of the hard stratum or boulder area is less than 20 m, the vertical shaft boring machine is used to excavate to the vertical shaft design depth after one blasting, if the depth of the hard stratum or boulder area is greater than 20 m, the depth of the blasting hole is controlled to be less than 20 m each time, the rock after blasting is excavated by the vertical shaft boring machine each time until the unblasted hard stratum is exposed, and the above steps are repeated until the vertical shaft design depth is reached, the depth of the blasting hole is less than 20 m each time during controlled blasting, which is beneficial to reducing the influence of controlled blasting on the surrounding environment. Since the depth of most subways in China is currently within 30 m, therefore, the subway vertical shaft is excavated by using the method, generally only 1-2 times of blasting is needed, the process is relatively simple, the construction personnel can be reduced or avoided to work in the vertical shaft, and the safety of the vertical shaft excavation is improved. In addition, the depth of the deepest subway station (Hongyan village subway station) in China is 116 m, that is, when the special geographical location and the hard rock range are wide, the vertical shaft excavation can be completed by using the method to perform blasting excavation at most 6 times, compared with the blasting hole depth of 1.5-4.5 m of the traditional drill and blast method single blasting, the blasting efficiency can be significantly improved.

[0047] When the controlled blasting method is used instead of the traditional drill and blast method, in order to reduce the vibration influence caused by blasting, reduce the waste of explosive energy, and improve the blasting efficiency, the present application designs and optimizes the blasting hole arrangement, charging structure and blasting parameters according to the geological conditions before blasting.

[0048] The arrangement of the blasting hole determines the distribution of the explosive energy in the rock, by optimizing the spacing between the blasting holes, the explosive energy can act on the rock more uniformly, by optimizing the shape of the blasting hole arrangement, that is, the angle and direction of the blasting hole, the blasting degree and blasting range of the rock can be controlled, and the hazards of flying stones and shock waves can be reduced. The blasting hole of the present application is arranged in a plum blossom shape, the slot charging hole, the main charging hole and the peripheral charging hole are arranged from the inside to the outside in the center of the hard rock or boulder area to be blasted, wherein the hole spacing of the slot charging hole is smaller, and the hole spacing of the main charging hole and the peripheral charging hole is larger, in addition, the empty holes are arranged between the main charging holes, which provide compensation space for the surrounding blasting holes. The existence of the empty hole can enhance the tensile failure of the rock, and is helpful to the reflection tensile action of the hole wall stress wave, and can make the rock between the empty hole and the blasting hole be subjected to shear action, thereby enhancing the damage effect of the rock.

[0049] The design of the shaped charge structure can significantly change the distribution and transmission mode of the energy when the explosive explodes. The present application adopts different shaped charge structures for hard rock at different positions of the shaft, which can more effectively improve the blasting effect and reduce the adverse effects of blasting. For example, the multi-directional shaped charge structure is adopted for the hard rock in the middle of the shaft, which corresponds to the arrangement shape of the charging hole, so that the high-energy jets generated by the charging structures of different holes are superimposed in several fixed directions, thereby more concentratedly and effectively acting on the rock and promoting the crushing of the rock; the bidirectional charging structure is adopted for the hard rock in the middle of the shaft, which avoids the high-energy jets generated by the charging structure from acting on the hard rock or soft soil layer outside the shaft, thereby reducing the influence on the external environment.

[0050] The explosive quantity, charging method and blasting method also affect the blasting effect, in order to reduce the influence of blasting vibration on the surrounding environment, the present application first calculates the maximum single section explosive quantity of single blasting within the completely allowable distance of blasting vibration, then in order to increase the explosive quantity to increase the blasting effect, the present application adopts the delay initiation method, on the one hand, the delay initiation of each hole can make the shock wave and stress wave produce superposition effect in the rock, optimize the rock crushing form, and at the same time, can reduce the vibration peak value generated by single initiation, reduce the vibration influence on the surrounding environment, and avoid and reduce the potential damage to the surrounding structure; on the other hand, the interval charging and segmented initiation are adopted for the relatively thick hard rock layer or boulder, which can realize the initiation of the hard rock layer or boulder in a large area at one time, and realize better blasting effect in the vertical direction and improve the blasting efficiency.

