Rapid construction method of large-diameter cyclone pool in confined space under Gobi pebble geology

Abstract

The present invention relates to the field of industrial engineering, specifically a method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, aiming to solve the problems of low construction efficiency, poor precision, high cost and high safety risk in the existing technology when constructing a large-diameter cyclone pool under Gobi pebble geology and confined space conditions. The present invention designs a variable-section cylinder and utilizes its "large at the bottom and small at the top" structure to reduce frictional resistance during the sinking process; adopts multi-level slope excavation to reduce the impact on the surrounding environment and occupation; combines thixotropic mud sinking technology to reduce frictional resistance between the cylinder and the soil; and through segmented scaffolding erection and cylinder manufacturing process and step-by-step deep caisson construction, combined with real-time monitoring and adjustment, ensures construction precision and safety, thereby improving the construction efficiency and precision of large-diameter cyclone pools under Gobi pebble geology and confined space conditions.

Description

Technical Field

[0001] The present invention belongs to the field of industrial engineering and relates to a rapid construction technology for a large-diameter cyclone pool under complex geological conditions and space limitations, specifically a rapid construction method for a large-diameter cyclone pool in a confined space under Gobi pebble geology. Background Art

[0002] In recent years, with advancements in technology, enhanced construction capabilities, and growing environmental awareness, large-scale steel mill construction projects have seen increasingly compact facility layouts. While this layout improves space utilization and production efficiency, it also places extremely high demands on the overall construction capabilities of the entire project. During actual construction, underground equipment foundations, underground structures, and above-ground buildings are often constructed simultaneously or interspersed. This not only increases the construction speed of each building but also significantly complicates safety risk management during construction. This is particularly true when the construction site encounters unique geological conditions.

[0003] For example, a large-diameter, ultra-deep cyclone tank was required to process large quantities of industrial water during the construction of a wide and heavy plate rolling mill for a steel production line. The tank's design specifications were extremely stringent: a cylinder diameter exceeding 18 meters and a depth exceeding 30 meters. Traditional caisson construction for a cyclone of this scale is rare, placing extremely high demands on construction technology. Furthermore, the complex Gobi pebble geology at the project site, with a thick layer of pebbles, large interpebble gaps, and poor stability, posed significant challenges to sinking and stabilizing the caisson. Under these geological conditions, the large-diameter cyclone tank caisson was susceptible to uneven resistance and friction from the pebble layer during sinking, resulting in loss of verticality and horizontality, seriously threatening construction accuracy and safety. Furthermore, limited space at the construction site significantly restricted the placement of construction equipment and personnel, complicating construction organization. These space constraints precluded the direct application of traditional scaffolding, formwork installation, and concrete pouring methods. Furthermore, the construction of a large-diameter, ultra-deep cyclone tank placed extremely high demands on the design and fabrication of the caisson tank. The traditional uniform cross-section caisson body design cannot effectively reduce the contact area and friction resistance with the pebble layer in Gobi pebble geology, which often leads to slow sinking and prolonged sinking cycle.

[0004] Specifically, the difficulties in constructing a cyclone pool of the above size under Gobi pebble conditions are:

[0005] First of all, large-scale excavation construction with graded slope requires large-scale excavation and slope treatment of the surrounding soil, which not only has a great impact on the synchronous construction of surrounding underground equipment foundations, underground structures and above-ground buildings, but also due to the unevenness and high hardness of the pebble layer, slope instability and collapse are prone to occur during the excavation process, which prolongs the construction period of the entire project and increases construction costs. At the same time, there are potential risks to the safety of the surrounding environment.

[0006] Secondly, top-down and semi-top-down methods require cast-in-place pile support and a horizontal support system during construction. However, in the Gobi pebble geology, the pebble layer has large voids and poor stability, making it difficult to ensure the quality of cast-in-place piles. Quality issues such as mud inclusion and broken piles are prone to occur, affecting the safety of the support structure. Furthermore, the installation and removal of the horizontal support system requires a significant amount of time, manpower, and material resources, resulting in a long construction period and high construction costs. Furthermore, construction is difficult in complex geological conditions.

[0007] Furthermore, traditional straight-tube caissons are difficult and slow to sink in the hard, gravelly Gobi geology. Due to the high frictional resistance of the gravel layer, the caisson must overcome significant friction during the sinking process. This not only increases the difficulty and risk of construction, but also the repeated sinking and raising of the caisson leads to poor construction accuracy, further extending the construction period and increasing construction costs.

[0008] In summary, the existing traditional construction methods such as large-scale excavation with graded slope, reverse construction, semi-reverse construction, and ordinary caisson method, when faced with the "confined space" formed by the Gobi pebble geological conditions and the compact layout of surrounding facilities, all have problems such as low construction efficiency, poor construction accuracy, high construction cost, and high safety risks. Therefore, it is difficult to meet the needs of quickly, safely, and low-costly construction of large-diameter cyclone pools. Summary of the Invention

[0009] In response to the deficiencies of the above-mentioned prior art, the present invention aims to provide a method for the rapid construction of a large-diameter cyclone pool in a confined space under Gobi pebble geology. By adopting comprehensive technical means such as variable-section cylinder design, thixotropic mud-assisted sinking technology, segmented scaffolding erection and cylinder segment production process, and step-by-step deep-descent caisson construction combined with real-time monitoring and adjustment, the present invention effectively solves the problems of low construction efficiency, poor precision, high cost and high safety risks of large-diameter cyclone pools under Gobi pebble geology and confined space conditions, and realizes the rapid, efficient and safe construction of cyclone pools.

