CN101608548B - Method for protecting underground structure of single round shield side face construction in close distance - Google Patents

Abstract

The invention relates to a method for protecting an underground structure by short-distance construction on the side of a single-circle shield in the technical field of construction engineering. Included steps: using the Robertson method; determining the parameters of the shield passing through the underground structure through the design drawings of the underground structure and tunnel; using a three-dimensional finite element model for numerical simulation; formulating a monitoring plan, and conducting on-site measuring point layout and monitoring before the crossing construction; testing According to the work efficiency of the trial push, select the construction parameters; carry out the construction through real-time monitoring feedback analysis; track and monitor the set monitoring points until the monitoring data stabilizes within the scope of the optimized safe construction parameters described in step (6). The invention ensures the normal use of the underground structure and the smooth excavation of the shield, and the technical measures adopted are suitable for the requirement that the single-circle shield pass through various underground structures at a short distance side, providing an important technical guarantee for it.

Description

The Method of Protecting Underground Structures by Close-distance Construction on the Side of Single-Circle Shield

technical field

The invention relates to a method in the technical field of construction engineering, in particular to a method for protecting an underground structure by short-distance construction on the side of a single-circle shield.

Background technique

With the acceleration of urban construction and the need to make full use of urban construction space resources, urban underground space is further developed, and underground pipelines, tunnels, and other underground buildings and structures are increasingly dense, and domestic urban rail transit construction is developing more and more rapidly. In the construction of rail transit, the shield tunneling method has been applied more and more in China due to its superiority. In order to form a rail transit network as soon as possible to achieve the expected scale effect, the construction of rail transit is also accelerating. However, urban planning and construction, especially along with the increase of development along the subway construction, the project construction is faced with more and more complex surrounding environment, and the situation of crossing obstacles or passing existing buildings (structures) at close range is becoming more and more difficult. more and more. During the construction of the project, it is necessary to protect the existing buildings (structures) and ensure the safety and smooth progress of the project itself. Therefore, it is necessary to adopt corresponding coping techniques for different situations. How to ensure the normal use of the adjacent built (structure) structures during the crossing construction process and after the crossing has become one of the problems to be solved urgently in shield tunneling engineering.

It is very important to determine the geological stratification and soil parameters of the site soil to ensure the successful short-distance crossing of the shield. In 1992, Robertson et al. (Estimating coefficient of consolidation from piezoconetets, Canadian Geotechnical Journal, 29(4), 551-557; Canadian Journal of Geotechnical Engineering sponsored by the Canadian National Science Council, "Using pore water pressure static contact Detecting the consolidation properties of soil layers and related calculation formulas") By applying the distribution law of pore water pressure to determine the distribution of soil layers and the consolidation properties of soil layers and related calculation formulas (hereinafter referred to as the Robertson method).

After searching the existing technical literature, it is found that the inventors are Zhou Wenbo, Gu Chunhua, Wu Huiming, etc., and the application number is CN200610116618.X. The technology adopts the pre-preparation for crossing buildings or structures, taking protective measures for buildings or structures in advance, construction monitoring, setting reasonable shield construction parameters when crossing buildings or structures at short distances, and double-circle shield tunneling after crossing. Grouting and other steps, but this technology is not suitable for the single-round shield to pass through the underground structure at close range. At the same time, the construction monitoring of this technology does not record the method of measuring point layout, nor does it clarify the relationship between real-time monitoring and shield construction. .

Contents of the invention

Aiming at the deficiencies and defects in the prior art, the invention proposes a method for protecting an underground structure by short-distance construction on the side of a single-circle shield. The invention ensures the normal use of the underground structure and the smooth excavation of the shield, and the technical measures adopted are suitable for the requirement that the single-circle shield pass through various underground structures at a short distance side, providing an important technical guarantee for it.

The present invention is achieved through the following technical solutions, comprising the following steps:

(1) Using the Robertson method to detect the formation penetration resistance and pore water pressure variation curve with depth (called the penetration resistance curve and pore water pressure distribution curve) by pore water pressure static penetration sounding; The horizontal axis is the ratio of pore water pressure to penetration resistance, and the vertical axis is the ratio of penetration resistance to initial formation stress. A relationship diagram is drawn, and the diagram is divided into several regions with different soil properties. Each characteristic represents a The type of soil; mark the data of the measured static penetrating curve on the map to judge the type of soil layer on the site; then compare the penetration resistance curve and pore water pressure distribution curve according to the type of soil to determine the depth and distribution of the soil layer Thickness, including the burial depth of sandy soil under the cohesive soil layer.

