Frontiers in Computing and Intelligent Systems ISSN: 2832-6024 | Vol. 10, No. 2, 2024 98 Numerical Simulation Analysis of Loess Slope Stability under the action of Power Tower foundations Yongsheng Ju, Yanjun Feng, Zhe Cao Development Division of State Grid Gansu Power Company, Lanzhou Gansu, 730000, China Abstract: Electric energy is the national key energy, and the safety construction of power tower is very important. In this paper, the influence of power tower foundation layout on slope stability in loess slope area is studied. Qingyangning County, Gansu Province is selected as the target area. Based on climate and rainfall data, numerical simulation method is adopted. Firstly, the study area is determined and the data are collected. Then, AUTO CAD and FLAC3 D are used to simulate the slope stability under different rainfall conditions and analyze the influence of rainfall. Then, several tower foundation layout schemes are determined, focusing on the influence of tower foundation on slope settlement under heavy rainstorm conditions, and calculating the slope safety factor and settlement of different schemes. Finally, the optimal tower foundation layout scheme is obtained, which provides reference for designers. This study is of great significance to the safety construction of power tower and the improvement of loess slope stability. Keywords: Tower Base; Stability of Loess Slope; Rainfall; Layout Location. 1. Introduction The safe transmission of electric energy relies on power tower construction. This paper studies the safety layout of power tower foundations in loess slope areas, using the ±800 kV UHV DC project from Longdong to Shandong as an example. Data on climate and rainfall were analyzed with AUTO CAD and FLAC3D modeling. The study discusses the impact of rainfall and tower foundation position on slope stability, evaluates safety factors and settlements under various schemes, and determines the optimal layout. Results show that rainfall and foundation position significantly affect slope stability, providing a scientific basis for safe foundation layout in loess slopes. Specific data are implicit in research methods and results. 2. Engineering Background The selected project in this paper is Longdong-Shandong ± 800 kV UHV DC transmission project (Gansu section). The main construction contents include new sending end converter station, DC transmission line and multiple AC line relocation. The project is through Qingyangning County, which is located in the eastern part of Gansu Province. The geographical location is 107 ° 41 ′ to 108 ° 34 ′ east longitude and 35 ° 15 ′ to 35 ° 52 ′ 57 north latitude [1-6]. The loess slope in Ningxian County belongs to the type of multi-stage rotating loess landslide, which has the characteristics of complex structure and large scale, and has great damage to the surrounding environment. The project is 22.3 km through Ningxian County. (1)The scope of the study area (2)The reflection of the slope in the study area Fig 1. The scene map of the study area 3. The Influence of Different Working Conditions on the Stability of Loess Slope 3.1. Model Establishment and Parameter Selection 3.1.1. Model Establishment According to the data collected from the loess slope in Ningxian County, a simplified model of the loess longitudinal section slope was established by Auto CAD software, and then imported into FLAC3 D to build a specific model. As shown in Figure 2. The height of the loess slope is 100 meters, the slope angle of the upper part of the slope is 30 °, there is a road in the middle with a width of 150 meters, and the slope angle of the lower slope is 30 ° [7]. 99 (1)Slope size (2)Slope division (3) Based on FLAC3D loess slope model Fig 2. Loess slope model and slope division (unit: m) 3.1.2. Parameter Selection The main physical and mechanical parameters of each geotechnical soil layer are shown in Table 1 [8]. Table 1. The main physical and mechanical parameters of each geotechnical soil layer Soil type Elastic modulus (MPa) Poisson 's ratiov Tensile strength(kPa) Dilatancy angle (°) LoessQ3eol 25 0.35 10 0 LoessQ2eol 30 0.35 10 0 In addition to Poisson 's ratio, tensile strength and shear angle, bulk modulus (K) and shear modulus (G) need to be set when setting constitutive model and material parameters in FLAC3D [9-11]. According to the characteristics of the influence of loess slope settlement on stability, it is determined that the upper surface of the model is a free surface, which only needs to be constrained on both sides of the X and Y directions and below the Z direction. 