[0010] In order to achieve the above object, the present invention is achieved as follows:

[0011] A method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology comprises the following steps:

[0012] Step 1: Design a variable cross-section cylinder. The outer contour of the variable cross-section cylinder gradually contracts inward in a stepped manner from bottom to top, forming a shape with a larger bottom and a smaller top, while the inner contour remains a straight cylinder structure to reduce the contact area and frictional resistance with the soil during the sinking process;

[0013] Step 2: Excavate a deep foundation pit by adopting a multi-level slope cutting method according to the available working area;

[0014] Step 3: Manufacture a circular cutting edge section. Conduct positioning measurement in the deep foundation pit, build a circular cutting edge brick formwork, install steel bars, anti-friction grouting pipes, and templates, and pour concrete to form a circular cutting edge section. The longitudinal section of the circular cutting edge is in the shape of an inclined cut angle, straight outside and inclined inside;

[0015] Step 4: Based on the circular cutting edge section, divide the variable cross-section cylinder into multiple segments. Successively carry out scaffolding erection, segment manufacturing, and large-drop deep well construction for each segment of the cylinder until the design elevation is reached; During the sinking process of each segment of the cylinder, use a high-pressure pump to evenly inject thixotropic mud around the cylinder as a lubricant between the cylinder and the soil to reduce the frictional resistance between the two;

[0016] Step 5: Implement the bottom sealing operation. After the sinking of each segment of the cylinder in Step 4 is completed and stabilized, install the steel bars and templates of the horizontal bottom plate, and pour concrete to complete the bottom sealing work of the swirl pool.

[0017] In the above method for quickly constructing a large-diameter swirl pool in a limited space under the gobi pebble geology, the variable cross-section cylinder includes three segments, and the outer diameter of each segment gradually decreases. Specifically: the outer diameter of the first segment of the cylinder is D1, the outer diameter of the second segment of the cylinder is D2, and the outer diameter of the third segment of the cylinder is D3, where D1 > D2 > D3, and the height of each segment of the cylinder is H1, H2, H3, satisfying H1 + H2 + H3 = total depth to maintain the inner diameter of the cylinder unchanged while reducing the frictional resistance between the side of the cylinder and the soil.

[0018] In Step 2 of the above method for quickly constructing a large-diameter swirl pool in a limited space under the gobi pebble geology, the multi-level slope cutting method for excavating the deep foundation pit includes the following steps:

[0019] Step 2.1: Conduct positioning measurement to determine the excavation range;

[0020] Step 2.2: Adopt a two-level slope cutting method to excavate the deep foundation pit. The depth of the deep foundation pit ≥ 9 meters, the slope ratio of the first-level slope cutting is i1, and the slope ratio of the second-level slope cutting is i2, where i1 < i2 to ensure the stability of the slope;

[0021] Step 2.3: Set an intermediate platform during the excavation process. The width of the platform should meet the requirements for placing construction equipment and materials;

[0022] Step 2.4: After excavation is completed, pour a concrete pad at the bottom of the foundation pit to provide a stable construction foundation.

[0023] In step 3 of the method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, the production of the annular blade foot segment includes the following steps:

[0024] Step 3.1: Conduct positioning measurements in the deep foundation pit to determine the position of the annular blade foot;

[0025] Step 3.2: Lay the annular blade foot brick membrane;

[0026] Step 3.3: Install the steel bars;

[0027] Step 3.4: bury the drag reduction grouting pipe;

[0028] Step 3.5: Install the template;

[0029] Step 3.6: pouring concrete and curing;

[0030] Step 3.7: Install steel plate guards on the inner and outer sides of the bottom of the annular blade to enhance wear resistance and soil cutting ability.

[0031] In step 4 of the method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, the scaffolding is erected as follows:

[0032] The inner and outer scaffolding of the first section of the cylinder are both ground-type steel pipe scaffolding, with the scaffolding uprights and horizontal bars set at intervals;

[0033] The outer scaffolding of the remaining sections of the cylinder adopts floor-standing steel pipe scaffolding, and the inner scaffolding adopts cantilevered steel pipe scaffolding set at intervals;

[0034] The cantilever steel pipe scaffold is erected by welding a cantilever tripod pre-buried in the upper inner side of the cylinder body. The position of the cantilever tripod is accurately measured to ensure the accuracy of the scaffold erection.

[0035] In step 4 of the method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, the thixotropic slurry injection method includes the following steps:

[0036] Use a high-pressure pump to inject thixotropic slurry evenly and at a constant speed around the cylinder;

[0037] There are multiple grouting pipes and they are buried at intervals;

[0038] Real-time monitoring of grouting pressure and mud flow during grouting to ensure grouting effect;

[0039] After grouting is completed, close the grouting holes to prevent mud from flowing back.

[0040] In step 4 of the method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, during the construction of the deep-drawn caisson, a theodolite and a level are set to detect and adjust the verticality and horizontality of the cylinder to ensure construction accuracy, which specifically includes the following steps:

[0041] Two theodolites with a 90° angle are set outside the cylinder with a measurement accuracy of ±5″ to monitor the verticality of the cylinder;

[0042] Set up a level with a measurement accuracy of ±1mm to monitor the horizontality of the cylinder and control the sinking depth;

[0043] The cylinder posture is adjusted in real time according to the monitoring data. The adjustment method is: when the verticality and horizontality deviations exceed the allowable values, the excavation depth is adjusted (in order to achieve rapid caisson, the caisson operation is carried out by excavating inside the cylinder and settling the cylinder by its own weight during the sinking process. During this process, if the geology of the area where the cylinder is located is hard, the excavation depth each time shall not exceed 500mm; if the area where the cylinder is located is soft soil, the excavation depth each time shall not exceed 300mm) and the sequence, and the injection position and injection amount of the thixotropic mud shall be adjusted in a targeted manner to ensure that the verticality and horizontality of the cylinder meet the design requirements.

