Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an early warning treatment method for a construction accident of pile foundation impact hole forming in a karst development area. The method can effectively warn construction accidents possibly occurring in the process of pile foundation impact hole forming in the karst development area, and workers can perform corresponding risk treatment, thereby obviously reducing the occurrence probability of the construction accidents, improving the construction efficiency of pile foundation hole forming, saving the fund and shortening the construction period.
The technical scheme for solving the technical problems is as follows: a pre-warning treatment method for a construction accident of pile foundation impact hole forming in a karst development area comprises the following steps:
step 1: geotechnical engineering drilling
Performing geotechnical engineering drilling in a karst development area to obtain drilling hole information;
step 2: three-dimensional geological information modeling
According to the drilling information obtained in the step 1, modeling a covering layer of the bedrock, the bedrock and a karst cave in the bedrock respectively to obtain a three-dimensional geological information model; wherein, the covering layer of the bedrock is modeled by adopting a common Kriging method, and the bedrock and the karst cave inside the bedrock are modeled by adopting an indication Kriging method;
and step 3: pile foundation impact hole-forming risk prejudgment
Obtaining the hole height, distribution and communication conditions of the karst cave in the pile foundation hole forming range through the three-dimensional geological information model obtained in the step 2; calculating the included angle between the bedrock surface and the horizontal plane in the pile foundation pore-forming range through a three-dimensional geological information model; obtaining the distribution condition of the half rocks within the pore-forming range of the pile foundation through a three-dimensional geological information model;
and 4, step 4: risk management for pile foundation pore-forming
Treatment for a single cavern: when the height of the karst cave is less than 1m and the karst cave is not communicated with other karst caves, treating according to a first preset scheme; when the height of the karst cave is less than 1m and is communicated with other karst caves, or the height of the karst cave is more than or equal to 1m, treating according to a second preset scheme;
treating the beaded karst cave: treating according to a third preset scheme;
treatment for the molten bath or the inclined rock: after the impact hammer falls, observing whether a steel wire rope connected with the impact hammer deviates from the center of the pile hole, and if not, treating according to a fourth preset scheme; if the deviation exists, treatment is carried out according to a fifth preset scheme;
treatment for the half rocks: when the height of the half rock is more than or equal to 5m, adjusting the pile foundation to avoid the half rock; and when the height of the half rocks is less than 5m, treating according to a treatment method aiming at the molten bath or the inclined rocks.
The principle of the early warning treatment method for the pile foundation impact pore-forming construction accident in the karst development area is as follows:
firstly, in step 1 of the invention, the drilling stratum information is layered information obtained according to original records after the drilling of the worker, and comprises the step of layering a covering layer on the upper part of the bedrock to obtain a drilling columnar section result. And rearranging the drilling serial number, the X coordinate, the Y coordinate, the corresponding top elevation of the rock-soil layer or the karst cave, the corresponding bottom elevation of the rock-soil layer or the karst cave and the orifice elevation of each drill hole into an Excel table according to the drilling columnar profile result.
The overburden, known by overburden, refers to loose accumulations, deposits of various origins overlying bedrock, such as gravel layers of sand eggs, sand layers, artificially filled gravel bodies, and the like. According to the particle size, compactness, porosity ratio and the like of the covering layer, the covering layer is layered and divided into a ploughing soil layer, a miscellaneous filling soil layer, a powdery clay layer, a slightly weathered limestone layer, a medium weathered limestone layer, a sand gravel layer, a pebble layer, a floating stone layer and the like.
In the same region, a plurality of drilling data need to be obtained, the more the drilling points are, the higher the precision of the three-dimensional geological information modeling of the step 2 is, and the better the pile foundation impact pore-forming risk pre-judgment of the step 3 and the pile foundation pore-forming risk treatment effect of the step 4 are. The invention is suitable for pile group foundations, in particular for the situation that a plurality of rows of pile foundations are arranged under one bearing platform of a building, because in the construction stage, each pile needs to be drilled for geotechnical engineering investigation, and correspondingly, more drilling data are obtained.
