A method for controlling foundation pit construction under asymmetric load

Abstract

The present invention belongs to the technical field of foundation pit construction, and relates to a foundation pit construction control method under asymmetric load, including: performing pile foundation support on the larger load side and the smaller load side of the foundation pit to be constructed respectively; performing layered excavation of the first stage of the foundation pit; arranging inclined anchor rods on the side wall of the constructed foundation pit on the larger load side for support, and the top of the inclined anchor rods is provided with a first jack; performing layered excavation of the second stage of the foundation pit, and gradually arranging multiple layers of internal supports in the constructed foundation pit, one end of the internal support is pressed on the side wall of the foundation pit on the smaller load side, and the other end is pressed on the side wall of the foundation pit on the larger load side through multiple second jacks; real-time monitoring of the displacement and deformation of the constructed foundation pit, and real-time regulation of the thrust of the first jack or / and the second jack according to the monitoring results. The present invention optimizes the setting of the foundation pit support system, and realizes real-time monitoring and regulation of the displacement and deformation of the foundation pit, ensuring the safety of the foundation pit construction under asymmetric load.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit construction, and in particular relates to a foundation pit construction control method under asymmetric load. Background Art

[0002] In the process of urban construction and underground space development, foundation pit excavation is an essential construction link. However, due to the complexity and diversity of the environment around the foundation pit, there is often an uneven load distribution around the foundation pit, especially in densely populated urban areas and areas with large terrain differences. This uneven load (i.e. asymmetric load) is more significant. Asymmetric load will cause the stress state of the foundation pit to be unbalanced, thereby causing displacement and deformation of the soil around the foundation pit, and in severe cases, even cause safety accidents such as foundation pit instability and collapse.

[0003] During foundation pit construction, traditional foundation pit support methods, such as soil nail wall, pile anchor support, steel sheet pile support, etc., are usually designed for symmetrical loads. When encountering asymmetrical loads, traditional foundation pit support methods are often difficult to cope with complex stress states, and often have problems such as uneven support, complex construction, and insufficient monitoring and feedback. Specifically:

[0004] 1) The traditional foundation pit support method cannot be finely designed for asymmetric load distribution, which easily leads to the situation that the support structure is not stable enough on the side with larger load and the support is excessive on the side with smaller load. This not only increases the construction cost, but also buries safety hazards. In order to cope with asymmetric loads, a large number of on-site adjustments and temporary support measures are usually required during the construction process, which not only prolongs the construction period, but also increases the difficulty and cost of construction.

[0005] 2) The traditional foundation pit support method lacks a real-time monitoring and feedback mechanism, and is unable to adjust the support plan in time to cope with emergencies that may occur under asymmetric loads. This can easily lead to uncontrollable displacement and deformation of the soil around the foundation pit, especially on the side with greater load, increasing the safety risk during foundation pit construction. Summary of the invention

[0006] In view of the deficiencies existing in the related art, the present invention provides a method for controlling foundation pit construction under asymmetric load to solve at least one technical problem mentioned in the background technology.

[0007] The present invention provides a foundation pit construction control method under an asymmetric load, comprising the following steps:

[0008] S1. Determine the side with a larger load and the side with a smaller load of the foundation pit to be constructed under an asymmetric load; arrange multiple pile foundations in the soil on the side with a larger load and the side with a smaller load for support; and drive multiple prestressed columns in the soil in the area of ​​the foundation pit to be constructed;

[0009] S2, carry out the first stage of layered excavation of the foundation pit until the preset foundation pit level is reached;

[0010] S3. Insert multiple inclined anchor rods into the soil of the side wall of the constructed foundation pit on the side with greater load for support; the top of the inclined anchor rod is connected to the first jack;

[0011] S4, carrying out layered excavation construction of the second stage of the foundation pit until the preset bottom surface of the foundation pit is reached; after each layer of excavation of the second stage of the foundation pit is completed, a layer of internal support is arranged in the constructed foundation pit; the internal support is connected to a plurality of prestressed columns, and one end of the internal support is pressed against the side wall of the constructed foundation pit on the side with a smaller load, and the other end is connected to a plurality of second jacks, so as to be pressed against the side wall of the constructed foundation pit on the side with a larger load through the plurality of second jacks;

[0012] When executing steps S3 and S4, the displacement and deformation of the constructed foundation pit are monitored in real time, and the thrust of the first jack and / or the second jack is adjusted in real time according to the monitoring results.