[0051] The present application will be further described in detail in combination with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. For the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures.

[0052] As shown in FIG. 2, the combined excavation method of the upper-soft-and-lower-hard composite stratum shaft of the present embodiment comprises the following steps:

[0053] S1: performing geological survey on the stratum of the shaft excavation area to determine the range of the soft stratum and the hard stratum;

[0054] Specifically, in step S1, the geological survey on the stratum of the shaft excavation area comprises the following steps:

[0055] S11: preparing rock samples by field coring to perform rock mechanics indoor experiment, obtaining rock mechanics strength, and determining the range of hard rock;

[0056] S12: If there is a boulder area in the stratum of the shaft excavation area, a boulder encryption detection is carried out to determine the boulder boundary: the boulder encryption detection is mainly encryption drilling, and the supplementary survey hole spacing is 1.5-2.5 m; referring to FIG. 3, the edge detection is carried out at the boulder survey hole 10 where the boulder is found, and the drilling holes are arranged in a plum blossom shape around the original hole site 10 at an interval of 600 mm, that is, the edge detection hole 12; if the edge detection hole 12 still exposes the boulder, the edge detection range is continuously expanded to the four directions, and the process is repeated until the boulder boundary is detected.

[0057] Among them, the soil layer and the rock with uniaxial compressive strength Rc less than 30 MPa are generally regarded as soft stratum, and the rock with Rc greater than 30 MPa is regarded as hard stratum, wherein the rock with Rc greater than 60 MPa is hard rock, and the rock with Rc of 30-60 MPa is medium-hard rock.

[0058] S2: Determine whether the distance from the bottom of the hard stratum within the shaft design depth to the ground is greater than 20 m; if greater than 20 m, process through step S3; if less than 20 m, process through step S4;

[0059] Due to the complex environment around the subway shaft, there may be a residential area or other buildings within 100 m of the edge of the blasting area, which belongs to complex environment blasting, and the harmful effects should be controlled during the blasting operation, therefore, the controlled blasting method is adopted for the hard stratum, and the blasting hole depth is limited within 20 m. Among them, the blasting hole depth is the distance from the bottom of the hard stratum within the shaft design depth to the ground or the surface of the shaft excavation area, that is, the depth of the blasting hole includes the thickness of the hard stratum and the thickness of the soft stratum above the hard stratum, but does not include the hard rock or boulder area beyond the shaft design depth.

[0060] Therefore, when the distance from the bottom of the hard stratum to be blasted to the ground is greater than 20 m, the soft stratum above the hard stratum to be blasted needs to be excavated and removed to reduce the blasting hole depth. If the distance from the hard stratum to be blasted to the soft-hard rock joint after the step S3 processing is still greater than 20 m, the blasting hole depth should be limited within 20 m in step S4 for multiple blasting excavations, that is, the hard stratum with a thickness less than 20 m above is first blasted, then the blasted debris is excavated, the waste is removed, and then the above steps are repeated until the shaft design depth is excavated.

[0061] When the distance from the bottom of the hard stratum to be blasted to the ground is less than 20 m, the hard stratum is directly blasted, and then the blasted debris is excavated, and the waste is removed. Different combined excavation schemes are determined for different hard rock strata or boulder ranges, which is beneficial to reduce the influence of blasting treatment on the environment around the shaft, optimize the excavation process, and improve the excavation efficiency.

[0062] S3: initial excavation of the soft stratum until the soft-hard rock combination site is exposed; then the step S4 is processed;

[0063] In step S3, the initial excavation adopts the vertical sinking shaft tunneling technology, and the soft stratum above the hard stratum to be blasted is excavated by the vertical shaft mechanical method combining the cutting type shaft tunneling machine and the assembled segment structure until the soft-hard rock combination site is exposed.

