岩土工程技术

2024, 38(6)

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2024, 38(6): 1-3.

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Review of Ground Treatment Techniques and Their Intelligentize

Hua Jianxin, Wang Hao, Zhang Dan, Liang Tao

2024, 38(6): 631-643. doi: 10.3969/j.issn.1007-2993.2024.06.001

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The ground treatment techniques for the 9th National Geotechnical Engineering Records Conference were reviewed, and new techniques, digitalization, and intelligence for ground treatment applications were introduced. Furthermore, some directions were provided which should be strengthened in future research. Ground treatment faces the challenge of transitioning towards green, low-carbon, and intelligent solutions. Future development directions include utilizing BIM and big data to construct intelligent foundation design systems and treatment construction management systems. Application research in soft ground foundation treatment, settlement control, and MICP technology should be emphasized. It is necessary to prompt the integration of theoretical knowledge with practical experience and update relevant standards and specifications to better meet the needs of national construction projects.

Key Technologies and Applications of Air-Ground Integrated Digital Engineering Investigation

Li Qingbo, Du Pengzhao, Liu Zhenhong, Qi Jumei, Pei Lina

2024, 38(6): 644-649. doi: 10.3969/j.issn.1007-2993.2024.06.002

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Combined with the major needs of digitalization and informatization construction in the engineering investigation industry, the current status and shortcomings of the digital technology for engineering investigation were systematically analyzed, the research on key technologies in the digital collection, integrated management, and collaborative application of investigation information was carried out, several research results with practical engineering application value were obtained. Taking the Dongzhuang Water Control Project as an example, through the application of the key technologies of air-ground integration digital engineering investigation, the work efficiency and achievement quality of water conservancy engineering investigation in the mountain canyon area were improved, this provides a reference for the geological work in large-scale, long-distance, and difficult areas in the field, and promoting the advancement of information technology in the investigation industry.

Checking Calculation Method of Integral Anti-Floating Stability of Anti-Floating Anchor

Wei Zhiqiang, Deng Wenzhong

2024, 38(6): 650-654. doi: 10.3969/j.issn.1007-2993.2024.06.003

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According to the technical code for geotechnical bolt and shotcrete support engineering (GB 50086—2015), the checking calculation of anti-floating stability of anti-floating bolt as a whole can be known, the overall stability of the anti-floating anchor was related to the total weight of the soil (W), the self-weight of the structure, other permanent loads (G) and the buoyancy of the groundwater (F_f) in the scope of the anti-floating anchor under the foundation, the self-weight and other permanent loads (G) of the structure and the buoyancy of the groundwater (F_f) can be calculated by relevant regulations. The stress of the anti-floating anchor was analyzed, and the calculation formula of anti-floating stability checking of the anti-floating anchor was put forward according to the relevant codes.

Design and Deformation Monitoring Analysis of Large Crown Beam in Deep Foundation Pit

Lyu Zhigang, Huang Jun, Yang Jianwei, Wang Yanyan

2024, 38(6): 655-661. doi: 10.3969/j.issn.1007-2993.2024.06.004

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For pile+internal support, to reduce or avoid the use of side truss bracing and inclined bracing systems, a method of increasing the crown beam section was proposed to expand the main support spacing. This method can control the deformation of the foundation pit and ensure the safety and stability of the foundation pit. Based on the basic theory research of the design of the large crown beam, combined with the engineering case, the Lizheng software and MIDAS/GTS finite element software were used for calculation and analysis. The results indicate that the design of the large crown beam can effectively control the deformation of the foundation pit. By comparing and analyzing actual monitoring data, the feasibility and reliability of the design of the large crown beam have been verified. Adopting this support scheme can not only ensure the safety of the foundation pit itself but also ensure the normal use of surrounding buildings. Increasing the spacing between supports for earthwork and underground structure construction can shorten the project duration and reduce engineering costs, which has engineering application value.

