岩土工程技术

2024, 38(2): 1-1.

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2024, 38(2): 1-3.

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Implementation of Key Technology for Survey Digital Platform Based on GIS

Li Chunliang, Liu Xu

2024, 38(2): 127-131. doi: 10.3969/j.issn.1007-2993.2024.02.001

[Abstract](101) [FullText HTML] (18) [PDF 1815KB](29)

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To solve the efficient loading and visual display of massive survey data, a digital survey solution based on GIS technology was proposed. The real-time visual rendering of a map of cross-age exploration boreholes, automatic construction and display of 3D borehole histogram, survey data analysis, and statistical application based on spatial characteristics were realized. Through the application of the survey results management in a large iron and steel complex, it has achieved good results and also provided a reference to carry out related technology research.

Classification of Surrounding Rock and Support Force Determination of Ice Water Accumulation Tunnel

Tao Qi

2024, 38(2): 132-136. doi: 10.3969/j.issn.1007-2993.2024.02.002

[Abstract](67) [FullText HTML] (20) [PDF 1052KB](20)

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To quantitatively evaluate the surrounding rock parameters of ice water accumulation body, a rapid classification method of surrounding rock of ice water accumulation body was proposed, and the deformation control standard of ice water accumulation body was given, which mainly includes the following contents: (1) the surrounding rock was classified in the design stage according to the relevant calculation methods of specifications, combined with the relevant foreign specifications and the basic characteristics and geomorphic characteristics of ice water accumulation body. (2) According to the dense state of soil, fine particle content and fine particle water content, the surrounding rock in the construction stage was classified. The river ice water accumulation body was divided into three basic grades and four sub grades. (3) According to the cementation between groundwater and surrounding rock, the surrounding rock classification was put forward. (4) Based on the classification of surrounding rock of ice water accumulation tunnel, the characteristic curves of surrounding rock and the allowable deformation of tunnel under different surrounding rock grades were calculated, and the determination method of tunnel support force based on the allowable deformation was proposed. The research results can provide a new reference for the classification of surrounding rock and the support force determination of ice water accumulation tunnel.

Influence of Pile Foundation Construction on Health Trend of Adjacent Shield Tunnel Structures

Lai Gaofeng, Pang Jin, Ye Jianhua, Shou Lingchao, Cao Zhendong

2024, 38(2): 137-142. doi: 10.3969/j.issn.1007-2993.2024.02.003

[Abstract](84) [FullText HTML] (22) [PDF 1058KB](16)

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To study the impact of deep bridge pile construction in soft soil areas on the health status of adjacent operating tunnel segments, a spatiotemporal distribution statistical comparison and data joint attribution analysis method were used. Segment cracks mainly arise and develop with the development of structural tension area, mainly longitudinal cracks in the waist, and the data variability and dispersion degree of the number of cracks are higher than the representative width. The extrusion effect of deep and large foundation piles in adjacent tunnels was generated, which controlled the development of the horizontal diameter difference of the segment, and the crack growth of the tunnel segment close to the foundation pile construction was weaker than that of the distant pile tunnel. The number of new cracks was positively nonlinear with the horizontal distance of the pile tunnel, and the increment of the number of cracks in the segment can be estimated. The horizontal diameter difference can be used to predict and prevent new cracks in the segment. The recommended threshold is 20 mm for the first layer and 38 mm for larger values of concern.

Environmental Impact Effect of Soft Soil Foundation Pit Group Engineering

Shen Jian, Hu Yun, Wang Huisheng

2024, 38(2): 143-148. doi: 10.3969/j.issn.1007-2993.2024.02.004

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The divided pit excavation and excavation process of foundation pit group engineering are complex, and the environmental impact superimposed effect is significant. The above problems cannot be analyzed by the standard design and calculation method. Taking a project in a soft soil area of Shanghai as the background, a variety of conceptual models were established to analyze the impact of different divided pit excavation of large-area foundation pits on the surrounding environment, and analyze the superimposed impact of different excavation sequences of adjacent foundation pits on the environment, and guide the overall zoning and working condition design of foundation pit group projects. The monitoring data showed that the impact of the project implementation on the environment is generally controllable, and the key strengthening areas have little impact on the sensitive protection objects such as the operating subway. The relevant analysis results and design countermeasures can be used as a reference for similar projects.

