Uniform Soil Research Articles

Influences of particle size distribution and fines content on the excess pore water pressure generation of sand-silt mixtures under cyclic loading

The mechanical behaviors of binary mixtures are different from that of uniform soils. However, experimental studies on the dynamic responses of sand-silt mixtures considering the combined effects of fines content (FC) and host sand gradation are limited in the literature. In this paper, an experimental program was designed concerning five binary mixtures with three grain size ratios (Rd) and three sand uniformity coefficients (Cus) for investigating the effects of fines content and host sand gradation on both the liquefaction resistance and the excess pore water pressure (EPWP) generation of sand-silt mixtures. Results show that the effect of FC on the liquefaction resistance of sand-silt mixtures depends on relative density (Dr), grain size ratio, and sand uniformity coefficient. The liquefaction resistance of sand-silt mixture can be uniquely characterized by the equivalent relative density Dr* regardless of FC, Dr, and host sand gradation. Relationship between the EPWP ratio Ru and the cycle ratio N/NL for the sand-silt mixtures can be well expressed by the Seed model, which is significantly affected by cyclic stress ratio (CSR), FC, and Dr but insensitive to the change of host sand gradation. A trained artificial neural networks (ANN) model is conducted to predict the fitting parameter β of the Seed model with a maximum difference of 25% between the predicted and measured values. Moreover, there is an arctangent relationship between Ru and shear strain amplitude γa of each specimen, and the fitting parameter A for the relationship is sensitive to the particle size distribution and stress amplitude. A unique relationship between a density-corrected parameter A/Dr* and CSR is proposed regardless of FC and host sand gradation.

Layered Green and Ampt Infiltration With Redistribution

AbstractNumerical solution of the one‐dimensional Richards equation (RE) accurately partitions precipitation into infiltration and runoff in capillary dominated soils. However, its application sometimes requires significant computational effort and presents reliability challenges. The Green and Ampt (G&A) approach represents a conservative and efficient method to calculate one‐dimensional infiltration but is limited to deep, well drained, uniform, non‐layered soils for a single rainfall event. The original G&A model and subsequent advancements represent wetting fronts as discrete objects, rather than discretizing the model domain in space, yielding a computationally simpler model than the RE. This paper describes an extension of the G&A method into layered soils on a continuous basis that we call Layered Green and Ampt with Redistribution (LGAR). Assumptions employed in the derivation include: uniform soil hydraulic properties within layers, single‐valued capillary head at the interface between soil layers, and no influence of groundwater table on soil moisture. Wetting fronts advance due to the combined effects of gravity and wetting front capillary drive in a layered soil profile. Results of multi‐month continuous LGAR simulations of infiltration using forcing and soil hydraulic data from USDA SCAN sites are compared against infiltration calculated using the HYDRUS‐1D RE solver using standard metrics. The assumptions employed in deriving the LGAR method limit its application to situations where cumulative potential evapotranspiration is greater than cumulative precipitation, typical of arid or semi‐arid conditions. LGAR is a mass‐conservative, computationally efficient, reliable and reasonably accurate method for simulating infiltration over extended time periods compared to the numerical solution of the RE in layered soils in arid and semi‐arid regions.

Structural response of the spiral-welded pipelines buried in different uniform soil types to the strike-slip fault

Buried steel pipelines, which are widely used in, often face the threat of Permanent Ground Deformations (PGD) caused by fault crossings. The structural response of the pipeline can be influenced by the pipe-trench-backfill interaction, resulting in various hoop strains, axial plastic strains, and consequently, formation of wrinkles at different locations in the fault zone. This paper investigates the structural response of spiral-welded pipelines at strike-slip fault crossings by incorporating the burial effects in a range of different soil materials. A dynamic explicit analysis is used to address the convergence issue commonly encountered in the analysis of post-buckling problems. The helix angles and the burial depth effects in different soil types and pipeline-ground interaction angles are examined. The study provides valuable insights into the influence of burial conditions and corresponding helix angle on the performance of spiral-welded pipelines in strike-slip faults.

