Energy-saving and environment-friendly vacuum preloading foundation treatment method

Abstract

The invention relates to the technical field of civil engineering, in particular to an energy-saving and environment-friendly vacuum preloading foundation treatment method which comprises the steps that a foundation soil body is divided into a plurality of foundation units, and a plurality of vacuum pumps are installed according to initial operation parameters; pre-suction is conducted on the foundation, the vacuum state of any foundation unit is judged, the suction power or the predicted demand power of the corresponding vacuum pump is adjusted, and the under-membrane vacuum pressure of the foundation unit is measured for the second time; the consolidation state of the foundation unit is judged according to the pore water pressure, and the fluctuation of pore water pressure change is detected to determine the foundation consolidation stage; drawing an intra-membrane vacuum pressure change curve in the main consolidation stage, judging the change trend of the curve, and determining the stability of the intra-membrane vacuum pressure and the working state of the sealing membrane according to the fluctuation of the curve; and in the secondary consolidation stage, the ground subsidence height is measured to predict whether the vacuum preloading reaches the load required by the design or not. By evaluating the consolidation degree and stability of the foundation soil body, the efficiency and accuracy of vacuum preloading treatment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of civil engineering, and particularly to an energy-saving and environment-friendly vacuum preloading foundation treatment method. Background Art

[0002] In architecture, the treatment of the foundation is very important. The superstructure depends entirely on the foundation. The main purpose of foundation treatment is to improve the foundation conditions by using various foundation treatment methods. As a new generation of soft foundation reinforcement method, the vacuum preloading method is widely used in engineering construction such as ports, docks, airports, industrial and civil buildings due to its advantages of short construction period, construction safety, no environmental pollution, and low cost. However, the backward theoretical research restricts its further popularization and application in engineering.

[0003] Chinese Patent Publication No.: CN104727298A discloses a vacuum preloading soft soil foundation treatment method, which sets at least three vertical vacuum pressure observation holes at at least three different treatment depth levels in the soft soil foundation to be treated, sets piezometers in the vacuum pressure observation holes, connects vacuum pressure gauges to the upper ends of the piezometers, and sets surface settlement observations near the orifices of each vacuum pressure observation hole on the surface of the soft soil foundation to be treated; after the formation of the formation vacuum pressure field and the end of the rapid surface settlement stage and the transition to the stable settlement stage, start the intermittent vacuum preloading control state, and perform multiple intermittent pump stop and pump start cycle operations; thus, the following problems exist in the described vacuum preloading soft soil foundation treatment method:

[0004] During the vacuum preloading process, when it stops, the pore water pressure in the soil body rises, resulting in a decrease in the soil body strength, thereby reducing the foundation bearing capacity and causing uneven settlement of the foundation, affecting the safety and stability of the building;

[0005] The cycle operation increases the construction duration of the vacuum preloading, increases the impact of the construction on the surrounding environment, and the energy consumption and environmental pollution during the construction process. Summary of the Invention

[0006] Therefore, the present invention provides an energy-saving and environment-friendly vacuum preloading foundation treatment method to overcome the problems in the prior art that the pore water pressure in the soil body rises, resulting in uneven settlement of the foundation, increasing energy consumption and environmental pollution, and affecting the safety and stability of the building.

[0007] To achieve the above object, the present invention provides an energy-saving and environment-friendly vacuum preloading foundation treatment method, including:

[0008] Dividing the foundation soil body into several foundation units according to the control area, respectively setting vacuum pumps in each of the foundation units, and starting the vacuum pumps set in each foundation unit according to the preset initial working parameters;

[0009] Determine the vacuum state of any foundation unit according to the vacuum pressure under the membrane of each foundation unit;

[0010] Determine the suction power of the vacuum pump in the corresponding foundation unit based on the vacuum state, and predict the required power of the corresponding vacuum pump;

[0011] Adjust the suction power of the vacuum pump to the determined rated power range, and re-obtain the vacuum pressure under the membrane of the foundation unit;

[0012] Confirm the timing of judging the consolidation state of the foundation unit according to the re-obtained vacuum pressure under the membrane, and determine the consolidation stage of the foundation unit;

[0013] Judge the volatility of vacuum preloading and the working state of the sealing membrane according to the determined consolidation stage of the foundation unit, or predict whether the vacuum preloading reaches the designed required load.

[0014] Furthermore, measure the vacuum pressure under the membrane of any foundation unit, compare it with the standard value range, and for the foundation units not within the standard value range, determine that they are in the first vacuum state or the third vacuum state, and the suction power of the corresponding vacuum pump needs to be adjusted.