Optimization and Improvement of the Dynamic Parameter Test with Dynamic Machine Model Foundation at a Nuclear Power Plant

Chen Xiaofeng, Sun Lichuan

2024, 38(2): 149-155. doi: 10.3969/j.issn.1007-2993.2024.02.005

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The steam turbine buildings of nuclear power plants are mostly located on hard rock subgrade, and the resonance frequency of the dynamic parameter test with model foundation reaches more than 100 Hz, Due to the defect of the low upper limit of the excitation frequency of mechanical exciters, the test method commonly used on soil subgrade is no longer applicable to the rock subgrade of nuclear power plants. Research has been conducted on the connection and testing methods between the exciter, cushion layer, exciter and model foundation. The testing equipment and methods have been optimized and improved, and a fully automatic constant disturbance force testing control system has been developed to make it more suitable for rock foundations in nuclear power plants. The test results could represent the dynamic characteristics of rock foundations accurately.

Reinforcement of Anti-pulling Bolts in Ultra-high Gravity Retaining Wall

Xu Shuping, Wang Zixuan, Ke Qianqian, Chen Lyu, Tu Yao, Cheng Jielin

2024, 38(2): 156-162. doi: 10.3969/j.issn.1007-2993.2024.02.006

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By installing horizontal anti-pulling bolts and anti-sliders in ultra-high retaining walls, the cross-sectional area of the retaining wall can be reduced. This reinforcement method can effectively reduce the active earth pressure. When different forms of anti-pulling bolts and anti-sliders were arranged, the stress distribution of soil behind the wall had a large impact, and the horizontal stress and horizontal displacement were numerically analyzed. According to the actual situation, the horizontal stress and displacement of the soil behind the gravity retaining wall under different working conditions were calculated to verify its safety and achieve the purpose of reducing the soil pressure. The results show that in the ultra-high gravity retaining wall, the best reinforcement effect can be obtained by using 3 layers of anti-pulling bolts and 2 anti-sliders on each layer of anti-pulling bolts. The pre-reinforcement of the soil behind the retaining wall should increase the stability of the soil behind the wall, and reduce the soil pressure of the soil behind the wall to the retaining wall.

Design and Construction of Steel Support + Diaphragm Wall Foundation Pit in Deep and Thick Sand Layer Soil

Wang Xing, Li Jicheng, Wei Qian, Li Chengxin, Huang Tian

2024, 38(2): 163-168. doi: 10.3969/j.issn.1007-2993.2024.02.007

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The foundation pit of a hotel in Sri Lanka is located in a deep and water-rich sand layer. The surrounding environment of the pit is complex. Chinese design and construction standards have been introduced, and a diaphragm wall+steel support system has been adopted, achieving ideal soil and water-retaining support effects, and controlling the deformation of surrounding buildings and the environment. The design and construction process and key technology of the foundation pit project can provide a reference for similar projects in the future.

Deformation Mechanism and Reinforcement Effect for Slope Excavated in Complex Accumulative Formation

Tu Xinbin, Wang Yanbing, Yang Xiangbin, Niu Yanbo, Yuan Mingsheng, Gao Xian, Lin Shaoyuan, Chen Xilong

2024, 38(2): 169-174. doi: 10.3969/j.issn.1007-2993.2024.02.008

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For a high excavation slope of a converter station in a power engineering project, the stability and deformation characteristics of the slope were analyzed using the limit equilibrium method and the strength reduction method, respectively. The results showed that the stability of the slope is significantly affected by rainfall and earthquakes. The slope was in an unstable state under both working conditions. Earthquake induced damage to the accumulation structure of slope zones. Not only does it reduce the overall stability of the slope, but it also promotes the extensive development of cracks within the slope. It was beneficial for rainfall infiltration and further deteriorating the hydrogeological conditions of the slope, and it caused an increase in pore water pressure and a decrease in effective stress in the slope. The slope reinforcement design adopted the support measures of pile sheet wall and lattice anchor rod. The stability coefficient of the reinforced slope reached 1.406, and the maximum total displacement decreased from 425 mm before reinforcement to 9 mm. It significantly improved slope stability and indicated that the protection plan can ensure the safety of the slope and achieve the purpose of prevention and risk control.