Code provisions evaluation for the punching shear capacity of R.C footings without reinforcement for punching shear

There is no agreement on how to predict punching shear for footings among different design codes, which is inconsistent with experimentally observed capacity. Such inconsistency is due to the following issues: (1) the different definitions used by design codes for the critical section that resists the punching shear; (2) the different handling of the main parameters' influences, such as the shear slenderness, longitudinal reinforcement ratio, yielding strength of reinforcement, and compressive strength of concrete; (3) the different modelling of the subsoil underneath the footings is affecting the prediction of punching; and (4) the different modelling of the subsoil beneath the footings is affecting the prediction of punching. The current study quantified the level of safety for the various international design codes using the 195 RC column footings that had been punching shear tested and obtained from earlier investigations. Six design codes, standards, or guidelines were selected, including ACI 318–19, PrEC2, JSCE (1997), CSA and BS 8110–1 (1997), and fib Model Code (2010). The effect of the main parameters on the safety of the punching shear capacity calculated using selected methods was examined. These main parameters are concrete and reinforcement material characteristics, effective depth, column dimension, shear slenderness, and reinforcement ratio. In addition, the effect of modelling the subsoil underneath the footing is considered a parameter. It is found that all selected methods underestimate calculated punching shear capacity compared to those measured experimentally. In addition, the BS8110 is the most conservative of all selected design codes, while the second generation of the Euro code (PrEC2) is the closest to measurements and the most reliable. Moreover, the safety (Vexp/Vcalc.) of the predicted capacity using all selected methods is inversely proportional to the effective depth, the concrete compressive strength, and the column dimensions. i.e., the predicted capacity is increased with increasing these parameters, while being directly proportional to the yielding strength of reinforcement and the shear slenderness ratio, i.e., the predicted capacity is decreased with increasing these parameters. All design codes do not consider the effect of reinforcement material characteristics, even though this parameter significantly affects the results. For the flexure reinforcement ratio, the safety of the predicted punching shear capacity using ACI, CSA, and fib Model Code is directly proportional. While it is inversely proportional to the safety calculated using the PrEC2, and JSCE design codes. This is due to the fact that the PrEC2, and JSCE design codes considered the flexure reinforcement ratio while the ACI, CSA, and fib model codes neglected its effect. All selected design codes predict the punching shear capacity well if the concrete compressive strength ranges from 20 to 30 MPa, the reinforcement yielding strength is less than 500 MPa, the reinforcement ratio is less than 0.4, the effective depth ranges from 200 to 300 mm, the shear slenderness ratios are less than 2 or more than 3, and the column periphery is related to the effective depth (bo/d) between 2.0 and 6.0. Additionally, the spring simulation of the subsoil provides capacity values close to those obtained experimentally, while the sand box model, which assumes uniform soil pressure, provides the divergence values of punching capacity. The PrEC2 and fib MC2010 LOAIII design codes provided less safety than the predicted punching shear capacity for different types of sub-soil simulations.

Revisiting the definition of field capacity as a functional parameter in a layered agronomic soil profile beneath irrigated maize

