A method for safe, phased mining of "I"-shaped pillars in mines.

Abstract

The application discloses a kind of suitable for "G" type pillar high stage step-by-step safe mining construction method, comprising S1: step-by-step mining area division, according to the geometric form of pillar and the strength difference of two sides filling body, the pillar is divided into several mining units along the trend, and 2m and 4m thick wall is left in the east side of the pillar, 2m wall is left in the west side, and 4m wall is left in the middle;S2: recovery and optimization of preparation engineering;S3: stage rock drilling and blasting design;S4: wall setting and filling body protection;S5: subsequent segmented filling: after completing a mining unit, use the cement sand ratio 1:4~8 of cementing material layer filling, and pre-embedded stress sensor in filling body.The application solves the problems of filling body instability, uneven blasting energy distribution and the like in high stage pillar mining, improves the recovery rate of pillar, reduces the damage area of filling body and reduces the support cost.

Description

Technical Field

[0001] This invention relates to the field of mining technology, and in particular to a safe mining construction method for high-stage, step-by-step mining of "I"-shaped pillars. Background Technology

[0002] The Datuanshan deposit (IV panel ore body) is a deeply buried blind ore body hosted in the Lower Triassic Xiaoliang Formation. Its occurrence is mainly controlled by geological strata and lithology, varying with the surrounding rocks. The ore body is stratiform, relatively stable in distribution, and simple in morphology, striking northeast at 30°–35° and dipping southeast at a moderate angle, with slight variations in dip in different sections, generally between 35° and 50°. The roof is composed of siliceous hornfels or hornfels interbedded with skarn, with some individual engineering rock masses being marble. The floor is composed of biotite hornfels and plagioclase-biotite hornfels. Fractures are well-developed within and around the ore body. Thick ore bodies are mainly located above -610m.

[0003] The vertical pillar in panel IV is located in a thick section of the ore body. Originally designed for mining above -565m, it was left as a backup due to excessive roof exposure and decreased stability. The pillar was designed to be 25m wide. During mining operations at 33A and 33B, roof instability occurred, and 1-3 rows of large boreholes were left unexploded. The widths at these locations were 33m and 36m respectively (partial collapse may have occurred, and this should be investigated during the current construction phase). This pillar is the subject of this design. The pillar's planar distribution is consistent with the stope in panel IV (lines 31A-35), approximately 95m long and 25-36m wide, vertically situated between -507 and -604m elevations. The total ore volume is approximately 498,600 tons, with an average geological grade of approximately 1.14%. The pillar's spatial morphology is such that the top is generally at -520m elevation, with the lower part sloping from north to south. The deepest point at 31B on the north side is generally above -580m.

[0004] Existing pillar mining methods mostly employ either monolithic caving or continuous mining, which present the following problems:

[0005] 1. During the mining of high-level pillars (>50m), the bottom structure is subjected to excessive impact loads, which can easily lead to instability of the filling body;

[0006] 2. When there is a significant difference in strength between adjacent backfill bodies, traditional symmetrical mining methods are prone to causing the collapse of the weaker backfill body;

[0007] 3. When restoring the original preparatory works, direct blasting excavation is likely to damage the original support system and increase the risk of collapse;

[0008] 4. Subsequently, the strength distribution of the filling material is unreasonable, making it difficult to form effective support.

[0009] Therefore, this application provides a method for safe, phased mining of "I"-shaped pillars in high stages to meet the requirements. Summary of the Invention

[0010] The purpose of this application is to provide a safe construction method for high-stage, step-by-step mining of "I"-shaped pillars, which can solve the technical problems of instability, collapse, inability to provide effective support, and high risk of caving in the existing construction process.

[0011] To achieve the above objectives, this application provides the following technical solution: a method for safe mining of high-stage, step-by-step "I"-shaped pillars, comprising the following steps;

[0012] S1: Step-by-step mining area division. Based on the geometric shape of the pillar and the strength difference of the filling bodies on both sides, the pillar is divided into several mining units along the strike. 2m and 4m thick mining walls are left at intervals on the east side of the pillar, 2m mining wall is left on the west side, and 4m mining wall is left in the middle to form an "I" shaped support structure.

[0013] S2: Mining preparation engineering restoration and optimization, involving the excavation and engineering modification of the ore extraction roadways and drilling chambers in the original backfilled goaf area, including bottom shoveling, roof lifting, and side widening, so that the roadway height reaches more than 3.5m. The rock mass is supported by shotcrete, concrete pouring, or rock bolts, and the support strength is adjusted.