(2) According to the design drawings of the underground structure and the tunnel, determine the total length L _d meters of the shield passing through the underground structure, the buried depth of the interval tunnel H _min ~ H _max meters, and the mutual distance between the underground structure and the shield tunnel L _min ~ L _max meters , the buried depth of the top of the tunnel is H meters, and the diameter of the tunnel is D meters.

(3) The three-dimensional finite element model is used to numerically simulate the entire passing process of the shield passing through the underground structure at close range. Three-dimensional finite element model range: the horizontal direction should be greater than (2H+3D+L _min ) meters, the depth direction should be greater than (2H+2D) meters, the length is determined according to the actual project, the tunnel is placed in the middle of the model, and the distance between the bottom surface and the tunnel bottom should be greater than 2D meters. The boundary conditions are set as follows: the inner side of the tunnel adopts a free boundary, the horizontal displacement is constrained on both sides of the model, and the vertical and horizontal displacement are constrained at the bottom of the model at the same time. The constitutive relation of the soil adopts the modified Cambridge model considering elastic-plastic strain, and the tunnel structure is taken as elastic body.

By the numerical simulation described in step (3), the obtained result is:

①Give the feasibility of the smooth crossing of the shield tunneling machine, the soil body and the underground structure during the crossing construction process.

The above conditions for judging the feasibility of shield tunneling smoothly should be met: surface displacement: -30mm～+10mm; underground structure displacement: cumulative value: -15mm～+15mm, single maximum change value: -5mm～+5mm ; Underground structure plastic zone volume: under the condition of V=0, there is no need to take any reinforcement measures for the soil and underground structures in specific areas.

②Determine the range L _e meters in which shield tunneling will affect the underground structure at short distances, and the section length L _i meters in which the underground structure needs to be protected during the pass.

(4) For the key protected crossing section L _i meters determined by numerical simulation in step (3), a detailed monitoring plan is formulated. Before the crossing construction, the measuring point layout and monitoring are carried out on site, including:

① Soil displacement, pore water pressure and earth pressure between tunnel and underground structure.

② Displacement and stress of the underground structure near the shield crossing section.

③Surface settlement in the direction of the tunnel cross section and along the direction of the tunnel axis and the settlement of important buildings in the key crossing section.

(5) Combined with the influence range L _e of the shield tunneling on the underground structure determined by the finite element analysis in step (3), the first 20 rings from the key protection section L _i meters are used as the trial excavation interval of the shield tunnel. At the same time, a number of monitoring points are arranged in the test section to observe the effect of the test push, mainly the surface settlement monitoring points parallel to the tunnel axis and perpendicular to the tunnel axis are arranged, and the corresponding horizontal displacement monitoring points are arranged on the underground structure. Through the trial advance in this interval, the construction parameters to be adopted when formally passing through the underground structure at close range are preliminarily determined, mainly including: shield thrust, propulsion speed, grouting amount, and grouting pressure.

(6) During the process of the shield passing through the L _i meter section of the key protection area, the on-site monitoring and construction are closely combined, and the construction is carried out through real-time monitoring and feedback analysis. Through the timely analysis of the monitoring results, it is judged whether the construction process and construction parameters of the previous step meet the expected requirements, so as to determine and optimize the construction parameters of the next step, to ensure the smooth progress of the project and to protect the safety of the underground structure. Safety judgment standards:

①Surface subsidence: -30mm～+10mm

②Soil horizontal displacement: cumulative value: -30mm～+30mm, single maximum change value: -15mm～+15mm

③Earth pressure: 250kPa

⑤ Pore water pressure: 200kPa

⑥Underground structural stress: -10kN/m ² ～10kN/m ²

⑦Underground structure displacement: cumulative value: -15mm～+15mm, single maximum change value: -5mm～+5mm

(7) After the shield machine passes through the underground structure smoothly, track and monitor the set monitoring points until the monitoring data stabilizes within the range of the optimized safe construction parameters described in step (6).

The present invention comprehensively adopts multiple protective technical measures when the shield passes through the underground structure at close range, adopts a scientific, reasonable and reliable method to determine the construction parameters of the shield, and ensures the normal use of the underground structure and the smooth excavation of the shield. The technical measures adopted in the invention can be applied to the situation that the single-circle shield passes through various underground structures at a short distance side, and provides an important technical guarantee for the single-circle shield to pass through the underground structures smoothly at a short distance.