The soil water content at the condition of field capacity (θFC) is a key parameter in irrigation scheduling and has been suggested to be determined by running a synthetic drainage experiment until the flux rate (q) at the bottom of the soil profile achieves a predefined negligible value (qFC). We question the impact of qFC on the assessment of field capacity. Moreover, calculating θFC as the integral mean of the water content profile when q is equal to qFC is strictly valid only for uniform soil profiles. By contrast, this practice is ambiguous and biased for stratified soil profiles due to the soil water content discontinuity at the layer interfaces. In this study, the concept of field capacity was revisited and adapted to practical agronomic heuristics. By resorting to the assessment of root-zone water storage capacity (W), we envision field capacity as a functional hydraulic parameter derived from synthetic irrigation scheduling scenarios to minimize drought stress, drainage, and nitrate leachate below the root zone. A functional analysis was carried out on a 135-cm-thick layered soil profile beneath maize in eastern Nebraska. On-farm irrigation scheduling applications and agricultural practices were recorded for 20 years (2001–2020) at a daily time step. Hydrus-1D was calibrated and validated with direct measurements of the soil water retention curve and soil water content data, respectively, in each soil layer. A set of functional field capacity values was derived from 24 irrigation scheduling scenarios, and the optimal water storage capacity at field capacity (WFC) was approximately 50 cm (corresponding to about 80% saturation in the soil profile). An average irrigation amount of 217.5 mm distributed over 21 events was obtained by using optimal irrigation scheduling, which was initiated when the matric pressure head took on a value of −700 cm and the irrigation rate was set at 1.0 cm d−1. This irrigation practice ensured water storage at approximately the same level (ideally at WFC) by sustaining only evapotranspiration fluxes in the uppermost portion of the root zone and by limiting excessive drainage. This protocol can be transferred to other agricultural fields.

Numerical modeling of ice–seabed interaction in layered soil: stiff over soft clay

This study presents a numerical investigation of free field ice gouging in layered cohesive seabeds comprising stiff over soft clay. A three-dimensional, half-space, dynamic large deformation finite element analysis was conducted using the Coupled Eulerian Lagrangian approach. To simulate the seabed, a Tresca soil model with the strain rate and strain-softening effects was coded into a user subroutine. The accuracy of the model was verified by comparing its results with those of published experimental studies. Additionally, a comprehensive parametric study was conducted to examine the effect of various ice gouging scenarios and seabed soil parameters on the subgouge soil deformation and the ice keel reaction forces. Our findings revealed that an interactive response occurs between the soil layers and the ice keel that may cause the peak subgouge soil deformation and keel reaction magnitudes to differ from those observed under uniform soil condition. The developed model was found to be an efficient tool for free field ice gouging analysis in cohesive layered seabeds.

Capacity and failure mechanism of monopile-wheel hybrid foundation in clay-overlaying-sand deposits under combined V–H-M loadings

Innovative monopile-wheel hybrid foundations are proposed to enhance the lateral load and moment capacities of monopile for offshore wind systems. This paper presents a comprehensive numerical study on the bearing capacities of this hybrid foundation in clay-overlaying-sand soil conditions under combined V–H-M (vertical-horizontal-moment) loadings. Numerical models are generated and validated by comparing with laboratory experiment results and available centrifuge testing data on similar foundation systems. Parametric analysis is then carried out to quantify the effects of potential influencing factors on the failure mechanisms and bearing capacities of hybrid foundations, including the hybrid foundation geometry, soil properties, upper clay thickness, height of the lateral loading and pre-vertical load. It is found that in clay-overlaying-sand deposits, the hybrid system manifests totally different failure mechanism compared with that in uniform soil deposits. The thickness of the upper clay layer (Tc/L), within the practical range of Tc/L = 0.1–0.7, has a significant influence on the failure patterns and the bearing capacities of the hybrid system, and the proportion of bearing capacity provided by the pile and wheel is determined by the ratios of Dw/L and L/Dp. In addition, the failure envelopes in the V–H-M space manifests that the failure envelopes are shrank with the increase of the normalized vertical resistance, V/Vult, which is highly related to the clay layer thickness (Tc/L).

