An integrated method for directional excavation and ex-situ remediation of contaminated soil based on rotary digging pile technology

Abstract

The application discloses a kind of based on rotary digging pile technology's contaminated soil directional excavation and ex situ repair integration method.The present application belongs to the cross field of environmental engineering and geotechnical engineering, to solve deep>15m, range<100m 2 The traditional excavation of contaminated soil has high support cost, mud pollution, lack of real-time monitoring and the problem of cutting off excavation and repair, and an integrated system and method are provided.The system includes a rotary drilling rig, a multi-section full protection cylinder assembly, an online detection device and a remote monitoring terminal;The method is: after determining the pollution range, the drilling rig is in place and the detection device is modified, the full protection cylinder is buried, the pollutant data is monitored in real time while drilling to dynamically adjust the excavation parameters, and after excavation, the acceptance is determined, the clay or cement mixed clay is backfilled layer by layer, and the full pollution area is covered by full sleeve hole jumping lap rotary digging.The present application realizes accurate excavation, integrated operation shortens construction period by 50-70%, there is no mud pollution, and the support cost is reduced by 60-80%.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of environmental engineering and geotechnical engineering, specifically to an integrated method for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology. Background Technology

[0002] With the redevelopment and utilization of industrial sites, particularly those with greater than 15m depth and smaller area (less than 100m)... 2 The need for thorough removal and ex-situ remediation of contaminated soil is increasingly urgent. Currently, traditional excavation methods for treating such deep, small-scale contaminated soil mainly include shallow slope excavation, deep support layered excavation, and caisson methods. However, all these methods have significant limitations. Shallow slope excavation is limited by excavation depth and site space, making it ineffective in removing deep contaminants. While deep support layered excavation can operate to deeper areas, it requires the construction of complex support systems, resulting in high support costs, often accounting for 30-50% of the total project cost, and extending the construction period by more than 60% compared to conventional methods. Although the caisson method is technically mature, it has a long construction period and poor economic efficiency, typically increasing the unit cost by 40-60%. In addition, existing technologies such as CN115846384A disclose a minimally invasive excavation method using full-rotation sleeve drilling. Although it can reach a relatively large depth, it usually uses mud for wall protection and suspended particle removal during the construction process. The introduction of mud not only easily causes secondary pollution to the construction site environment, but also results in a relatively slow construction speed, making it difficult to meet the requirements of green construction.

[0003] More critically, existing technologies generally lack effective means for real-time monitoring of pollutants (such as VOCs and heavy metals) during the excavation process. The determination of the excavation range and depth often relies entirely on preliminary geological survey reports, making dynamic adjustments impossible based on the actual soil contamination levels. This "blind excavation" approach easily leads to inaccurate excavation scope, either increasing treatment costs due to over-excavation or leaving pollutant residues due to insufficient excavation. Furthermore, in existing technologies, excavation, groundwater extraction, acceptance, and backfilling are typically separate and independent steps, lacking an integrated solution. This increases project complexity and turnaround time, reducing overall remediation efficiency. Therefore, a highly efficient construction technology capable of achieving precise directional excavation, real-time monitoring, and integrated remediation is urgently needed. Summary of the Invention

[0004] The present invention aims to solve the technical problems of existing technologies when dealing with deep and small-area contaminated soil, such as high support costs, mud pollution, lack of real-time monitoring methods, and low efficiency caused by the disconnect between excavation and remediation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a system for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling technology, including a rotary drilling rig, a full casing assembly, an online detection device, and a remote monitoring terminal. The full casing assembly is configured to be vertically buried in the contaminated area to form an isolation space; the rotary drilling rig is equipped with a power head drive sleeve and a drill bit; the online detection device is installed on the power head drive sleeve and configured to collect soil data in real time during drill bit operation; the online detection device is connected to the remote monitoring terminal via a wireless communication module for transmitting the collected soil data.

