Construction method for rapidly consolidating foundation pit and crossing foundation pit

Abstract

The invention provides a construction method for quickly consolidating a foundation pit and a crossing foundation pit, and the construction method for quickly consolidating the foundation pit comprises the following steps: excavating a soil layer with weak shallow soil body bearing capacity to form a mechanical operation pit; the method comprises the following steps: manufacturing consolidation modules, digging a foundation pit body in a ground layer in a mechanical operation pit according to the size of the foundation pit, piling and filling the consolidation modules into the foundation pit body, waiting for forming of the foundation pit, and taking out the consolidation modules piled in the foundation pit after forming. The crossing foundation pit is formed through the construction method for rapidly consolidating the foundation pit. The method is low in construction cost, low in cost and excellent in effect. The crossing foundation pit is fast in forming and high in bearing capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of ground construction of oil and gas pipelines, and in particular to a construction method for a rapid consolidation foundation pit and a method for crossing and spanning a foundation pit. Background Art

[0002] Because crossing and spanning projects often require crossing ditches and rivers, the soil is often in a water-rich state. Furthermore, due to the construction characteristics of crossing and spanning projects, the excavation of crossing anchor pits, directional drilling connection pits, and shallow foundation pits for artificial jacking pipes differ from the requirements of traditional construction foundation pits and often require small-scale, rapid, and short-term foundation pit construction. However, since crossing and spanning points are often located in water-rich areas and the construction process requires slurry injection, the soil layers in the areas requiring excavation are often water-rich, meaning the bearing capacity is weak (less than 0.03 MPa) and difficult to form. Not only do these layers fail to meet the requirements for foundation pit excavation, but they also cannot effectively support conventional excavation machinery such as excavators, causing the excavation machinery to sink. If foundation pit forming is required, extensive soil replacement, rotary jet grouting, or steel sheet pile support are often required. These measures are costly, time-consuming, and ineffective. A construction method that allows for quick entry and exit, enabling rapid formation of crossing and spanning foundation pits, and at a low cost is needed.

[0003] In long-distance oil and gas transmission or gathering pipeline crossing and spanning projects, it is usually necessary to make anchor piers, excavate connection pits, excavate shallow jacking foundation pits, and connect the crossing pipes. However, because crossing and spanning projects are mostly located near rivers and water, the soil moisture content is high, the bearing capacity of the foundation pit implementation point is weak, and the formation is poor, especially in silt, silt sand and other strata, which are more difficult to implement. Conventional large-scale replacement, rotary grouting or compaction grouting, steel sheet pile support and other methods require large investment and long implementation time. Most foundation pits in crossing and spanning projects are shallow (within 6m), small in size (within 10m of the section), and temporary (within 3-30 days). Large-scale replacement requires excavation and replacement of the weak supporting soil in the foundation pit. The replacement time is long, the excavation section is wide, and dense soil needs to be transported out. It is mostly used in projects with long implementation time and large investment. Spray grouting or compaction grouting often uses a high-pressure grouting machine to inject a binder to improve weakly cemented soil, increasing its internal friction angle and reducing its permeability. This also takes a long time to implement, making it difficult to quickly enter and exit the site. Furthermore, the grouting may affect nearby land and water quality. Steel sheet pile support allows for quick implementation and supports slopes, but it requires significant investment and requires consideration of steel sheet pile transportation and the construction of access routes for equipment. Furthermore, steel sheet piles cannot effectively address soil moisture issues. Therefore, given the characteristics of pipeline crossing and spanning foundation pits, it is necessary to design a foundation pit excavation and forming method that can be implemented quickly, is inexpensive, allows for rapid pit shaping suitable for machinery operations, and can quickly reduce soil moisture. Summary of the Invention

[0004] The present invention aims to address at least one of the aforementioned deficiencies in the prior art. For example, one object of the present invention is to provide a convenient and efficient method for rapidly consolidating a foundation pit. Another object of the present invention is to provide a structurally stable through-and-across foundation pit.