3.2. The Influence of Tower Foundation Layout on the Stability of Loess Slope 3.2.1. Model Establishment (1) Layout position ( unit : m ) (2) Scheme 1 (3)Scheme 2 Fig 3. Layout size and scheme of tower foundation ( unit : m ) According to the engineering investigation, the layout model of the power tower foundation on the loess slope is established ( see Fig 3 ). The model analyzes the influence of the tower foundation on the overall and local stability at different slope positions. The pile foundation is deeply buried. The total weight of the tower foundation is 70 t. It is 100 composed of four cube piles with a side length of 2 meters and a height of 15 meters. The pile spacing is 8 meters and the buried depth is 12 meters. The modeling scheme is shown in Fig.3 (2,3). The tower foundation is laid at two positions of the slope, and the displacement, stress cloud diagram and slope safety factor under natural and rainfall conditions are compared, and the monitoring points are set to analyze the settlement. 3.2.2. Rainfall Conditions Comparing stress and displacement cloud maps, scheme 2 under natural conditions stabilizes the slope more, as the slope is naturally stable and rainfall significantly affects it. Heavy rainstorm impacts loess slope stability more, necessitating detailed comparison of both schemes under these conditions. Since rainfall is continuous, soil water content increases. Figure 4 shows soil water saturation for schemes 1 and 2. (1)Scheme 1 (2)Scheme 2 Fig 4. Variation of soil water saturation Through the comparative analysis of the soil water saturation under the two groups of pictures and the non-layout tower foundation, it can be known that the layout of the power tower foundation will not affect the saturation change of the soil water during continuous rainfall. (1) Stress comparison According to the model of the two parameters, the parameters are set to simulate the rainfall conditions. Firstly, the stress cloud diagrams of the two schemes are generated and compared. Fig.5 is the stress cloud diagram of scheme 1 and the stress cloud diagram of scheme 2. (1) Scheme 1 stress cloud diagram (2) Scheme 2 stress cloud diagram Fig 5. Stress cloud diagram of different schemes under rainfall conditions Table 2. Slope stress stability values of different schemes ( unit : kN ) Scheme Slope Monitoring points Stress stability value Scheme 1 Slope1 1 78 2 92 3 100 Slope2 4 60 5 80 6 42 Scheme 2 Slope1 1 80 2 90 3 94 Slope2 4 57 5 82 6 42 101 Comparing and analyzing the stress cloud diagram of the two schemes under continuous rainfall, it is found that the change of soil stress caused by the layout of tower foundation in the two schemes becomes smaller after continuous rainfall. Because it is difficult to compare the difference between the two schemes from the stress cloud map, the detection points are set up to analyze the difference between the two schemes. The monitoring points are the same as when the tower foundation is not laid. The stress stability value obtained by the analysis of the stress cloud monitoring point data is shown in the table 2. (2) Settlement comparison The displacement cloud images of the two schemes under heavy rainstorm conditions are generated for comparison. Fig 6 is the displacement cloud image of scheme 1 and the displacement cloud image of scheme 2. (1) Scheme 1 (2) Scheme 2 Fig 6. Displacement nephogram of different schemes (3) Layout comparison From the analysis, different layout positions affect loess slope stability. To compare stability with and without a tower foundation, settlement data under various conditions are analyzed. Table 3 shows 80 mm/hr rainfall for different conditions, and Fig. 7 displays settlement stability values of slope observation points. This comparison focuses on slope stability data. Table 3. Working condition classification Condition 1 Rainstorm conditions without tower foundation layout Condition 2 Carry out the rainstorm condition in scheme 1 Condition 3 Carry out the rainstorm condition in scheme 2 Fig 7. Comparison of settlement curves under different working conditions According to Figure 7: