# Experimental Study on Shear Strength Parameters of Round Gravel Soils in Plateau Alluvial-Lacustrine Deposits and Its Application

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## Abstract

**:**

## 1. Introduction

## 2. Experimental Study of Shear Property Parameters of Round Gravel Soil

#### 2.1. Testing Instruments

#### 2.2. Experimental Soil Samples

#### 2.2.1. Round Gravel Soil Particle Size Composition

#### 2.2.2. Maximum Dry Density Experiment of Round Gravel Soil

^{3}, and the corresponding wet density is 2.26 g/cm

^{3}. Since the maximum dry density cannot be reached in the field for round gravel soil, in order to make the experimental specimens closer to the actual engineering site, the wet density corresponding to 0.87 of the maximum dry density is taken as 1.97 g/cm

^{3}for the indoor direct round gravel soil with reference to a large amount of relevant literature. The soil sample was prepared for the indoor direct shear experiment.

#### 2.3. Experimental Methods and Procedures

#### 2.3.1. Experimental Methods

^{3}, the sample was loaded and compacted in layers, the inter-layer hair scraping treatment was required, and strictly control the filling density of the sample. For the direct shear experiment of round gravel soil under saturated conditions, after filling samples, water was added to the test chamber to cover the shear box, and the shear test shall be conducted after 24 h saturation. The experimental loading was strain-controlled, and the straight shear test was performed by fast shear, as shown in Figure 5.

#### 2.3.2. Experimental Procedure

- (1)
- Loading sample: according to the determined density, gradation, and moisture content of the filler, weigh the soil material in three parts, mix and blend, and load into the shear box in layers of compaction, each time loading to 1/3 of the total height of the shear box, until the control height, after completion, level the surface.
- (2)
- Vertical loading: according to this experiment to determine the load level (low pressure: 100, 200, 300, 400 kPa) using servo motor control loading, stable pressure after observing the vertical displacement and event change curve until the stability standard control in the stability standard control at 0.002 mm/min.
- (3)
- Horizontal shear: after the soil sample vertical loading stability, according to the same strain rate horizontal shear, the shear rate of 1 mm/min, while observing the experimental machine data acquisition system until the specimen damage. Experiment until the soil sample horizontal shear displacement reaches 15% of the diameter of the specimen when the end of shear.
- (4)
- The specimen damage determination: when the horizontal stress table readings fall, no longer rise or rise very little, the deformation change is large, that has been shear damage. If none of the above, when the shear deformation reaches 15% of the diameter of the shear box, stop the shear experiment. After the experiment, clear the soil on the shear box, analyze the shear surface characteristics, and take pictures.

#### 2.4. Test Results and Analysis

#### 2.4.1. Shear Stress-Shear Displacement Curve Change Characteristics Analysis

#### 2.4.2. Characterization of Shear Strength Parameters

## 3. Engineering Application Study on Shear Strength Parameters of Round Gravel Soil

#### 3.1. Project Overview

^{2}, and the depth of pit support is 14~33 m. The pit is divided into four sections, one of which includes the intake pump room and aeration and sand sink. The modeling object is the intake pump room, with a design depth of 33 m, plan size of 32 m long and 25 m wide, perimeter length of 114 m, and area of 800 m

^{2}. 1200 mm diaphragm wall + reinforced concrete internal bearing and anchor cable support form is used for the enclosure structure. The wall height is 43.75 m and 67.5 m, and the width is 5.10~6.00 m, the length of the single reinforcement cage is 44.25 m and 68 m, and the depth of continuous wall embedded in the subgrade is 22.8~42.1 m according to the geological condition. As Figure 10 and Figure 11 show the section of the pit of the inlet pump room and the internal bearing structure, respectively.