[0005] In order to achieve the above-mentioned purpose, the present invention provides, on the one hand, a method for constructing a rapid consolidation foundation pit, which may include the following steps: excavating a shallow soil stratum with weak bearing capacity to form a mechanical working pit; excavating a foundation pit body on the stratum within the mechanical working pit, and stacking consolidation modules in the foundation pit body; and taking out the consolidation modules stacked in the foundation pit after the foundation pit is formed.

[0006] According to one or more exemplary embodiments of one aspect of the present invention, the rapid consolidation foundation pit construction method may further include: before excavating the foundation pit body, dewatering the water-rich soil layer in the mechanical operation pit according to the stratum conditions.

[0007] According to one or more exemplary embodiments of one aspect of the present invention, the dewatering operation may include: when the water-rich soil layer in the mechanical operation pit is a fluidized silt formation or a quicksand formation with a bearing capacity of less than 30 kPa, a gelling agent may be mixed into the 500 mm soft formation in the mechanical operation pit and then compacted on site.

[0008] According to one or more exemplary embodiments of an aspect of the present invention, the dewatering operation may include: dewatering a water-rich soil layer in the mechanical operation pit until the water level is below a construction water level.

[0009] According to one or more exemplary embodiments of one aspect of the present invention, the construction method of the rapid consolidation foundation pit may also include: before excavating the mechanical working pit, evaluating the geological conditions of the shallow soil strata with weak bearing capacity, the water content of the strata, and the influencing factors around the excavation area.

[0010] According to one or more exemplary embodiments of an aspect of the present invention, the method for manufacturing the consolidation module may include the steps of: stirring an original soil layer with a gelling agent to form a mixture, placing the mixture into a module container, and solidifying the mixture to obtain a consolidation module.

[0011] According to one or more exemplary embodiments of an aspect of the present invention, the module container may include a canvas big bag.

[0012] According to one or more exemplary embodiments of an aspect of the present invention, the stacking thickness of the consolidation modules may be 1 to 3 meters.

[0013] Another aspect of the present invention provides an oil and gas pipeline crossing foundation pit, which may include a crossing foundation pit excavated and formed by the above-mentioned rapid consolidation foundation pit construction method.

[0014] According to one or more exemplary embodiments of another aspect of the present invention, the oil and gas pipeline crossing the foundation pit structure may include a mechanical operation pit and a foundation pit, a foundation pit is opened at the bottom of the mechanical operation pit, the diameter of the foundation pit opening is smaller than the diameter of the mechanical operation pit opening, and the position height of the foundation pit opening is lower than the position height of the mechanical operation pit opening.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The construction method provided by the present invention is convenient and efficient, and can be quickly and safely finalized;

[0017] (2) The construction method provided by the present invention has low construction cost, low price and excellent effect;

[0018] (3) The construction method provided by the present invention has a wide range of applications, consumes little time, and can be used on water-rich soil layers with few construction restrictions.

[0019] (4) The present invention provides a short time-consuming and long-distance foundation pit ground forming structure and a strong bearing capacity.

[0020] Figures in the specification

[0021] The above and other objects and / or features of the present invention will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of the structure of a mechanical working pit according to an exemplary embodiment of the present invention is shown;

[0023] Figure 2 A schematic diagram of the structure of a foundation pit for foundation pit construction according to an exemplary embodiment of the present invention is shown;

[0024] Figure 3 A schematic diagram showing the placement of consolidation modules in a foundation pit according to an exemplary embodiment of the present invention is shown;

[0025] Figure 4 A schematic diagram of the formed foundation pit structure according to an exemplary embodiment of the present invention is shown.

[0026] Description of reference numerals:

[0027] 1- Mechanical operation pit, 2- Foundation pit, 3- Consolidation module. DETAILED DESCRIPTION

[0028] The following text describes in detail a method for rapidly consolidating a foundation pit and a method for crossing and spanning a foundation pit according to the present invention, with reference to the accompanying drawings and exemplary embodiments. It should be noted that terms such as "first" and "second" are used solely for ease of description and distinction and should not be construed as indicating or implying relative importance. Terms such as "upper," "lower," "inner," and "outer" are used solely for ease of description and to establish relative orientations or positions, and do not indicate or imply that the components referred to must have a specific orientation or position.