The second point, step 2 of the present invention, is modeling based on the drilling data of step 1. And modeling the covering layer of the bedrock by adopting a common Kriging method, and constructing the contact surfaces of every two adjacent rock-soil layer supports. And modeling the bedrock and the karst cave in the bedrock by adopting an indication Krigin interpolation method to obtain a three-dimensional geological information model. And 2, obtaining a three-dimensional geological information model of the karst development area, realizing visualization of karst caves, cracks and rock surface fluctuation conditions in the pile foundation pore-forming range, prompting the risks of accidents such as hole deviation, slurry leakage, drill sticking, hole collapse and the like, guiding pile foundation pore-forming construction, helping workers to optimize pile foundation design, and avoiding extremely unfavorable geological phenomena such as half rocks, bead-shaped karst caves and the like from the pile foundation design.
Kriging interpolation methods include normal kriging, simple kriging, pan-kriging, cooperative kriging, log normal kriging, indicator kriging, probability kriging, and disjunctive kriging. The common kriging method is also called a spatial local interpolation method, and is a method for carrying out unbiased optimal estimation on regional variables in a limited region on the basis of a variation function theory and structural analysis. The essence of the ordinary kriging method is that the linear unbiased and optimal estimation is carried out on unknown sampling points by utilizing the original data of the regionalized variables and the structural characteristics of the variation function. The application range of the common kriging method is that the regional variables have spatial correlation, namely if the results of the mutation function and the structural analysis show that the regional variables have spatial correlation, the kriging method can be used for interpolation or extrapolation; otherwise, it is not feasible. However, in the prior art, no report exists on the use of the ordinary kriging method for overburden modeling of bedrock. The invention considers that the overburden of the bedrock is formed by geological action and has obvious spatial correlation, so that interpolation and extrapolation by adopting a common Kriging method are feasible. The covering layer on the upper part of the bedrock has no folds, the boundary line between layers is smooth, and the modeling by adopting the common Kriging method has higher precision. For special geological structures such as invaded rocks, karst caves and the like, the geological structures cannot be modeled by using a common kriging method, and an indication kriging method needs to be introduced to solve the problem.
The Indicator Kriging method (Indicator Kriging) is a non-parametric geostatistics method, converts the research on regionalized variables into the research on Indicator functions thereof, and is an improvement of the common Kriging method. Compared with the common kriging method, the indication kriging method does not require regional variables to meet inherent assumptions, allows the special values actually existing in the researched geological region to directly obtain the cumulative integral distribution function of each point to be estimated, and constructs a probabilistic geological model under certain risk conditions. In the prior art, no report exists for using the indication kriging method for matrix rock and karst cave modeling in the matrix rock. The invention considers that the karst development is caused by the fact that water flows among rocks to carry away rock substances, although the karst development has certain regularity macroscopically, the distribution of karst development phenomena such as karst caves, cracks, karst troughs, half rocks and the like has the characteristics of spatial attribute variation and discontinuity, and therefore, interpolation and extrapolation by adopting an indication Krigin method are feasible. The bedrock and the karst cave in the bedrock are modeled by an indication Kriging method, so that the model precision is higher.
Thirdly, in the step 3 of the invention, the risk of the construction accident which may happen is pre-judged according to the three-dimensional geological information model obtained in the step 2, and measures are prepared in advance.
The half rock is a geological phenomenon that one side is rock and the other side is filling materials such as clay and gravel. The karst development area often meets the half rock, because rock hardness, intensity are high, and filler hardness and intensity such as clay, gravel are less than the basement rock, and when the pile foundation impacted the pore-forming met half rock, the impact hammer can incline to filler one side. In order to ensure vertical hole forming, the rubble needs to be continuously backfilled and repeatedly punched and hammered. The existing automatic pile driver is commonly used in pile foundation construction, if backfilling is not timely, pore-forming inclination is easily caused, and the treatment after pore-forming inclination is extremely time-consuming. The geological condition of the half-edge rock can be visually found through the three-dimensional geological information model so as to take measures in advance in the pore-forming construction process.
And (4) calculating the included angle between the bedrock surface and the horizontal plane in the pile foundation pore-forming range, and adopting the theorem of a three-vertical-line method. The theorem refers to a straight line in a plane that, if perpendicular to the projection of a diagonal line through the plane at the plane, is also perpendicular to the diagonal line.