A, B, C: Working condition two and three settlements are equal, less than condition one.D, E, F, G, H: Settlements of condition two and three are less than condition one.D, E specify condition two settlement as smallest. F, H specify condition three settlement as smallest.G states settlements of condition two and three are equal. D and E (near scheme 2 tower foundation) show different settlements in conditions 2 and 3, but relationship undetermined. Points F, G, H indicate condition three settlement is smallest at some positions. Scheme 2 settlement near tower foundation may be greater than scheme 1, but overall, lower tower foundation placement reduces loess slope settlement and improves stability. (4) Slope safety factor Finally, the slope safety factors of the two schemes under different working conditions are compared by FLAC3D using the strength reduction method, and the optimal scheme is found for the tower foundation layout. Table 4 is the slope 102 safety factor of the two schemes under different working conditions. Table 4. Slope safety factors under different working conditions Rainstorm Nature No tower base layout was carried out 1.11 1.31 Scheme 1 1.15 1..26 Scheme 2 1.17 1.28 It can be found from the above table that when the tower foundation is laid, the stability of the loess slope will be reduced under natural conditions, but it is still in the stable area. However, due to the layout of the tower foundation, the stability of the loess slope will be greatly improved under rainfall conditions. At the same time, by comparing the data in the table, it can be found that the tower foundation layout in scheme 2 improves the safety factor of loess slope more obviously. 4. Conclusion Taking the loess slope of the Loess Plateau in Qingyangning County, Gansu Province as the research object, the characteristics, diseases and stability influencing factors of the loess slope were analyzed by means of network investigation, engineering geological analysis and finite element software numerical simulation. The settlement under rainfall conditions is mainly studied, and the influence of tower foundation layout position on slope stability is evaluated. The main conclusions include: (1) Unique loess structure affects stability. (2) Failures include slope deformation and slump (primary form). Three failure types summarized. (3) Rainfall and freeze-thaw are critical stability factors. (4) FLAC3D modeled a typical slope under natural and rainfall conditions, finding rainfall crucial, especially in the second slope prone to landslides. Strength reduction analysis showed rainfall types impact slope safety. (5) Tower foundation placement improves stability under rainfall; optimal position is slope's lower part. References [1] Chen Xiaohui. How to do a good job in the quality control of subgrade construction in collapsible loess area [J]. Technology horizon, 2017, ( 09 ) : 225. [2] Wang Changru. Floristic study on Asteraceae plants in Loess Plateau [D]. Northwest University of Agriculture and Forestry, 2007. [3] Party on the voyage. Study on stability evaluation and protective measures of sand loess tower foundation slope [D]. Chang 'an University, 2019. [4] Sun Ping. Water sensitivity of loess and prediction of rainfall- induced shallow loess landslides [D]. Northwest University, 2020. [5] Lu Yaqi, Jiao Meiling, Cao Yanchao. Climatic characteristics of the Loess Plateau in Qingyang, Gansu Province in the past 35 years [J]. China Agricultural Bulletin, 2015,31 (29) : 181- 190. [6] Li Wen. Study on the influence of water content on the shear strength of loess slope in Gansu [D]. Chang 'an University, 2010. [7] Keyao. Study on the influence of oil pipeline layout on the stability of loess slope [D]. Lanzhou Jiaotong University, 2022. [8] Zhang Mao, Li Tonglu. Study on the inducing factors and formation mechanism of loess landslide [J]. Journal of Engineering Geology, 2011,19 (04) : 530-540. [9] Wang Xiaoran. Study on the evolution law of loess slope on the north bank of Jinghe River in Pingliang City [D]. Lanzhou University, 2017. [10] Li Yanwu. Study on disease analysis and prevention countermeasures of highway subgrade in loess area [D]. Chang 'an University, 2001. [11] Zeng Lei. Study on hydrological effect and stability of loess slope during seasonal freezing-thawing process [ D ].Chang 'an University, 2018.