[0064] Specifically, referring to FIG. 4, before the initial excavation of the soft stratum above the hard stratum, the shaft tunneling machine 100 needs to be assembled and debugged, which specifically includes the following steps:

[0065] S311: lock mouth ring beam 102 is constructed, and the base of the shaft well lifting system is pre-buried;

[0066] Wherein, before the construction of the lock mouth ring beam 102, the foundation bearing capacity needs to be calculated based on the building foundation specification. If the foundation bearing capacity meets the design requirements, the lock mouth ring beam 102 is directly constructed. If the foundation bearing capacity does not meet the design requirements, the soil 101 within a certain depth range around the shaft is reinforced to improve the foundation bearing capacity, and the lock mouth ring beam 102 is constructed. Wherein, the foundation bearing capacity can be calculated according to the shaft well depth, the segment self-weight, the equipment weight and the geological conditions.

[0067] S312: the blade foot ring 104 is constructed inside the lock mouth ring beam 102, and the steel strand holder anchor box is pre-buried for installing the steel strand. The soil is excavated and the assembly of the equipment installation ring segment 106 is simultaneously completed;

[0068] Wherein, the blade foot ring 104 is constructed by cast-in-place reinforced concrete or precast assembled steel segment filled with concrete, and the steel strand holder anchor box is pre-buried at the blade foot ring 104. After the strength of the blade foot ring 104 meets the design requirements, the steel strand is installed to the steel strand holder anchor box, so that the shaft lifting system is anchored at the base of the lock mouth ring beam 102. Then the soil inside the blade foot ring 104 (i.e. the soil of the shaft excavation area) is excavated until the required depth and bottom contour of the shaft tunneling machine equipment 100 installation are completed, and the assembly of the equipment installation ring segment 106 is completed. Wherein, the steel strand holder anchor box is used to fix and hold the steel strand to prevent it from sliding or falling off during work, and has the functions of adjusting and dispersing the external force of the steel strand, which is beneficial to maintain the stability and safety of the system and prolong the service life of the steel strand.

[0069] S313: assemble and debug the shaft tunneling machine 100;

[0070] The shaft tunneling machine 100 comprises a main machine system and a supporting device. When the shaft tunneling machine 100 is assembled, the main machine system of the shaft tunneling machine 100 is first assembled and fixed at a pre-buried steel plate welding base of the equipment mounting ring pipe piece 106, and then the supporting device of the shaft tunneling machine 100 is fixed on the lock joint ring beam 102. Then, the shaft tunneling machine 100 is debugged to ensure that the main machine system and the supporting device of the shaft tunneling machine 100 operate well. In an optional embodiment, the shaft tunneling machine 100 is used to perform trial tunneling work on the shaft excavation area, and the construction parameters of the shaft tunneling machine 100 are simultaneously adjusted and optimized to ensure that the parameters of the shaft tunneling machine 100 are normal in the actual tunneling process.

[0071] After the construction parameters are adjusted and optimized, the normal tunneling is performed in steps S321-S323.

[0072] S321: Balance mud is poured into the shaft, and the liquid level in the shaft is ensured to be higher than the underground water level.

[0073] S322: The shaft tunneling machine 100 is used to perform underwater layered excavation of soil and soft rock by using a cutting type cutter head 108. When the excavation of one ring pipe piece 106 is completed, a ring prefabricated pipe piece is assembled on the ground. The blocks of the prefabricated pipe piece are connected by inclined straight bolts, and two sets of scissor lock devices are arranged on each ring pipe piece. The ring pipe piece assembled later is connected to the ring pipe piece assembled earlier by vertical through bolts. When the pipe piece is assembled, the whole shaft is lifted by one ring height by the shaft lifting system.

[0074] S323: Step S322 is repeated until the shaft excavation depth reaches the soft rock and hard rock boundary line. Then, step S4 is performed to perform blasting treatment on the hard rock area.