Fourthly, in the step 4 of the present invention, the string-bead cave refers to a series of string-bead cave groups formed by karst action, and the string-bead cave groups have a plurality of larger chambers, and the chambers are connected by narrower tunnels.
The dissolving tank is formed by dissolving and eroding surface water along the joint cracks of the erodable rock to form criss-cross grooves with large depth and multiple grooves on the surface of the bedrock.
The sloping rock is the condition that the fluctuation of bedrock is large and the included angle between the bedrock and the horizontal plane is more than 10 degrees. When strikeing the pore-forming and meet the solution tank or the sloping rock, pile foundation operating personnel if do not notice, perhaps do not handle in time, will cause the pile foundation pore-forming slope.
In conclusion, the method can effectively warn construction accidents possibly occurring in the process of pile foundation impact hole forming in the karst development area, and workers can perform corresponding risk treatment, thereby obviously reducing the occurrence probability of the construction accidents, improving the construction efficiency of pile foundation hole forming, saving the fund and shortening the construction period.
The early warning treatment method for the construction accident of pile foundation impact hole forming in the karst development area has the beneficial effects that:
1. the invention carries out early warning treatment on the basis of geotechnical engineering drilling, does not additionally increase the workload of geotechnical engineering investigation, saves time and labor and has obvious effect.
2. The invention solves the defects that the drilling method in the prior art can not fully reveal the karst cave distribution, the bedrock surface inclination and the like in the karst development area, and can clearly see the karst development condition in the pile foundation pore-forming range. The staff can be according to the karst development condition construction accident that probably appears in the pile foundation pore-forming in-process of prejudging in advance, and the staff can carry out corresponding risk punishment, is showing the emergence probability that reduces the construction accident, improves the efficiency of construction of pile foundation pore-forming, practices thrift the fund, reduction of erection time.
3. The method is simple and intuitive, easy to operate and strong in guidance, and can guide pile foundation operators to carry out construction and guide designers to recheck and correct pile foundation design.
4. The invention can reduce the probability of construction accidents within the range of pile foundation impact hole forming, and can also be used for pile foundation construction organization design. The principle of the pile foundation construction organization design in the karst development area is that the pile foundation with high construction difficulty is constructed firstly, and the pile foundation with low construction difficulty is constructed later, and meanwhile, different hole forming methods can be adopted according to the karst development condition of the pile foundation hole forming range, if no karst cave exists in the pile foundation hole forming range, and when the pile length is small, the efficiency can be improved by adopting a rotary drilling hole forming mode, and when the karst cave is more, the impact hole forming mode is required.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, in step 1, the drilling hole plane position is set at the center of the pile foundation.
The adoption of the further beneficial effects is as follows: and the data is shared with the construction survey of the pile foundation, so that the survey cost is not additionally increased.
Further, in step 1, the drilling information includes a drilling number, an X coordinate, a Y coordinate, an orifice elevation, a top elevation of the corresponding rock-soil layer or the karst cave, and a bottom elevation of the corresponding rock-soil layer or the karst cave of each drill hole.
The adoption of the further beneficial effects is as follows: and (3) obtaining the drilling information, and facilitating the subsequent three-dimensional geological information modeling of the step (2).
Further, in the step 3, when the included angle is larger than 10 degrees, putting rubbles into the pile hole, and performing deviation rectification treatment; when the included angle is less than or equal to 10 degrees, the correction processing is not needed.
The adoption of the further beneficial effects is as follows: when the included angle between the rock surface and the horizontal plane is larger than 10 degrees, inclined holes are easy to be caused when the rock is impacted into the pile hole, and therefore, the rubble needs to be thrown into the pile hole to perform deviation rectification treatment. When the included angle is less than or equal to 10 degrees, the inclined hole phenomenon is not easy to occur generally, and the deviation rectification treatment is not needed. The fact that the included angle is 10 degrees is determined to be a boundary point is obtained by summarizing the inventor according to the construction records of more than 300 pile foundations, and the method has practical application significance.