#### 3.2. Pit Modeling and Parameter Selection

#### 3.2.1. Computational Models

#### 3.2.2. Calculation Parameters Selection

#### 3.3. Results Analysis

#### 3.3.1. Analysis of the Evolution Law of Foundation Pit and Surrounding Soil Displacement

#### 3.3.2. Analysis of Displacement Variation Law of Diaphragm Wall

#### 3.3.3. Analysis of Displacement Variation Law of Diaphragm Wall

#### 3.3.4. Analysis of the Variation Law of Interior Bearing Axial Force

#### 3.3.5. Anchor Cable Axial Force Variation Characteristics Analysis

## 4. Conclusions

- (1)
- The shear strength characteristics of plateau alluvial-lacustrine alluvial round gravel soil under different water content conditions are studied and analyzed through large-scale direct shear tests. Under different water content conditions, the variation law of shear stress-shear displacement of round gravel soil is slightly different. At low water content, with the increase of shear displacement, the particles of round gravel soil are sheared, and the shear surface contacts closely until shear failure, and the soil strength slightly increase. However, the shear resistance curve of round gravel soil with high water content gradually weakened with the increasing confining pressure.
- (2)
- Large-scale direct shear experiments of round gravel soil show that the cohesion of round gravel soil in the natural state is 8.56 kPa, and the angle of internal friction is 31.9°. In the saturated state, the cohesion of round gravel soil is 7.37 kPa, and the angle of internal friction is 30.5°. With the increased water content, the round gravel soil’s cohesive force and internal friction angle decrease significantly.
- (3)
- The numerical simulation results of foundation pit excavation show that after the completion of construction, the pit bottom is subject to the joint influence of the reinforcement area and lattice columns. There is a large uplift, and the surrounding surface soil also shows a bulge within a certain range. Hence, further strengthening the monitoring and reinforcement of the surrounding structures is necessary. The stress deformation of the supporting structure is small, far less than the design value. With the increase of the conglomerate soil’s internal friction angle and cohesion, the foundation support and soil deformation decreased, indicating that increasing the shear strength parameter of the conglomerate soil can effectively reduce the foundation deformation. The construction can be carried out by selecting conglomerate strata with different water content in practical engineering to achieve, reduce the project cost and improve the project economy.