[0006] Furthermore, the online detection device includes a real-time detection module, which is equipped with a sampling channel, a PID sensor, and an electrochemical sensor. The PID sensor is configured to detect the concentration of volatile organic compounds, and the electrochemical sensor is configured to detect the content of heavy metals. The data transmission module is configured to use a 4G or 5G wireless communication protocol to package and send the data collected by the sensors to a gateway device and then transmit it to the remote monitoring terminal. The full casing assembly is composed of multiple casing sections connected together, with the connection length covering the range from the ground to a preset pollution depth.

[0007] On the other hand, the present invention also provides a construction method based on the above system, including the following steps: determining the extent of contaminated soil exceeding the standard, and if necessary, determining the extent of contaminated groundwater exceeding the standard, and conducting surveying and setting out; positioning the rotary drilling rig, installing an online detection device on the power head drive sleeve, and burying the full casing assembly; then controlling the rotary drilling rig drill bit to rotate and start drilling, using the online detection device to monitor soil pollutant data in real time during the drilling process and transmitting it to a remote monitoring terminal, with the operator dynamically adjusting the excavation depth and range based on the real-time data; when the drill bit is full of soil, lifting it out of the hole and dumping it away; repeating drilling and excavation until the preset depth is reached, and cleaning the hole; taking fixed-point samples at the bottom of the hole for acceptance; after acceptance, backfilling with clay or clay mixed with cement in layers and compacting it; finally, pulling out the full casing assembly, moving the rotary drilling rig to carry out the construction of the next set of holes using the full casing skip-hole overlapping rotary drilling method, until the entire contaminated area is covered.

[0008] Compared with the prior art, the beneficial effects of the present invention are: 1. Achieving Precise Directional Excavation and Real-Time Monitoring: By adding an online detection device to the drive sleeve of the rotary drilling rig's power head, "excavation and testing" were achieved during the construction process. The system can provide real-time feedback on VOCs and heavy metal indicators, transmitting the data to a computer in real time. This allows construction personnel to dynamically adjust the excavation range based on the actual pollution situation, avoiding over-excavation or under-excavation caused by relying on preliminary surveys in traditional methods, and significantly improving the accuracy and efficiency of excavation.

[0009] 2. Integrated Process and Efficient Construction: This invention integrates excavation, groundwater extraction, sampling and testing, acceptance, and backfilling into a single construction process. Compared to traditional deep-support layered excavation, this method eliminates the need for a complex support system, significantly shortens the construction period, reduces construction risks, and enables immediate backfilling after excavation, minimizing the exposure time of the foundation pit.

[0010] 3. Environmentally friendly, low-carbon, and economically efficient: The full casing method eliminates the need for mud slurry wall protection, preventing secondary pollution of the site and enabling dry operation and clean construction. Furthermore, for deeper and smaller contaminated sites, this method significantly reduces support costs (by 60-80%) and earthwork transportation volume compared to caisson methods and deep foundation pit excavation, resulting in substantial economic benefits.

[0011] 4. Controllable quality: The full casing structure effectively prevents the risk of borehole collapse during deep drilling and can strictly isolate contaminated soil from the surrounding clean soil. The clean soil protection rate is high and the contaminated soil removal rate is high, ensuring that the remediation effect achieves the expected goal. Attached Figure Description

[0012] Figure 1 This is an installation diagram (test diagram) of the power head drive sleeve device of the present invention.

[0013] Figure 2 This is a front view of the power head drive sleeve device of the present invention.

[0014] Figure 3 This is a flowchart of the intelligent control process of the present invention.

[0015] Figure 4 This is an integrated flowchart of the present invention.

[0016] Figure 5 This diagram illustrates the arrangement of the excavation holes and the driving sequence for the rotary drilling piles of this invention. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The method for integrated directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology disclosed in this invention is applicable to depths greater than 15m and areas less than 100m. 2 This invention involves targeted excavation and remediation of deeply contaminated soil and groundwater over small areas. The following detailed explanation, using specific engineering examples, outlines the implementation process, technical parameters, and key operational points of this invention.