[0075] Before step S4 is performed, the main machine system of the shaft tunneling machine is lifted out to avoid affecting the blasting treatment of step S4.

[0076] S4: The hard stratum is directly blasted, and then the blasted rock is excavated to remove the waste.

[0077] Step S4 is repeated until the shaft design depth is excavated.

[0078] In order to reduce the influence on the surrounding environment, especially the residential area, the controlled blasting method is used for blasting treatment in this embodiment. The effective control of explosion energy is realized by using electronic digital detonator and shaped charge structure, including the following steps:

[0079] S41: A drilling machine is used to drill holes in the hard stratum to be blasted.

[0080] Wherein, in order to achieve better blasting effect and reduce harmful effects, reasonable blasting parameters are designed according to hard rock range, rock mechanics performance and explosion mechanics theory before drilling.

[0081] The embodiment assumes that the blasting is the joint action of stress wave and detonation gas, and therefore the following formula is used to calculate the blasting hole spacing D according to the explosion mechanics theory, stress wave action principle theory and elastic mechanics principle:

[0082] In the formula, d b is the blasting hole diameter, mm;

[0083] σ t is the tensile strength of rock, MPa;

[0084] α is the tensile stress wave attenuation coefficient,

[0085] λ is the ratio of tangential stress and radial stress,

[0086] μ is the Poisson's ratio;

[0087] P is the initial stress peak value acting on the blasting hole wall,

[0088] p2 is the static pressure when the detonation gas expands to fill the blast hole.

[0089] Wherein, P can be calculated by the following formula:

[0090] In the formula, n is the pressure increase multiple, and the value is 8-10;

[0091] l is the charge axial coefficient, and the value is 1;

[0092] ρ0 is the density of ordinary emulsion explosive, kg / cm 3 ;

[0093] V is the explosive detonation velocity, m / s;

[0094] d c is the diameter of the charge column, mm;

[0095] P calculated by formula (2) and (3) is substituted into formula (1) to calculate the value range of the blasting hole spacing D.

[0096] In the embodiment, the diameter of the charge column of the shaped charge structure is 63 mm, the diameter of the blasting hole is 90 mm, and the blasting hole spacing D calculated by formula (1)-(3) is 1.0 m-1.8 m.

[0097] According to the blast hole spacing D, a blast hole arrangement scheme is designed: referring to FIG. 5, the blast hole 2 includes a cut charging hole 22, a main charging hole 24 and a peripheral charging hole 28. In order to reduce the blasting vibration, in the embodiment, the blast hole 2 is arranged in a plum blossom shape, that is, a 100mm diameter empty hole 20 is first drilled in the center of the hard rock range or the boulder range, then six cut charging holes 22 are arranged in a plum blossom shape around the empty hole 20, the hole spacing between the cut charging holes 22 is 0.5m, six main charging holes 24 are arranged around the cut charging holes 22, the hole spacing is 1.5m, and an empty hole 26 is arranged between every two main charging holes 24. In this way, the peripheral charging holes 28 are arranged outward, the hole spacing is within the range of 1m to 1.8m (i.e. the blast hole spacing D), and the number of blast holes 2 is calculated. In addition, the empty hole 20 and the empty hole 26 are not charged, and they provide compensation space for the six main charging holes 24 around them.

[0098] Referring to FIG. 6, according to the blast hole arrangement scheme, a geological drilling machine is selected to drill a hole in the hard stratum to be blasted, the hole diameter is 90mm, in order to avoid hole collapse of the upper soft stratum, a 110mm to 120mm casing is used for hole protection, the hole depth is from the ground or the soft and hard rock joint to the shaft bottom, after the hole is formed, a 65mm to 75mm charging casing is lowered into the hole. In order to control the actual blast hole depth to be less than 20m, when the thickness of the hard stratum to be blasted exceeds 20m, the hard rock layer within the thickness of 20m above is first blasted.