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

- Tan, F.; Wu, S.; Huang, Z.F.; Chen, Z. Discussion on ground bearing capacity of the sandy pebble in the foundation of tall buildings in Chengdu area. Build. Struct.
**2013**, 43, 30–32, 83. [Google Scholar] - Hou, L.J.; Chen, X.C.; Chen, H.; Cui, C.L. Research on models of surface wave velocity method for determining bearing capacity of cobble soil foundation. Rock Soil Mech.
**2008**, 29, 2572–2576. [Google Scholar] - Soleimani, S.; Jiao, P.; Rajaei, S.; Forsati, R. A new approach for prediction of collapse settlement of sandy gravel soils. Eng Comput.
**2018**, 34, 15–24. [Google Scholar] [CrossRef] - Rücknagel, J.; Götze, P.; Hofmann, B.; Christen, O.; Marschall, K. The influence of soil gravel content on compaction behaviour and pre-compression stress. Geoderma
**2013**, 209, 226–232. [Google Scholar] [CrossRef] [Green Version] - Ghanizadeh, A.R.; Delaram, A.; Fakharian, P.; Armaghani, D.J. Developing Predictive Models of Collapse Settlement and Coefficient of Stress Release of Sandy-Gravel Soil via Evolutionary Polynomial Regression. Appl. Sci.
**2022**, 12, 9986. [Google Scholar] [CrossRef] - Jiang, J.C. Research on strong dewatering technology for deep foundation excavation in Kunming round gravel stratum. Constr. Technol.
**2012**, 41, 107–111. [Google Scholar] - Sun, T.; Chen, G.X.; Wang, B.H.; Li, X.J. Experimental research of effect of granule shape on shear modulus and damping ratio of gravel. Chin. J. Rock Mech. Eng.
**2014**, 33, 4211–4217. [Google Scholar] - Wang, Y.X.; Shao, S.J.; Wang, Z. Experimental study on mechanical behaviors and particle breakage of sandy gravel. Chin. J. Rock Mech. Eng.
**2020**, 39, 1287–1296. [Google Scholar] - Hara, T.; Kokusho, T.; Hiraoka, R. Undrained strength of gravelly soils with different particle gradations. Mouth
**2004**, 277, 1920. [Google Scholar] - Kuenza, K.; Towhata, I.; Orense, R.P.; Wassan, T.H. Undrained torsional shear tests on gravelly soils. Landslides
**2004**, 1, 185–194. [Google Scholar] [CrossRef] - Rollins, K.M.; Singh, M.; Roy, J. Simplified equations for shear-modulus degradation and damping of gravels. J. Geotech. Geoenviron. Eng.
**2020**, 146, 04020076. [Google Scholar] [CrossRef] - Hubler, J.F.; Athanasopoulos-Zekkos, A.; Zekkos, D. Monotonic and cyclic simple shear response of gravel-sand mixtures. Soil Dyn. Earthq. Eng.
**2018**, 115, 291–304. [Google Scholar] [CrossRef] - Liu, J.; Tang, Y.; Yi, L.; Peng, Y.C.; Zhou, Y.F. Creep Constitutive Model of Cobbly Soil and Its Engineering Application. J. Yangtze River. Sci. Res. Inst.
**2022**, 39, 107–112. [Google Scholar] - Tong, J.J.; Wang, M.N.; Yu, L.; Liu, D.G.; Xu, R. A study of the land subsidence around the deep foundation pit of the Chengdu subway station. Hydrogeol. Eng. Geol.
**2015**, 42, 97–101. [Google Scholar] - Penumadu, D.; Zhao, R. Triaxial compression behavior of sand and gravel using artificial neural networks (ANN). Comput. Geotech.
**1999**, 24, 207–230. [Google Scholar] [CrossRef] - Tang, K.S.; Xie, X.Y.; Yang, L. Research on mechanical characteristics of gravel soil based on large-scale triaxial tests. Chin. J. Under Space Eng.
**2014**, 10, 580–585. [Google Scholar] - Ma, S.K.; Wang, B.; Liu, Y.; Shao, Y.; Wang, H.G.; Wang, Y.L. Large-scale dynamic triaxial tests on saturated gravel soil in Nanning metro area. Chin. J. Geotech. Eng.
**2019**, 41, 168–174. [Google Scholar] - Ma, S.K.; Duan, Z.B.; Liu, Y.; Wang, B.; Shao, Y. Large triaxial test study on dynamic characteristics of round gravel. Arab. J. Geosci.
**2020**, 13, 1–9. [Google Scholar] [CrossRef] - Stark, N.; Hay, A.E.; Cheel, R.; Lake, C.B. The impact of particle shape on the angle of internal friction and the implications for sediment dynamics at a steep, mixed sand–gravel beach. Earth Surf. Dynam.
**2014**, 2, 469–480. [Google Scholar] [CrossRef] [Green Version] - Enomoto, T.; Qureshi, O.H.; Sato, T.; Koseki, J. Strength and deformation characteristics and small strain properties of undisturbed gravelly soils. Soils Found.
**2013**, 53, 951–965. [Google Scholar] [CrossRef] [Green Version] - Chen, C. Research on modified constitutive model of Shenyang circular-gravel based on disturbed state. J. Henan Polytech. Univ. Nat. Sci.
**2017**, 36, 125–131. [Google Scholar] - Saberi, M.; Annan, C.D.; Konrad, J.M. Constitutive modeling of gravelly soil–structure interface considering particle breakage. J. Eng. Mech.
**2017**, 143, 04017044. [Google Scholar] [CrossRef] - Liu, G.; Lu, R.; Zhao, M.Z.; Luo, Q.; Lv, C. Ellipsoid model based packing characteristics analysis of round gravels. Rock. Soil Mech.
**2019**, 40, 4371–4379. [Google Scholar] - Ou, X.D.; Huang, Z.Z.; Jiang, J.; Luo, F.Z.; Liang, Y.H. Influence of pit-in-pit excavation on double-row piles in composite stratum of round gravel and mudstone. J. Yangtze River. Sci. Res. Inst.
**2022**, 39, 78–85. [Google Scholar] - Ni, X.R.; Li, Z.L.; Wang, Y. Application of auger drilling secondary pressure fed technology into concrete piles in dry sand and gravel formations. Constr. Technol.
**2015**, 44, 134–136. [Google Scholar] - GB/T50123-2019; CSBTS (China State Bureau of Quality and Technical Supervision) Chinese Standard for Soil Test Method. CSBTS: Beijing, China, 2019.
- Liu, L.L.; Sun, Q.C.; Wu, N.Y.; Liu, C.L.; Ning, F.L.; Cai, J.C. Fractal analyses of the shape factor in kozeny–carman equation for hydraulic permeability in hydrate-bearing sediments. Fractals
**2021**, 29, 2150217. [Google Scholar] [CrossRef] - Wei, R.C.; Liu, L.L.; Jia, C.; Zhao, H.L.; Dong, X.; Bu, Q.T.; Liu, C.L.; Wu, N.Y. Undrained Shear Properties of Shallow Clayey-Silty Sediments in the Shenhu Area of South China Sea. Sustainability.
**2023**, 15, 1175. [Google Scholar] [CrossRef] - Wang, X.Z.; Wang, X.; Shen, J.H.; Ding, H.Z.; Wen, D.S.; Zhu, C.Q.; Lv, S.Z. Foundation filling performance of calcareous soil on coral reefs in the South China Sea. Appl. Ocean Res.
**2022**, 129, 103386. [Google Scholar] [CrossRef] - Wang, X.; Shan, Y.; Cui, J.; Zhong, Y.; Shen, J.H.; Wang, X.Z.; Zhu, C.Q. Dilatancy of the foundation filling material of island-reefs in the South China Sea. Constr. Build. Mater.
**2022**, 323, 126524. [Google Scholar] [CrossRef] - Wang, Y.P.; Lu, Y.W.; Zhang, E.S.; Peng, Y.C.; Zuo, Y.Z.; Li, H.M. Comprehensive experimental study of strength and deformation characteristics and mechanical model parameters of sandy pebble soil. J. Yangtze River. Sci. Res. Inst.
**2022**, 39, 93–98. [Google Scholar] - Fragaszy, R.J.; Su, J.; Siddiqi, F.H.; Ho, C.L. Modeling strength of sandy gravel. J. Geotech. Eng.
**1992**, 118, 920–935. [Google Scholar] [CrossRef] - Guo, Y.H.; Yan, M.; Song, Q.; Yuan, G.; Fu, X.B. The influence of deep foundation pit excavation on the adjacent existing high pressure natural gas pipeline. Chin. J. Under Space Eng.
**2021**, 17, 840–847. [Google Scholar]