Further, in step 4, the first preset scheme specifically includes: observing whether slurry leaks or not, and if the slurry leaks, punching the punching hammer through the karst cave and vertically entering bedrock below the karst cave;
and if the slurry leakage condition exists, replenishing the slurry in time, putting a mixture of the rubbles and the clay into the pile hole until the mixture exceeds the top of the karst cave by 1-2 m, and then continuously punching the punching hammer until the punching hammer penetrates through the karst cave and vertically enters the bedrock below the karst cave.
The adoption of the further beneficial effects is as follows: by adopting the scheme, the treatment of the single karst cave with the height of less than 1m and without being communicated with other karst caves can be realized.
And (4) observing whether slurry leaks or not, if the slurry leaks, adopting a mode of frequently lifting the drill and lightly dropping the hammer to punch the hammer to penetrate through the karst cave and vertically enter the bedrock below the karst cave. And if the slurry leakage condition exists, replenishing the slurry in time, putting a mixture of the rubbles and the clay into the pile hole until the mixture exceeds the top of the karst cave by 1-2 m, and then continuously punching the punching hammer until the punching hammer penetrates through the karst cave and vertically enters the bedrock below the karst cave. Generally, whether the slurry leaks or not is judged by observing the change of the slurry surface of the pile foundation hole forming slurry. When the heavy hammer impacts the karst cave, if the pile foundation hole-forming slurry surface suddenly drops, slurry leakage occurs.
Furthermore, the volume ratio of the flaky stones to the clay is (2-4): 1.
The further beneficial effects of the adoption are as follows: by adopting the parameters, the plugging effect is better.
Further, in step 4, the second preset scheme specifically includes: observing whether slurry leaks or not, and if the slurry leaks, backfilling the rubbles until the rubbles exceed the top of the karst cave by 1-2 m;
if the slurry leakage condition exists, replenishing slurry in time, putting a mixture of rubbles and clay into the pile hole until the mixture exceeds the top of the karst cave by 1-2 m, and then continuously punching and observing whether a steel wire rope connected with a punching hammer deviates from the center of the pile hole; if the deviation does not exist, punching the punching hammer until the punching hammer penetrates through the karst cave and vertically enters the bedrock below the karst cave; and if the deviation exists, stopping punching, backfilling the flaky stones, or backfilling a mixture of the flaky stones and the clay until the distance exceeds 1m-2m of the top of the karst cave, and punching the punching hammer to penetrate through the karst cave and vertically enter the bedrock below the karst cave.
The adoption of the further beneficial effects is as follows: by adopting the scheme, the treatment of a single karst cave with the cave height of less than 1m and communicated with other karst caves or with the cave height of more than or equal to 1m can be realized.
Furthermore, the volume ratio of the flaky stones to the clay is (2-4): 1.
The further beneficial effects of the adoption are as follows: by adopting the parameters, the plugging effect is better.
Further, in step 4, the third preset scheme is any one of the following three methods:
the method comprises the following steps: adjusting the pile foundation to avoid the beaded karst cave;
the second method comprises the following steps: a full-casing method is adopted for follow-up, a steel casing penetrates through the beaded karst cave, and meanwhile, slurry is prevented from leaking into the beaded karst cave;
the third method comprises the following steps: and repeatedly backfilling the mixture of the rubble and the clay in the process of impacting and forming the hole until the punch hammer penetrates through the beaded karst cave and vertically enters the bedrock below the beaded karst cave.
The adoption of the further beneficial effects is as follows: by adopting the scheme, the treatment of the beaded karst cave can be realized. The first method can avoid the beaded karst cave in design, and avoids overhigh treatment cost and overlong construction period in construction; secondly, when the beaded karst cave cannot be avoided from the design, the full casing method is adopted for follow-up, and the construction time and the construction cost can be expected; the third method has lower requirements on equipment, can ensure that the formed holes are vertical, avoid hole deviation and avoid hole collapse and hammer blocking caused by slurry leakage.
Further, in step 4, the fourth preset scheme specifically is: the ram is punched through the fluid bowl or the diagonals and into the bedrock vertically below the fluid bowl or the diagonals.