Description of drawings

Figure 1 Plane view of the side of the shield passing through the underground diaphragm wall at close range

Figure 2 Sectional view of the side of the shield passing through the underground diaphragm wall at close range

Figure 3 Plane layout of observation points for land subsidence

Figure 4 Plane layout of steel bar stress gauge, inclinometer pipe, pore water pressure gauge and earth pressure gauge

Figure 5 Facade Layout of Inclinometer Tube, Pore Pressure Gauge, and Earth Pressure Gauge

Figure 6 Facade Layout of Reinforcement Stress Gauge

Detailed ways

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings: the present embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are provided, but the protection scope of the present invention is not limited to the following implementations example.

Example:

There is an underground passage to be built next to the tunnel of a certain subway section. The construction of the underground diaphragm wall of the passage has been completed. It passes through the side of the section tunnel at a short distance. The main structure inside the passage is under construction, and part of the lining structure has been completed. The underground diaphragm wall of the channel is connected with the receiving shaft of the shield machine at the end in an L shape, as shown in Figures 1 and 2. The figure shows the plane of the shield machine passing through the diaphragm wall at close range on the side of the shield machine and the section of the shield machine passing through the diaphragm wall at a short distance on the side of the shield machine , the length of each segment of shield tunneling is 1.2m, and the thickness is 0.35m.

The specific implementation steps of this embodiment are as follows:

(1) After detailed geological exploration, the distribution of soil layers and soil physical and mechanical indicators in the crossing area are determined. The soil layer that the shield section tunnel mainly passes through is: the ④ _1st layer saturated soft cohesive soil (partially the ⑤ _1st layer). All are saturated cohesive soils with high water content, high compressibility, low strength and low permeability. They have high sensitivity and obvious thixotropic characteristics. Under dynamic action, they are very easy to destroy the soil structure and reduce the soil strength suddenly. , easily lead to instability of the excavation face.

(2) The total crossing length of the shield is about L _d = 200m, the buried depth of the tunnel in the interval is H _min ~ H _max = 8.5m ~ 9.1m, and the distance between the underground structure and the tunnel is L _min ~ L _max = 3.8m ~ 12.4 m, buried depth at the top of the tunnel H=9m, tunnel diameter D=6.2m. The vertical slope ratios of the interval tunnel and the underground diaphragm wall are both about 9%, so the vertical relative position relationship between the interval tunnel and the underground diaphragm wall does not change much during the entire lateral crossing process. Attached drawing 1 is a plan view of the side of the shield passing through the underground diaphragm wall at short distance, and Fig. 2 is a cross-sectional view of the side of the shield passing through the underground diaphragm wall at short distance.

(3) ① Establish a three-dimensional finite element model. The horizontal direction of the model is 60m, the depth direction is 50m, the length is 200m, and the distance between the bottom of the tunnel and the bottom of the model is 15m. Numerical simulation is carried out on the whole passing process of the shield passing through the underground structure at close range. Calculations show that by setting appropriate construction parameters, the maximum surface displacement can be controlled within -16mm ~ +6mm; the cumulative maximum displacement of underground structures can be controlled within: -10mm ~ +10mm, and the single maximum change value can be controlled within: - 3mm～+3mm; and the volume of the plastic zone can be easily controlled at V=0, so the smooth crossing can be realized without taking additional reinforcement measures for the soil or underground structures.

②Analyze the results of finite element calculations from multiple angles, and determine that the scope of the shield TBM’s impact on the underground diaphragm wall during short-distance crossing is L _e = 60m, and the crossing section that needs to be protected is the distance from the shield receiving well L _i = 30m range.

(4) For the key protection range of L _i =30m determined in step (3), on-site monitoring is carried out when the shield passes through at close range, and the stress and deformation properties of the on-site soil, underground diaphragm wall and inner lining structure are observed. The ground surface displacement is observed with a total station theodolite and a level, the displacement of the adjacent underground diaphragm wall and soil mass is observed with an inclinometer, the internal force change of the lining wall is observed with a steel stress gauge, and the pressure change in the soil is observed with an earth pressure cell and a pore water pressure gauge observe. Accompanying drawing 3 is the plane layout of observation points for surface settlement, and accompanying drawing 4 is the plane layout of steel bar stress gauges, inclinometer pipes, pore water pressure gauges, and soil pressure gauges. The facade layout of the pressure gauge, and attached drawing 6 is the facade layout of the steel bar stress gauge.