[0013] In some of the embodiments, in step S1, the diameter of the pile foundation arranged on the side with greater load is greater than the diameter of the pile foundation arranged on the side with less load, and the spacing between the multiple pile foundations arranged on the side with less load is greater than the spacing between the multiple pile foundations arranged on the side with greater load.

[0014] In some embodiments, in step S1, the pile is fixed to the soil based on the length of the pile. and the diameter of the pile foundation The method of determining is to first assume that and The initial value is then iterated according to formula (1)-formula (2) until the total bearing capacity of the pile foundation is Satisfy the requirements of formula (3); the spacing of multiple pile foundations Calculate according to formula (4);

[0015] (1);

[0016] (2);

[0017] (3);

[0018] (4);

[0019] In formulas (1) to (4), is the average lateral friction of the soil; is the unit bearing capacity of the soil at the pile end; is the preset safety factor; is the design value of the total bearing capacity of the pile foundation; and are empirical coefficients. , .

[0020] In some embodiments, in step S2, the total excavation depth of the first stage of the foundation pit is recorded as The total number of excavations is recorded as , each excavation depth is recorded as ,in, ; During the first stage of the foundation pit excavation, the excavation depth should meet ,and .

[0021] In some of the embodiments, a plurality of settlement meters are arranged on the surrounding surface of the larger load side and the smaller load side of the foundation pit to be constructed, so as to monitor the settlement of the surface around the foundation pit in real time, and adjust the foundation pit excavation speed and / or each excavation depth during the layered excavation of the foundation pit accordingly.

[0022] In some embodiments, in step S3, the total length of the inclined anchor rod is Equal to the free length of the inclined anchor and anchor length the sum of According to formula (5), Calculate according to formula (6)-formula (7); the spacing of multiple inclined anchors Calculate according to formula (8);

[0023] (5);

[0024] (6);

[0025] (7);

[0026] (8);

[0027] In formula (5) to formula (8), is the inclination angle of the inclined anchor, ; is the diameter of the inclined anchor rod; is the sliding surface depth of the soil; is the expected value of the pull-out force of the inclined anchor; is the interface pull-out strength between the inclined anchor bolt anchoring section and the soil; and are empirical coefficients. , ; is the cohesion of soil; It is the total excavation depth of the second stage of foundation pit.

[0028] In some of the embodiments, in step S4, each layer of inner support includes multiple main support members, which extend from the smaller load side to the larger load side, and one end of the main support member in the length direction is crimped onto the side wall of the constructed foundation pit on the smaller load side; a beam body is vertically connected between the multiple main support members close to the larger load side, and multiple second jacks are connected to the beam body.

[0029] In some of the embodiments, it is also included that, as the foundation pit is excavated and constructed in stages and layers, a plurality of displacement sensors are arranged on the surface of the larger load side of the foundation pit to be constructed and on the side walls of the constructed foundation pit on the larger load side and the smaller load side, so as to monitor the displacement of the constructed foundation pit in real time and evaluate its deformation; a plurality of inclination sensors are arranged on the top of the pile foundation and on the side walls of the constructed foundation pit on the larger load side and the smaller load side, so as to monitor the inclination deformation of the pile foundation and the constructed foundation pit in real time; a plurality of stress sensors are arranged on the inclined anchor rods, each main support member and each beam body of each layer support, so as to monitor their stress changes in real time; and the thrust of the first jack and / or the second jack is controlled in real time according to all monitoring results.

[0030] In some of the embodiments, an RFID tag is provided on each main support member of each layer of inner support.

[0031] Based on the above technical scheme, the foundation pit construction control method under asymmetric load in the embodiment of the present invention improves the stiffness and bearing capacity of the foundation pit support system, enhances the anti-slip ability of the side with larger load of the foundation pit, and can monitor the displacement and deformation of the foundation pit in real time and dynamically and accurately control it, thereby ensuring the safety of the foundation pit construction under asymmetric load. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 It is a flow chart of the foundation pit construction control method under asymmetric load of the present invention;

[0034] Figure 2 It is a structural schematic diagram of the foundation pit construction in the present invention;

[0035] Figure 3 It is a cross-sectional view of the foundation pit during the staged and layered excavation construction in the present invention;

[0036] Figure 4 It is a schematic diagram of the arrangement of the monitoring device in the present invention;

[0037] Figure 5The present invention is a flow chart of the control system for real-time monitoring and regulation of the foundation pit.