[0044] The above-mentioned method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology also includes prediction and monitoring steps:

[0045] First, before the caisson construction, according to the design parameters and geological conditions of the cyclone pool, the horizontal excavation area S of the cyclone pool, the total time required for caisson T, and the total friction resistance value T between the side wall and the soil are calculated using the following formula: f , to predict key parameters during construction:

[0046] The calculation formula for the horizontal excavation area S of the cyclone pool is:

[0047]

[0048] Where D is the outer diameter of the cyclone pool (unit: meter, m), B is the width of the construction working surface around the cyclone pool (unit: meter, m), H is the excavation depth of the cyclone pool (unit: meter, m), b is the width of the middle platform (unit: meter, m), i is the designed slope ratio (dimensionless), n is the slope level (dimensionless), and the calculated result S is in square meters (m 2 );

[0049] The calculation formula for the total time T required for caisson is:

[0050]

[0051] Among them, F i is the friction force during the sinking process of the i-th section of the cylinder (unit: Newton, N), d i is the length of the i-th section of the cylinder (unit: meter, m), v i is the excavation speed of the i-th section cylinder (unit: meters per hour, m / h), P i is the grouting pressure when the i-th section of the cylinder sinks (unit: Pascal, Pa), n is the number of sections of the cylinder (dimensionless), and the calculated result T is in hours (h);

[0052] Total friction resistance value T between the side wall and the soil f The calculation formula is:

[0053]

[0054] Among them, U i is the perimeter of the side wall in the i-th soil layer (unit: meter, m), f ki is the standard value of unit friction resistance of the i-th layer of soil (unit: kilonewton per square meter, kN / m 2 ), H i is the thickness of the i-th soil layer (unit: meter, m), m is the number of soil layers (dimensionless), the calculated result T f The unit is kilonewton (kN), since 1 kN = 10 3 N, so f needs to be calculated ki Convert to N / m 2 To ensure dimensional consistency;

[0055] Secondly, during the caisson construction process, the sinking speed, verticality, horizontality, and injection volume and pressure of the caisson are monitored in real time and compared with the predicted values ​​to enable timely adjustments and optimization of the construction process to ensure construction quality and safety.

[0056] Finally, when the caisson construction is completed in stages, the calculation formula is used to dynamically predict and adjust the caisson time, friction resistance and other parameters of the subsequent construction sections based on the monitoring data to optimize the construction plan and improve construction efficiency and accuracy.

[0057] The proposed method for rapidly constructing large-diameter cyclone pools in confined spaces under Gobi pebble geology is designed to effectively address the numerous shortcomings and deficiencies of existing cyclone pool construction technologies in Gobi pebble geology and confined spaces. Specifically, the present invention addresses the following prominent issues in the prior art:

[0058] Difficulty and inefficiency in sinking: Traditional straight-tube caissons are difficult and slow to sink in the hard, gravelly Gobi geology. The high frictional resistance of the gravel layer requires overcoming significant friction during the sinking process, which not only increases the difficulty and risk of construction, but also leads to poor construction accuracy due to repeated sinking and raising. This further prolongs the construction period.

[0059] Insufficient construction accuracy: In the existing technology, the integral caisson technology is adopted. Once the cylinder deviates during the caisson process, it is difficult to take corrective measures in time, so the verticality and horizontality of the caisson operation cannot be controlled within the limited space, resulting in the inability to guarantee construction accuracy and affecting the construction quality of the cyclone pool.

[0060] High costs: Excavation with graded sloping and large-scale excavation impacts the simultaneous construction of surrounding underground equipment foundations, underground structures, and above-ground buildings, extending the project construction period and increasing construction costs. Reverse and semi-reverse methods require cast-in-place pile support and a horizontal support system, resulting in a long construction period and high construction costs.

[0061] High safety risks: Under complex geological conditions, traditional construction methods pose significant safety risks, such as slope instability and collapse, posing a threat to construction workers and the surrounding environment.

[0062] In response to the above problems, the present invention has achieved significant improvements and enhancements through innovative technical solutions:

[0063] This invention proposes a method for rapidly constructing a large-diameter cyclone in a confined space under Gobi pebble geology. The core of this technical solution lies in the introduction of a "variable-section cylinder." This concept, by gradually converging the outer contour of the cylinder from bottom to top to form a "large at the bottom, small at the top" structure, significantly reduces the contact area during the sinking process, thereby significantly reducing friction with the surrounding soil. This key design effectively overcomes the existing difficulties in sinking and construction efficiency caused by excessive frictional resistance, ensuring smooth and efficient caisson construction.

[0064] Secondly, the present invention introduces thixotropic slurry sinking technology, further enhancing the friction reduction effect. During caisson construction, a high-pressure pump evenly injects thixotropic slurry around the caisson, forming an effective lubricating layer that significantly reduces friction between the caisson's sides and the soil. This technical approach not only significantly increases the caisson's sinking speed but also effectively reduces energy consumption and equipment wear during construction, thereby lowering overall construction costs.

[0065] Furthermore, the present invention adopts the process of segmented scaffolding erection and segmented cylinder manufacturing, which optimizes the construction process and greatly improves the construction efficiency and accuracy. By dividing the variable cross-section cylinder into multiple sections, scaffolding erection, segment manufacturing and large-depth caisson construction are carried out separately, and when each section of the cylinder is manufactured, the embedded parts of the cantilevered tripod are pre-embedded in the upper inner side of the cylinder, thereby ensuring the accuracy of subsequent scaffolding erection. This segmented construction method not only improves the flexibility and adaptability of construction, but also facilitates quality control and safety management during the construction process, and effectively avoids the problem of insufficient construction accuracy caused by limited space in traditional methods.