Application of a Modified Particle Swarm Optimization Algorithm with Early-Stopping Error Function Summation Mechanism

Kang Hengyi

2024, 38(6): 662-671. doi: 10.3969/j.issn.1007-2993.2024.06.005

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The direct calibration of constitutive models requires that the model parameters have clear physical significance, which corresponds to the geometric interpretation of the testing data. However, for the complex constitutive models with multiple hyperparameters, the optimization technique shall be applied to calibrate those parameters. The particle swarm optimization (PSO) was utilized, which can calibrate the model parameters based on raw data of the stress-strain curves. Technical details of properly implementing the algorithm were illustrated, which focuses on the quantity of particles, and the data requirements for the von Wolfersdorff hypoplastic model and the Drucker-Prager elastoplastic model. Also, the behavior of the PSO algorithm in analyzing the real experimental data was discussed. Since the calculation of the error function is a summation, the stress integration can be terminated for those particles, whose error function has exceeded its historical optimum or reached an overflow state. The early-stopping mechanism was proved to significantly improve computation efficiency.

Disturbance Mechanism of Pipe-Jacking Construction on Surrounding Environment

Wang Binghua, Li Wenqing, Wang Zhonghua, Meng Qingjun, Sun Feixiang

2024, 38(6): 672-679. doi: 10.3969/j.issn.1007-2993.2024.06.006

[Abstract](93) [FullText HTML] (31) [PDF 2293KB](20)

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To determine the impact of pipe-jacking construction on the surrounding environment, engineering data was collected and combined with case monitoring results to study the mechanism and laws of surface and existing tunnel deformation caused by pipe-jacking construction. The conclusions are as follows: (1) The settlement law of the surface section conforms to the Peck formula, with an influence range of about 1.4~2.6 times the diameter of the top pipe. The surface deformation development curve is divided into two forms: "uplift first and then settlement" and "full settlement". (2) The overall uplift of existing tunnels presents a "reverse" Peck curve, and the uplift amount was affected by the stiffness of the existing tunnel and the magnitude of the disturbance it is subjected to. With the increase of time, the uplift amount first increases rapidly and then tends to stabilize. (3) Monitoring and analysis were conducted on the pipe-jacking project of the existing tunnel, and the deformation patterns of the surface and tunnel were basically consistent with existing research patterns. Several measures were taken to control the deformation of the surface and existing tunnel, with a maximum settlement of about 11 mm on the surface and a maximum uplift of about 1.6 mm on the existing tunnel. The research results can provide certain references for the design and construction of related pipe-jacking.

Applicability Analysis of Design Method for Settlement Reducing Pile Considering Pile-Soil Interaction

Yang Jun, Yang Min, Chen Haibing

2024, 38(6): 680-691. doi: 10.3969/j.issn.1007-2993.2024.06.007

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Regarding the applicability of settlement-reducing piles in complex stratum conditions, the influence of factors such as the site condition and building type, maximum settlement control standard, and pile and soil stiffness distribution on the design of settlement-reducing piles based on a large number of practical engineering projects were discussed. The application criteria and design methods of settlement reducing pile as the optimization objective were proposed, and the rationality was verified by engineering cases. The results show that the settlement-reducing pile has good adaptability to various sites and building types. The important grade of the foundation, the bearing capacity of the foundation, and the stiffness distribution of the pile and soil are the key factors to determine its application. To save the amount of piles and ensure the overall safety of the foundation, it was recommended that the bearing capacity of the foundation in soft and hard soils should not be less than 0.5 and 0.65, respectively. Considering the contribution of raft-bearing capacity, the dimensionless influence coefficient of Gibson soil and layered soil was recommended not to be less than 2.3 and 1.5, respectively. Meeting the above requirements can be used as the premise to determine the applicability of the settlement-reducing pile.

Softening Effect and Control Measures of Surrounding Rock in Deep Buried Saturated Loess Tunnel