[0038] In the figure:

[0039] 10. Foundation pit; 10a. Side with greater load; 10b. Side with less load; 20. Soil; 21. Pile foundation; 22. Column; 23. Inclined anchor rod; 30. Internal support; 31. Main support member; 32. Auxiliary support member; 33. RFID tag; 40. Beam; 50. Second jack; 61. Settlement meter; 62. Displacement sensor; 63. Inclination sensor; 64. Stress sensor. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "top", "bottom", "inside", "outside", "left", "right", "front", "back", "vertical", "horizontal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0042] The terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] refer to Figure 1-Figure 5 As shown, the present invention provides a foundation pit construction control method under asymmetric load, comprising the following steps:

[0045] S1. Analyze the load conditions around the foundation pit 10 to be constructed in detail, and determine the side 10a with a larger load and the side 10b with a smaller load opposite to the side 10a with asymmetric load. It is understandable that the foundation pit 10 is usually square, and the other two sides of the foundation pit 10 to be constructed except the side 10a with a larger load and the side 10b with a smaller load are referred to as the moderately loaded sides. This embodiment focuses on the lateral pressure on the side 10a with a larger load and the possible risk of foundation instability. Conduct a detailed geological survey before construction to obtain the mechanical parameters of the soil 20 around the foundation pit 10 to be constructed, groundwater level information, etc., to guide subsequent construction.

[0046] Referring to the relevant technical specifications and requirements of the construction industry, a plurality of pile foundations 21 are arranged in the soil 20 on the side 10a with a larger load and in the soil 20 on the side 10b with a smaller load for support, and the pile foundations 21 can be arranged in a regular row; the types of pile foundations 21 include but are not limited to bored piles, rotary piles, etc.; the pile foundations 21 on the side 10a with a larger load are usually constructed first. After the pile foundations 21 are constructed, static load tests and inspections are performed on them to ensure that their bearing capacity meets the technical standards.

[0047] With reference to relevant technical specifications and requirements of the construction industry, a plurality of cylindrical prestressed columns 22 are driven into the soil 20 in the area of ​​the foundation pit 10 to be constructed. The prestressed columns 22 can be regularly arranged in rows and columns. Specifically, the arrangement density of the prestressed columns 22 gradually decreases from the larger load side 10a to the smaller load side 10b.

[0048] S2, carry out the first stage of layered excavation of the foundation pit 10 until the preset horizontal surface of the foundation pit 10 is reached. Figure 3 As shown, the first stage of excavation of the foundation pit 10 is mainly to excavate the original loading surface formed by the terrain difference between the side 10a with a larger load and the side 10b with a smaller load; the excavation sequence is from top to bottom, layer by layer, and the side walls of the constructed foundation pit 10 are gradually maintained, such as pouring reinforced concrete, etc., to prevent the soil 20 around the constructed foundation pit 10 from collapsing; after each layer of excavation is completed, the size is measured and recorded to ensure that it meets the design requirements.

[0049] S3. Insert a plurality of inclined anchor rods 23 into the soil 20 of the side wall of the constructed foundation pit 10 on the side with greater load 10a for support; specifically, the inclined anchor rods 23 are usually made of high-strength steel bars, and the insertion point of the inclined anchor rods 23 on the side wall of the foundation pit 10 is substantially at the same height as the horizontal plane of the foundation pit 10, and the inclined anchor rods 23 are inserted downwardly into the soil 20 of the side wall of the constructed foundation pit 10 on the side with greater load 10a; during construction, first use special drilling equipment to drill holes on the side wall of the foundation pit 10 to a designed depth, then insert the inclined anchor rods 23 into the holes, and use high-performance anchoring agents for anchoring to ensure that the inclined anchor rods 23 are fully combined with the surrounding soil 20; thus, through the setting of the inclined anchor rods 23, the side wall of the foundation pit 10 on the side with greater load 10a can resist greater lateral pressure, significantly enhance the anti-slip ability of the side wall of the foundation pit 10 on the side with greater load 10a, and further enhance the stability of the side wall of the foundation pit 10 on the side with greater load 10a.