[0015] Furthermore, when it is determined that the suction power of the vacuum pump needs to be adjusted, for the foundation units in the third vacuum state, reduce the suction power of the corresponding vacuum pump, and determine the reduction range through the ratio of the vacuum pressure under the membrane to the standard value range;

[0016] For the foundation units in the first vacuum state, predict the required power of the vacuum pump to be adjusted, compare it with the rated power of the vacuum pump, and determine whether the control area of the vacuum pump needs to be adjusted.

[0017] Furthermore, after re-obtaining the vacuum pressure under the membrane of the foundation unit, confirm the vacuum state of the foundation unit again. When it is determined that any foundation unit is in the second vacuum state, perform formal vacuum preloading according to the determined initial working parameters and judge the consolidation state of the foundation unit.

[0018] Furthermore, the process of judging the consolidation state of the foundation unit includes,

[0019] Detect the pore water pressure at different depths, and determine whether the average decline rate at different depths of the foundation unit is within the normal range;

[0020] Determine whether the consolidation of the foundation soil of the corresponding foundation unit is uniform according to the proportion of drainage boards not within the normal range in the foundation unit;

[0021] When the consolidation of the foundation soil is not uniform, reduce the gap between the drainage boards in the corresponding foundation unit.

[0022] Further, the process of determining the foundation consolidation stage includes

[0023] Calculating the variance value based on the average pore water pressure of the drainage plates in the foundation unit at the same depth, comparing it with the critical value, determining the volatility of the pore water pressure change, and determining whether the foundation unit is in the primary consolidation stage or the secondary consolidation stage.

[0024] Further, when the foundation is in the primary consolidation stage, draw a change curve based on the vacuum pressure in the membrane, calculate the derivative function of the change curve accordingly, and determine the change trend of the change curve;

[0025] When it is determined that the change curve shows an upward trend, it is judged that the vacuum pressure in the membrane continues to rise, reduce the pumping power of the vacuum pump, and determine the reduction range by the ratio of the absolute value of the derivative function to the standard speed;

[0026] When it is determined that the change curve shows a downward trend, it is judged that the vacuum pressure in the membrane is approaching the standard pressure and there is volatility in the change curve;

[0027] When the derivative function value of the change curve is equal to zero, reduce the pumping power of the vacuum pump, and determine the reduction range according to the ratio of the vacuum pressure to the standard pressure on the change curve at this moment.

[0028] Further, when there is volatility in the change curve,

[0029] Compare the absolute value of the derivative function corresponding to this moment with the standard speed to determine whether the vacuum pressure in the membrane is stable, and perform subsequent continuous pumping, or preload the foundation by the method of vacuum-surcharge preloading.

[0030] Further, the process of determining the working state of the sealing membrane includes

[0031] Compare the vacuum pressure in the membrane on the change curve with the standard pressure, and combine the corresponding derivative function value to determine whether there is damage to the sealing membrane;

[0032] When the corresponding derivative function value is equal to zero, increase the pumping power of the vacuum pump, and determine the increase range according to the ratio of the vacuum pressure to the standard pressure on the change curve at this moment.

[0033] Further, when the foundation is in the secondary consolidation stage, calculate the average ground settlement rate according to the ground settlement

[0034] When it is determined that the average ground settlement rate is greater than the standard settlement rate, it is judged that the vacuum preloading has not reached the designed required load, and continue to continuously pump the foundation;

[0035] When it is determined that the number of consecutive days when the average ground settlement rate is less than or equal to the standard settlement rate is greater than or equal to the standard number of days, it is judged that the vacuum preloading has reached the designed required load, and stop the vacuum preloading of the foundation.

[0036] Compared with the prior art, the beneficial effect of the present invention is that vacuum preloading foundation is an engineering technology for improving the bearing capacity and stability of the foundation, which is mainly suitable for soft soil foundation. The moisture and air in the foundation soil are sucked out by a vacuum pump to accelerate the consolidation and strength improvement of the soil. A certain amount of wastewater and waste are often generated during the construction process, such as wastewater and waste sealing film extracted during construction. As the construction time increases, the possibility of the sucked wastewater causing pollution to the surrounding environment gradually increases accordingly; since the moisture and air distributed in the foundation are irregular, if the operating parameters and suction area of ​​the vacuum pump are not adjusted in a targeted manner, energy waste will be caused, and long-term noise and vibration will also affect the lives and health of surrounding residents. The present invention divides the foundation units and determines the vacuum state accordingly to reflect the distribution of moisture and air in the foundation soil, adjusts the suction power of the vacuum pump corresponding to the foundation unit according to the distribution, shortens the construction time of vacuum preloading by adaptively adjusting the suction power, reduces energy consumption and environmental pollution during the construction process, effectively reduces the impact of construction on the surrounding environment, and significantly improves the reinforcement effect of the foundation.