[0019] 1. Project Overview: In a redevelopment project of an industrial site, preliminary investigation and testing revealed that the 0-15m soil layer was artificial fill (uncontaminated), while the volatile organic compounds (VOCs) and heavy metals content in the soil at a depth of 17-18m exceeded the standards, with the contamination concentrated at 20m. 2 Within this area, thorough excavation and remediation are required. Based on site conditions and pollution characteristics, the integrated technical solution of this invention was selected. The excavation depth is controlled at 18.5m (including 0.5m over-excavation to ensure complete removal of contaminated soil). A full-casing, skip-hole, overlapping rotary drilling process is employed, along with an intelligent detection module to achieve full digital management and control.

[0020] 2. Pre-construction preparations: 2.1 Precise Investigation and Location of Contaminated Areas: A comprehensive site survey was conducted using a combination of ground-penetrating radar (GPR) detection and drilling sampling to clearly define the distribution boundaries, vertical depth, pollutant types (VOCs and heavy metals), and concentration gradients of the contaminated soil, resulting in a detailed pollution distribution map. Based on the survey results, the excavation scope, extraction area, and workload were determined. A total station was used for surveying and layout, and borehole layout maps were marked on the ground. The spacing between boreholes was determined based on the diameter of the rotary drill bit, ensuring that adjacent boreholes overlapped to cover the entire contaminated area.

[0021] 2.2 Equipment Selection and Modification: Select a rotary drilling rig suitable for deep excavation. Its power head output torque, drilling depth and drill bit diameter must meet the construction requirements (in this example, a rotary drilling rig with a drill bit diameter of 800mm and a maximum drilling depth of ≥20m is selected).

[0022] An auxiliary online detection device is installed on the power head drive sleeve of the rotary drilling rig. The device is encapsulated in a shell with a shockproof, dustproof, and waterproof structure. Its shape is adapted to the outer structure of the power head drive sleeve and does not affect the normal operation of the drill rod.

[0023] The online detection device includes a real-time detection module and a data transmission module: The real-time detection module is equipped with a sampling channel, a PID sensor (for detecting VOCs concentration), and an electrochemical sensor (for detecting heavy metal content). The sensor detection accuracy meets the relevant national environmental monitoring standards. The data transmission module adopts the 5G wireless communication protocol and is configured with a 485 instrument panel for real-time data display on site. At the same time, it packages the data collected by the sensors and sends it to the gateway device, which then transmits it to the remote monitoring terminal (computer) via the Internet.

[0024] 2.3 Materials and Site Preparation Prepare the complete casing assembly: Use multi-section steel casing, each section is 5m long, with a total length of 15m (covering 0-15m of backfill to prevent hole collapse). The casing joints are sealed to ensure isolation effect.

[0025] Backfill repair materials: Clay and modified clay mixed with 5% cement (by volume) are selected. The clay must meet the technical requirements such as plasticity index and moisture content. Ordinary Portland cement is selected to ensure the stability and impermeability of the soil after backfilling.

[0026] Site layout: Set up a fence around the excavation area to divide the area into a temporary storage area for contaminated soil and a storage area for clean soil. The ground of the temporary storage area is covered with HDPE membrane to prevent secondary pollution. Equip the area with earthmoving vehicles, tampers, groundwater extraction equipment and testing and sampling tools.

[0027] 3. Core construction process (integrated operation): 3.1 Full casing installation: Position the rotary drilling rig at the first borehole location, adjust the rig's level and verticality to ensure the casing is installed vertically during drilling. Use the rotary drilling rig to lower the casing section by section, with the top of the casing 30cm above the ground and the bottom embedded in the uncontaminated soil layer (15m depth), forming a closed isolation space to prevent contaminated soil from contacting the surrounding clean soil.

[0028] 3.2 Directional excavation and real-time monitoring: The rotary drilling rig is started, and the drill bit rotates to start drilling after it touches the ground. During the drilling process, the sampling channels of the online detection device collect soil and gas samples simultaneously. The PID sensor and electrochemical sensor detect pollutant concentration data in real time and transmit it to the remote monitoring terminal through the 5G module.