[0050] Furthermore, the top of the inclined anchor rod 23 is connected to a first jack (not shown in the figure); the first jack is a hydraulic jack, and the hydraulic system is started to drive the first jack to apply prestress to the inclined anchor rod 23. After the required prestress is reached, a locking device (such as an anchor nut or a locking washer, etc.) is used to fix the inclined anchor rod 23 to ensure that the applied prestress is maintained in the anchor body; after the construction of the inclined anchor rod 23 is completed, a tension test is performed to ensure its support effect on the foundation pit 10; thereby, the inclined anchor rod 23 generates the required tension through prestressing, ensuring that it can effectively resist the pressure of the soil 20 and maintain the stability of the foundation pit 10.

[0051] Furthermore, when executing step S3, the displacement and deformation of the constructed foundation pit 10 are monitored in real time, and the thrust of the first jack, i.e., the working stroke, is adjusted in real time according to the monitoring result; specifically, when the foundation pit 10 or the soil 20 is subjected to force, displacement often occurs; the tension of the inclined anchor rod 23 can be adjusted by the first jack to generate a reaction force toward the soil 20, thereby offsetting part of the displacement caused by the soil pressure, thereby effectively controlling the displacement and deformation of the constructed foundation pit 10, especially the displacement and deformation of the side wall of the constructed foundation pit 10 on the side 10a with a larger load.

[0052] S4. Carry out the second phase of layered excavation of the foundation pit 10 until the preset bottom surface of the foundation pit 10 is reached; it can be understood that the order of layered excavation of the second phase of the foundation pit 10 is also from top to bottom, layer by layer, and the side walls of the constructed foundation pit 10 are gradually maintained, such as pouring reinforced concrete, etc., to prevent the soil 20 around the constructed foundation pit 10 from collapsing.

[0053] Further, after each layer of excavation in the second stage of the foundation pit 10 is completed, a layer of inner support 30 is arranged in the constructed foundation pit 10; for the sake of clarity, Figure 2Only one layer of inner support 30 is shown in the figure. One end of the inner support 30 is pressed against the side wall of the constructed foundation pit 10 on the side 10b with a smaller load, and the other end is connected with a plurality of second jacks 50, so as to be pressed against the side wall of the constructed foundation pit 10 on the side 10a with a larger load through the plurality of second jacks 50. The second jacks 50 are also hydraulic jacks, and the supporting force of the inner support 30 on the side wall of the foundation pit 10 can be adjusted through the second jacks 50; it can be understood that the inner support 30 is also pressed against the two side walls of the constructed foundation pit 10 on the side with a moderate load. Each layer of internal support 30 is also connected to a plurality of prestressed columns 22; specifically, after the excavation of each layer of the second phase of the foundation pit 10 is completed, molds and steel bars are arranged in the constructed foundation pit 10, and the concrete pouring of the internal support 30 is carried out, and each layer of internal support 30 is combined with the prestressed columns 22 as a whole, ensuring that the prestressed columns 22 and the multiple layers of internal support 30 form a stable integral support frame, thereby forming an overall resistance system. It is further explained that the inclined anchor rods 23, the internal support 30 and the prestressed columns 22 together constitute the support system of the foundation pit 10, which significantly improves the rigidity and bearing capacity of the support system of the foundation pit 10, thereby being able to better resist the uneven deformation and asymmetric load on both sides of the foundation pit 10.

[0054] Furthermore, when executing step S4, the displacement and deformation of the constructed foundation pit 10 are monitored in real time, and the thrust, i.e., the working stroke, of the first jack and / or the second jack 50 is adjusted in real time according to the monitoring results, thereby realizing dynamic and precise regulation of the displacement and deformation of the foundation pit 10, and ensuring that the displacement and deformation of the constructed foundation pit 10 under asymmetric load is controlled within a safe range.

[0055] The above-mentioned schematic embodiment optimizes the setting and construction process of the foundation pit 10 support system through the arrangement of the inclined anchor rods 23, the internal supports 30 and the prestressed columns 22, improves the stiffness and bearing capacity of the foundation pit 10 support system, enhances the anti-slip ability of the side 10a with a larger load of the foundation pit 10, solves the problem that the traditional foundation pit 10 support method is not stable enough on the side 10a with a larger load, and can better resist the uneven deformation and asymmetric load of the foundation pit 10; through real-time monitoring of the constructed foundation pit 10 and the arrangement of the first jack and the second jack 50, the displacement and deformation of the foundation pit 10 are monitored in real time and dynamically and accurately controlled, thereby improving the safety of the foundation pit 10 during construction under asymmetric loads.