[0099] S42: After the emulsion explosive is loaded into the shaped charge structure, the charging structure is placed into the hard stratum to be blasted in the blast hole along the charging casing;

[0100] The shaped charge structure is designed based on the shaped jet principle, so that the blasting energy can be concentrated in a specific direction, thereby improving the blasting effect.

[0101] Therefore, before charging, the embodiment first designs a shaped charge structure that meets the blasting energy control according to the shaft stratum conditions, the surrounding environment and the shaped jet principle, wherein the shaped cone angle is within the range of 60° to 75°, and the number of shaped grooves can be set according to the utilization of the blasting energy. In order to reduce the blasting vibration and avoid damage to the surrounding rock mass, in the embodiment, the shaped groove cone angle is 65°, the multi-directional shaped charge structure is used in the middle of the shaft, the number of shaped grooves is 3 to 8, and the bidirectional shaped charge structure is used around the shaft, which has two shaped grooves.

[0102] Specifically, the partial hard rock treatment in the middle part of the shaft adopts a multi-directional shaped charge structure as shown in FIG. 7, and adopts a blast hole arrangement scheme as shown in FIG. 6, referring to FIGS. 8-9, the multi-directional shaped charge structure with six shaped grooves can better match the quincunx arrangement of the blast holes, and maximize the cracking effect of the blasting energy. When the hard rock region is at the periphery of the shaft, the partial hard rock treatment at the periphery of the shaft adopts a bidirectional shaped charge structure as shown in FIG. 10, and adopts a blast hole arrangement scheme as shown in FIG. 11, wherein the two shaped grooves of the bidirectional shaped charge structure are on the same straight line, which generates cracks along the circumferential direction of the shaft, and the cracks are all inside the shaft, which can avoid damage to the surrounding rock mass.

[0103] Step S42 further includes designing a reasonable charge amount according to the number of blast holes to control the vibration impact generated by blasting, and the explosive amount Q can be obtained according to the calculation formula of the safe allowable distance R of blasting vibration:

[0104] In the formula, R is the safe allowable distance of blasting vibration, m;

[0105] Q is the maximum explosive amount of single blasting, and when delay blasting, Q is the maximum explosive amount of single section, kg;

[0106] v is the safe allowable particle velocity of the location of the protected object, cm / s;

[0107] K and a are coefficients and attenuation exponents related to the topography and geological conditions from the blasting point to the protected object, and the following table is taken under the condition of no experiment.

[0108] Table 1 K and a values of different rock types in the blasting area

[0109] In this embodiment, it is assumed that a general civil building is located near a 50m hard stratum to be blasted in a shaft. According to the blasting safety regulations GB6722-2022, the minimum value 1.5cm / s is taken as the limit value of the blasting vibration velocity; referring to Table 1, K is taken as 100 and a is taken as 1.4, and Q is calculated to be 15.4kg according to the above formula (4). Therefore, the maximum single section explosive amount should not be higher than 15.4kg when designing the blasting parameters. When the blast holes adopt continuous charging, the maximum charge amount of each hole is 15.4kg, and when delay initiation is adopted, the blast holes can adopt interval charging, and the maximum charge amount of each explosive column in the blast hole is 15.4kg.

[0110] In this embodiment, referring to FIG. 12, when the height of the hard stratum to be blasted is less than 1m, a single continuous explosive column is used for the hard stratum to be blasted, and the charge amount is not higher than Q; when the height of the hard stratum to be blasted is greater than 1m, an interval charging structure is used for the hard stratum to be blasted, and the single section explosive column is 0.8m long and the charge amount is not higher than Q.

[0111] After charging is completed, the blast holes are backfilled and plugged.