Analysis of Construction Disturbance Measurement of Three Lane Rectangular Pipe Jacking Tunnel with Small Clear Distance

Yuan Senlin

2024, 38(2): 175-180. doi: 10.3969/j.issn.1007-2993.2024.02.009

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The on-site measurement and analysis were conducted on the internal force, soil pressure, jacking force, vertical attitude, and surface settlement caused by the construction of a 1.2 m ultra-small clear distance three-lane pipe-jacking rectangular tunnel under the Jiaxing Ring Road, which passes through Nanhu Avenue. During the later implementation of tunnel excavation, the internal force of the double line pipe-jacking of rectangular tunnel fluctuated due to posture adjustment and the effect of lubricating mud. As the tunnel construction approaches, the internal force of the previous pipe weakens, strengthens, and then recovers, resulting in a maximum reinforcement stress increase of about 30%; Compared with conventional single-line rectangular pipe jacking, the surface settlement caused by construction exhibits a relatively flat peck settlement curve, and the maximum settlement was concentrated on the originating well side, showing a certain drag effect as the jacking distance increases; The main factor of the settlement difference between the north and south lines was the vertical attitude control of tunneling, and the jacking force did not show a large difference due to the small clearance.

Application of Intelligent Grouting Equipment in Grouting Reinforcement of Plain Fill Soil

Song Jie, Kang Zengzhu, Wu Tao, Yang Chunyu, Li Kai, Liu Guanglei

2024, 38(2): 181-186. doi: 10.3969/j.issn.1007-2993.2024.02.010

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An intelligent grouting equipment was developed, and grouting reinforcement tests were conducted on plain fill soil using the grouting equipment. The influence of grouting depth on grouting construction parameters was studied. The applicability and effectiveness of different grouting methods were analyzed, and the actual diffusion of slurry was explored. The results showed that the grouting pressure is closely related to the grouting depth, grouting method, and grouting sequence, and grouting parameters can be determined based on the results of pre-project grouting tests. The slurry diffuses along some weak channels within the soil layer, forming multiple slurry veins. Using intelligent grouting equipment for grouting reinforcement testing can quickly determine suitable grouting parameters and provide technical guidance for subsequent construction.

Engineering Practice and Application of Automatic Monitoring Technology for Long-distance Subway Tunnel

Zhang Lei, Xu Min, Bi Shuangshuang, Ge Minhui, Zhang Qin, Cheng Guohua

2024, 38(2): 187-195. doi: 10.3969/j.issn.1007-2993.2024.02.011

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The monitoring range of subway protection engineering is longer and the working conditions are more complex and more difficult. Long-distance (>400 m) monitoring range, and multiple (>3) instrument series projects are also common, and the requirements for automatic monitoring technology are increasingly high. Based on the protection monitoring of Hangzhou Metro Line 1, the monitoring technology and data analysis of the series system of 5+2 measuring robots were conducted, and the accuracy and reliability of the series automatic monitoring technology of multiple measuring robots were proved, which provides references for similar projects in the future.

Application of High-frequency Ground Penetrating Radar in the Evaluation of Ancient City Wall Restoration Effect

Meng Tianhua, Huang Li, Zhang Haijiao, Wang Haohang, Lu Yuhe, Jiang Zichao

2024, 38(2): 196-202. doi: 10.3969/j.issn.1007-2993.2024.02.012

[Abstract](56) [FullText HTML] (13) [PDF 2169KB](13)

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Under the combined influence and action of long-term environmental pollution, the wall structure of Deshengbao on the Ming Great Wall has developed cracks, hollowing and cracking, erosion of the wall foundation, alkalinity, and plant root system diseases. In this research, the three representative wall areas of Deshengbao were detected by ground-penetrating radar technology. The ground penetrating radar profiles showed that the condition of the repaired city wall has improved, especially the repaired ancient city wall with the traditional technique of layer-by-layer ramming process. The continuity of each layer of the ramming layer is perfect, and the thickness of the ramming layer of 0.02 m can be obtained easily, which can effectively prevent cracks, hollowing, capillarity, plant roots, and other diseases. Although the adobe brick method may have helped preserve the city wall, the long-term preservation effect of the wall is not the best due to the uncompacted adobe brick, which is easy to provide conditions for capillary water, natural precipitation, animals, and plants to produce cracks, hollowing, plant roots, and other diseases. So the method of ground penetrating radar can quickly detect the preservation status and repair performance of the ancient city wall, which is suitable for large-scale investigation of the ancient city wall.