The further beneficial effects of the adoption are as follows: by adopting the scheme, the steel wire rope can be treated without deviating from the molten bath or the inclined rock in the center of the pile hole.
Further, in step 4, the fifth preset scheme specifically is:
step A: backfilling rubbles in the pile hole until the rubbles exceed the top of the deflection section by 1-2 m, continuously punching and observing whether a steel wire rope connected with a punching hammer deviates from the center of the pile hole;
and B: if the deviation does not exist, punching the punching hammer until the punching hammer penetrates through the solution tank or the inclined rock and vertically enters the bedrock below the solution tank or the inclined rock; if so, repeating step A until the hammer passes through the fluid bowl or the diagonals and vertically enters the bedrock below the fluid bowl or the diagonals.
The further beneficial effects of the adoption are as follows: by adopting the scheme, the treatment of the steel wire rope deviating from the molten bath or the inclined rock at the center of the pile hole can be realized.
Detailed Description
The principles and features of this invention are described below in conjunction with the following detailed drawings, which are given by way of illustration only and are not intended to limit the scope of the invention.
Example 1
The academic bridge of this embodiment is located Guangxi Guilin City Yangshou county new city district, and the common design has 44 pile foundations, discovers that this region has great solution cavity in the preliminary investigation of geotechnical engineering.
The early warning treatment method for the pile foundation impact pore-forming construction accident in the karst development area of the bridge of the college comprises the following steps:
step 1: geotechnical engineering drilling
Carrying out geotechnical engineering drilling in a karst development area, wherein 44 exploration holes are arranged in a pile foundation exploration field in total, the number of the exploration holes is QK 1-1-QK 44-1, drilling is carried out by adopting one pile and one hole, and the plane position of a drilling hole is positioned in the center of the pile foundation. The results of drilling the pillar-shaped cross-section are shown in Table 1, which is only an example of QK3-1, because the data is too numerous to be listed.
TABLE 1 drilling columnar Profile results
According to table 1, the drill hole number, X coordinate, Y coordinate, hole opening elevation, top elevation of the corresponding rock-soil layer or cavern, and bottom elevation of the corresponding rock-soil layer or cavern of each drill hole are compiled in an Excel table in the order of table 2.
TABLE 2
Step 2: three-dimensional geological information modeling of karst development zone
Screening out a matrix covering layer from the Excel table compiled in the step 1, converting the matrix covering layer into PGF files by using a Generator PGF File tool in an EVS, repeating the same steps to Generate PGF files of the matrix and karst caves in the matrix at the lower part, carrying out sequence division on the PGF files of the covering layer of the matrix by using make _ geo _ hierarchy to Generate GMF files, inputting the GMF files into a krig _3d _ geology module (a common kriging interpolation method) to adjust the grid precision, carrying out spatial difference calculation by using a 3d _ geology _ map module to Generate a stratum model of the covering layer of the matrix, carrying out lithology modeling on the corresponding PGF files by using an indicator _ geology module (an indication kriging interpolation method) on the matrix and the karst caves in the matrix, and finally extracting and integrating the boundary by using a subset _ layers module. A final three-dimensional geological model is obtained as shown in figure 2. The two rectangular boxes in the figure represent karsts with a hole height ≧ 5 m.
And step 3: pile foundation impact hole-forming risk prejudgment
Obtaining the hole height, distribution and communication conditions of the karst cave in the pile foundation hole forming range through the three-dimensional geological information model obtained in the step 2; calculating the included angle between the bedrock surface and the horizontal plane in the pile foundation pore-forming range through a three-dimensional geological information model; and obtaining the distribution condition of the half rocks within the pile foundation pore-forming range through the three-dimensional geological information model.