Wang Wenzhuo, Hu Jinxin, Qiu Chenghu, Yang Zhijun

2024, 38(6): 692-697. doi: 10.3969/j.issn.1007-2993.2024.06.008

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Under the action of groundwater, the surrounding rock of a loess tunnel will undergo varying degrees of softening, greatly weakening its strength, which brings many difficulties to the design and construction of the tunnel. Based on a loess tunnel in Longdong, different degrees of softening were set up, and finite element numerical simulation software was used to calculate and analyze the deformation of the tunnel surrounding rock and the stress changes of lining structure under different degrees of rock softening. At the same time, a comparative analysis was conducted on the on-site reinforcement measures after the softening of the surrounding rock and the lining structure of the enlarged arch foot. The results show that after the strong softening of the deeply buried loess tunnel, the settlement of the arch top increased by 271%, the uplift of the arch bottom increased by 283%, the horizontal convergence increased by 205%, and the maximum principal stress of the initial support increased by 107%. The most unfavorable stress position appeared at the arch shoulder. After adopting two reinforcement measures and expanding the arch foot, the vertical displacement of the surrounding rock decreases by 5.1% to 77.81%, and the maximum principal stress of the initial support decreases by 17.7% to 46.5%. From the reinforcement effect, it can be seen that the locking foot steel pipe pile reinforcement only improves the deformation of the arch foot surrounding rock and the stress on the lining, but the effect is not significant. Using enlarged arch feet in the lining structure can effectively control the deformation and stress of the lining structure, and the construction difficulty is small and the cost is low. The curtain grouting reinforcement has the best effect on improving the deformation and supporting structure stress of saturated loess tunnel surrounding rock after softening.

A New Model for Estimating V_S30 Based on Engineering Boreholes Data

Zhang Weichao, Ren Hao, Tian Qinhu, Sun Yu

2024, 38(6): 698-703. doi: 10.3969/j.issn.1007-2993.2024.06.009

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The average shear wave velocity to a depth of 30 m below the ground surface （V_S30） is an important parameter for evaluating the site condition and the site earthquake response. There are a large number of borehole data with depths of less than 30 m in China, and these borehole data cannot be directly used to calculate V_S30 by definition equation code. Under this situation, referencing the correlated research results which include the parameter of V_S30 were prevented. It is important to estimate V_S30 accurately. Using the data of 590 boreholes with depths greater than 30 m in Guanzhong plain of Shaanxi Province to research the V_S30 estimation model. The results show that the average shear wave velocity at different depths (Z<30 m) and the elevation of the borehole have a strong log-linear relationship with the measured value of V_S30 along the depth, so a new model of log-linear extrapolation, which comprehensively considers the average shear wave velocity at different depths and the elevation of the borehole, was proposed. Compared with the velocity gradient extrapolation model and the double-depth parameter extrapolation model, when the calculation depth is smaller, the new model has higher estimation accuracy and better stability, and this advantage is more prominent.

Influence of New Pier Construction on Adjacent Existing High Speed Railway Pier Foundation

Wang Caikou, Huang Tao, Chang Wei, Wang Haiyuan, Pu Shikun, Zhai Yongyong

2024, 38(6): 704-711. doi: 10.3969/j.issn.1007-2993.2024.06.010

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To study the influence of new pier construction on adjacent high-speed rail pier foundation, the whole construction process calculation model of the new pier was established based on the hardening soil model with small-strain stiffness (HSS model) and PLAXIS 3D finite element software, and then the soil displacement characteristics of adjacent existing high-speed rail pier foundation were analyzed. The reliability of the finite element model was verified by compared with the field monitoring data. The displacement of the pier and pile was calculated and analyzed. The results show that the HSS model is helpful to obtain more reliable displacement results in finite element calculation. In terms of soil mass, the maximum horizontal displacement and settlement are 1.53 mm and 5.49 mm in the horizontal direction of the foundation pit. The maximum settlement of the existing pier and cap is less than 6 mm, and the total settlement of the pier cap and the differential settlement of the adjacent pier cap is less than the standard limit. The outer top of the pile group of the existing pile foundation has a displacement to the four sides, while the top of the middle pile has a small settlement and bears the "open pattern" displacement state. During the construction of the new pier, the construction of the new bored pile, the insertion of the steel sheet pile, and the backfilling of the foundation pit have a great influence on the horizontal displacement and settlement of the existing high-speed railway pier foundation.