[0037] Furthermore, the vacuum pressure inside the membrane is an important parameter in the vacuum preloading process. During the preloading process, due to the differences in foundation soils in different areas, it should be avoided to uniformly set the vacuum pump operating parameters corresponding to different areas of the foundation soil. The present invention judges the vacuum state of the foundation unit according to the vacuum pressure under the membrane, which reflects the porosity of the foundation soil. The porosity is the ratio of the pore volume in the soil to the volume of its solid particles. Generally speaking, the larger the porosity, the looser the soil and the higher the compressibility. Different adjustment measures are taken according to the vacuum state of the foundation unit to adjust the suction power and control area of ​​the vacuum pump. The vacuum pressure inside the membrane of each foundation unit is controlled within an appropriate range, which improves the adaptability to different conditions of the foundation soil during the subsequent formal vacuum preloading, and adaptably adjusts the vacuum pump suction power and control area according to the specific states of different foundation units in the foundation soil. Compared with the existing preloading process, the construction time of vacuum preloading is shortened, and the energy consumption caused by the operation of the vacuum pump during the preloading process and the impact on the lives of surrounding residents are reduced. At the same time, by treating the construction wastewater to ensure that it meets the emission standards and environmental pollution, the possibility of vacuum preloading causing pollution to the environment is effectively reduced.

[0038] Furthermore, during the process of vacuum preloading the foundation, the degree of consolidation of the foundation soil has a great influence on the vacuum preloading process. During the vacuum pumping process, the water in the soil is discharged, and the pore water pressure will gradually decrease. This method determines the consolidation condition of the soil in each foundation unit by monitoring the change relationship of the pore water pressure between several drainage plates, so as to judge the stability and safety of the vacuum preloaded foundation. If the pore water pressure drops too fast or too slow, it may mean that the consolidation of the soil is uneven. By reducing the gap between the drainage plates 2 and increasing the number of drainage plates, the stability and accuracy of the vacuum preloading treatment of the foundation are improved, the adaptability of the preloading construction to different regions of the foundation soil is further increased, and the situation of secondary preloading or extended preloading duration due to the uneven consolidation of the soil resulting in the non-compliance of the soil settlement for a long time is avoided, effectively reducing the impact of the construction on the surrounding environment and significantly improving the reinforcement effect of the foundation.

[0039] Furthermore, during the primary consolidation stage, the foundation settlement is mainly caused by the dissipation of pore water pressure. During the secondary consolidation stage, the pore water pressure tends to be stable, and the soil continues to undergo slow compression deformation. This method controls and analyzes the vacuum pressure inside the membrane when the foundation is in the primary consolidation stage, and analyzes and predicts whether the vacuum preloading reaches the designed required load based on the ground settlement during the secondary consolidation stage, improving the stability and flexibility of the vacuum preloading analysis of the foundation and avoiding the impact on the accuracy of the analysis caused by predicting when the foundation settlement is unstable.

[0040] Furthermore, the vacuum pressure inside the membrane is an important parameter in the vacuum preloading process. By plotting the change curve of the vacuum pressure, the change trend of the vacuum pressure inside the membrane and the volatility of the curve are judged. According to the curve volatility, the stability of the vacuum pressure is judged. The vacuum-surcharge preloading method is used to preload the foundation. By applying an additional load, the effective stress of the soil is further increased, the bearing capacity of the foundation is improved, and the settlement of the soil is reduced. According to the change trend of the vacuum pressure inside the membrane, the sealing state of the sealing membrane is judged, avoiding the rise of the pore water pressure in the soil when the sealing membrane is damaged, reducing the bearing capacity of the foundation and the decrease of the soil strength, and affecting the stability of the foundation and subsequent construction. And according to the rising speed of the vacuum pressure inside the membrane, the operating parameters of the vacuum pump are adjusted to further improve the construction efficiency of the vacuum preloading of the foundation and reduce unnecessary energy consumption.

[0041] Furthermore, the average ground settlement rate refers to the average speed of ground settlement within a certain period of time. By calculating the average ground settlement rate, the settlement trend of the entire foundation is reflected. According to the number of consecutive days when the average ground settlement rate is less than or equal to the standard settlement rate, it is judged whether the vacuum preloading reaches the designed required load of the foundation, improving the accuracy of evaluating the foundation stability and predicting the settlement development. Description of the Drawings

[0042] Figure 1It is the flow chart of the steps of the vacuum preloading foundation treatment method in the embodiment of the present invention;

[0043] Figure 2 It is the structural schematic diagram of the vacuum preloading foundation treatment method in the embodiment of the present invention;

[0044] Figure 3 It is the flow schematic diagram for judging the vacuum state of the foundation unit in the embodiment of the present invention;

[0045] Figure 4 It is the schematic diagram for judging whether the vacuum preloading reaches the designed required load in the embodiment of the present invention;

[0046] In the figure: 1 - vacuum pump, 2 - drain board, 3 - vacuum pipe network, 4 - sealing film, 5 - sand cushion, 6 - surcharge fill. Detailed implementation manners

[0047] In order to make the objectives and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] The preferred implementation manners of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these implementation manners are only used to explain the technical principle of the present invention and do not limit the protection scope of the present invention.