(5) The first 20 rings in the key protection area are used as the trial excavation interval for crossing the pipeline. It is preliminarily determined that in the construction process of the shield tunneling through the diaphragm wall, the pressure of the soil bin is set at 0.16MPa-0.25MPa; the grouting pressure is set at 0.28MPa-0.3MPa; the grouting amount for each stroke (1.2m) is 2.0m ³ ~ 3.3m ³ ; the propulsion speed should be controlled at 15mm/min ~ 30mm/min, excavation at a constant speed, and continuous operation for 24 hours.

(6) The monitoring information during the whole propulsion process shows that the impact of shield tunneling on the underground diaphragm wall is relatively stable, and only a few special cases have occurred. When the shield passed the first pore water pressure gauge measurement point, it was found that the readings of the pore water pressure gauge fluctuated sharply and in a large range. At the same time, the monitoring of the surface settlement showed that the surface began to bulge here, and the displacement of the underground diaphragm wall changed. Reached 4.8mm. The abnormal reading of the pore water pressure gauge is due to the fact that the advancing speed of the shield machine is too fast at this time, and the pore water pressure continuously accumulates in the enclosed space and cannot be dissipated immediately, resulting in a sharp rise in pressure. Based on this phenomenon, the countermeasures of temporary suspension of push were taken during construction, and the advance was continued after the accumulated pore water pressure dissipated. Afterwards, the propulsion process was also changed to adopt the measures of advancing during the day and stopping at night to fully dissipate the pore water pressure and ensure the smooth progress of the subsequent propulsion. The on-site monitoring data is analyzed and summarized, and the final construction parameters for the shield passing through the underground diaphragm wall at close range are given: the set value of earth pressure: 210kPa, and the actual earth pressure is controlled below 200kPa during normal advance; advance speed: 20mm/ min; unearthed volume: 37.88m ³ ; total thrust of shield machine: 12750kN; grouting pressure: 0.56MPa, grouting volume: 3.0m ³ .

(7) After the shield machine successfully passed through the underground diaphragm wall and entered the shield receiving well, tracking and monitoring showed that the range of changes in surface settlement, soil displacement, earth pressure, and pore water pressure gradually decreased, and finally reached stability. The internal force of the underground diaphragm wall There is no change in deformation and deformation, and the entire traversal process is successfully completed.

In this embodiment, during the shield tunneling process, the surface subsidence value varies in the range of -2.9mm to +2.6mm; the cumulative value of the horizontal displacement of the soil ranges from -28.9mm to +17.5mm, and the maximum change value is -10.3mm; The change value of the earth pressure is 208kPa; the maximum change value of the pore water pressure is 159kPa; the maximum cumulative value of the horizontal displacement of the adjacent underground diaphragm wall is +12.8mm, and the maximum change value is +4.8mm; the internal force of the inner wall reinforcement is -0.07kN/ Change within the range of m ² ~0.89kN/m ² . It can be seen from the monitoring results that by adopting the protective measures of the present invention, the shield construction has less impact on the surrounding environment, and at the same time, the smooth excavation of the shield is guaranteed. In addition, the displacement and internal force of the adjacent underground structure are at a relatively low level, and this embodiment plays a very good role in protecting the adjacent underground structure.

Claims (9)