**Figure 2.**Photos of round gravel soil sampling points: (

**a**) project site photos; (

**b**) photo of sampling point.

**Figure 5.**Experimental steps for direct shear of round gravel soil: (

**a**) sieving soil; (

**b**) soil mixing and enclosing; (

**c**) load soil sample into shear box; (

**d**) lift the shear box into the test chamber; (

**e**) install the sensor and start the experiment; (

**f**) observe the shape of the cutting surface.

**Figure 7.**Shear displacement-shear stress curve of round gravel soil with saturated moisture content.

**Figure 8.**Fitted shear strength curves for natural and saturated moisture content of round gravel soils.

**Figure 13.**The schematic diagram of the calculation model of the foundation support structure of the intake pump room: (

**a**) diaphragm wall; (

**b**) interior bearing; (

**c**) anchor cable.

**Figure 14.**Cloud map of vertical displacement of surrounding surface and soil at the bottom of the pit: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 15.**Vertical displacement change curve of the ground surface around the foundation pit: (

**a**) diaphragm wall 2 short side; (

**b**) diaphragm wall 1 side.

**Figure 16.**X-direction displacement clouds of the surrounding surface and the soil at the bottom of the pit: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 17.**Y-direction displacement clouds of the surrounding surface and the soil at the bottom of the pit: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 19.**Horizontal displacement cloud in X-direction of diaphragm wall: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 20.**Horizontal displacement cloud in Y-direction of diaphragm wall (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 21.**Horizontal displacement variation curve of diaphragm wall: (

**a**) horizontal displacement in X direction; (

**b**) horizontal displacement in Y direction.

**Figure 22.**Vertical displacement cloud of diaphragm wall: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 23.**Minimum principal stress cloud of diaphragm wall: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 24.**Maximum principal stress cloud of diaphragm wall: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 25.**Axial force cloud diagram of interior bearing system: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