Deformation of trenched multilayer pipelines during large lateral displacement due to subsea geohazards

Large lateral displacement of trenched multilayer pipelines may be induced by ground movement, landslides, ice gouging, etc. The significant difference between the shear strength of the backfill material and the native soil may affect the pipeline-backfill-trench interaction, the failure mechanisms, and consequently the lateral soil resistance. However, this challenging and less-explored aspect has not been covered thoroughly in design codes, even for rigid pipes. This paper investigates the influences of multilayer pipeline-backfill-trench interaction on the deformation of pipe section, soil failure mechanism, resultant lateral soil resistance, and soil pressure on the pipe by large deformation finite element analyses. A decoupled model consisting a Coupled Eulerian-Lagrangian (CEL) approach with a rigid pipe in ABAQUS was created along with a finite element (FE) model of multilayer flexible pipe in ANSYS to assess their relative merits for this problem. A parametric study was conducted to investigate the influences of key factors, including the trench geometry, stiffness of backfill material, native seabed soil properties, burial depth, and intensity of pipeline-trench bed interaction. The study showed that the ignorance of the pipeline-backfill-trench interaction by using uniform soil might result in underestimation and overestimation of the lateral soil resistance at different displacement amplitudes.

Iterative Horizontal Method of Slices for Global Stability of Slurry Trench in Layered Cohesive-Frictional Soils

This paper presents an iterative horizontal method of slices (iterative HMS) for the global stability analysis of a slurry trench in layered cohesive-frictional soils. The iterative HMS differs from existing HMS models in terms of the assumptions on interslice forces. Preceding HMS techniques postulate that normal interslice forces can be evaluated from overburden pressures, which can lead to the violation of failure criteria along interslice boundaries. The iterative HMS ensures that a limit equilibrium system is established without violating the failure criterion throughout the entire soil mass. This is achieved by iteratively adjusting interslice forces by means of enforcing the failure criterion for the aforementioned problematic slice boundaries violating the failure conditions. The performance of the iterative HMS is evaluated in example problems of a slurry trench in uniform clayey soils and cohesive-frictional strata. The results are compared against solutions obtained using finite-element limit analysis (FELA) and a shear strength reduction FEM (SSRFEM). This comparative analysis shows that the adjustment in interslice forces is important for reasonably assessing trench stability conditions. A parametric analysis is performed by using the iterative HMS to show under what trench construction parameters the adjustment of interslice forces cannot be neglected in the stability analysis of a slurry trench.

Assessment of the Response of Trenched–Backfilled Pipelines to Strike-Slip Faults: An Analytical Approach

Trenched pipelines may experience significant lateral displacement due to natural geohazards such as strike slip-fault movements, landslides, etc. Using pre-excavated soil to backfill trenches is a cost-effective option to protect pipelines against large deformations. These backfilling materials are heavily remolded and therefore softer than the native ground. Therefore, the shear strength difference between the backfill and native ground may affect the pipeline–backfill–trench interaction and the failure mechanism of the surrounding soil. By assuming a simplified uniform soil domain, the influence of softer pre-excavated backfilling material on the pipeline–backfill–trench interaction is neglected in the analytical methods that are usually used in the structural health monitoring of buried pipelines. In this study, the effects of trenching and backfilling were incorporated into an analytical solution for a fast assessment of the pipeline response at the early stages of engineering design projects and structural health monitoring. In comparison with other methods, this methodology provides a convenient and efficient method for computing pipeline strain and deflection curves in geohazardous regions.

3D large-deformation modelling on face instability and sinkhole formation during tunnelling through non-uniform soils

Natural soils exhibit spatially non-uniform properties, bringing some uncertainties on the evaluation of tunnel stability. This study therefore investigates the face instability and in particular to the sinkhole formation in spatially non-uniform soils by conducting large-deformation finite-element (LDFE) analyses combined with a three-dimensional random field. The results from LDFE analyses indicate that soil spatial non-uniformity greatly affects the failure mechanism as well as the face stability. The stability factor in non-uniform soils is averagely smaller than the deterministic solution in a uniform soil, implying the assumption of uniform soil conditions likely underestimates probability of failure of a tunnel face. With regard to the sinkhole behaviour, the average ground settlement obtained from random analysis is greater than that from deterministic analysis. This underscores the necessity of considering the soil spatial non-uniformity in the analysis of the sinkhole behaviour. This study provides an improved understanding on the face stability and sinkhole formation during tunnelling through non-uniform soils.