[0056] refer to Figure 2 , Figure 4As shown, in some embodiments, in step S4, each layer of inner support 30 includes a plurality of main support members 31 and a plurality of auxiliary support members 32 vertically connected to the plurality of main support members 31; the main support members 31 extend from the side 10b with less load to the side 10a with greater load, one end of the main support member 31 in the length direction is pressed on the side wall of the constructed foundation pit 10 on the side 10b with less load, and the other end is pressed on the side wall of the constructed foundation pit 10 on the side 10a with greater load through the second jack 50; the two ends of the auxiliary support member 32 are respectively pressed on the two side walls of the constructed foundation pit 10 on the side with moderate load. A beam body 40 is vertically connected between the plurality of main support members 31 close to the side 10a with greater load, and the beam body 40 can be a reinforced concrete beam or a steel beam, and a plurality of second jacks 50 are connected to the beam body 40. In this exemplary embodiment, by disposing the beam body 40 , the force exerted by the second jack 50 on the beam body 40 can be evenly applied to the inner support 30 , thereby preventing the structural damage of the inner support 30 caused by the bias pressure.

[0057] refer to Figure 4 As shown, in some embodiments, it is also included that, as the foundation pit 10 is excavated and constructed in stages and layers, multiple displacement sensors 62 are arranged at key positions such as the surface of the side 10a of the foundation pit 10 to be constructed with a larger load, and on the side walls of the constructed foundation pit 10 on the side 10a of the larger load and the side 10b of the smaller load, so as to monitor the displacement of the constructed foundation pit 10 in real time and evaluate its deformation. Multiple inclination sensors 63 are arranged at key positions such as the top of the pile foundation 21, and on the side walls of the constructed foundation pit 10 on the side 10a of the larger load and the side 10b of the smaller load, so as to monitor the inclination deformation of the pile foundation 21 and the constructed foundation pit 10 in real time. Multiple stress sensors 64 are arranged at key positions on the inclined anchor rod 23, each main support member 31 of each layer of internal support 30, and each beam body 40, so as to monitor their stress changes in real time; the thrust of the first jack or / and the second jack 50 is adjusted in real time according to all monitoring results. These sensors are monitoring devices used during the construction of the foundation pit 10.

[0058] For further explanation, see Figure 5As shown, the real-time monitoring and control work during the construction of the foundation pit 10 is carried out by the control system. The control system includes a central control unit, a data preprocessing unit, a data analysis module, a threshold judgment unit, an alarm system, a control command generation module, an execution structure control unit, etc., which are used for data collection, data transmission and preprocessing, data analysis and judgment, feedback and alarm, adjustment and control, etc. Specifically, all sensors continuously collect data of the foundation pit 10 and transmit the monitoring results to the central control unit in real time; the data preprocessing unit and the data analysis module process and analyze the monitoring results in real time to determine the displacement and deformation of the foundation pit 10; if the monitoring results exceed the preset safety threshold, the alarm system sends an alarm signal, the control command generation module sends an instruction, and the actuator control unit makes real-time dynamic adjustments to the support system of the foundation pit 10, and adjusts the thrust of the first jack or / and the second jack 50 to accurately control the tension of the inclined anchor rod 23 and / or the supporting force of the inner support 30; after the adjustment is completed, continue to monitor the adjustment effect to ensure that the displacement and deformation of the foundation pit 10 are restored to a safe range; if the displacement and deformation of the foundation pit 10 after adjustment still exceed the safe range, the alarm system sends an alarm signal to notify the staff to conduct on-site inspection and evaluation, and take emergency reinforcement measures or stop construction if necessary. Thus, the control system realizes a closed-loop control operation mode to ensure that the displacement and deformation of the foundation pit 10 are always in a controllable state.

[0059] The above-mentioned illustrative embodiment refines the specific settings of the monitoring device and the control system, realizes real-time monitoring and dynamic and precise regulation of the displacement and deformation of the foundation pit 10, improves the automation level and response capability of the construction, and can better cope with emergencies that may occur during the construction of the foundation pit 10 under asymmetric loads, avoid the risk of instability or collapse of the foundation pit 10, and ensure the safety of the construction of the foundation pit 10 under asymmetric loads.