Experimental Study on Shear Characteristics of Silt under Different Temperature-humidity Freeze-thaw Cycles

Peng Yatao, He Wenyuan, Li Li, Wang Zhiliu

2024, 38(2): 203-210. doi: 10.3969/j.issn.1007-2993.2024.02.013

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To explore the influence of freeze-thaw cycles on the shear characteristics of compacted silt under different temperature and humidity conditions, the silt in the Yellow River flooding area of Zhengzhou was taken as the research object. Under the freeze-thaw cycles of -5°C to 5°C and -15°C to 15°C, the soil samples with water content of 6%, 10%, 14%, 18% and saturation moisture content were subjected to freeze-thaw cycles. The results show that during the freeze-thaw cycle, the contact mode, arrangement and pore characteristics of compacted silt particles change, and the shear strength first decreases and then tends to be stable. Due to the phase change of water in the soil and the change of the inter-particle force, the greater the moisture content of the soil sample, the more obvious the attenuation effect of the freeze-thaw temperature amplitude on the shear strength of the soil sample. Under the condition of the same temperature amplitude, due to the comprehensive effect of particle surface cementation and inter-pore water film lubrication, the higher the moisture content of the compacted silt, the smaller the attenuation ratio of shear strength and cohesion, and the greater the attenuation ratio of internal friction angle during the freeze-thaw cycle.

Experiments on One-dimensional Consolidation Characteristics of Marine Soft Clay in Yangtze Estuary

Ma Rui, Wu Xianyong, Zhao Dingfeng

2024, 38(2): 211-215. doi: 10.3969/j.issn.1007-2993.2024.02.014

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To investigate the consolidation characteristics and the variation of consolidation parameters (consolidation coefficient C_v, compression coefficient a_v and permeability coefficient k) of saturated marine soft clay in the Yangtze estuary, a series of multistage one-dimensional consolidation tests were conducted on the marine soft clay of an offshore wind platform project in the Yangtze estuary of Qidong city. The results show that during the natural deposition process, the marine soft clay in the Yangtze estuary has a weak structure due to the co-action of the Yangtze River current and the tidal waves of the Yellow Sea and the East China Sea. Furthermore, during the consolidation process, the development of consolidation deformation of the marine soft clay can be divided into three stages: linear development stage, rapid deformation stage, and stabilization stage, and the increment of consolidation deformation ΔS_ti decreases first and then increases with the increase of consolidation stress. Moreover, during the consolidation process, the C_v of marine clay and marine silty clay first decreases and then increases, and the a_v and k gradually decrease. The C_v and k of marine silty clay were larger, and the a_v was smaller than those of marine clay. This study can provide basic parameters for the foundation design of marine engineering in this region.

Energy Evolution and Failure Tendency Index of Beishan Granite

He Kang, Lu Hui, Wang Chuanle, Han Yang, Li Erbing

2024, 38(2): 216-225. doi: 10.3969/j.issn.1007-2993.2024.02.015

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To investigate the energy evolution of granite obtained from the Beishan pre-selected area for geological disposal of high-level radioactive waste under different loading and unloading paths, an indoor triaxial test on Beishan granite round column specimens under different initial surrounding pressure and different loading and unloading conditions was conducted. Indoor triaxial tests were carried out on the granite specimens with different initial envelope pressure and different loading and unloading conditions, the test data were processed and compared, and a new type of rock damage energy propensity index was established. The results show that the total strain energy, elastic strain energy and dissipative strain energy of the critical damage of the rock increase with the increase of the initial surrounding pressure; there is a strong correlation between the characteristic parameters of acoustic emission and dissipative energy during the damage of the rock; the rock failure mode under the unloading condition is divided into internal damage failure and axial strain damage failure; the energy propensity index of rock damage increases first and then decreases under different unloading test conditions, and the higher the efficiency of converting elastic strain energy into dissipative energy, the smaller the energy propensity index and the higher the degree of rock damage.