[0066] In addition, the present invention effectively improves the safety and accuracy of construction by carrying out deep caisson construction in stages and combining it with real-time monitoring and adjustment. During the caisson process, the verticality and horizontality of the cylinder are monitored in real time by setting up a theodolite and a level, and the cylinder posture is adjusted in time according to the monitoring data to ensure construction accuracy. Once the cylinder deviates during the sinking process, it is immediately corrected by targeted thixotropic mud injection and uneven excavation within the cylinder using its own settlement. At the same time, the sinking speed, verticality, horizontality, and injection volume and pressure of the cylinder are monitored in real time, and compared with the predicted values ​​for analysis, so as to make timely adjustments and optimizations to the construction process, ensure construction quality and safety, and effectively reduce the high safety risks existing in traditional construction methods.

[0067] Finally, this invention uses a mathematical model to estimate caisson time and optimizes construction parameters based on the estimated results, further improving construction efficiency and reducing construction time and resource consumption. By predicting and monitoring key construction parameters, such as the horizontal excavation area of ​​the cyclone pool, the total caisson time required, and the total frictional resistance between the sidewall and the soil, the contractor can formulate a reasonable construction plan and resource allocation plan in advance, ensuring an efficient and orderly construction process. This effectively overcomes the long construction period and high cost of existing technologies.

[0068] In summary, the present invention effectively solves the problems existing in the prior art through innovative technical solutions, significantly improves the efficiency, precision and safety of the construction of large-diameter cyclone pools under Gobi pebble geology and confined space conditions, while reducing costs, providing new ideas and methods for similar engineering construction, and has significant engineering application value and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is a schematic diagram of the rapid caisson construction process of a large-diameter ultra-deep cyclone pool in Gobi pebble geology and confined space conditions in an embodiment of the present invention.

[0070] Figure 2 This is a schematic diagram of the design of a variable-section caisson body for a large-diameter, ultra-deep cyclone pool in an embodiment of the present invention.

[0071] Figure 3 This is a schematic diagram of the segmented production and gradual deep-descent sinking of the variable-section caisson body of a large-diameter, ultra-deep cyclone pool in an embodiment of the present invention.

[0072] Figure 4 This is a schematic diagram of the internal steel cantilever tripod arrangement of a variable-section caisson shell for a large-diameter, ultra-deep cyclone pool in an embodiment of the present invention.

[0073] Figure 5 This is a schematic diagram of the planar layout of the internal and external scaffolding of the variable-section caisson for a large-diameter, ultra-deep cyclone pool in an embodiment of the present invention after the first and second sinking.

[0074] Figure 6 This is a schematic elevation view of the scaffolding erected inside and outside the large-diameter, ultra-deep cyclone pool variable-section caisson after the first and second sinking in an embodiment of the present invention.

[0075] Figure 7 This is a schematic diagram of the planar layout of the variable-section caisson drag reduction mud pipe in the large-diameter ultra-deep cyclone pool in an embodiment of the present invention.

[0076] Figure 8 This is a schematic diagram of the vertical layout of the variable-section caisson drag reduction mud pipe in a large-diameter ultra-deep cyclone pool in an embodiment of the present invention. DETAILED DESCRIPTION

[0077] In order to solve the outstanding problems of accuracy, efficiency, cost and safety in the construction of large-scale, ultra-deep cyclone pools under Gobi pebble conditions in the traditional construction method in the background art and ensure smooth and high-quality construction, the following method for rapid construction of large-diameter cyclone pools in confined space under Gobi pebble geology is proposed. The construction process flow and structural schematic diagram are shown as follows: Figure 1 、 Figure 8 Specifically, the rapid construction method includes:

[0078] Step 1: Variable cross-section cylinder design, such as Figure 2 、 Figure 3 As shown;

[0079] When constructing a cyclone using the caisson method, a variable-section cylinder significantly reduces frictional resistance on the cylinder's sides compared to traditional straight cylinders, making it easier to sink the cylinder. Therefore, based on the cyclone's cylinder diameter, wall thickness, and depth, while maintaining the inner diameter of the cylinder unchanged, the outer diameter of the cylinder is designed to be a three-section, variable-section cylinder, starting from the top of the annular blade, that gradually tapers inward from bottom to top, forming a "large at the bottom, small at the top" structure. The specific dimensional relationship is: the outer diameter of the first section is D1, the outer diameter of the second section is D2, and the outer diameter of the third section is D3, where D1>D2>D3. The heights of each section are H1, H2, and H3, satisfying the equation H1 + H2 + H3 = total depth.

[0080] Step 2: Excavate the deep foundation pit with two-level slope reduction;

[0081] When the swirl pool is constructed by the traditional open caisson method, the depth of the first-level excavation of the foundation pit generally does not exceed 5 meters. When constructing the open caisson in the geological conditions of戈壁卵石 (戈壁 pebble), the first-level excavation of the foundation pit adopts two-level slope reduction with a depth of 9 meters, reducing the depth of the cylindrical open caisson, reducing the risk of sinking deviation, reducing the number of manufacturing times and the number of heightening times, accelerating the construction progress, and improving the construction accuracy. The excavation process includes:

[0082] Step 2.1: Conduct positioning measurement to determine the excavation range;

[0083] Step 2.2: Excavate the deep foundation pit by the two-level slope reduction method. The depth of the deep foundation pit is ≥9 meters. The slope ratio of the first-level slope reduction is i1, and the slope ratio of the second-level slope reduction is i2, where i1 < i2, to ensure the stability of the slope;

[0084] Step 2.3: Set up an intermediate platform during the excavation process. The width of the platform should meet the requirements for placing construction equipment and materials;

[0085] Step 2.4: After the excavation is completed, pour a concrete cushion layer at the bottom of the foundation pit to provide a stable construction foundation.