[0029] First Exemplary Embodiment

[0030] This exemplary embodiment provides a construction method for rapidly consolidating a foundation pit.

[0031] Figure 1 A schematic diagram of the structure of a mechanical working pit according to an exemplary embodiment of the present invention is shown; Figure 2 A schematic diagram of the structure of a foundation pit for foundation pit construction according to an exemplary embodiment of the present invention is shown; Figure 3 A schematic diagram showing the placement of consolidation modules in a foundation pit according to an exemplary embodiment of the present invention is shown; Figure 4 A schematic diagram of the formed foundation pit structure according to an exemplary embodiment of the present invention is shown.

[0032] The following combination Figures 1 to 4 The construction method of the rapid consolidation foundation pit of this exemplary embodiment will be described.

[0033] In this exemplary embodiment, the construction method of the rapid consolidation foundation pit mainly includes the following steps: Figure 1 As shown in , the foundation pit is set at a certain location, and the shallow soil layer with weak bearing capacity is excavated to form a mechanical operation pit 1. The depth of the mechanical operation pit can usually be 3 to 5 meters. Figure 2 As shown in , according to the size of the foundation pit to be formed, the foundation pit 2 is excavated in the mechanical operation pit 1. However, because the area to be excavated and formed in the foundation pit is in a fluid plastic or soft plastic stratum with high water content, weak shear resistance and small internal friction angle, it cannot be formed after mechanical excavation and cannot meet the needs of the foundation pit operation. At this time, Figure 3 As shown in , a consolidation module can be made, and the consolidation modules 3 can be filled and stacked one by one into the pit body of the pit 2 according to the size of the planned pit 2, until the pit body of the pit 2 around the consolidation module 3 is basically formed, for example, after 3 to 36 hours, such as 3 hours, 10 hours, 16 hours, 24 hours, 27 hours or 36 hours, the pit body around the consolidation module can reach the basic forming capacity. After the pit body of the pit 2 is basically formed, the filled and stacked consolidation modules 3 can be lifted out to obtain the following Figure 4The formed foundation pit 2 shown in Figure 2 is now capable of bearing a load of over 50 kPa. This improved bearing capacity allows for the movement of construction machinery. Furthermore, before consolidating the foundation pit, the number of pre-formed consolidation modules can be determined based on the pre-formed pit dimensions.

[0034] In this exemplary embodiment, the steps for making the consolidation module may include: mixing the original soil layer with a gelling agent to form a mixture, and placing the partially solidified mixture into a module container. The consolidation module is obtained after 2-3 hours. Because the mixture formed by mixing the original soil layer with the gelling agent cannot be immediately formed, directly placing it into the preformed foundation pit may not effectively shape the foundation pit. After 2-3 hours, the mixture has initially solidified and formed. At this point, the consolidation module is placed into the preformed foundation pit. This not only provides a certain degree of support for the foundation pit, but also allows the consolidation module to continue to fully consolidate within the foundation pit. By adapting the shape of the foundation pit, the foundation pit is ultimately formed. The module container may comprise a canvas ton bag. Canvas ton bags are easy to purchase and transport, and are inexpensive. Using canvas ton bags for making consolidation modules and consolidating the foundation pit is convenient and cost-effective. Of course, the present invention is not limited to this; any consolidation module that provides a consolidation and shaping function and is economical and practical can be used. However, using stone as a consolidation module is not recommended. First, the water permeability between the stones is good, but the waterproof performance is relatively poor, which makes it unsuitable for the foundation pit consolidation construction of the present invention. Second, stones are not available at all construction sites, which may lead to increased construction costs.