[0112] S43: based on digital electronic detonator technology, using hole interval charging segmented delay initiation, and using hole-by-hole initiation network to perform delay initiation;

[0113] In step S43, first, delay parameters are set according to the delay initiation method, wherein the hole-by-hole initiation network refers to initiating the blast holes from the inside to the outside. Referring to FIG. 6, taking the blast hole arrangement scheme in which the hard stratum to be blasted is located in the middle of the shaft as an example, in this arrangement scheme, three circles of blast holes 2 are arranged around the central hole 20, therefore, three sections of the hole-by-hole initiation network are set, specifically: first, initiating the 6 cut charging holes 22, then initiating the 6 hexagonal main charging holes 24 outside the cut charging holes 22, and finally initiating the outermost peripheral charging holes 28, to complete the blasting of the hard rock area. In an optional embodiment, the hole interval charging segmented delay initiation uses a top-down delay blasting sequence in the hole, after the blasting of each section of charging structure in a single hole is completed, the blast holes 2 in the outer circle of the hole are initiated. The delay initiation method of step S43 can reduce the single-hole in-hole explosive quantity, achieve the control of the maximum single-shot explosive quantity, and reduce the blasting vibration.

[0114] S44: after the blasting is completed, the blasted rock is subjected to main excavation, and the waste is removed;

[0115] When the distance from the bottom of the hard stratum in the shaft design depth to the ground in step S2 is less than 20 m, the blasted rock in step S4 includes the blasted hard stratum and the unblasted soft stratum, the soft stratum includes the soft stratum above or below the hard stratum, and the soft stratum intercalated in the middle of the hard stratum; when the distance from the bottom of the hard stratum in the shaft design depth to the ground in step S2 is greater than 20 m, the blasted rock in step S4 includes the blasted hard stratum, and possibly includes the soft stratum below the hard stratum.

[0116] In an optional embodiment, the main excavation adopts the vertical sinking shaft tunneling technology, and the cut-off shaft tunneling machine and the assembled segment structure are combined to mechanically excavate the blasted rock. After the hard stratum to be blasted is directly subjected to blasting treatment in step S4, the steps of the main excavation are the same as those of the initial excavation in step S3, and are as follows:

[0117] S441: the lock circle beam 102 is constructed, and the base of the shaft lining lifting system is pre-buried; the blade foot ring 104 is constructed on the inner side of the lock circle beam 102, and the steel strand holder anchor box is pre-buried for installing the steel strand; the soil is excavated and the assembly of the equipment installation segment 106 is simultaneously completed;

[0118] S442: the shaft tunneling machine 100 is assembled and debugged;

[0119] S443: Pouring balance slurry into the shaft well and ensuring that the liquid level in the well is higher than the underground water level;

[0120] S444: Using the cutting type cutter head 108 of the shaft tunneling machine 100 to underwater layer-by-layer excavate the soil and soft rock, when excavating a ring of segments 106 depth, assembling a ring of prefabricated segments on the ground, using inclined straight bolts to connect the blocks of the prefabricated segments, and providing two sets of scissors lock devices on each ring of segments, and connecting the later assembled ring of segments to the previously assembled ring of segments through vertical through-bolts, when the segments are assembled, controlling the overall sinking of the shaft well by one ring height through the shaft well lifting system;

[0121] S445: Repeating steps S444 until the unblasted hard rock area is exposed. At this time, the shaft excavation depth is the design depth of the shaft.

[0122] If step S3 is performed first and then step S4 is used to blast the hard stratum to be blasted, the specific steps of the main excavation are: re-fixing the main system of the shaft tunneling machine 100 at the pre-buried steel plate welded base of the equipment installation ring segment 106, and then performing steps S443-S445. In addition, after the main excavation is completed, when judging whether the shaft depth reaches the design depth, if not, repeating steps S41-S44 until the excavation of the design depth of the shaft is stopped.

[0123] In another optional embodiment, other shaft tunneling machines can be used for main excavation.