[0086] Step 3: Manufacture the annular cutting edge section;

[0087] The annular cutting edge is the most critical section of the cylindrical body for cutting soil and sinking. It is designed with an inclined cutting angle, straight outside and inclined inside. To prevent damage when encountering hard objects and facilitate cutting soil and sinking, steel plate foot protection is adopted on the inner and outer sides of the bottom of the annular cutting edge. In order to grout to reduce resistance and assist sinking during the open caisson process, resistance-reducing grouting pipes are buried during the manufacture of the annular cutting edge section; The manufacture process of the annular cutting edge section includes:

[0088] Step 3.1: Conduct positioning measurement in the deep foundation pit to determine the position of the annular cutting edge;

[0089] Step 3.2: Build the brick formwork for the annular cutting edge;

[0090] Step 3.3: Install steel bars;

[0091] Step 3.4: Bury the resistance-reducing grouting pipes;

[0092] Step 3.5: Install the formwork;

[0093] Step 3.6: Pour concrete and maintain it;

[0094] [[ID=||ID=44]]Step 3.7: Set steel plate foot protection on the inner and outer sides of the bottom of the annular cutting edge to enhance wear resistance and soil cutting ability. [[ID=||ID=46]]

[0095] Step 4: Manufacture each section of the cylindrical body and conduct the construction of the large deep open caisson, such as Figures 4 to 7 As shown;

[0096] Step 4.1, erection of ground-type steel pipe scaffolding inside and outside the first section of variable-section cylinder:

[0097] Pour a circular concrete cushion along the inner and outer sides of the annular blade to ensure the safety of the scaffolding inside and outside the first section of the variable cross-section cylinder. The scaffolding inside and outside the first section of the variable cross-section cylinder is erected above the soil, so a ground-type steel pipe scaffolding is used. After the erection is completed, it is convenient for the construction of the inner and outer formwork of the cylinder. The inner and outer scaffolding of the cylinder are circular along the cylinder, so the inner steel pipe scaffolding is larger on the inside and smaller on the outside, while the outer steel pipe scaffolding is larger on the outside and smaller on the inside.

[0098] Step 4.2, production of the first section of variable cross-section cylinder:

[0099] When manufacturing the first section of the variable-section cylinder, embedded parts of the cantilevered tripod are pre-buried in the upper inner part of the cylinder to facilitate the use of the inner cantilevered steel pipe scaffolding required for welding the cylinder extension; in order to reduce drag and assist sinking by grouting during the caisson, the first section of the variable-section cylinder can be considered to be buried with the same drag-reducing grouting pipe as the annular blade foot section. The manufacturing process includes: installing the steel bars of the first section of the variable-section cylinder, burying the drag-reducing grouting pipe, burying the embedded parts of the cantilevered tripod in the upper inner part of the cylinder, supporting the cylinder formwork, pouring concrete, and subsequent demoulding and maintenance. Draw vertical lines at the four equal points on the outer side of the formed cylinder, and mark horizontal scale lines on the vertical lines to facilitate monitoring and adjustment of the vertical and horizontal postures of the cylinder during the first caisson to ensure construction accuracy.

[0100] Step 4.3: First large-depth caisson construction:

[0101] During the first caisson excavation, a high-pressure pump was used to inject thixotropic mud to aid sinking, preventing the occurrence of sinking problems caused by high friction resistance on the side of the caisson. The mud-assisted sinking allowed the sinking depth to exceed 10 meters, making it easier to sink and deeper than ordinary caisson construction, speeding up the construction progress. The first caisson depth must meet the requirement that the weight of the caisson is greater than the friction resistance on the side of the caisson to ensure that it can sink under theoretical conditions. Excavation at the blade foot must be uniform and symmetrical, with each circle of excavation height of 0.2 to 0.5 meters to prevent the caisson from tilting due to high friction resistance on the side of the caisson. During the actual excavation and sinking process of the first caisson, two longitude and latitude measuring instruments at a 90° angle were set up outside the caisson for vertical correction, and a level was set up for horizontal correction and sinking depth control to ensure the accuracy of the caisson construction. After the first caisson, the exposed soil height must be 0.5 meters to facilitate the installation of formwork when the caisson is extended. After the first caisson is completed, the gap between the outside of the caisson and the soil is backfilled with yellow sand to facilitate the erection of the external frame when the caisson is extended.

[0102] Step 4.4: Erection of the outer floor-standing steel pipe scaffolding and inner cantilevered steel pipe scaffolding of the second section of the variable-section cylinder:

[0103] After the first caisson was completed, the excavator was hoisted out and a circular concrete cushion was poured along the outside of the first section of the variable-section cylinder to ensure the safety of the scaffolding on the outside of the second section of the variable-section cylinder; the scaffolding on the outside of the second section of the variable-section cylinder was erected above the soil, so a ground-based steel pipe scaffolding was used; a cantilevered tripod was welded along the upper embedded parts on the inside of the first section of the variable-section cylinder, so a cantilevered steel pipe scaffolding was used on the inside of the second section of the variable-section cylinder. Compared with the traditional method of erecting a ground-based steel pipe scaffolding on the inside of the cylinder, the caisson method of erecting a cantilevered steel pipe scaffold on the inside of the cylinder greatly shortens the period of erecting and dismantling the scaffolding, thereby greatly improving construction efficiency; the scaffolding inside and outside the cylinder is circular along the cylinder, so the inner steel pipe scaffolding is larger inside and smaller outside, and the outer steel pipe scaffolding is larger outside and smaller inside.

[0104] Step 4.5, production of the second section of variable cross-section cylinder:

[0105] When manufacturing the second section of the variable-section cylinder, embedded parts of the cantilevered tripod are pre-buried in the upper inner part of the cylinder to facilitate the use of the inner cantilevered steel pipe scaffolding required for welding the cylinder extension; in order to reduce drag and assist sinking by grouting during the caisson, the second section of the variable-section cylinder can be manufactured by burying the same drag-reducing grouting pipe as the annular blade foot section. The specific manufacturing process includes: installing the steel bars of the second section of the variable-section cylinder, burying the drag-reducing grouting pipe, burying the embedded parts of the cantilevered tripod in the upper inner part of the cylinder, supporting the cylinder formwork, pouring concrete, and subsequent demoulding and maintenance. Draw vertical lines at the four equal points on the outer side of the formed cylinder, and mark horizontal scale lines on the vertical lines to facilitate monitoring and adjustment of the vertical and horizontal postures of the cylinder during the second caisson to ensure construction accuracy.