Analysis and Treatment of Subgrade Settlement in a Certain Section of the Yechi Railway

Zhang Liangbing, Pan Qihui, Han Yinshan

2024, 38(6): 712-717. doi: 10.3969/j.issn.1007-2993.2024.06.011

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A certain section of the Yechi Railway was affected by subgrade settlement disease. Through on-site geological investigation and analysis, it was found that the mining of coal seams changed the stress balance state of the surrounding strata, causing plastic deformation of the fault fracture zone along the F1 fault downwards, in addition, the Quaternary strata experienced drift sand along the fault, ultimately leading to subsidence and deformation of the ground. Based on the engineering situation, the treatment scheme of grouting in the Quaternary strata and grouting in fault zones was adopted to improve the mechanical properties of the Quaternary strata in the railway roadbed and enhance the plastic deformation resistance of the fractured zone. The characteristics of directional quantitative sizing and repeatability of sleeve valve pipe grouting were reflected by this plan. This scheme can provide a reference for similar projects.

Shield Muck Generated from Soft Soil Stratum for Preparation of Grouting Material and Its Engineering Applications

Yang Guohua

2024, 38(6): 718-724. doi: 10.3969/j.issn.1007-2993.2024.06.012

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Based on the Suzhou Rail Transit Line 8 subway project, the synchronous grouting slurry was prepared using shield muck generated from soft clay stratum to reduce slag discharge. Based on lab testing, the strength, initial setting time, consistency, bleeding rate, etc. of the shield muck-produced grouting slurry were evaluated. Through engineering practice, the shield muck produced grouting slurry was used for grouting during shield excavation. The results show that the shield muck-produced grouting slurry met the performance requirements for synchronous grouting, and the performance of the muck-produced slurry could be improved by adjusting the mix ratio, demonstrating the feasibility of using soil pressure balance shield muck in soft soil strata to prepare synchronous grouting slurry. The slurry has been used for synchronous grouting during the excavation of the shield in the Suzhou Rail Transit Line 8 project, and the shield settlement and uplift value of lining segments are well controlled. Using shield muck for the preparation of grouting material can reduce the tunnel cost by approximately 750 thousand Yuan per kilometer and decrease the soil discharge by 10%, achieving considerable economic and environmental benefits.

Cause Analysis of High Pressure Water Gushing in Hongtu Extra-Long Tunnel

Zhang Xiujie, Cheng Xiaoyong

2024, 38(6): 725-731. doi: 10.3969/j.issn.1007-2993.2024.06.013

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The Hongtu extra-long tunnel is the key control project of the Dafenghua Expressway crossing Lianhua Mountain in Guangdong Province. The maximum buried depth of the tunnel is 740 m. In the process of tunnel excavation, a large flow of water was encountered under the pressure of 4.8 MPa, and the maximum water volume is 1.4×10⁵ m³/d. By analyzing the influence of tunnel geological structure, the situation of high-pressure water inflow and its main water-conducting structure were expounded during the excavation process. At the same time, the water volume during the water inflow process was tracked, and the water quality of water inflow at different tunnel sections was compared. Three water storage structure modes, such as Tongziyang syncline water storage structure, rock mass intrusion contact water storage structure, and fracture fissure water storage structure, were proposed under the influence of the Lianhuashan fault in the Hongtu extra-long tunnel. Based on the relationship between the water inflow characteristics of the whole tunnel and the geological structure, it was proposed that the high-pressure water inflow mechanism of the tunnel was mainly affected by the horst-type hydrogeological model formed by the influence of the Lianhuashan fault, which makes the tunnel encounter high-pressure and large-flow water inflow during excavation. After penetration, it was controlled by the deep water storage cycle. After the stability of the groundwater system was rebuilt, nearly 60000 m³ large-flow water inflow per day is consistent with the actual situation.

Failure Mode and Path Analysis of High and Steep Rock Slope in Mountainous Areas, Southwestern China: A Case Study in Bowa Hydropower Station