Undrained capacity of circular shallow foundations on two-layer clays under combined VHMT loading

Wind turbines are typically designed based on fatigue and serviceability limit states, but still require an accurate assessment of bearing capacity. Overconsolidated clay deposits in Canada often have a thin layer of crust with a relatively high undrained shear strength. However, existing bearing capacity design methods do not consider surficial crusts. This paper studies the undrained VHMT (vertical, horizontal, moment, and torsional) failure envelope of circular foundations founded on a surficial crust underlain by a uniform soil using finite element analysis. Crust correction factors have been introduced to account for the effects of the stiff layer on the vertical and moment capacities. The same forms of equation that are used for uniform soils, but with different parameters provide satisfactory fits for the failure envelopes for a soil with a crustal layer. An analytical expression for the 4-D VHMT failure envelope is derived, and an application of this method is provided.

Experimental Study on the Seismic Mitigation Performance of Metafoundations on a Uniform Soil Layer

ABSTRACT The seismic mitigation performance of a metafoundation with soil-structure interaction was investigated utilizing shaking table tests. The results indicated that the metafoundation’s performance strongly depended on the coupling among the frequencies of the soil layer, structural systems, and input motions. Due to resonant effects, the response of the controlled structure could be greater than that of the uncontrolled superstructure at small input PGAs. By contrast, the metafoundation exhibited excellent mitigation effects at large PGAs. A simplified elastic model was validated by the experimental results. Then the validated model contributed to the interpretation of experimental phenomena based on equivalent linear parameters.

TECHNOLOGICAL EQUIPMENT FOR PERFORMING SELECTIVE CAPITAL REPAIR OF PIPELINES

The article provides an analysis of the technical condition of main pipelines and technologies for performing selective overhaul of their linear part. Known technological schemes for performing selective repair of pipelines do not provide for effective soil compaction after its completion due to the lack of technical means for effective and uniform soil compaction. The lack of compaction of the soil under the repaired pipeline leads to its uncontrolled subsidence relative to the line of original laying, which can cause an emergency situation. In order to ensure high-quality, fast and safe execution of the entire complex of earthworks during the selective overhaul of main pipelines with one excavator, a research and industrial universal set of interchangeable work equipment for a single-bucket crawler excavator weighing 20 tons has been designed, manufactured and tested. The set of replacement equipment consists of digging equipment, compaction equipment, a bucket for performing earthworks during the opening of the pipeline and filling the soil in the trench, a universal grip for attaching the replacement equipment to the handle of a single-bucket excavator, a system for positioning and monitoring the position of the replacement equipment relative to the pipe. Technology for implementation of earth-moving works at capital repair of linear portion of main pipelines and complex of technological equipment for its realization are patented in Ukraine. The productivity of digging equipment is 35...55 m3/h, the productivity of compacting equipment is 35...45 m/h. The use of a set of equipment allows one excavator to perform the entire complex of earthworks during the selective capital repair of main gas pipelines with a diameter of 530...1420 mm.

Probabilistic Assessment on 3D Stability and Failure Mechanism of Undrained Slopes Based on the Kinematic Approach of Limit Analysis

Most slope collapses have three-dimensional (3D) characteristics due to the uniform soil. The traditional plane-strain analyses neglect the 3D effects and could yield an overestimation or underestimation of the slope stability. The present study analyzes the stability of 3D slopes characterized by spatially variable undrained shear strength. A 3D slope reliability analysis approach that can fully consider the spatial variability of soil properties is proposed based on the plastic limit analysis upper-bound theorem. Within the framework of Monte Carlo simulation, the effects of strength gradient, the coefficient of variation, and the scale of fluctuation of soil undrained shear strength on the slope reliability index are examined. The length of the 3D failure surface is highlighted as an essential characteristic in 3D slope analysis. The slope failure mechanisms are classified, and the occurrence probability of each type is quantified. The obtained results indicate that the degree of nonstationarity and the coefficient of variation of undrained shear strength have significant impacts on the slope failure width, and the variation of failure mechanism highly depends on the combined effect of slope inclination and soil strength. The findings could guide slope reinforcement and facilitate a more efficient and accurate risk evaluation of slopes.