[0106] Step 4.6, Second large-depth caisson construction:

[0107] During the second caisson excavation, a high-pressure pump injected thixotropic slurry to aid sinking, preventing the high friction resistance on the sides of the caisson from preventing it from sinking. This slurry-assisted sinking allowed the caisson to descend to a depth of over 10 meters, making it easier to sink and reach a greater depth than with conventional caissons, accelerating construction progress. Excavation at the cutting edge was performed evenly and symmetrically, with each excavation height ranging from 0.2 to 0.5 meters to prevent the caisson from tilting due to high friction resistance on the sides. During the actual excavation and sinking of the second caisson, two vertical and horizontal scales at 90° angles were installed outside the caisson for verticality correction. A level was also installed for horizontality correction and depth control to ensure construction accuracy. Upon completion, the exposed soil height of the second caisson was maintained at 0.5 meters to facilitate formwork installation during the caisson extension process. After completion, the gap between the caisson and the soil was backfilled with sand to compact the gap, facilitating the erection of the external scaffolding for the caisson extension. The second caisson was lowered to the design elevation.

[0108] Step 4.7: Erection of the outer floor-standing steel pipe scaffolding and inner cantilevered steel pipe scaffolding of the third section of the variable-section cylinder:

[0109] After the second caisson was completed, the excavator was hoisted out and a circular concrete cushion was poured along the outside of the second section of the variable-section cylinder to ensure the safety of the scaffolding on the outside of the third section of the variable-section cylinder; the scaffolding on the outside of the third section of the variable-section cylinder was erected above the soil, so a ground-based steel pipe scaffolding was used; a cantilevered tripod was welded along the upper embedded parts on the inside of the second section of the variable-section cylinder, so a cantilevered steel pipe scaffolding was used on the inside of the third section of the variable-section cylinder. Compared with the traditional method of erecting a ground-based steel pipe scaffolding on the inside of the cylinder, the caisson method of erecting a cantilevered steel pipe scaffold on the inside of the cylinder greatly shortens the period of erecting and dismantling the scaffolding, thereby greatly improving construction efficiency; the scaffolding inside and outside the cylinder is circular along the cylinder, so the inner steel pipe scaffolding is larger inside and smaller outside, and the outer steel pipe scaffolding is larger outside and smaller inside.

[0110] Step 4.8, production of the third section of variable cross-section cylinder:

[0111] Install the reinforcement and formwork of the third section of the variable-section cylinder, pour concrete, and start the production of the third and final section of the variable-section cylinder.

[0112] Step 5: Back Cover

[0113] After the caisson is stable, install the steel bars and formwork of the horizontal bottom plate, pour concrete, and seal the bottom of the vortex pool.

[0114] Furthermore, before the construction of the above-mentioned caisson, the horizontal excavation area S of the cyclone pool, the total time required for caisson T, and the total friction resistance value T between the side wall and the soil can be calculated using the following formula based on the design parameters and geological conditions of the cyclone pool: f , to predict key parameters during construction:

[0115] 1) The calculation formula for the horizontal excavation area S of the cyclone pool is:

[0116]

[0117] Where D is the outer diameter of the cyclone pool (unit: meter, m), B is the width of the construction working surface around the cyclone pool (unit: meter, m), H is the excavation depth of the cyclone pool (unit: meter, m), b is the width of the middle platform (unit: meter, m), i is the designed slope ratio (dimensionless), n is the slope level (dimensionless), and the calculated result S is in square meters (m 2 );

[0118] 2) The calculation formula for the total time T required for caisson is:

[0119]

[0120] Among them, F i is the friction force during the sinking process of the i-th section of the cylinder (unit: Newton, N), d i is the length of the i-th section of the cylinder (unit: meter, m), v i is the excavation speed of the i-th section cylinder (unit: meters per hour, m / h), P i is the grouting pressure when the i-th section of the cylinder sinks (unit: Pascal, Pa), n is the number of sections of the cylinder (dimensionless), and the calculated result T is in hours (h);

[0121] 3) Total friction resistance value T between the side wall and the soil f The calculation formula is:

[0122]

[0123] Among them, U i is the perimeter of the side wall in the i-th soil layer (unit: meter, m), f ki is the standard value of unit friction resistance of the i-th layer of soil (unit: kilonewton per square meter, kN / m 2 ), H i is the thickness of the i-th soil layer (unit: meter, m), m is the number of soil layers (dimensionless), the calculated result T f The unit is kilonewton (kN), since 1 kN = 10 3 N, so f needs to be calculated ki Convert to N / m 2 To ensure dimensional consistency.

[0124] Furthermore, during the caisson construction process, the sinking speed, verticality, horizontality of the caisson, and the injection volume and pressure of the thixotropic mud are monitored in real time and compared with the predicted values ​​to enable timely adjustment and optimization of the construction process to ensure construction quality and safety.

[0125] Furthermore, based on the monitoring data, the calculation formula is used to dynamically predict and adjust parameters such as the caisson time and friction resistance of subsequent construction sections, and experience is accumulated to optimize subsequent construction plans for similar working conditions, thereby continuously improving the construction technology level, efficiency and accuracy.