Suitability of the Expansion Index for Paleogene Mudstone in Nanning Section of Guinan High-speed Railway

Bu Qiang, Zhang Lei, Pang Weifu, Dong Bin, Sun Hejin

2024, 38(2): 226-232. doi: 10.3969/j.issn.1007-2993.2024.02.016

[Abstract](51) [FullText HTML] (11) [PDF 822KB](8)

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Paleogene mudstone in the Nanning section of the Guinan high-speed railway is a semi-formed mudstone deposited in lakes and marshes, which is easy to soften when it meets water or to disintegrate when it loses water and has certain swelling and shrinking properties. Based on the expansive test data of mudstone samples in the Nanning section of the Guinan high-speed railway and the actual phenomenon of herringbone skeleton cracking on cutting slope, the applicability of expansive discrimination indexes was studied by using analysis methods of correlation, linear regression, and matching degree. The results show that the grading results of single-index expansion potential by dry-saturated water absorption rate is close to the actual situation, and the grading results of single-index expansion potential of natural humidity samples by expansion force, cation exchange capacity, montmorillonite content or free expansion rate are easy to drop by 1-2 grades.

Effect of pH on Physical and Mechanical Properties and Microstructure of Collapsible Loess

Hao Junfeng, Feng Feihong, Wang Tao, Gu Menghui

2024, 38(2): 233-237. doi: 10.3969/j.issn.1007-2993.2024.02.017

[Abstract](59) [FullText HTML] (16) [PDF 1039KB](13)

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Acid-base pollution seriously affects the long-term stability of geotechnical engineering. Unconfined compressive strength, collapsibility test, and shear strength test were used to study the effect of different pH values on the physical and mechanical properties of loess. XRD and SEM were used to further explore the mechanism of the effect of different pH values on loess. The test results showed that compared with the control group (pH=7), the decrease in pH led to a significant decrease in the intensity of the diffraction peaks of the mineral components, and the proportion of medium and large pores in pH=3 and pH=5 was 93.3% and 89.9% respectively, which in turn led to a decrease in the unconfined compressive strength, collapsibility, and shear strength. With the increase of pH, a large amount of gelling material is generated in the alkaline environment and the intensity of the diffraction peak of mineral composition increases. Compared with pH=7, the micropores and small pores of pH=9 and pH=11 increase by 25.0% and 59.96% respectively, which improves the physical and mechanical properties of the loess. Acid pollution will reduce the physical and mechanical properties of loess, but alkali pollution can improve the physical and mechanical properties of loess, which can provide a reference basis for the prevention and control of acid and alkali pollution in loess areas.

Research and Prospect of Electro-Osmosis Techique for Soil Reinforcement

Li Junyi

2024, 38(2): 238-245. doi: 10.3969/j.issn.1007-2993.2024.02.018

[Abstract](100) [FullText HTML] (35) [PDF 630KB](17)

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The research and development of the electro-chemical reinforcement test for sea siltation in Zhanjiang Port were summarized, and the development of electro-osmotic methods for soil reinforcement technology was proposed. The innovation and development of electro-osmotic methods for soil reinforcement technology should be based on promoting the progress of foundation treatment technology and meeting the needs of the times. The electro-osmotic method and its combined method for soil reinforcement technology should adhere to the concept of transdisciplinary and shared development, innovate ecological models, and establish a practical system of soil treatment+electro-osmotic soil treatment technology, making it widely applicable in the fields of foundation treatment and environmental protection.

Introduction and Comparison of Composite Vertical Barrier Technology

He Shunhui, Zhang Jian, Xie Shiping, Zheng Yongya

2024, 38(2): 246-252. doi: 10.3969/j.issn.1007-2993.2024.02.019

[Abstract](40) [FullText HTML] (11) [PDF 2136KB](9)

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Currently composite vertical barrier systems are mainly inclusive of HDPE cut-off wall and GCL vertical barriers, both of which are made of wall-backfilled materials, such as soil-bentonite, cement-bentonite or soil-cement-bentonite, etc., and introduced high-performance geosynthetic lining materials. They are made and applied to better address the percolation issues with single structural cut-off walls that usually cannot meet the environmental protection requirement. The basic information of two kinds of composite vertical barrier systems as well as geosynthetic panel connections and their field applications are presented, which could provide references for project selection.

2024 Vol. 38, No. 2