In a three-dimensional geological information model of a bridge of a college, two positions are found to have larger karst caves, the karst caves belong to drilling areas of QK 2-1-QK 8-1, the karst caves are fully filled or semi-filled with fluid plastic clay, the areas touch the caves and a silt soft soil layer, the karst and the development thereof, the limestone development and the beaded caves, the individual caves are larger, and the caves are communicated. In addition, the fact that the QK3-1 has a large soil-dissolving hole is found, in order to accurately find the range of the large soil-dissolving hole, 2 drill holes are additionally arranged near the QK3-1, the three-dimensional geological information model with higher accuracy is built again after data of new drill holes are arranged and added, and the geology of the position of the pile foundation at the QK3-1 is independently displayed, as shown in figure 3. The maximum soil cave height at the QK3-1 position is found to be 11.1m, the maximum soil cave height appears in the section of 5.4-16.5m of the QK3-1 drilling hole, the inner part is half filled with the fluid plastic clay, and the filler is contained below 10.00m, so that engineering problems such as hole collapse, slurry leakage and the like can occur on the pile foundation at the QK3-1 position. Meanwhile, the maximum included angle between the bedrock rock face and the horizontal plane at the pile foundation is 11 degrees and exceeds 10 degrees of a boundary point, so that the problem that the construction drill bit deviates from the direction due to uneven stress at the inclined rock face can occur.
And 4, step 4: risk management for pile foundation pore-forming
And (4) pre-judging a matching treatment scheme according to the pile foundation impact pore-forming risk in the step (3). Due to the fact that local financial income is limited, when a pile foundation treatment scheme is selected, the disposal cost is considered preferentially, and therefore the karst cave treatment method of the bridge of the college adopts a method of backfilling a mixture of rubbles and clay.
In the aspect of construction organization design, a difficult-before-easy sequence is adopted, and the problem that the whole progress is influenced by overlong individual difficult pile foundation hole forming time is avoided. The construction method comprises the steps of firstly constructing the pile foundations at the positions of QK 2-1-QK 8-1, wherein the hole forming time of each pile foundation is more than 40 days, then constructing other pile foundations, and finally completing the construction of all the pile foundations in 6 months.
In the karst cave treatment, an assembling manipulator is pre-used for meeting the conditions of the development details of the karst of the pile, the elevation of the inclined pile and the like before the pile foundation is drilled. When the pile foundation punching hole is close to the karst cave, clay, stones and an excavator are prepared.
Treatment for a single cavern: when the height of the karst cave is less than 1m and the karst cave is not communicated with other karst caves, treating according to a first preset scheme; when the height of the karst cave is less than 1m and is communicated with other karst caves, or the height of the karst cave is more than or equal to 1m, treating according to a second preset scheme; treating the beaded karst cave: and treating according to a third preset scheme.
Wherein, the first preset scheme specifically comprises: observing whether slurry leaks or not, and if the slurry leaks, punching the punching hammer through the karst cave and vertically entering bedrock below the karst cave;
and if the slurry leakage condition exists, replenishing the slurry in time, putting a mixture of the rubbles and the clay into the pile hole until the mixture exceeds the top of the karst cave by 1-2 m, and then continuously punching the punching hammer until the punching hammer penetrates through the karst cave and vertically enters the bedrock below the karst cave.
The second preset scheme specifically comprises the following steps: observing whether slurry leaks or not, and if the slurry leaks, backfilling the rubbles until the rubbles exceed the top of the karst cave by 1-2 m;
if the slurry leakage condition exists, replenishing slurry in time, putting a mixture of rubbles and clay into the pile hole until the mixture exceeds the top of the karst cave by 1-2 m, and then continuously punching and observing whether a steel wire rope connected with a punching hammer deviates from the center of the pile hole; if the deviation does not exist, punching the punching hammer until the punching hammer penetrates through the karst cave and vertically enters the bedrock below the karst cave; and if the deviation exists, stopping punching, backfilling the flaky stones, or backfilling a mixture of the flaky stones and the clay until the distance exceeds 1m-2m of the top of the karst cave, and punching the punching hammer to penetrate through the karst cave and vertically enter the bedrock below the karst cave.
The third preset scheme is any one of the following three methods:
the method comprises the following steps: adjusting the pile foundation to avoid the beaded karst cave;
the second method comprises the following steps: a full-casing method is adopted for follow-up, a steel casing penetrates through the beaded karst cave, and meanwhile, slurry is prevented from leaking into the beaded karst cave;
the third method comprises the following steps: and repeatedly backfilling the mixture of the rubble and the clay in the process of impacting and forming the hole until the punch hammer penetrates through the beaded karst cave and vertically enters the bedrock below the beaded karst cave.