[0014] S3: Staged rock drilling and blasting design, adopting two-stage downward deep hole drilling. The first stage drilling depth does not exceed 45m. The second stage dynamically adjusts the blasting parameters according to the stability of the filling body. The blasting height of each stage is controlled at 10-15m.

[0015] S4: Mine wall protection and backfill protection. During the mining process, the deformation data of the backfill is monitored in real time. By adjusting the mine wall thickness and blasting sequence, the exposed area of ​​the backfill is controlled to not exceed the critical value.

[0016] S5: Subsequent segmented backfilling: After each mining unit is completed, cementing material with a ash-sand ratio of 1:4~8 is used for layered backfilling, and stress sensors are pre-embedded in the backfill to form a strength gradient distribution of the backfill.

[0017] By using phased mining (S3) and I-beam support (S1), the single blasting height is reduced (10-15m), stress concentration is dispersed, and the impact load on the bottom structure is reduced.

[0018] The "I"-shaped mine wall (2m / 4m alternating on the east side, 2m on the west side, and 4m in the middle) is protected differently for the low-strength backfill (1.29MPa) on the east side and the high-strength backfill (5.23MPa) on the west side to prevent collapse on the weak side;

[0019] In the first stage, the drilling depth does not exceed 45m. The borehole deviation rate increases significantly with the depth. After exceeding 45m, the borehole deviation may lead to uneven charging and unbalanced blasting energy distribution, affecting the size of the ore fragments. Furthermore, segmented charging technology is required for deeper holes. If the hole depth exceeds 45m, the charge density at the bottom is difficult to control, and the phenomenon of "charge separation" is likely to occur, resulting in a decrease in blasting energy utilization.

[0020] By shoveling the bottom, lifting the top, and widening the sides (S2), the original roadway is restored and the original support structure is preserved, reducing the amount of new excavation and lowering construction risks;

[0021] Improve the support effect of the filling body: Layered filling (S5) forms a strength gradient (layer 1:4~8 cement-sand ratio), which enhances the bottom bearing capacity and avoids the overall failure of the filling body.

[0022] As a preferred embodiment of this example, in S1, the mining is arranged along the strike of the ore body and is carried out continuously along the strike of the ore body. Due to the engineering limitations in the -610m section and the large amount of waste rock in the lower part, a large funnel bottom structure is adopted for ore extraction. The funnel is formed by large-hole blasting, with a specification of 6m×6m and a height of 14-17m. The inclination angle of the funnel opening is ≥50°.

[0023] The large funnel structure (6m×6m) expands the outlet area, and with the expansion angle of the funnel ≥50°, it prevents ore blockage, improves the smoothness of ore discharge, and the funnel is formed by large-hole blasting, which reduces the direct impact of blasting vibration on the filling body and protects the stability of the bottom structure.

[0024] As a preferred embodiment of this example, in step S2, a bottom-shoveling method is used to preserve the integrity of the original support structure. The bottom-shoveling depth does not exceed 1.5m, and the top-shoveling height does not exceed 0.8m.

[0025] Limiting the extent of bottom shoveling and top lifting avoids damaging the existing shotcrete or concrete support, maintains roadway stability, utilizes existing engineering modifications to reduce the amount of new support work, and saves approximately 25% in costs.

[0026] As a preferred embodiment of this example, in S3, the blasting adopts an asymmetric charge structure, the charge coefficient is reduced by 20%-30% on the side closer to the filling body, and the detonation sequence adopts a progressive detonation from high to low and from weak to strong.

[0027] Asymmetric charges reduce the blast energy near the filling material, preventing vibration-induced cracking of the filling material. The progressive detonation sequence guides the energy release towards the free surface, reducing disturbance to the surrounding rock.

[0028] As a preferred embodiment of this example, in step S5, the strength gradient distribution of the filling body is achieved through layered filling. The bottom layer is filled with a 1:4 lime-sand ratio, the middle layer with a 1:6 lime-sand ratio, and the top layer with a 1:8 lime-sand ratio. The construction time between each layer is not less than 72 hours.

[0029] A high cement-sand ratio of 1:4 (with a high cement content) is adopted to ensure that the bottom filling body has sufficient compressive strength and stability. The compressive strength of the filling body with a 1:4 cement-sand ratio can reach more than 4.5MPa, which can effectively support the pressure of the upper pillar and surrounding rock and prevent the bottom structure from becoming unstable.