[0049] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0050] In addition, it should be noted that in the description of the present invention, unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" 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 mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0051] Please refer to Figures 1 - 4 as shown in Figure 1 It is the flow chart of the steps of the vacuum preloading foundation treatment method in the embodiment of the present invention; Figure 2 It is the structural schematic diagram of the vacuum preloading foundation treatment method in the embodiment of the present invention; Figure 3Schematic flowchart for determining the vacuum state of a foundation unit in an embodiment of the present invention; Figure 4 Schematic diagram for determining whether the vacuum preloading reaches the designed required load in an embodiment of the present invention.

[0052] The present invention provides an energy-saving and environment-friendly vacuum preloading foundation treatment method, including:

[0053] Step S1: Lay the sand cushion layer 5 in layers on the soft soil foundation, set a sealing wall around the vacuum preloading area, drive the vacuum pipe network 3, and bury monitoring instruments;

[0054] Step S2: Lay a geotextile and a sealing film 4 on the sand cushion layer 5, set a vacuum pump 1 on the sealing film 4, the vacuum pump extracts air through the pipe network to form a negative pressure, divides the foundation soil into several foundation units according to the controlled area, sets a vacuum pump in each of the foundation units, and starts the vacuum pumps set in each foundation unit according to the preset initial working parameters;

[0055] Step S3: Conduct pre-pumping on the foundation, and determine the vacuum state of any foundation unit according to the vacuum pressure under the film of each foundation unit;

[0056] Step S4: Determine the pumping power of the vacuum pump in the foundation unit corresponding to the determined vacuum state, and predict the required power of the corresponding vacuum pump;

[0057] Step S5: Adjust the pumping power of the vacuum pump to the determined rated power range, and re-obtain the vacuum pressure under the film of the foundation unit;

[0058] Step S6: Confirm the timing for judging the consolidation state of the foundation unit according to the re-obtained vacuum pressure under the film, and determine the consolidation stage of the foundation unit;

[0059] Step S7: Judge the volatility of the vacuum preloading and the working state of the sealing film according to the determined consolidation stage of the foundation unit, or predict whether the vacuum preloading reaches the designed required load, release the vacuum to stop preloading, and remove the sealing film 4 and the sand cushion layer 5;

[0060] Wherein, the initial working parameters include the pumping power of the vacuum pump and the controlled area.

[0061] It can be understood that the vacuum pipe network 3 includes drainage boards 2, filter pipes and plastic hoses. Driving the vacuum pipe network 3 includes laying filter pipes and plastic hoses. The technological process of driving the vacuum pipe network 3 is common knowledge for construction technicians in the art and will not be elaborated here.

[0062] Before the layered filling of the sand cushion 5, measure whether the road surface is flat. If there are local potholes, fill them with plain soil. When backfilling the plain soil, control the thickness to ensure the bearing capacity required by the slab machine. After the backfilling of the plain soil is completed, use a level to measure the elevation of the top surface of the soil according to a 10m×10m grid and conduct acceptance. Only after passing the acceptance can the construction of the sand cushion be carried out. The sand cushion 5 needs to be filled to a thickness of 40 cm with an error within the specification requirements. Use a wick drain machine to drive the wick drains 2. After the wick drains 2 are driven, install monitoring instruments at the positions given on the drawing and the designated monitoring unit and do a good job in protecting the instruments.

[0063] Specifically, the vacuum preloading foundation is an engineering technology used to improve the bearing capacity and stability of the foundation, mainly applicable to soft soil foundations. By using a vacuum pump to suck out the water and air in the foundation soil, the consolidation of the soil and the improvement of its strength are accelerated. During the construction process, a certain amount of wastewater and waste will be generated, such as the wastewater pumped out during construction and the discarded sealing film. As the construction duration increases, the possibility of the pumped-out wastewater polluting the surrounding environment gradually increases. Since the distribution of water and air in the foundation is irregular, if the operating parameters and suction area of the vacuum pump are not adjusted specifically, it will cause energy waste, and the long-term noise and vibration will also affect the lives and health of the surrounding residents. In the present invention, the foundation is divided into units, and the vacuum state is determined accordingly to reflect the distribution of water and air in the foundation soil. According to the distribution, the suction power of the vacuum pump corresponding to the foundation unit is adjusted. By adaptively adjusting the suction power, the construction time of vacuum preloading is shortened, the energy consumption and environmental pollution during the construction process are reduced, the impact of the construction on the surrounding environment is effectively reduced, and at the same time, the reinforcement effect of the foundation is significantly improved.