Example 2
The total length of the whole bridge of the Persen Yangjiang grand bridge is 2578.97m, the main bridge is designed into a prestressed concrete short-tower cable-stayed bridge of 145m +280m +145m, and the bridge is the Asian maximum span of the same type of bridge. The geological karst in the main pier bridge site area of the Xiangzhou bank is highly developed, the boulder covering layer is as thick as 10m, the bedrock is high and complete, the compressive strength is high, and 104 karst caves which are different in size and mutually communicated are distributed in the positions where the 24 pile foundations are located in the investigation. In order to ensure the smooth construction, a three-dimensional geological information model is established to guide the construction of the pile foundation.
The early warning treatment method for the pile foundation impact hole forming construction accidents in the karst development area of the major pier bridge site area of the Xiangzhou bank comprises the following steps:
step 1: geotechnical engineering drilling
Carrying out geotechnical engineering drilling in a karst development area, wherein 24 exploration holes are arranged in a pile foundation exploration field in total, the number of the exploration holes is ZKZ-1-ZKZ-24, drilling is carried out by adopting one pile and one hole, and the plane position of a drilling hole is positioned in the center of the pile foundation. The results of drilling the cylindrical sections are shown in Table 3, which is only an example of ZKZ-13, because the data is too numerous to be listed.
TABLE 3 drilling columnar Profile results
According to table 3, the drill hole number, X coordinate, Y coordinate, hole opening elevation, top elevation of the corresponding rock-soil layer or cavern, and bottom elevation of the corresponding rock-soil layer or cavern of each drill hole are compiled in an Excel table in the order of table 4.
TABLE 4
Step 2: three-dimensional geological information modeling of karst development zone
Screening out a matrix covering layer from the Excel table compiled in the step 1, converting the matrix covering layer into a PGF File by using a Generator PGF File tool in an EVS (event-driven System), repeating the same steps to Generate PGF files of a karst cave in a matrix and a matrix at the lower part, carrying out sequence division on the PGF files of the covering layer of the matrix by using make _ geo _ hierarchy to Generate GMF files, inputting the GMF files into a krig _3d _ geology module (common kriging interpolation method) to adjust the grid precision, carrying out spatial difference calculation by using a 3d _ geology _ map module to Generate a stratum model of the covering layer of the matrix, modeling the PGF files corresponding to the karst cave in the matrix and the matrix by using an indicator _ geology module (indicating kriging interpolation method), and finally extracting and integrating boundaries by using a sublayer module to obtain a three-dimensional geological information model of a karst development zone, as shown in figure 3.
And step 3: pile foundation impact hole-forming risk prejudgment
Obtaining the hole height, distribution and communication conditions of the karst cave in the pile foundation hole forming range through the three-dimensional geological information model obtained in the step 2; calculating the included angle between the bedrock surface and the horizontal plane in the pile foundation pore-forming range through a three-dimensional geological information model; and obtaining the distribution condition of the half rocks within the pile foundation pore-forming range through the three-dimensional geological information model.
In the established three-dimensional geological information model of the main pier bridge site area of the Xiangzhou bank, ZKZ-1, ZKZ-9, ZKZ-12, ZKZ-15, ZKZ-16, ZKZ-18 and ZKZ-20 single drill holes can be found to disclose 6-7 karst caves, wherein the maximum difference between the top elevation and the bottom elevation of the karst caves in the drill holes is 7.4m, the karst caves appear in the section of 9.3-16.7m of the drill holes ZKZ-23, and loose fine sand-sandwiched pebbles are filled in the drill holes. ZKZ-2, ZKZ-3, ZKZ-4, ZKZ-5, ZKZ-7, ZKZ-8, ZKZ-11 and ZKZ-19, wherein the maximum difference between the elevation of the top of the cavern and the elevation of the bottom of the cavern in the drilling hole is 9.2m, and the cavern appears in a section of 30.4-39.6m of the drilling hole ZKZ-8 and is an empty cavern. ZKZ-6, ZKZ-10, ZKZ-13, ZKZ-14, ZKZ-17, ZKZ-21, ZKZ-22, ZKZ-23 and ZKZ-24, wherein the maximum difference between the top elevation and the bottom elevation of the karst cave in the drill hole is 14.5m, the karst cave is found in the section of 7.50-22.00m of the drill hole of ZKZ-23, and loose boulders, pebbles, gravel sand and cohesive soil are filled in the drill hole.