[0124] Compared with the prior art, the present application has the following advantages:

[0125] (1) The present application uses a cutting type shaft tunneling machine to excavate soft rock or soft soil, has economic advantages, and combines with a controlled blasting method to pre-split the hard rock area, thereby ensuring the safe and stable excavation of the soft rock or soft soil area, avoiding the problems of large tool wear, low construction efficiency or even inability to excavate when the cutting type cutter head shaft tunneling machine excavates the hard rock stratum. The combined excavation method of the present application utilizes the advantages of two rock breaking methods, optimizes the tunneling method on the basis of the traditional shaft construction process, can realize efficient excavation of the soft-over-hard composite stratum shaft, and reduces the influence on the surrounding environment during excavation, reduces blasting vibration, reduces tool wear of the tunneling machine, reduces construction cost, and improves the efficiency of vertical mechanical excavation of the hard rock stratum shaft, thereby providing a new method for safe, efficient and low disturbance construction of urban subway shafts.

[0126] (2) The control blasting adopted in the present application mainly realizes blasting hazard control based on digital electronic detonator technology and energy-gathering charge structure, according to a blasting vibration safety calculation formula, a reasonable maximum single segment charge is derived, the use amount and blasting mode of explosives are accurately controlled through digital electronic detonator segmentation and delay technology, more uniform and more accurate blasting effect is realized, the rock is broken more uniformly, the generation of large rocks is reduced, thereby the excavation efficiency is improved, in addition, the control blasting method can also significantly reduce the influence of blasting on the surrounding soil and structure, reduce the hazards such as vibration, noise and flying rock, thereby the safety and stability of the surrounding environment are protected.

[0127] (3) Based on the principle of energy-gathering jet, different charge structures are designed to be applied in hard rock located in different areas of the shaft, among them, the multi-directional energy-gathering charge structure with six energy-gathering grooves is adopted for the hard rock stratum in the middle of the shaft, and the each blasting hole is arranged in a plum blossom shape, so that the energy-gathering grooves of the multi-directional energy-gathering charge structure in each blasting hole are opposite to the energy-gathering grooves of other multi-directional energy-gathering charge structures, thereby the energy of the explosives is highly concentrated in a certain direction to form a high-speed and high-energy jet, thereby a strong impact force is generated in a specific direction, the rock is subjected to highly concentrated energy in this direction, thereby the rock is more easily broken, the excavation efficiency is improved, the generation of large rocks is reduced, and the difficulty of subsequent processing is reduced. In addition, since the energy of the energy-gathering jet is highly concentrated and the direction and range of the blasting energy can be accurately controlled, the present application can reduce the influence on the surrounding environment while realizing accurate destruction of the target area.

[0128] (4) For the hard rock stratum around the shaft, especially the hard rock stratum across the shaft, the bidirectional energy-gathering charge structure with two energy-gathering grooves is adopted, the direction of the energy-gathering jet is controlled to be along the circumferential direction of the shaft, which can avoid damaging the hard rock or soil outside the shaft, and reduce the safety risks such as collapse and landslide. In addition, the principle of energy-gathering jet can more effectively utilize the energy of the explosives for the destruction of the target area, thereby reducing the waste of energy, reducing the construction cost and improving the economic benefit.

[0129] (5) When the mechanical excavation of the cutting type shaft boring machine is carried out, the wellbore is filled with balanced mud, which can ensure that the liquid level in the wellbore is higher than the underground water level, realize the balance between the inside and outside of the wellbore, and realize the underwater excavation of the shaft boring machine in the whole process. In addition, the cutting type shaft boring machine can quickly and effectively break and excavate rock, significantly improve the excavation speed, and has high safety and stability, can adapt to different geological conditions, and has less noise, vibration and dust pollution, which helps to protect the surrounding environment and improve the quality of life of residents.

[0130] The present application is not limited to the above-described embodiments, and various modifications or alterations can be made to the present application without departing from the spirit and scope of the present application, and it is intended that such modifications and alterations be included within the scope of the present application recited in the following claims and their equivalents.