**Figure 26.**Anchor cable axial force cloud: (

**a**) natural moisture content shear strength parameters; (

**b**) saturated moisture content shear strength parameters.

Gradation Type | Percentage of Mass Smaller Than a Certain Particle Size/% | ||||||
---|---|---|---|---|---|---|---|

>60 mm | 60~40 mm | 40~20 mm | 20~10 mm | 10~5 mm | 5~2 mm | <2 mm | |

Prototype gradation | 0.48 | 7.39 | 25.61 | 21.62 | 13.73 | 11.01 | 20.16 |

Scaled gradation | 7.43 | 25.73 | 21.72 | 13.80 | 11.06 | 20.26 |

Soil Sample Number | Design Water Content ω (%) | Weight of Cylinder and Soil (g) | Weight of Solid Barrel (g) | Combat Cylinder Volume (cm^{3}) | Wet Density ρ (g/cm ^{3}) | After Experiment Water Content ω (%) |
---|---|---|---|---|---|---|

1 | 5 | 7653 | 3080 | 2159 | 2.12 | 8.5 |

2 | 7 | 7973 | 3080 | 2159 | 2.27 | 10.9 |

3 | 9 | 7913 | 3080 | 2159 | 2.24 | 12.2 |

4 | 11 | 7867 | 3080 | 2159 | 2.22 | 13.3 |

5 | 13 | 7833 | 3080 | 2159 | 2.20 | 15.1 |

The Angle of Internal Friction φ (°) | Cohesive Forces c (kPa) | |
---|---|---|

Natural moisture content of round gravel soil | 31.9 | 8.56 |

Saturated moisture content of round gravel soil | 30.5 | 7.37 |

Number | Name of Soil Type | Volumetric Weight (kN/m^{3}) | Cohesive Forces (kPa) | The Angle of Internal Friction (°) | Poisson’s Ratio | Elastic Modulus (MPa) |
---|---|---|---|---|---|---|

1 | Miscellaneous fill | 18.7 | 19.5 | 8.5 | 0.28 | 7 |

2 | Peat soil | 13.2 | 20 | 6 | 0.40 | 12.1 |

3 | Round gravelly soil (natural) | 19.4 | 8.56 | 31.9 | 0.46 | 196.67 |

4 | Round gravelly soil (saturated) | 19.4 | 7.37 | 30.5 | 0.46 | 196.67 |

5 | Silty clay | 19 | 40 | 12 | 0.30 | 16 |

Components | Elastic Modulus (MPa) | Poisson’s Ratio | Volumetric Weight (kN/m^{3}) |
---|---|---|---|

Diaphragm wall | 31,500 | 0.3 | 26 |

Anchor cable | 195,000 | 0.3 | 78.5 |

Wai purlin | 31,500 | 0.3 | 26 |

Interior bearing | 31,500 | 0.3 | 26 |

Lattice column | 31,500 | 0.3 | 26 |

Compaction grouting | 25,000 | 0.3 | 26 |

Retaining wall | 31,500 | 0.3 | 26 |

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## Share and Cite

**MDPI and ACS Style**

Kong, Z.; Guo, Y.; Mao, S.; Zhang, W.
Experimental Study on Shear Strength Parameters of Round Gravel Soils in Plateau Alluvial-Lacustrine Deposits and Its Application. *Sustainability* **2023**, *15*, 3954.
https://doi.org/10.3390/su15053954

**AMA Style**

Kong Z, Guo Y, Mao S, Zhang W.
Experimental Study on Shear Strength Parameters of Round Gravel Soils in Plateau Alluvial-Lacustrine Deposits and Its Application. *Sustainability*. 2023; 15(5):3954.
https://doi.org/10.3390/su15053954

**Chicago/Turabian Style**

Kong, Zhijun, Yanhui Guo, Shilin Mao, and Wei Zhang.
2023. "Experimental Study on Shear Strength Parameters of Round Gravel Soils in Plateau Alluvial-Lacustrine Deposits and Its Application" *Sustainability* 15, no. 5: 3954.
https://doi.org/10.3390/su15053954