Estimation of Soil–Structure Model Parameters for the Millikan Library Building Using a Sequential Bayesian Finite Element Model Updating Technique

We present a finite element model updating technique for soil–structure system identification of the Millikan Library building using the seismic data recorded during the 2002 Yorba Linda earthquake. A detailed finite element (FE) model of the Millikan Library building is developed in OpenSees and updated using a sequential Bayesian estimation approach for joint parameter and input identification. A two-step system identification approach is devised. First, the fixed-base structural model is updated to estimate the structural model parameters (including effective elastic modulus of structural components, distributed floor mass, and Rayleigh damping parameters) and some uncertain components of the foundation-level motion. Then, the identified structural model is used for soil–structure model updating wherein the Rayleigh damping parameters, the stiffness and viscosity of the soil subsystem (modeled using a substructure approach), and the foundation input motions (FIMs) are estimated. The identified model parameters are compared with state-of-practice recommendations. While a specific application is made for the Millikan Library, the present work offers a framework for integrating large-scale FE models with measurement data for model inversion. By utilizing this framework for different civil structures and earthquake records, key structural model parameters can be estimated from the real-world recorded data, which can subsequently be used for assessing and improving, as necessary, state-of-the-art seismic analysis and structural modeling techniques. This paper presents an effort towards using real-world measurements for large-scale FE model updating in the soil and structure, uniform soil time domain for joint parameter and input estimation, and thus paves the way for future applications in system identification, health monitoring, and diagnosis of civil structures.

Investigation of the installation process of drag-in plate anchors from LDFE modelling

The installation of drag-in plate anchors is investigated using advanced large-deformation finite-element (LDFE) analysis. A new modelling technique that can realise the continuously evolving loading angle on the anchor line is described. The entire anchor trajectory is simulated until the anchor reaches an ultimate state after dragging for a very large distance, typically in the range of 40–70 times the anchor width. An installation in simple uniform and non-sensitive soil is first presented with agreement against well-established plasticity analysis and an analytical solution offering verification of the techniques developed. The effects of anchor padeye position, seabed soil conditions, anchor line properties and the anchor–soil interface on the installation response are then discussed. The findings highlight that plasticity and analytical approaches are not necessarily conservative when the yield surface derived from deep embedded anchors is applied in shallow conditions. The LDFE results also demonstrate the importance of accounting for soil remoulding around both the anchor and anchor installation line. The results of this study provide insights for offshore engineers to consider and incorporate when estimating a drag anchor installation trajectory and holding capacity.