[0126] In this embodiment, the invention proposes a method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, which makes two core improvements for confined spaces and Gobi pebble geology:

[0127] 1. A variable-section cyclone tank body that is easy to sink is proposed. Compared with a straight-type body, the variable-section body with a "larger bottom and smaller top" shape reduces the contact area with the soil during sinking, and the frictional resistance between the sides of the body and the soil is relatively reduced, which is conducive to sinking.

[0128] 2. A rapid caisson method is proposed in combination with the variable-section cyclone tank cylinder. First, when the caisson sinks, a high-pressure pump is used to inject thixotropic mud around the cyclone tank cylinder to lubricate and assist the sinking. Therefore, the caisson construction is relatively easy and the sinking speed is fast. Secondly, the use of secondary caisson construction is conducive to shortening the construction period, reducing construction costs, and improving construction accuracy.

[0129] Furthermore, this technical solution, as a new cyclone pool construction method, compared with traditional construction methods such as slope excavation, reverse or semi-reverse construction, and ordinary caisson construction, has the following beneficial effects when constructing large-diameter and deep cyclone pools under the Gobi pebble geological conditions and confined space of the project site:

[0130] 1. If the slope excavation method is adopted, the excavation area formula is S=π[D / 2+niH+(n-1)b+B] 2 , where D is the diameter of the cyclone pool, H is the excavation depth of the cyclone pool, n is the number of slope levels, b is the width of the intermediate platform, B is the width of the pit bottom working surface, and i is the slope ratio; based on the cyclone pool diameter of 18m, excavation depth of 30m, 6-level slope, intermediate platform width of 1m, pit bottom working surface width of 2m, and medium-dense pebble layer minimum slope ratio of 1:0.75, the excavation area is approximately S=4654㎡.

[0131] The rapid caisson construction method of a large-diameter ultra-deep cyclone pool under Gobi pebble geology and confined space conditions described in this technical solution only requires two-level slope excavation to excavate a 9m deep foundation pit. According to the aforementioned area formula, with a cyclone pool diameter of 18m, an excavation depth of 9m, two-level slope excavation, a middle platform width of 1m, a pit bottom working surface width of 2m, and a minimum slope ratio of 1:0.75 for the medium-dense pebble layer, the excavation area is approximately S=1104㎡. Compared with the slope excavation method, the excavation area is small, which does not affect the synchronous construction of nearby underground equipment foundations, underground structures, and ground buildings, as well as the safety of the surrounding environment. It shortens the construction period of the entire project, improves the construction efficiency of the entire project, reduces construction costs, and reduces safety risks.

[0132] 2. If the reverse method or semi-reverse method is adopted, cast-in-place pile support and horizontal support system support are required, which will result in a long construction period and high construction cost.

[0133] The method for rapid caisson construction in a large-diameter, ultra-deep cyclone pool under Gobi pebble geology and confined space conditions described in this technical solution allows caisson construction to be carried out directly after the cylinder is directly manufactured on the ground, without the need for cast-in-place pile support and horizontal support system support, thereby shortening the construction period and reducing construction costs.

[0134] 3. If the ordinary caisson method is adopted, the caisson is a straight cylinder, and the contact area with the soil is large during sinking, so the friction resistance on the side of the cylinder is large, and the soil of the Gobi pebble layer is relatively hard, which increases the friction resistance on the side of the large cylinder, which may cause it to be unable to sink or sink slowly; the excavation depth of the first layer is relatively shallow, generally not more than 5 meters. When the total depth of the cylinder remains unchanged, the corresponding caisson depth is relatively large. The deep caisson requires more production times and more times of connection, resulting in a long construction period, high construction cost and poor construction accuracy; each time the cylinder is connected, ground-based scaffolding needs to be erected from low to top inside and outside the cylinder, and the ground-based scaffolding needs to be dismantled before each caisson construction, resulting in a long construction period and high construction cost.

[0135] The method for rapid caisson construction in Gobi pebble geology and confined space conditions using a large-diameter ultra-deep vortex pool as described in this technical solution is that the caisson is a variable-section cylinder with a "large at the bottom and small at the top" shape. When sinking, the contact area with the soil is relatively small, so the friction resistance on the side of the cylinder is relatively small. When the caisson sinks, a high-pressure pump is used to inject thixotropic mud around the cylinder to lubricate and assist in sinking. Therefore, the caisson construction is relatively easy and the sinking speed is relatively fast. The excavation depth of the first floor is deep, generally greater than 10 meters. When the total depth of the cylinder remains unchanged, the corresponding caisson depth is small. The number of production and connection times required for a small caisson depth is small, which shortens the construction period, reduces construction costs, and improves construction accuracy. Each time the cylinder is connected, only a ground-type scaffolding is erected from low to top on the outside of the cylinder, and a cantilevered scaffolding is erected on the inside of the cylinder, the height of which is only about half of the height of the ground-type scaffolding, which shortens the scaffolding installation and dismantling time, improves construction efficiency, shortens the construction period, and reduces construction costs.

[0136] In summary, the technical solution shown in the present invention solves the problems of low construction efficiency and quality of large-diameter ultra-deep cyclone pools under Gobi pebble geological conditions and confined space conditions using traditional construction methods such as slope excavation, reverse excavation or semi-reverse excavation, and ordinary caisson method. This greatly improves the construction efficiency and quality of large-diameter ultra-deep cyclone pools under Gobi pebble geological conditions and confined space conditions, reduces energy consumption, and is economical and environmentally friendly.