[0030] The middle layer of filling material is located between the bottom and top layers. It must withstand a certain amount of pressure from the top and provide support for the top layer of filling material. The 1:6 cement-sand ratio design ensures a certain strength while taking into account economy. The compressive strength of the filling material with a 1:6 cement-sand ratio is about 3.0MPa, which can effectively share the pressure from the top and provide stable support for the top layer of filling material. As a transition layer between the bottom and top layers, the middle layer of filling material can balance the stress distribution between the upper and lower layers and avoid local damage caused by stress concentration.

[0031] The upper filling material bears relatively less pressure and its main function is to seal voids and prevent the upper surrounding rock from collapsing. Therefore, a low cement-sand ratio of 1:8 (lower cement content) is used to save on material costs.

[0032] By using a layered design, a high-cement-sand ratio filling material is used only in the bottom layer, while the cement-sand ratio is gradually reduced in the middle and upper layers. This significantly reduces the amount of cement used and lowers the filling cost. The layered filling design can save about 15%-20% of the filling material cost.

[0033] As a preferred embodiment of this example, in S2, when the rock mass RQD value is less than 50%, anchor bolt + shotcrete support is used, with an anchor bolt spacing of 1.2m; when the rock mass RQD value is greater than 80%, only concrete support is used.

[0034] For low RQD rock masses (fractured zones), anchor bolts and shotcrete are used to enhance the support strength, while for high RQD rock masses (intact), the support is simplified and materials are saved. Adjusting the support scheme according to the RQD value can reduce redundant operation time by about 30%.

[0035] As a preferred embodiment of this example, in S1, the ore pillar is divided into multiple stages along the vertical direction, and the downward large-hole stage void subsequent filling method is adopted, and the ore is blasted in the order of "retreating from the center to both ends".

[0036] The retreating blasting sequence gradually reduces the free face, thereby reducing the risk of exposure of the filling material. The central detonation forms a stable free face, reducing the hazards of flying rocks and shock waves from the blast.

[0037] As a preferred embodiment of this example, the ore pillar is vertically divided into 4 stages, each stage being 10m high. Downward deep-hole retreating caving is adopted, with each caving step being 5m. Starting from the 33A line slotting chamber, retreating lateral caving is carried out along the ore pillar from the center to both ends.

[0038] The design is divided into four stages, each with a height of 10m and a step distance of 5m, to ensure that the energy of each blast is controllable, reduce over-excavation or under-excavation, and reduce ore residue by using a retreating blasting sequence, thereby increasing the recovery rate to over 92%.

[0039] In summary, the technical effects and advantages of this invention are as follows:

[0040] The present invention has a reasonable structure. It adopts technologies such as step-by-step mining, mine wall retention, asymmetric blasting and gradient filling, which solves the problems of instability of filling body and uneven distribution of blasting energy in high-stage pillar mining. It also improves the pillar recovery rate, reduces the damage area of ​​filling body and reduces support costs. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 Construction plan of Datuanshan-610m;

[0043] Figure 2 for Figure 1 Sectional view of AA in the middle;

[0044] Figure 3 for Figure 1 Cross-sectional view of line 33A. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Taking the mining of the -610m vertical pillar in the IV panel of the Datuanshan mining section as an example, the mining process includes the following steps:

[0047] S1: Based on the geometric shape of the pillar (95m long × 25-36m wide), it is divided into 4 mining units (each unit is about 24m). 2m and 4m mining walls are left alternately on the east side, 2m mining wall is left on the west side, and 4m mining wall is left in the middle to form an "I" shaped support.

[0048] Verification of results: Stability monitoring of the pillar showed that the displacement on both the east and west sides was less than 5 mm, and no collapse occurred.

[0049] S2: The bottom of the -565m mining roadway will be scraped (1.2m deep) and the top will be raised (0.6m high) to 3.5m. Anchor bolts and shotcrete will be used for support (RQD=45% area), with an anchor bolt spacing of 1.2m; concrete support will be used only in the RQD=85% area.

[0050] Results verification: Tunnel deformation <3mm, support cost reduced by 18%.

[0051] S3: First stage drilling depth 45m, hole diameter 165mm, charge density 0.8kg / m³; Second stage, based on the filling body monitoring data (deformation <2mm), adjust the charge coefficient to 70% (filling body side):

[0052] Effect verification: After blasting, the qualified rate of ore block size (<300mm) reached 90%, and the filling body was free of cracks.