TUNNEL REACTION TO GROUND MOVEMENT USING A SIMPLIFIED MODEL

Purpose: the analysis is performed by modal superposition of the response of a simplified model containing connected bending and shear beams supported by Winkler-type springs.
 Objective: to present a simplified model using coupled Bernoulli and shear beams supported by Winkler-type springs for the systematic identification of tunnels subject to earthquake-induced ground motions. A model formulation is introduced and closed-form solutions for the modal characteristic equation and mode shape are derived.
 Research methods: the formulation of the model is introduced and closed-form solutions are derived for the equation of modal characteristic and mode shape. The latter are checked by the results of numerical models. A system identification algorithm is then presented, demonstrating its ability to recover the model parameters when the recorded acceleration time intervals along the tunnel are perturbed by noise and sensor locations change. The presented framework can be used for initial and simple recovery of tunnel response in the presence of monitoring data or for planning monitoring campaigns in newly constructed or existing tunnels.
 Main results: using a simple genetic algorithm and the proposed simplified model, it was shown that system identification can be performed for variable conditions. The model was tested for two different earthquakes of different frequencies, and the influence of the distribution of sensors along the length of the tunnel was also parametrically investigated. The test results were intentionally compromised by adding white Gaussian noise with a variance equal to that observed during ground motion. It was observed that for values ​​of α >3.0 (ie, when the effect of the shear beam is significant), the model parameters can be successfully recovered. Therefore, for such conditions, the proposed approach can be used to recover important tunnel dynamic properties (e.g., T1 or α) as well as soil-structure interaction by tracking kb changes after earthquakes. For values ​​< 3, a Bernoulli beam with a Winkler basis is a valid representation, while observing differences with a model involving a Pasternak basis are marginal.
 Scientific novelty: another approach to parametric system identification using simplified models. For tunnels, such models usually consist of beams on independent Winkler-type springs, including both numerical and analytical schemes. However, the seismic response of the continuum (i.e., soil) can be better modeled by including a transverse beam above the Winkler foundation, which allows interaction between individual springs, rather than using a single layer of independent springs. In geotechnical seismic resistance, a similar approach was used to assess the seismic response of pile foundations and retaining walls.
 Conclusions and practical challenge: different sensor distributions and reduced number of sensors did not lead to significant differences in the final results. This first shows that sensor position is not the dominant parameter for the case of five sensors along the length of the tunnel, fixed at both ends, and uniform soil conditions and other assumptions made in the paper. Further tests should be performed on real data and sensors to examine the impact of other aspects such as sensor noise.
 Key words: winkler springs, soil; soil; model; system identification algorithm is presented.

Assessment of Frequency-Dependent Parameters of Stratified Soils for Lightning Response of Earth Electrodes

Typically, the frequency dependence of soil parameters is predicted by models or formulas that assume a uniform soil, although it usually presents a stratified structure. This work develops analytical expressions that allow to evaluating of the errors associated with the uniform soil hypothesis, in comparison with the hypothesis of a two-layered soil, taking as reference a field methodology for measuring the variation of soil parameters with frequency. The results suggest that in the case of a stratified soil, the frequency dependence of its parameters can be considered individually for each layer.

Study of Construction Technology of Large Diameter and Ultradeep Cement Mixing Pile in Road Engineering

As the soft soil in the Pearl River Delta area is deep, 50 cm-diameter cement mixing pile composite foundation is often used for road engineering. A municipal road in the Hongwan District of Zhuhai adopted a mixing pile with a diameter of 80 cm and a length of 27 m, which brought great difficulty to the construction of the project. To ensure the engineering quality, the bit optimization scheme was adopted to improve the blades from the conventional two layer and four groups of blades to three layer and six groups of blades. The projection direction of each layer of blades was vertical, which could increase the mixing times and improve the mixing uniformity. At the same time, double-channel teeth were added to effectively increase the smoothness of slurry flow. The optimized nozzle is improved from a nozzle located at the bottom of the drill bit to the left and right sides of the bottom of the drill pipe to effectively relieve the blockage of the nozzle, silt backflow, and other problems. The grouting pressure is generally 0.4–0.6 MPa. After the optimization of the grout pressure, the upper limit of 0.6 MPa was used in the first stirring and spraying process, and 0.4 MPa was used in the second stirring and spraying process. The advantage is that in the first mixing, excess cement grout is ejected for mixing, and in the second mixing, the total grout dosage can be controlled by reducing the grouting pressure, which effectively improves the quality of pile body and controls the cost. To ensure uniform soil mixing, measures were taken to improve the drilling speed of the drill pipe, accelerate the speed when sinking, slow down the speed when lifting. Through the above measures, the strength of the mixing pile body was improved, and the integrity of the pile body was guaranteed. Pile integrity, effective pile diameter, pile length, and pile strength uniform accord with the design. The difficult problem of large diameter and deep cement mixing pile is solved, which provides a good reference value for similar engineering.