[0035] As an embodiment of the present invention, the gelling agent for preparing the consolidation module may include formulated cement. The components of the formulated cement may include silicate cement, lime and accelerator. The components of the formulated cement can be determined according to the bearing capacity and water content of the original soil of the foundation pit. And according to the water content of the original soil, specific adjustments can be made again through on-site experiments. For example, the components of the formulated cement may specifically include cement: lime: accelerator: original soil = 0.1:0.05:0.02:1 by weight. Here, the original soil layer may include excavated soil that is difficult to shape. Using the original soil layer on site eliminates the need to transport it from other places, which is convenient and efficient while saving costs. In addition, the strength of the mixture only needs to reach 200Kpa, and no high-strength structure is required. This can not only meet the support requirements of the foundation pit, but also has good economic benefits. At the same time, the consolidation module can be crushed and returned to the field after the foundation pit is formed.

[0036] In this exemplary embodiment, the thickness of the consolidation modules stacked in the foundation pit may be 1 to 3 m, for example, 1.2 m, 1.7 m, 1.9 m, 2.6 m, or 2.8 m.

[0037] In this exemplary embodiment, before excavating the foundation pit, to ensure excavation safety and pit quality and to prevent the impact of elevated groundwater levels on construction, the water-rich soil layer within the mechanical working pit can be dewatered. This water-rich soil layer can include fluidized silt or quicksand with a bearing capacity of less than 30 kPa. Once the foundation pit is formed, the crossing and jointing operations can be performed. Different methods can be used to dewater the mechanical working pit strata depending on the difficulty of the operation. For example, for a relatively simple operation requiring a short construction time, such as one requiring only 3 to 12 hours, formulated cement can be added to the soft ground layer within 500 mm of the mechanical working pit, mixed, and then compacted in situ. The formulated cement used for dewatering can differ from the cement used to prepare the consolidation module. For example, the formulated cement used for dewatering can have a weight ratio of: cement: lime: accelerator: original soil = 0.08:0.05:0.01:1. The composition of this cement formula can also be further adjusted based on the moisture content of the original soil through field testing. The strength of the cement formula required for dewatering can be lower than that of the consolidation module, meaning it only needs to be strong enough to support the excavation machinery. This can reduce construction costs. For difficult and time-consuming operations, such as those requiring 24-36 hours of construction time and a longer pit maintenance period, the strata within the pit can be dewatered to lower the groundwater level below the bottom of the pit. After dewatering, further cement addition and compaction are no longer necessary, saving construction costs. Dewatering methods can include light wellpoint peripheral dewatering. This ensures that the stratum in the excavator's position has a bearing capacity of at least 30 kPa, allowing the excavator to quickly establish its position. Once the excavation is completed, the excavated pit can be fully backfilled, eliminating the need for pit maintenance.

[0038] In this exemplary embodiment, before excavating the shallow soil layer with weak bearing capacity, the geological conditions of the foundation pit for the oil and gas pipeline to be excavated, the moisture content of the stratum, and the impact on the surrounding area of the excavation area can also be evaluated. The soil layer with weak bearing capacity of the shallow soil body is dewatered, and the mechanical operation pit is excavated in conjunction with the excavator. The dewatering method may include traditional water collection well dewatering methods. The soil layer with weak bearing capacity of the shallow soil body is dewatered to facilitate subsequent foundation pit construction. If the dewatering construction requirements can be met after dewatering the soil layer with weak bearing capacity of the shallow soil body, there is no need to dewater the stratum in the mechanical operation pit again. However, if the stratum moisture content is high or the water permeability coefficient is low, the stratum in the mechanical operation pit can be dewatered again.

[0039] Second Exemplary Embodiment

[0040] This exemplary embodiment provides an oil and gas pipeline passing through a foundation pit.

[0041] Figure 4 The schematic diagram of the foundation pit structure after forming according to an exemplary embodiment of the present invention is shown below. Figure 4 The oil and gas pipeline passing through the foundation pit of this exemplary embodiment is described.

[0042] In this exemplary embodiment, the oil and gas pipeline crossing foundation pit is formed by digging the foundation pit using the rapid consolidation foundation pit construction method in the first exemplary embodiment. The structure of the oil and gas pipeline crossing foundation pit mainly includes a mechanical operation pit and a foundation pit. Figure 4 As shown in Figure 2, foundation pit 2 is located at the bottom of the machine working pit. The opening of foundation pit 2 is located at a lower elevation than the opening of the machine working pit. The diameter of the opening of foundation pit 2 is smaller than that of the machine working pit. The purpose of excavating the foundation pit is to facilitate operations such as crossing and connecting joints, so a large excavation space is not required. However, the machine working pit needs to accommodate the positioning and movement of operating machinery such as excavators, so a larger space can be provided.