[0029] The remote monitoring terminal displays the detection data in real time. Operators compare the data with preset standards (pollution boundary accuracy ±5cm, contaminated soil removal rate ≥99.5%, clean soil protection rate ≥98%) to determine the soil pollution status. If the test data exceeds the standard, continue excavation at the current depth; If the test data meets the standards, dynamically adjust the drill rod angle or the excavation range to avoid over-excavation; Once the drill bit is full of soil, the drill rod is lifted out of the hole, and the contaminated soil is dumped into a temporary storage area covered with HDPE membrane. Then the drill bit valve is closed, and the rotary drilling rig is reset to continue drilling.

[0030] 3.3 Groundwater extraction and treatment: If contaminated groundwater accumulates in the borehole during the excavation process, the extraction equipment will be activated to pump the contaminated groundwater to a dedicated storage tank through the pumping pipe. After testing and confirming that the groundwater meets the standards, it will be discharged or transported to a professional treatment facility for treatment to prevent the spread of groundwater pollution.

[0031] 3.4 Hole Cleaning and Depth Verification: After drilling to the preset depth of 18.5m, stop drilling and use a hole cleaner to remove sediment from the bottom of the hole, ensuring that the bottom is flat and free of residual soil. Use a measuring rope to verify the hole depth, and control the deviation within ±5cm. If the preset depth is not reached or the soil at the bottom of the hole exceeds the standard, continue excavation until the requirements are met.

[0032] 3.5 Digital Fixed-Point Sampling and Acceptance: Three representative samples are selected from different locations at the bottom of the borehole. These samples are taken using a specialized sampler and sent to a qualified testing institution for VOCs and heavy metal content testing. If the test results meet the remediation target requirements, the backfilling process can proceed. If the test results fail, the borehole must be excavated again and samples taken for acceptance again until the standards are met.

[0033] 3.6 Layered Backfilling and Compaction: After acceptance, backfilling shall be carried out immediately, using a layered backfilling method. The thickness of each layer shall be controlled within 30cm. First, clay shall be backfilled to a depth of 17m, then modified clay mixed with cement shall be backfilled to 1m below ground level, and finally plain soil shall be backfilled to the ground level. After each layer of backfilling, a rammer shall be used for layered compaction, and the compaction degree shall reach more than 90% to ensure the density of the backfilled soil and prevent future ground settlement.

[0034] 3.7 Casing Removal: After backfilling is completed and the surface soil has initially consolidated (approximately 24 hours), the entire casing is removed section by section using the reverse torque of a rotary drilling rig. The removal process should be carried out slowly to avoid disturbing the surrounding soil.

[0035] 4. Cyclic Operation and Site Restoration: Following the "1-2-3-4" skip-hole drilling sequence, move the rotary drilling rig to the next set of holes and repeat the core construction process described above. By overlapping adjacent holes (overlap width ≥ 10cm), achieve full coverage excavation and remediation of all contaminated areas. After all holes are completed, clean up the construction equipment and materials on site, transport all contaminated soil to a compliant disposal site, recycle the HDPE membrane in the temporary storage area, level the site, and restore the ground to its original condition.

[0036] 5. Construction quality control and safety assurance: Key points for quality control: Hole position deviation ≤ 5cm, casing verticality deviation ≤ 1%; real-time monitoring data must be recorded synchronously to form a digital construction archive for easy traceability; backfill materials must be tested in batches to ensure that the quality meets the requirements, and compaction testing must be carried out after each layer of compaction.

[0037] Safety measures: Warning signs should be set up at the construction site, and operators must wear protective equipment (gas masks, gloves, etc.); online detection devices must be calibrated regularly to ensure accurate detection data; rotary drilling rigs must be supervised by a dedicated person during operation to prevent equipment tipping over or casing detachment.