[0064] Install the vacuum pump 1 and the filter pipe according to the control area of the vacuum pump 1. The number of vacuum pumps 1 in each area meets the requirements of the construction plan proposed in the design.

[0065] Pre-suck the foundation, divide the foundation soil into several foundation units according to the control area of the vacuum pump, and measure the vacuum pressure under the membrane of each foundation unit.

[0066] If the vacuum pressure under any membrane is less than or equal to the first standard value, it is determined that the corresponding foundation unit is in the first vacuum state.

[0067] If the vacuum pressure under any membrane is greater than the first standard value and less than or equal to the second standard value, it is determined that the corresponding foundation unit is in the second vacuum state.

[0068] If the vacuum pressure under any membrane is greater than the second standard value, it is determined that the corresponding foundation unit is in the third vacuum state.

[0069] Among them, the first standard value is 60 kPa, the second standard value is 85 kPa, and the first standard value and the second standard value form a standard value range.

[0070] When the foundation unit is in the third vacuum state, reduce the suction power of the corresponding vacuum pump according to the ratio of the vacuum pressure under the membrane to the second standard value;

[0071] When the foundation unit is in the first vacuum state, predict the required power of the suction power of the vacuum pump to be adjusted, and judge whether it is necessary to adjust the control area of the corresponding vacuum pump;

[0072] If the product of the ratio of the first standard value to the vacuum pressure under the membrane and the suction power of the corresponding vacuum pump is less than or equal to the rated power of the vacuum pump, it is judged that the required power of the vacuum pump does not exceed the operating range of the vacuum pump, and there is no need to adjust the control area of the vacuum pump;

[0073] If the product of the ratio of the first standard value to the vacuum pressure under the membrane and the suction power of the corresponding vacuum pump is greater than the rated power of the vacuum pump, it is judged that the required power of the vacuum pump exceeds the operating range of the vacuum pump, and it is necessary to adjust the control area of the vacuum pump;

[0074] Specifically, reduce the control area of the vacuum pump according to the ratio of the rated power to the required power, and correspondingly reduce the area of the foundation unit.

[0075] Specifically, the vacuum pressure in the membrane is an important parameter in the vacuum preloading process. During the preloading process, due to the differences in the foundation soil in different regions, the situation of uniformly setting the operating parameters of the vacuum pumps corresponding to different regions of the foundation soil should be avoided; the present invention judges the vacuum state of the foundation unit according to the vacuum pressure under the membrane, reflects the void ratio of the foundation soil, and the void ratio is the ratio of the pore volume in the soil to the volume of its solid particles. Generally speaking, the larger the void ratio, the looser the soil and the higher the compressibility; different adjustment measures are taken according to the vacuum state of the foundation unit, adjusting the suction power and control area of the vacuum pump, controlling the vacuum pressure in the membrane of each foundation unit within an appropriate range, improving the adaptability to different situations of the foundation soil during the subsequent formal vacuum preloading, and adaptively adjusting the suction power and control area of the vacuum pump according to the specific state of different foundation units in the foundation soil. Compared with the existing preloading process, the construction time of vacuum preloading is shortened, the energy consumption caused by the operation of the vacuum pump during the preloading process and the impact on the lives of surrounding residents are reduced, and at the same time, by treating the construction wastewater, the discharge up to standard and environmental pollution are ensured, effectively reducing the possibility of environmental pollution caused by vacuum preloading.

[0076] After adjusting the initial operating parameters of the vacuum pump, measure the vacuum pressure under the membrane of each foundation unit for the second time. When any foundation unit is in the second vacuum state, carry out formal vacuum preloading according to the adjusted operating parameters of the vacuum pump;

[0077] During formal vacuum preloading, the pore water pressures at different depths around several drainage plates are detected according to the initial detection period. In this embodiment, the pore water pressures at different depths are detected by piezometers with different burial depths.

[0078] It can be understood that piezometers, standpipe piezometers, fiber optic piezometers, pneumatic piezometers, silicon piezometers, etc. can be adopted as needed, as long as they can detect the pore water pressure around the drainage plates.

[0079] According to several pore water pressures, calculate the average decline rate of the pore water pressure around any drainage plate during the initial detection period, and determine whether the average decline rate of the pore water pressure around the corresponding drainage plate is within the normal range according to the preset standard speed range.

[0080] Detect the number of drainage plates 2 whose average decline rate of the pore water pressure in the foundation unit is not within the normal range, compare it with the total number of drainage plates 2 in the foundation unit, and calculate the actual proportion.

[0081] If the actual proportion is less than or equal to the standard proportion, it is judged that the consolidation of the foundation soil in the corresponding foundation unit is relatively uniform.