[0060] refer to Figure 2 , Figure 4 As shown, in some embodiments, in step S1, the diameter of the pile foundation 21 arranged on the side 10a with a larger load is greater than the diameter of the pile foundation 21 arranged on the side 10b with a smaller load, and the spacing between the multiple pile foundations 21 arranged on the side 10b with a smaller load is greater than the spacing between the multiple pile foundations 21 arranged on the side 10a with a larger load; that is, the pile foundations 21 with a larger pile diameter, a longer embedded length and a denser pile spacing are arranged on the side 10a with a larger load of the foundation pit 10 for support to meet the support needs of the side 10a with a larger load of the foundation pit 10; and the pile foundations 21 with a smaller pile diameter, a shorter embedded length and a sparser pile spacing are arranged on the side 10b with a smaller load of the foundation pit 10 opposite to the side 10a with a larger load to economically and effectively meet the support needs of the side 10b with a smaller load of the foundation pit 10; thus, it is helpful to solve the problem that the traditional support method of the foundation pit 10 is not stable enough on the side 10a with a larger load and has excessive support on the side 10b with a smaller load, thereby reducing the construction cost.

[0061] refer to Figure 2 , Figure 4 As shown, in some embodiments, in step S1, the embedding length of the pile foundation 21 in the soil 20 is (i.e. the effective length of the pile foundation 21) and the diameter of the pile foundation 21 The method of determining is to first assume that and The initial value is then iterated according to formula (1)-formula (2) until the total bearing capacity of pile foundation 21 is Satisfy the requirement of formula (3); the spacing of the plurality of pile foundations 21 Calculate according to formula (4);

[0062] (1);

[0063] (2);

[0064] (3);

[0065] (4);

[0066] In formulas (1) to (4), is the average lateral friction of the soil 20; is the unit bearing capacity of the soil 20 at the pile end; is the preset safety factor; is the design value of the total bearing capacity of pile foundation 21; and are empirical coefficients. , It is understandable that the mechanical parameters of the soil 20 on the larger load side 10a and the smaller load side 10b of the foundation pit 10 are different, and the bearing capacity requirements of the pile foundation 21 are also different, so the diameter, embedding length and spacing of the pile foundation 21 on these two sides are also different.

[0067] The above-mentioned exemplary embodiment refines the numerical calculation method of the diameter, embedding length and spacing of the pile foundation 21 on the larger load side 10a and the smaller load side 10b of the foundation pit 10, providing a theoretical calculation basis for the design and arrangement of the pile foundation 21 during the construction of the foundation pit 10 under asymmetric loads.

[0068] refer to Figure 3 As shown, in some embodiments, in step S2, the total excavation depth of the first stage of the foundation pit 10 is recorded as The total number of excavations is recorded as , each excavation depth is recorded as ,in, The number of excavations is determined according to the load conditions and geological conditions of the 10 foundation pits to be constructed. Figure 3 The first stage of excavation of foundation pit 10 is divided into three times for illustration. When the first stage of layered excavation of foundation pit 10 is carried out, the excavation depth meets ,and ,Right now The value is based on the first stage of excavation of foundation pit 10 The remaining depth after the excavation is determined; during the excavation of the foundation pit 10, the displacement of the foundation pit 10 and the stability of the side walls are monitored in real time to prevent excessive deformation or instability. It should be noted that the total number of excavations and the setting of the depth of each excavation in the second stage of the layered excavation construction of the foundation pit 10 can refer to the conventional method of excavation construction of the foundation pit 10 under symmetrical loads, and no specific limitation is made here. This illustrative embodiment clarifies the setting principle of the layered excavation depth of the first stage of the foundation pit 10, which is conducive to maintaining the stability of the side walls during the excavation of the foundation pit 10.

[0069] refer to Figure 4 As shown, in some embodiments, it also includes laying a plurality of settlement meters 61 on the surrounding ground surfaces of the larger load side 10a and the smaller load side 10b of the foundation pit 10 to be constructed, so as to monitor the settlement of the ground surface around the foundation pit 10 in real time, thereby evaluating the settlement and settlement trend of the soil 20 during the excavation of the foundation pit 10, and adjusting the excavation speed of the foundation pit 10 or / and the excavation depth of each layer when the foundation pit 10 is excavated in layers accordingly. Specifically, when the settlement value monitored exceeds the preset warning value, the control system determines that the excavation of the foundation pit 10 may affect the stability of the surrounding foundation, and the control system will automatically issue instructions to slow down the excavation speed of the foundation pit 10 or / and adjust the layered excavation depth, etc., to prevent further settlement.