Qiang Xingang, Li Jiahao, Ye Kun, Li Jiayu, Zhang Guangze

2024, 38(6): 732-739. doi: 10.3969/j.issn.1007-2993.2024.06.014

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Southwestern China has become the most concentrated area for the construction of hydropower stations in China due to its rich hydropower resources. When building a hydropower station in the Alpine Valley area, it often causes the problem of destruction on steep rock slopes because of the excavation. To solve this problem, taking the No. 3 dangerous rock mass on the left bank slope of the Bowa Hydropower Station as the research object, combined with the 3D realistic modeling method of unmanned aerial vehicles, the deformation and failure modes and paths of the dangerous rock mass were qualitatively and quantitatively discussed using the stereographic projection method and limit equilibrium method. The results were analyzed and verified using numerical simulation methods. The main findings were as follows: The failure of No. 3 dangerous rock mass was mainly controlled by the preferred planes of both sides, belonging to a multi-stage and multiple wedge-shaped failure mode. It is relatively stable under natural engineering conditions, but it may occur under extreme conditions such as heavy rain and earthquakes. The numerical simulation results show a failure form of "sliding first and then dumping", which verifies the correctness of the theoretical analysis. Research results provide certain engineering experience and scientific reference value for similar steep rock slope problems of hydropower stations.

Origin and Physical-Mechanical Properties Study of Haikou Ultra-Lightweight Volcanic Ash Soft Clay

Xie Shuling, Xie Linxi, Zhai Fengyan, Wang Ying, Yang Yongkang

2024, 38(6): 740-744. doi: 10.3969/j.issn.1007-2993.2024.06.015

[Abstract](63) [FullText HTML] (24) [PDF 3194KB](13)

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A comprehensive geotechnical investigation was conducted at a construction project site on Hainan Island. Specific geotechnical parameters of volcanic ash deposits in high-order areas and volcanic rock plateaus in northern Hainan Island were summarized. The distinct engineering characteristics of this unique soil and rock type were investigated. A multi-faceted approach was employed, including on-site drilling, standard penetration tests, seismic velocity tests, laboratory soil physical-mechanical experiments, optically stimulated luminescence tests, X-ray fluorescence semi-quantitative analysis, and mineral X-ray diffraction analysis. The depositional origin and era of these deposits were examined. Furthermore, recommended values for fundamental engineering characteristic parameters were proposed, providing a solid foundation for the utilization and foundation treatment of this soil type, thereby reducing engineering risks.

Experimental Study on Compressive Bearing Performance of Bilateral Helix-Stiffened Cement Mixing Piles

Guo Chengyu, Zong Zhongling, Huang Yunhan, Zhuang Xiaoxuan

2024, 38(6): 745-749. doi: 10.3969/j.issn.1007-2993.2024.06.016

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Bilateral Helix-Stiffened Cement Mixing Piles (BHCMP) is a new type of stiff composite pile. To study the feasibility of the construction process and the compressive bearing performance of BHCMP, three test piles were designed, and the on-site pile formation test and the compressive bearing performance test of the pile foundation were conducted. Comparative analysis of the pile forming process and bearing properties of helical piles, helical stiffened cement mixing piles, and BHCMP was carried out. The test results show that: the vertical bearing capacity of the helical pile is improved by synchronized rotary grouting around the helical pile to form a hydraulic soil column, which is about 1.85 times that of the helical pile, while the BHCMP has a 49% increase in ultimate compressive bearing capacity compared with the helical stiffened cement mixing piles through the secondary mixing and downward drilling, which makes the mixing of silt soil and cement in the re-drilled section more adequate and forms a hydraulic soil column with higher strength.

Dynamic Experimental Study on Group Well Effect of Resource Recharge

Li Xuguang, Liu Wenbin, Yu Tianfei, Ma Jian, Zhao Gang, Wang Yuanchuan

2024, 38(6): 750-753. doi: 10.3969/j.issn.1007-2993.2024.06.017

[Abstract](56) [FullText HTML] (18) [PDF 663KB](10)

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Recharge is one of the effective measures to protect groundwater resources in urban construction. To reasonably consider the influence of group well effect in the design of a recharge project, the influence of group well effect on the recharge capacity of a single well was experimentally studied by adjusting the number and spacing of recharge wells dynamically in the selected recharge area, and the change law of the recharge capacity of a single well with the number and spacing of recharge wells was summarized. The results show that the group well effect has a significant effect on the recharge capacity of a single well. Once the recharge area is selected, the recharge capacity of a single well decreases with the increase of the number of recharge wells, and the relationship between the recharge capacity of a single well and the spacing of recharge wells is roughly logarithmic.

Current Issue 2024, Volume 38, Issue 6

Current Issue
2024, Volume 38, Issue 6