[0082] If the actual proportion is greater than the standard proportion, it is judged that the consolidation of the foundation soil in the corresponding foundation unit is uneven, reduce the gap between the drainage plates 2 in the corresponding foundation unit, and increase the number of drainage plates 2 arranged.

[0083] Among them, the standard proportion is 10%, and the standard speed range is a preset value set according to the historical data of the pore water pressure.

[0084] Specifically, during the process of vacuum preloading the foundation, the degree of consolidation of the foundation soil has a great influence on the vacuum preloading process. During the vacuum pumping process, the water in the soil is discharged, and the pore water pressure will gradually decrease; this method determines the consolidation of the soil in each foundation unit by monitoring the change relationship of the pore water pressure between several drainage plates 2, so as to judge the stability and safety of the vacuum preloaded foundation; if the pore water pressure drops too fast or too slow, it may mean that the consolidation of the soil is uneven. By reducing the gap between the drainage plates 2 and increasing the number of drainage plates 2 arranged, the stability and accuracy of the vacuum preloading treatment of the foundation are improved, the adaptability of the preloading construction to different regions of the foundation soil is further increased, the situation of secondary preloading or extended preloading duration due to the failure of the soil settlement to meet the standard for a long time caused by uneven soil consolidation is avoided, the impact of the construction on the surrounding environment is effectively reduced, and at the same time, the reinforcement effect of the foundation is significantly improved.

[0085] After adjusting the setting parameters of the drainage plates in the foundation unit, calculate the average pore water pressure of several pore water pressures of different drainage plates at the same depth, and calculate the variance value of the average pore water pressure according to the initial detection period.

[0086] If the variance value of the average pore water pressure is greater than the critical value, it is determined that the fluctuation of the pore water pressure change is large, and the foundation is in the primary consolidation stage, and the vacuum pressure in the membrane is analyzed.

[0087] If the variance value of the average pore water pressure is greater than the critical value, it is determined that the fluctuation of the pore water pressure change is stable, and the foundation is in the secondary consolidation stage, and the ground settlement is analyzed.

[0088] Wherein, the variance value is a preset value set according to the pore water pressure data in the secondary consolidation stage.

[0089] Specifically, in the primary consolidation stage, the foundation settlement is mainly caused by the dissipation of pore water pressure. In the secondary consolidation stage, the pore water pressure tends to be stable, and the soil continues to undergo slow compression deformation. This method controls and analyzes the vacuum pressure in the membrane when the foundation is in the primary consolidation stage, and analyzes the ground settlement in the secondary consolidation stage to predict whether the vacuum preloading reaches the designed required load, improving the stability and flexibility of the vacuum preloading analysis of the foundation, and avoiding the influence on the accuracy of the analysis caused by predicting when the foundation settlement is unstable.

[0090] In this embodiment, the vacuum pressure in the membrane is detected by a vacuum pressure gauge. When the foundation is in the primary consolidation stage, a curve of the change of the vacuum pressure in the membrane is drawn, and the derivative function of the curve is calculated accordingly.

[0091] If the vacuum pressure on the curve of the change of the vacuum pressure in the membrane at any moment is greater than the standard pressure, and the derivative function value corresponding to this moment is greater than zero, it is determined that the curve shows an upward trend, and the vacuum pressure in the membrane continues to rise, and the suction power of the vacuum pump 1 is reduced according to the ratio of the absolute value of the derivative function to the standard speed.

[0092] If the derivative function value corresponding to this moment is equal to zero, the suction power of the vacuum pump 1 is reduced according to the ratio of the vacuum pressure on the curve of the change of the vacuum pressure in the membrane at this moment to the standard pressure.

[0093] If the vacuum pressure on the curve of the change of the vacuum pressure in the membrane at any moment is greater than the standard pressure, and the derivative function value corresponding to this moment is less than zero, it is determined that the curve shows a downward trend, and the vacuum pressure in the membrane is approaching the standard pressure, and there is fluctuation in the curve.

[0094] If the absolute value of the derivative function corresponding to this moment is less than the standard speed, it is determined that the fluctuation of the curve is small, and the vacuum pressure in the membrane is relatively stable, and subsequent continuous suction can be carried out.

[0095] If the absolute value of the derivative function corresponding to this moment is greater than the standard speed, it is determined that the curve has large fluctuations and the vacuum pressure in the membrane is relatively unstable, and the vacuum-surcharge preloading method is used to preload the foundation;

[0096] When using vacuum-surcharge preloading, vacuum pumping should be carried out first according to the requirements of vacuum preloading. After the vacuum pressure reaches the design requirements and stabilizes, surcharge should be applied, and pumping should continue. When applying surcharge, protective materials such as geotextiles should be laid under the fill soil 6 on the membrane.