[0137] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology, characterized in that: The following steps are involved: Step 1: Design a variable-section cylinder. The outer contour of the variable-section cylinder gradually shrinks inward in a stepped manner from bottom to top, forming a "large at the bottom and small at the top" shape, while the inner contour remains a straight cylinder structure to reduce the contact area and friction resistance with the soil during the sinking process. Step 2: Based on the available working area, excavate the deep foundation pit using a multi-level sloping method; Step 3: Produce the annular blade foot section, perform positioning measurement in the deep foundation pit, lay the annular blade foot brick membrane, install steel bars, drag reduction grouting pipes, formwork, and pour concrete to form the annular blade foot section. The longitudinal section of the annular blade foot is beveled, straight on the outside and inclined on the inside. Step 4: Based on the annular blade foot section, the variable-section cylinder is divided into multiple sections. Scaffolding is erected, the sections are fabricated, and the deep-descent caisson is constructed for each section in sequence until the design elevation is reached. During the caisson process of each section, a high-pressure pump is used to evenly inject thixotropic mud around the cylinder as a lubricant between the cylinder and the soil to reduce friction between the two. Step 5: Implement the bottom sealing operation. After the caisson of each section of the cylinder described in step 4 is completed and stabilized, install the steel bars and formwork of the horizontal bottom plate, and pour concrete to complete the bottom sealing work of the cyclone pool.

2. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: The variable-section cylinder includes three sections, and the outer diameter of each section gradually decreases. Specifically, the outer diameter of the first section is D1, the outer diameter of the second section is D2, and the outer diameter of the third section is D3, wherein D1>D2>D3, and the height of each section is H1, H2, and H3, satisfying H1+H2+H3=total depth, so as to keep the inner diameter of the cylinder unchanged while reducing the friction resistance between the side of the cylinder and the soil.

3. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: In step 2, the multi-level sloping method is used to excavate a deep foundation pit, including the following steps: Step 2.1: Conduct positioning measurement to determine the excavation scope; Step 2.2: Excavate the deep foundation pit using a two-stage sloping method. The first sloping slope is i1, and the second sloping slope is i2, where i1 < i2, to ensure slope stability. Step 2.3: Set up an intermediate platform during the excavation process. The platform width should be sufficient to accommodate construction equipment and materials. Step 2.4: After excavation is completed, pour a concrete pad at the bottom of the foundation pit to provide a stable construction foundation.

4. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: In step 3, the production of the annular blade foot segment includes the following steps: Step 3.1: Conduct positioning measurements in the deep foundation pit to determine the position of the annular blade foot; Step 3.2: Lay the annular blade foot brick membrane; Step 3.3: Install the steel bars; Step 3.4: bury the drag reduction grouting pipe; Step 3.5: Install the template; Step 3.6: pouring concrete and curing; Step 3.7: Install steel plate guards on the inner and outer sides of the bottom of the annular blade to enhance wear resistance and soil cutting ability.

5. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: In step 4, the erection method of each section of the cylinder scaffolding is as follows: the inner and outer scaffolding of the first section of the cylinder are both ground-type steel pipe scaffolding; the outer scaffolding of the remaining sections of the cylinder is ground-type steel pipe scaffolding, and the inner scaffolding is cantilevered steel pipe scaffolding; when each section of the cylinder is produced, embedded parts of the cantilevered tripod are pre-embedded in the upper inner side of the cylinder, and the cantilevered steel pipe scaffolding is erected through the embedded parts.

6. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: In step 4, the method for injecting the thixotropic slurry comprises the following steps: Use a high-pressure pump to inject thixotropic slurry evenly and at a constant speed around the cylinder; There are multiple grouting pipes and they are buried at intervals; Real-time monitoring of grouting pressure and mud flow during grouting to ensure grouting effect; After grouting is completed, close the grouting holes to prevent mud from flowing back.

7. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: In step 4, during the construction of the deep caisson, the verticality and horizontality of the cylinder are detected and adjusted by setting a theodolite and a level to ensure construction accuracy, which specifically includes the following steps: Two theodolites with a 90° angle are set outside the cylinder with a measurement accuracy of ±5″ to monitor the verticality of the cylinder; Set up a level with a measurement accuracy of ±1mm to monitor the horizontality of the cylinder and control the sinking depth; The cylinder posture is adjusted in real time according to the monitoring data. The adjustment method is: when the verticality deviation and horizontality deviation exceed the allowable value, the excavation depth and sequence are adjusted, and the injection position and injection amount of the thixotropic mud are adjusted in a targeted manner to ensure that the verticality and horizontality of the cylinder meet the design requirements.

8. The method for rapidly constructing a large-diameter cyclone pool in a confined space under Gobi pebble geology according to claim 1, characterized in that: It also includes prediction and monitoring steps: Before caisson construction, according to the design parameters and geological conditions of the cyclone pool, the horizontal excavation area S, the total time required for caisson construction T, and the total friction resistance value between the side wall and the soil T are calculated using the following formula: f , to predict key parameters during construction: The calculation formula for the horizontal excavation area S of the cyclone pool is: Where D is the outer diameter of the cyclone pool, B is the width of the construction surface around the cyclone pool, H is the excavation depth of the cyclone pool, b is the width of the middle platform, i is the designed slope ratio, and n is the number of slope levels; The calculation formula for the total time T required for caisson is: Among them, F i is the friction force during the sinking process of the i-th section of the cylinder, d i is the length of the i-th section of the cylinder, v i is the excavation speed of the i-th section cylinder, P i is the grouting pressure when the i-th section of the cylinder sinks, and n is the number of sections of the cylinder; Total friction resistance value T between the side wall and the soil f The calculation formula is: Among them, U i is the perimeter of the side wall in the i-th layer of soil, f ki is the standard value of unit friction resistance of the i-th layer of soil, H i is the thickness of the i-th soil layer, and m is the number of soil layers; During the caisson construction process, the sinking speed, verticality, horizontality, and injection volume and pressure of the caisson are monitored in real time, and compared with the predicted values ​​to make timely adjustments and optimizations to ensure construction quality and safety. After the caisson construction is completed in stages, the calculation formula is used to dynamically predict and adjust the caisson time and friction resistance of subsequent construction sections based on monitoring data to optimize the construction plan and improve construction efficiency and accuracy.

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