[0070] refer to Figure 4 As shown, in some embodiments, in step S3, the total length of the inclined anchor rod 23 is Equal to the length of the free section of the inclined anchor rod 23 (i.e. the part of the inclined anchor rod 23 that does not participate in anchoring) and anchor length The free section length of the inclined anchor rod 23 According to formula (5), the anchoring length of the inclined anchor rod 23 is Calculate according to formula (6)-formula (7); the spacing of multiple inclined anchor rods 23 Calculate according to formula (8);

[0071] (5);

[0072] (6);

[0073] (7);

[0074] (8);

[0075] In formula (5) to formula (8), is the inclination angle of the inclined anchor rod 23, , select according to project needs; is the diameter of the inclined anchor rod 23, and the diameter of the inclined anchor rod 23 is selected with reference to the commonly used high-strength steel bar specifications; is the sliding surface depth of the soil body 20, determined based on geological survey; is the expected value of the pull-out force of the inclined anchor rod 23, which is determined through an on-site pull-out test; is the interface pull-out strength between the anchoring section of the inclined anchor rod 23 and the soil 20; is the empirical coefficient, , It depends on the combination of construction technology, soil 20 and anchoring materials; is the empirical coefficient, ; is the cohesion of the soil 20; It is the total excavation depth of the second stage of foundation pit 10.

[0076] The above exemplary embodiment refines the numerical calculation method of the length and spacing of the inclined anchor rods 23, and provides a theoretical calculation basis for the design and arrangement of the inclined anchor rods 23 during the construction of the foundation pit 10 under asymmetric loads.

[0077] refer to Figure 2 As shown, in some embodiments, each main support member 31 of each layer of inner support 30 is provided with an RFID tag 33. RFID is a non-contact automatic identification technology that automatically identifies the target object and obtains relevant data through radio frequency signals. The identification work does not require manual intervention and is a wireless version of a barcode. Through the setting of the RFID tag 33, the main support member 31 that needs to adjust the support force can be quickly and accurately automatically located, so that the corresponding second jack 50 can be adjusted in real time to achieve dynamic and precise control of the displacement and deformation of the foundation pit 10.

[0078] In summary, the foundation pit construction control method under asymmetric load of the present invention significantly improves the rigidity and bearing capacity of the foundation pit 10 support system through the comprehensive application of different pile foundations 21 supports on both sides of the asymmetric load of the foundation pit 10, the inclined anchor rod 23 supports on the side 10a with a larger load, and the multi-layer internal supports 30 and prestressed columns 22 supports inside the foundation pit 10, solves the problem that the traditional foundation pit 10 support method is not stable enough on the side 10a with a larger load and has excessive support on the side 10b with a smaller load, and does not need to perform a large number of on-site adjustments and temporary support measures, thereby reducing the construction difficulty and construction efficiency. cost and shorten the construction period; through the setting of the first jack on the inclined anchor rod 23 and the second jack 50 on the inner support 30, the arrangement of the monitoring device and the control system, the real-time monitoring and dynamic precise regulation of the displacement and deformation of the foundation pit 10 are realized, and the displacement and deformation of the foundation pit 10 are effectively controlled. It can better deal with the emergencies that may occur during the construction of the foundation pit 10 under asymmetric loads, avoid the risks of instability and collapse of the foundation pit 10, and ensure the safety of the construction of the foundation pit 10 under asymmetric loads. It is particularly suitable for the construction of the foundation pit 10 in high-density urban areas and under complex geological conditions.