[0053] S4: Monitor the deformation data of the backfill body in real time during the mining process, and control the exposed area of ​​the backfill body to not exceed the critical value by adjusting the thickness of the mine wall and the blasting sequence;

[0054] The bottom layer of S5 is filled with a mortar-sand ratio of 1:4 (compressive strength 4.5MPa), the middle layer is 1:6 (3.0MPa), and the top layer is 1:8 (2.0MPa). The pre-embedded stress sensor shows that the stress concentration factor of the bottom layer has decreased to 1.2 (originally 1.8).

[0055] Effect verification: The overall stability of the filling body was improved, and there was no sinking phenomenon.

[0056] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for safe, phased mining of "I"-shaped pillars in high-stage mines, characterized in that: Includes the following steps; S1: Step-by-step mining area division. Based on the geometric shape of the pillar and the strength difference of the filling bodies on both sides, the pillar is divided into several mining units along the strike. 2m and 4m thick mining walls are left at intervals on the east side of the pillar, 2m mining wall is left on the west side, and 4m mining wall is left in the middle to form an "I" shaped support structure. S2: Mining preparation engineering restoration and optimization, involving the excavation and engineering modification of the ore extraction roadways and drilling chambers in the original backfilled goaf area, including bottom shoveling, roof lifting, and side widening, so that the roadway height reaches more than 3.5m. The rock mass is supported by shotcrete, concrete pouring, or rock bolts, and the support strength is adjusted. S3: Staged rock drilling and blasting design, adopting two-stage downward deep hole drilling. The first stage drilling depth does not exceed 45m. The second stage dynamically adjusts the blasting parameters according to the stability of the filling body. The blasting height of each stage is controlled at 10-15m. S4: Mine wall protection and backfill protection. During the mining process, the deformation data of the backfill is monitored in real time. By adjusting the mine wall thickness and blasting sequence, the exposed area of ​​the backfill is controlled to not exceed the critical value. S5: Subsequent segmented backfilling: After each mining unit is completed, cementing material with a ash-sand ratio of 1:4~8 is used for layered backfilling, and stress sensors are pre-embedded in the backfill to form a strength gradient distribution of the backfill.

2. The method for safe, phased mining of "I"-shaped pillars according to claim 1, characterized in that: In S1, the mining is arranged along the strike of the ore body and is carried out continuously. Due to the engineering limitations in the -610m section and the large amount of waste rock in the lower part, a large funnel bottom structure is adopted for ore extraction. The funnel is formed by large-hole blasting, with a specification of 6m×6m and a height of 14-17m. The inclination angle of the funnel opening is ≥50°.

3. The method for safe, phased mining of "I"-shaped pillars in high-stage, step-by-step operations according to claim 1, characterized in that: In S2, the bottom-shoveling method is adopted to preserve the integrity of the original support structure. The bottom-shoveling depth does not exceed 1.5m, and the top-shoveling height does not exceed 0.8m.

4. The method for safe, phased mining of "I"-shaped pillars in high-stage, step-by-step operations according to claim 1, characterized in that: In S3, the blasting adopts an asymmetric charge structure, with the charge coefficient on the side closer to the filling body reduced by 20%-30%, and the detonation sequence adopts a progressive detonation from high to low and from weak to strong.

5. The method for safe, phased mining of "I"-shaped pillars in high-stage, step-by-step operations according to claim 1, characterized in that: In S5, the strength gradient distribution of the filling body is achieved through layered filling. The bottom layer is filled with a 1:4 lime-sand ratio, the middle layer with a 1:6 lime-sand ratio, and the top layer with a 1:8 lime-sand ratio. The construction interval between each layer is not less than 72 hours.

6. The method for safe, phased mining of "I"-shaped pillars in high-stage, step-by-step operations according to claim 1, characterized in that: In S2, when the rock mass RQD value is less than 50%, anchor bolt + shotcrete support is used with an anchor bolt spacing of 1.2m. When the rock mass RQD value is greater than 80%, only concrete support is used.

7. The method for safe, phased mining of "I"-shaped pillars according to claim 1, characterized in that: In S1, the ore pillar is divided into multiple stages along the vertical direction, and the downward large-hole stage open space is filled in the subsequent filling method, and the ore is caving in the order of "retreating from the center to both ends".

8. A method for safe, phased mining of "I"-shaped pillars in high-stage, step-by-step operations, as described in claim 7, characterized in that: The ore pillar was vertically divided into 4 stages, each with a height of 10m. Downward deep-hole retreating caving was adopted, with each caving step being 5m.

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