[0038] Through the construction practice of this embodiment, the contaminated soil removal rate of the contaminated site reached 99.8%, the clean soil protection rate was 98.5%, the accuracy of contaminated boundary identification was controlled within ±3cm, the support cost was reduced by 75% compared with traditional deep support and layered excavation, the construction period was shortened by 60%, and there was no mud pollution during the construction process, thus achieving the goal of precise, efficient and environmentally friendly contaminated soil remediation.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A system for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology, characterized in that, The system includes a rotary drilling rig, a full casing assembly, an online detection device, and a remote monitoring terminal. The full casing assembly is configured to be vertically buried in the contaminated area to form an isolation space. The rotary drilling rig is equipped with a power head drive sleeve and a drill bit. The online detection device is installed on the power head drive sleeve and is configured to collect soil data in real time as the drill bit operates. The online detection device is connected to the remote monitoring terminal via a wireless communication module for transmitting the collected soil data.

2. The system for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology according to claim 1, characterized in that, The online detection device includes a real-time detection module, which is equipped with a sampling channel, a PID sensor, and an electrochemical sensor. The PID sensor is configured to detect the concentration of volatile organic compounds, and the electrochemical sensor is configured to detect the content of heavy metals.

3. The system for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology according to claim 2, characterized in that, The online detection device also includes a data transmission module, which is configured to use a 4G or 5G wireless communication protocol to package and send the data collected by the sensor to the gateway device and then to the remote monitoring terminal.

4. The system for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology according to claim 1, characterized in that, The full casing assembly is composed of multiple casing sections connected together, and the connection length of the casing sections is configured to cover the range from the ground to a preset contamination depth.

5. The system for directional excavation and ex-situ remediation of contaminated soil based on rotary drilling pile technology according to claim 1, characterized in that, The online detection device is encapsulated in a housing with a shockproof, dustproof, and waterproof structure, and the shape of the online detection device is adapted to the outer structure of the power head drive sleeve.

6. A construction method for a directional excavation and ex-situ remediation system for contaminated soil based on rotary drilling pile technology as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Determine the extent of contaminated soil exceeding standards, and if necessary, determine the extent of contaminated groundwater exceeding standards, and conduct surveying and setting out. Step 2: Position the rotary drilling rig and install the online detection device on the power head drive sleeve; Step 3: Install the full casing assembly; Step 4: Control the rotary drilling rig's drill bit to touch the ground and rotate to start drilling. During the drilling process, use an online detection device to monitor soil pollutant data in real time and transmit it to a remote monitoring terminal. Step 5: Once the drill bit is full of soil, lift it out of the hole, dump and remove the contaminated soil; Step Six: Repeat the drilling and excavation steps until the preset depth is reached, and then clean the hole; Step 7: Take samples at the bottom of the hole for acceptance testing; Step 8: After acceptance, backfill the repair material in layers and compact it. Step 9: Remove the entire casing assembly; Step 10: Move the rotary drilling rig to the next set of holes and repeat the above steps.

7. The construction method of the contaminated soil directional excavation and ex-situ remediation system based on rotary drilling pile technology according to claim 6, characterized in that, In step ten, the next set of holes is constructed using a full-sleeve skip-hole overlapping rotary drilling method, and the entire contaminated area is covered by overlapping of adjacent rotary drilling holes.

8. The construction method of the contaminated soil directional excavation and ex-situ remediation system based on rotary drilling pile technology according to claim 6, characterized in that, In step four, the operator judges the soil pollution situation based on the real-time pollutant data received by the remote monitoring terminal, and dynamically adjusts the excavation depth and scope accordingly.

9. The construction method of the contaminated soil directional excavation and ex-situ remediation system based on rotary drilling pile technology according to claim 6, characterized in that, In step eight, the backfill repair material is clay or clay mixed with cement, and a tamping hammer is used to compact it in layers during the backfilling process.

10. The construction method of the contaminated soil directional excavation and ex-situ remediation system based on rotary drilling pile technology according to claim 6, characterized in that, The construction method also includes the step of extracting and treating the contaminated groundwater in the borehole during or after the excavation process.

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