[0097] If the vacuum pressure on the vacuum pressure change curve of the membrane at any moment is less than the standard pressure, and the derivative function value corresponding to this moment is less than zero, and the curve shows a downward trend, it is determined that the sealing membrane 4 is damaged, and the pump is stopped to check and repair the sealing membrane 4;

[0098] If the vacuum pressure on the vacuum pressure change curve of the membrane at any moment is less than the standard pressure, and the derivative function value corresponding to this moment is greater than zero, and the curve shows an upward trend, it is determined that the vacuum pressure in the membrane is approaching the standard pressure, and the vacuum preloading is in the starting stage.

[0099] Among them, if the absolute value of the derivative function is less than the standard speed, it is determined that the rising speed of the vacuum pressure in the membrane is slow, and the suction power of the vacuum pump 1 is increased according to the ratio of the absolute value of the derivative function to the standard speed;

[0100] If the derivative function value corresponding to this moment is equal to zero, the suction power of the vacuum pump 1 is increased according to the ratio of the vacuum pressure to the standard pressure on the vacuum pressure change curve of the membrane at this moment.

[0101] In this embodiment, the standard pressure is 85 kPa, and the standard speed is a preset value set according to the operating parameters of pre-pumping;

[0102] The vacuum pumping equipment uses a jet vacuum pump 1. The vacuum pump 1 is connected to the filter pipe through a plastic hose, and a stop valve is provided. When stopping the pump, the stop valve is closed first. When the intake hole of the vacuum pumping equipment is closed, its vacuum pressure should not be less than 96 kPa; the vacuum degree under the membrane after pumping should be kept not less than 85 kPa, and the control area of each vacuum pump 1 is 900 - 1100 m 2 ;

[0103] When applying surcharge, after the vacuum preloading reaches 80 kPa, a 40 kPa surcharge is constructed at one time; during the surcharge period, a drainage ditch is set at the edge of the surcharge area, and the water is drained outside the working area by pumping with a pump.

[0104] Specifically, the vacuum pressure inside the membrane is an important parameter in the vacuum preloading process. By plotting the curve of the vacuum pressure change, the change trend of the vacuum pressure inside the membrane and the volatility of the curve are judged. According to the volatility of the curve, the stability of the vacuum pressure is judged. The vacuum-surcharge preloading method is used to preload the foundation. By applying an additional load, the effective stress of the soil is further increased, the bearing capacity of the foundation is improved, and the settlement of the soil is reduced. According to the change trend of the vacuum pressure inside the membrane, the sealing state of the sealing membrane 4 is judged to avoid the rise of the pore water pressure in the soil when the sealing membrane 4 is damaged, reduce the bearing capacity of the foundation and the strength reduction of the soil, and affect the stability of the foundation and subsequent construction. And according to the rising speed of the vacuum pressure inside the membrane, the operating parameters of the vacuum pump 1 are adjusted, which further improves the efficiency of vacuum preloading of the foundation and reduces unnecessary energy consumption.

[0105] During the continuous suction of the foundation, when the foundation is in the secondary consolidation stage, the ground settlement height is measured in real time, and the average daily ground settlement rate is calculated.

[0106] If the average daily ground settlement rate is greater than the standard settlement rate, it is judged that the vacuum preloading has not reached the designed required load, and the continuous suction of the foundation is continued.

[0107] If the number of consecutive days when the average daily ground settlement rate is less than or equal to the standard settlement rate is greater than or equal to the standard number of days, it is judged that the vacuum preloading has reached the designed required load, and the vacuum pump 1 can be stopped and unloaded, and the vacuum preloading of the foundation is stopped.

[0108] Among them, the standard settlement rate is 2 mm / d, the standard number of days is 10 days, and the number of consecutive days when the average daily ground settlement rate is less than or equal to the standard settlement rate can be adjusted according to the design requirements.

[0109] In this embodiment, the vacuum state of the foundation unit shows a gradually decreasing trend from outside to inside, and the corresponding standard settlement amount of the foundation unit gradually increases from outside to inside.

[0110] Specifically, the average daily ground settlement rate refers to the average speed of ground settlement within a certain period of time. By calculating the average daily ground settlement rate, the settlement trend of the entire foundation is reflected. According to the number of consecutive days when the average daily ground settlement rate is less than or equal to the standard settlement rate, it is judged whether the vacuum preloading has reached the designed required load of the foundation, and the accuracy of evaluating the foundation stability and predicting the settlement development is improved.