[0043] In summary, the advantages of the present invention may include at least one of the following:

[0044] (1) The construction method provided by the present invention can effectively reduce the moisture content of the construction soil layer, so as to facilitate the later construction operations;

[0045] (2) The construction method provided by the present invention can replace large-scale foundation pit construction modes such as steel sheet piles and rotary jet piles. According to the characteristics of the through-through foundation pit, it can replace large-scale foundation pit measures such as sheet piles and rotary jet piles at locations such as through-through joints, small operation foundation pits, and anchor pits to solve the problem that the foundation pit of soft foundation near water is difficult to form, the construction time is greatly reduced, the construction cost is low, and the completion efficiency is high;

[0046] (3) The cross-over foundation pit structure provided by the present invention is simple and can adapt to the construction of water-rich soil layers.

[0047] Although a construction method for rapidly consolidating a foundation pit and a method for crossing a foundation pit have been described above in conjunction with exemplary embodiments, it should be clear to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined by the claims.

Claims

1. A construction method for rapid consolidation of foundation pit, characterized in that: The construction method of the rapid consolidation foundation pit comprises the following steps: Excavation of shallow soil layers with weak bearing capacity to form mechanical working pits; Excavate a foundation pit body on the stratum within the mechanical operation pit, and pile up consolidation modules in the foundation pit body; After the foundation pit is formed, the consolidation modules stacked in the foundation pit are taken out.

2. The construction method of rapid consolidation foundation pit according to claim 1, characterized in that: Before digging the foundation pit body, the method also includes dewatering the water-rich soil layer in the mechanical operation pit according to the ground conditions.

3. The construction method of rapid consolidation foundation pit according to claim 2, characterized in that: The dewatering operation includes: when the water-rich soil layer in the mechanical operation pit is a fluidized silt layer or a quicksand layer with a bearing capacity of less than 30kPa, a gelling agent is mixed into the 500mm soft layer in the mechanical operation pit and then compacted on site.

4. The construction method for rapid consolidation of foundation pit according to claim 2, characterized in that: The dewatering operation includes: dewatering the water-rich soil layer in the mechanical operation pit until the water level is below the construction water level.

5. The construction method of rapid consolidation foundation pit according to claim 1, characterized in that: The construction method of the rapid consolidation foundation pit also includes: before excavating the mechanical operation pit, evaluating the geological conditions of the shallow soil strata with weak bearing capacity, the water content of the strata, and the influencing factors around the excavation area.

6. The construction method of rapid consolidation foundation pit according to claim 1, characterized in that: The manufacturing method of the consolidation module comprises the steps of: stirring an original soil layer and a gelling agent to form a mixture, and placing the mixture into a module container to obtain a consolidation module.

7. The construction method of rapid consolidation foundation pit according to claim 6, characterized in that: The modular container includes a canvas big bag.

8. The construction method of rapid consolidation foundation pit according to claim 1, characterized in that: The stacking thickness of the consolidation modules is 1 to 3 meters.

9. An oil and gas pipeline passing through a foundation pit, characterized in that: The oil and gas pipeline crossing foundation pit includes a crossing foundation pit excavated and formed by the construction method of the rapid consolidation foundation pit according to any one of claims 1 to 8.

10. The oil and gas pipeline crossing foundation pit according to claim 9, characterized in that: The oil and gas pipeline passes through the foundation pit structure, which includes a mechanical operation pit and a foundation pit. A foundation pit is opened at the bottom of the inner side of the mechanical operation pit. The diameter of the foundation pit mouth is smaller than the diameter of the mechanical operation pit mouth, and the position height of the foundation pit mouth is lower than the position height of the mechanical operation pit mouth.

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