[0079] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0080] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A foundation pit construction control method under asymmetric load, characterized in that: The following steps are involved: S1. Determine the side with a larger load and the side with a smaller load of the foundation pit to be constructed under an asymmetric load; arrange multiple pile foundations in the soil on the side with a larger load and the side with a smaller load for support, respectively, the diameter of the pile foundation arranged on the side with a larger load is larger than the diameter of the pile foundation arranged on the side with a smaller load, and the spacing between the multiple pile foundations arranged on the side with a smaller load is larger than the spacing between the multiple pile foundations arranged on the side with a larger load; and drive multiple prestressed columns in the soil of the foundation pit area to be constructed; S2, carry out the first stage of layered excavation of the foundation pit until the preset foundation pit level is reached; S3, inserting a plurality of inclined anchor rods into the soil of the side wall of the constructed foundation pit on the side with greater load for support; the top of each inclined anchor rod is connected to a first jack; S4, carrying out layered excavation construction of the second stage of the foundation pit until the preset foundation pit bottom surface is reached; after each layer of excavation of the second stage of the foundation pit is completed, a layer of internal support is arranged in the constructed foundation pit; the internal support is connected to a plurality of prestressed columns, and one end of the internal support is pressed onto the side wall of the constructed foundation pit on the side with a smaller load, and the other end is connected to a plurality of second jacks, so as to be pressed onto the side wall of the constructed foundation pit on the side with a larger load through the plurality of second jacks; In step S1, the pile is embedded in the soil based on the length and the diameter of the pile foundation The method of determining is to first assume that and The initial value is then iterated according to formula (1)-formula (2) until the total bearing capacity of the pile foundation is Satisfy the requirements of formula (3); the spacing between the plurality of pile foundations Calculate according to formula (4); (1)； (2)； (3)； (4)； In formulas (1) to (4), is the average lateral friction of the soil; is the unit bearing capacity of the soil at the pile end; is the preset safety factor; is the design value of the total bearing capacity of the pile foundation; and are empirical coefficients. , ; In step S3, the total length of the inclined anchor rod Equal to the free length of the inclined anchor and anchor length the sum of According to formula (5), Calculate according to formula (6)-formula (7); the spacing of the plurality of inclined anchor rods Calculate according to formula (8); (5)； (6)； (7)； (8)； In formula (5) to formula (8), is the inclination angle of the inclined anchor rod, ; is the diameter of the oblique anchor rod; is the sliding surface depth of the soil; is the expected value of the pull-out force of the inclined anchor rod; is the pull-out strength of the interface between the anchoring section of the inclined anchor rod and the soil; and are empirical coefficients, , ; is the cohesion of soil; is the total excavation depth of the second stage of foundation pit; When executing steps S3 and S4, the displacement and deformation of the constructed foundation pit are monitored in real time, and the thrust of the first jack and / or the second jack is adjusted in real time according to the monitoring results.

2. The foundation pit construction control method under asymmetric load according to claim 1 is characterized in that: In step S2, the total excavation depth of the first stage of the foundation pit is recorded as The total number of excavations is recorded as , each excavation depth is recorded as ,in, ; During the first stage of the foundation pit excavation, the excavation depth should meet ,and .

3. The foundation pit construction control method under asymmetric load according to claim 1 or 2, characterized in that: It also includes laying out a plurality of settlement meters on the surrounding surface of the larger load side and the smaller load side of the foundation pit to be constructed, so as to monitor the settlement of the surface around the foundation pit in real time, and adjust the foundation pit excavation speed and / or each excavation depth during the layered excavation of the foundation pit accordingly.

4. The foundation pit construction control method under asymmetric load according to claim 1, characterized in that: In step S4, each layer of the inner support includes a plurality of main support members, and the main support members extend in the direction from the smaller load side to the larger load side, and one end of the main support member in the length direction is crimped onto the side wall of the constructed foundation pit on the smaller load side; a beam body is vertically connected between the plurality of main support members close to the larger load side, and a plurality of the second jacks are connected to the beam body.

5. The foundation pit construction control method under asymmetric load according to claim 4 is characterized in that: It also includes that, as the foundation pit is excavated and constructed in stages and layers, a plurality of displacement sensors are arranged on the ground surface on the larger load side of the foundation pit to be constructed and on the side walls of the constructed foundation pit on the larger load side and the smaller load side, so as to monitor the displacement of the constructed foundation pit in real time and evaluate its deformation; a plurality of inclination sensors are arranged on the top of the pile foundation and on the side walls of the constructed foundation pit on the larger load side and the smaller load side, so as to monitor the inclination deformation of the pile foundation and the constructed foundation pit in real time; a plurality of stress sensors are arranged on the inclined anchor rods and on each main support member and each beam body of each layer support, so as to monitor their stress changes in real time; and the thrust of the first jack and / or the second jack is adjusted in real time according to all monitoring results.

6. The foundation pit construction control method under asymmetric load according to claim 5, characterized in that: Each main support member of each layer of the inner support is provided with an RFID tag.

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