1. A kind of method for the close-range construction protection underground structure of side of single circle shield, it is characterized in that, comprises the following steps: (1) The Robertson method is used to detect the penetration resistance of the formation and the variation curve of pore water pressure with depth by pore water pressure static sounding; then the ratio of the measured pore water pressure to penetration resistance is taken as the horizontal axis, Taking the ratio of penetration resistance to initial formation stress as the vertical axis, draw a relational diagram, and divide the diagram into several areas with different soil properties, each of which represents a type of soil; Mark on this map to judge the type of soil layer of the site; then compare the penetration resistance curve and pore water pressure distribution curve according to the type of soil to determine the depth and thickness of the soil layer distribution, including the buried depth of sandy soil under the cohesive soil layer; (2) According to the design drawings of the underground structure and tunnel, determine the total length L _d meters of the shield tunnel passing through the underground structure, the buried depth of the interval tunnel H _min ~ H _max meters, and the mutual distance between the underground structure and the shield tunnel L _min ~ L _max m, the buried depth of the top of the tunnel is H meters, and the diameter of the tunnel is D meters; (3) Using a three-dimensional finite element model to numerically simulate the entire passing process of the shield through the underground structure at close range; (4) for step (3) determined by numerical simulation key protection crossing section L _m , formulate monitoring scheme, before crossing construction, carry out measuring point arrangement and monitoring on the spot; (5) Combining with the influence range L _e of the shield tunneling on the underground structure determined by the finite element analysis in step (3), the first 20 rings from the key protected crossing section L _i meters are used as the trial tunneling interval of the shield; at the same time, the trial tunneling Arrange a number of monitoring points in the interval to test the work efficiency of the test push and select the construction parameters; (6) In the process of shield tunneling through the L _i meter section of the key protection area, the method of closely combining on-site monitoring and construction is adopted, and construction is carried out through real-time monitoring feedback analysis; (7) After the shield machine passes through the underground structure smoothly, track and monitor the set monitoring points until the monitoring data stabilizes within the range of the optimized safe construction parameters described in step (6). 2. the method for the close-range construction protection underground structure of single circle shield side according to claim 1, it is characterized in that, the numerical simulation described in step (3), adopts three-dimensional finite element model range: horizontal direction should be greater than (2H +3D+L _min ) meters, the depth direction should be greater than (2H+2D) meters, the length is based on the actual size of the underground structure, the tunnel is placed in the middle of the model, and the distance between the bottom surface and the bottom of the tunnel is greater than 2D meters; the boundary conditions are set as follows: inside the tunnel The free boundary is used, the horizontal displacement is constrained on both sides of the model, and the vertical and horizontal displacement are constrained at the bottom of the model. The constitutive relationship of the soil adopts the modified Cambridge model considering elastic-plastic strain, and the tunnel structure is taken as an elastic body. 3. the method for the close-distance construction protection underground structure of single circle shield side according to claim 2, it is characterized in that, by the numerical simulation described in step (3), the obtained result is: ①Give the feasibility of judging the smooth crossing of the shield tunneling machine, soil mass and underground structure during the crossing construction process: ②Determine the range L _e meters in which the short-distance crossing of the shield tunnel will affect the underground structure, and the underground structure needs to be protected in the crossing section L _i meters during the crossing process. 4. The method according to claim 3 for the protection of underground structures by close-distance construction on the side of a single-circle shield, characterized in that, the condition for judging the feasibility of the smooth passage of the shield should be satisfied: surface displacement: -30mm～ +10mm; underground structure displacement: cumulative value: -15mm～+15mm, single maximum change value: -5mm～+5mm; underground structure plastic zone volume: under the condition of V=0, there is no need to make specific area soil and underground Take any reinforcement measures for the structure. 5. the method for the close-range construction protection underground structure of single round shield side according to claim 1, is characterized in that, the monitoring described in step (4), comprises: ① Soil displacement, pore water pressure and earth pressure between tunnel and underground structure; ② Displacement and stress of the underground structure near the shield crossing section; ③Surface settlement in the direction of the tunnel cross section and along the direction of the tunnel axis and the settlement of important buildings in the key crossing section. 6. The method according to claim 1, wherein the side construction of the single-circle shield at close range protects the underground structure, wherein the work efficiency of the detection test push described in step (5) means that the arrangement is parallel to the tunnel axis and perpendicular to the tunnel axis. As for the surface settlement monitoring points of the tunnel axis, the corresponding horizontal displacement monitoring points are arranged on the underground structure. 7. the method for the protection of underground structures by close-distance construction on the side of the single-circle shield according to claim 1, characterized in that, the selection of construction parameters described in step (5) means that by trial advancement, it is initially determined that the short-distance passes through the underground The construction parameters to be used in the structure include: shield thrust, propulsion speed, grouting amount, and grouting pressure. 8. the method for the close-range construction protection underground structure of single round shield side according to claim 1, it is characterized in that, the real-time monitoring feedback analysis described in step (6) refers to whether the previous step construction technology and construction parameters are judged Meet expected requirements to determine and optimize safe construction parameters. 9. The method for close-range construction protection of underground structures on the side of a single-circle shield according to claim 8, wherein said determination and optimization of safe construction parameters include: ①Surface settlement: 30mm～+10mm; ②Soil horizontal displacement: cumulative value: -30mm～+30mm, single maximum change value: -15mm～+15mm; ③Earth pressure: 250kPa; ⑤ Pore water pressure: 200kPa; ⑥Underground structural stress: -10kN/m ² ～10kN/m ² ; ⑦Underground structure displacement: cumulative value: -15mm～+15mm, single maximum change value: -5mm～+5mm.

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