Claims

1. A method of combined excavation of a shaft in a soft over hard composite formation, characterized by, The method comprises the following steps: S1: geological survey is conducted on the stratum of the shaft excavation area to determine the range of soft stratum and hard stratum; S2: it is judged whether the distance from the bottom of the hard stratum in the shaft design depth to the ground is greater than 20m; If greater than 20m, the step S3 is processed; if less than 20m, the step S4 is processed; S3: the soft stratum is initially excavated until the soft-hard stratum joint part is exposed; then the step S4 is processed; S4: the hard stratum is directly treated by blasting, and then the blasted rubble is subjected to main excavation and the waste is removed; The step S4 is repeated until the excavation depth reaches the shaft design depth and stops.

2. The method of claim 1, wherein, The blasting treatment of the step S4 further comprises the following steps: an empty hole is drilled from the center of the hard stratum to be blasted; a circle of 6 interval slotting charge holes, a plurality of interval main charge holes and at least a circle of a plurality of interval peripheral charge holes are arranged outwardly in sequence as blasting holes; in each circle of main charge holes, an empty hole is arranged between adjacent main charge holes.

3. The method of claim 2, wherein, The burst spacing D of the main charge hole and the peripheral charge hole is designed according to formula (1): wherein: D is the blast spacing of the main charge hole or the peripheral charge hole, d b is the diameter of the blast hole, mm; σ t is the tensile strength of the rock, MPa; and α is the tensile stress wave attenuation coefficient, λ is the ratio of tangential to radial stress, μ is Poisson's ratio; P is the initial stress peak value acting on the wall of the blasting hole, and p2 is the static pressure when the blast gas expands to fill the blast hole.

4. The method of claim 3, wherein, The interval between the slotting charge holes is 0.5m, and the depth of the slotting charge hole, the main charge hole and the peripheral charge hole is less than 20m.

5. The method of claim 4, wherein, The blasting treatment of the step S4 further comprises calculating the single-hole explosive quantity Q of the cut charging hole, the main charging hole and the peripheral charging hole according to formula (4): In the formula, R is a safety allowable distance of blasting vibration, m; Q is the explosive quantity of a single hole, kg; v is a safety allowable particle velocity of a protection object, cm / s; K and α are coefficients and attenuation exponents related to the topography and geological conditions from the blasting point to the protection object.

6. The method of claim 5, wherein, The blasting treatment of the step S4 further comprises the following steps: an empty hole is drilled from the center of the hard stratum to be blasted; a circle of 6 interval slotting charge holes, a plurality of interval main charge holes and at least a circle of a plurality of interval peripheral charge holes are arranged outwardly in sequence as blasting holes; in each circle of main charge holes, an empty hole is arranged between adjacent main charge holes.

7. The method of claim 6, wherein, When the hard stratum to be blasted is located in the middle of the shaft, the shaped charge structure has six shaped grooves; when the hard stratum to be blasted is located at the periphery of the shaft, the shaped charge structure has two shaped grooves.

8. The method of claim 7, wherein, The blasting treatment of the step S4 further comprises the following steps: the blasting holes are sequentially delayed detonated from the slotting charge hole to the peripheral charge hole, and the segmented delay detonation of the explosive column in the interval charge blasting hole is controlled.

9. The method of claim 1-8, wherein, The initial excavation of the step S3 comprises the following steps: S31: a lock mouth ring beam is constructed, and a base of a shaft wellhole lifting system is pre-buried; a blade foot ring is constructed, and a steel strand holder anchor box is pre-buried for installing a steel strand; the soil body is excavated and the assembly of the equipment installation ring pipe piece is simultaneously completed; the shaft boring machine is fixed on the equipment installation ring pipe piece; S33: balanced mud is poured into the shaft wellhole, the shaft boring machine is used to cut and excavate the soil layer and soft rock underwater in layers, and the sinking ring pipe piece is simultaneously assembled, until the excavation depth reaches the soft rock and hard rock boundary line and stops.

10. The method of claim 9, wherein, The main excavation of the step S4 comprises the following steps: balanced mud is poured into the shaft wellhole, the shaft boring machine is used to cut and excavate the soil layer and soft rock underwater in layers, and the sinking ring pipe piece is simultaneously assembled, until the hard rock stratum not subjected to blasting treatment is exposed.

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