In the established three-dimensional geological information model, the geological condition in the pore-forming range of each pile foundation is checked, and the karst cave distribution condition is focused. As can be clearly seen from the model, extremely complicated and variable karst caves exist in the section of 8m-30m below the earth surface, and special attention is needed to construct the pile foundation in the section. The model was displayed separately for the pile foundations at ZKZ-10 drill holes, as shown in fig. 4. Because the construction drill bit can penetrate through a filling or semi-filling karst cave and is mixed with weathered limestone, plastic silty clay and the like in the middle, the maximum included angle between the bedrock rock surface and the horizontal plane at the pile foundation is 12 degrees and exceeds a boundary point of 10 degrees through calculation, so that the construction drill bit can cause uneven stress of the drill bit and deviation of the drill bit when the construction drill bit meets a soft and hard soil layer interface or an inclined rock surface.
And 4, step 4: risk management for pile foundation pore-forming
As the lateral karst cave of Xiangzhou is too developed strongly, the impact hole forming method is adopted, and the correction and filling of the karst cave are required to be repeatedly backfilled by a mixture of the rubble and the clay. The bridge is a bridge on a highway and is a key node for all-road traffic on time. In order to ensure the construction period, a construction unit abandons an impact hole forming method on a main bridge pile foundation and adopts a full-pile casing full-convolution method for construction, the construction cost is 3 times of that of the impact hole forming method, but the construction period is guaranteed.
Comparative example
The geological conditions of karst development areas are complex, and even if the geological conditions of different pile foundations of the same bridge are different, the designed pile lengths are different. The pile foundation is once formed, and repeated tests cannot be carried out. In order to verify the effect of the invention, the pile foundation construction of the scenic spot bridge and the scenic spot bridge near the college bridge is compared with the pile foundation construction of the college bridge. The sightseeing bridge is 1000m away from the college bridge and is completed 2 years earlier than the college bridge. The sightseeing two bridges are 500m away from the college bridge and are completed 1 year earlier than the college bridge. The three bridges are all positioned in the river basin of the countryside, and the development conditions of karst are similar.
The construction method comprises the steps that the large brow bridge is provided with 160 pile foundations, the second brow bridge is provided with 20 pile foundations, the large brow bridge and the second brow bridge are constructed by adopting a traditional method, namely, a reconnaissance hole is drilled in the center of each pile, and the percussion hole-forming method is adopted for construction according to a drilling cylindrical sectional view.
In the pile foundation construction of the scenic spot bridge, because a large number of inclined piles cannot be found in time, a large number of rubble and clay mixtures are backfilled for correcting the deviation, and the deviation is corrected by repeatedly punching and smashing. Only the usage amount of the rubble exceeds 10000m3Large amount of capital is consumed, the construction period is delayed, and the vehicle is communicated 1 year later than the scheduled completion dateAnd finally, great disputes are caused in engineering measurement.
The two bridge brows is collapsed for 2 times and causes 2 times of hammer clamping in the construction process, finally a diver is required to repeatedly dive and salvage collapsed objects, the construction period is delayed, and construction is finished after 20 pile foundations are always used for 1 year.
Therefore, the invention solves the defects that the drilling method in the prior art can not fully reveal the karst cave distribution, the bedrock surface inclination and the like in the karst development area, and can clearly see the karst development condition in the pile foundation pore-forming range. The staff can be according to the karst development condition construction accident that probably appears in the pile foundation pore-forming in-process of prejudging in advance, make sufficient counter measure in advance in the work progress, carry out corresponding risk treatment, effectively reduce the emergence probability of construction accident, improve the efficiency of construction of pile foundation pore-forming, practice thrift the fund, reduction of erection time.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.