[0111] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, those skilled in the art can easily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0112] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An energy-saving and environmentally friendly vacuum preloading foundation treatment method, characterized in that: include: Dividing the foundation soil into a plurality of foundation units according to the control area, respectively arranging a vacuum pump in each of the foundation units, and respectively starting the vacuum pumps arranged in each of the foundation units according to preset initial working parameters; According to the vacuum pressure under the membrane of each foundation unit, the vacuum state of any foundation unit is determined; Determine the suction power of the vacuum pump in the corresponding foundation unit according to the vacuum state, and predict the required power of the corresponding vacuum pump; Adjust the suction power of the vacuum pump to a certain rated power range to regain the vacuum pressure under the membrane of the foundation unit; The timing of judging the consolidation state of the foundation unit is confirmed according to the re-acquired vacuum pressure under the membrane, and the consolidation stage of the foundation unit is determined; According to the determined consolidation stage of the foundation unit, the volatility of the vacuum preloading and the working state of the sealing membrane are determined, or it is predicted whether the vacuum preloading reaches the required design load.

2. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 1 is characterized in that: Measure the vacuum pressure under the membrane of any foundation unit and compare it with the standard value range. For foundation units that are not within the standard value range, determine whether they are in the first vacuum state or the third vacuum state, and adjust the corresponding vacuum pump suction power.

3. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 2 is characterized in that: When it is determined that the suction power of the vacuum pump needs to be adjusted, for the foundation unit in the third vacuum state, the suction power of the corresponding vacuum pump is reduced, and the reduction range is determined by the ratio of the vacuum pressure under the membrane to the standard value range; For the foundation unit in the first vacuum state, the required power of the vacuum pump that needs to be adjusted is predicted and compared with the rated power of the vacuum pump to determine whether the control area of ​​the vacuum pump needs to be adjusted.

4. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 3 is characterized in that: After reacquiring the vacuum pressure under the membrane of the foundation unit, the vacuum state of the foundation unit is confirmed again. When it is determined that any foundation unit is in the second vacuum state, a formal vacuum preloading is performed according to the determined initial working parameters to determine the consolidation state of the foundation unit.

5. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 4 is characterized in that: The process of determining the consolidation state of a foundation element includes, Detect the pore water pressure at different depths to determine whether the average decline rate at different depths of the foundation unit is within the normal range; According to the proportion of drainage panels that are not within the normal range in the foundation unit, determine whether the foundation soil of the corresponding foundation unit is uniformly consolidated; When the foundation soil is unevenly consolidated, reduce the gap between the drainage boards in the corresponding foundation unit.

6. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 1 is characterized in that: The process of determining the stage of foundation consolidation includes, The variance value is calculated based on the average pore water pressure of the drainage plate at the same depth in the foundation unit, and compared with the critical value to determine the volatility of the pore water pressure change and determine whether the foundation unit is in the primary consolidation stage or the secondary consolidation stage.

7. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 6 is characterized in that: When the foundation is in the main consolidation stage, a change curve is drawn according to the vacuum pressure in the membrane, and the derivative function of the change curve is calculated accordingly to determine the change trend of the change curve; When it is determined that the change curve shows an upward trend, it is determined that the vacuum pressure in the membrane continues to rise, and the suction power of the vacuum pump is reduced. The reduction range is determined by the ratio of the absolute value of the derivative function to the standard speed; When it is determined that the change curve shows a downward trend, it is determined that the vacuum pressure in the membrane is approaching the standard pressure and the change curve has fluctuations; When the derivative function value of the change curve is determined to be zero, the suction power of the vacuum pump is reduced, and the reduction range is determined according to the ratio of the vacuum pressure on the change curve at that moment to the standard pressure.

8. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 7 is characterized in that: When the change curve is volatile, The absolute value of the derivative function corresponding to the moment is compared with the standard speed to determine whether the vacuum pressure in the membrane is stable, and subsequent continuous suction is performed, or the foundation is pre-pressed by a combination of vacuum loading and pre-pressing.

9. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 1 is characterized in that: The process of determining the working condition of the sealing membrane includes, Compare the vacuum pressure inside the membrane on the change curve with the standard pressure, and combine the corresponding derivative function value to determine whether the sealing membrane is damaged; When the corresponding derivative function value is equal to zero, the suction power of the vacuum pump is increased, and the increase range is determined according to the ratio of the vacuum pressure to the standard pressure on the change curve at that moment.

10. The energy-saving and environmentally friendly vacuum preloading foundation treatment method according to claim 6, characterized in that: When the foundation is in the secondary consolidation stage, the average ground settlement rate is calculated based on the ground settlement. When it is determined that the average ground settlement rate is greater than the standard settlement rate, it is determined that the vacuum preloading has not reached the design load requirement, and the foundation is continuously pumped; When it is determined that the number of consecutive days when the average ground settlement rate is less than or equal to the standard settlement rate is greater than or equal to the standard number of days, it is determined that the vacuum preloading has reached the design load requirement and the vacuum preloading of the foundation is stopped.

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