Soil Mixing Wall Research Articles

Development and performance evaluation of a novel anti-friction agent for H-beam extraction in soil mixing walls

This study focuses on the development and assessment of an innovative anti-friction agent designed to reduce the extraction force required for H-beams in Soil Mixing Walls (SMW). The composition of the new formula for the anti-friction agent was determined using orthogonal experimental methods: vaseline (25 g), paraffin (300 g), rosin (65 g), polytetrafluoroethylene powder (9.75 g), ZDDP (10 g), benzoic acid (4 g), ammonium polyphosphate (2 g), alcohol ester-12 (1.5 g), and theaflavin (1.5 g). Performance evaluation of the new anti-friction agent is carried out through indoor model tests, on-site tests, and indoor bending experiments. The results indicate that compared to commonly used anti-wear agents in the field (Nanjing site anti-friction agent, Guangzhou site anti-wear agent), the new anti-wear agent can significantly reduce friction, by 16.4 % and 14.2 % respectively. The new material has little impact on the bending performance of composite structures before cement-soil failure, in contrast to the Nanjing anti-friction agent typically used in field applications. During on-site applications, if the H-beam coated with conventional anti-friction agent cannot be pulled out while the H-beamcoated with the new anti-friction agent can, then the cost of piles treated with the new anti-friction agent is reduced by 97 %. If both types of steel coated with anti-friction agents can be pulled out, then the cost of piles treated with the new anti-friction agent increases by 0.9 %.

Study on Excavation Response of Deep Foundation Pit Supported by SMW Piles Combined with Internal Support in Soft Soil Area

Based on a foundation pit project in Fuzhou, China, the influence of foundation pit excavation on the supporting structure and surrounding environment in a soft-soil area is studied. This study was based on actual monitoring data and investigated the variations in the supporting structure, surrounding constructions, and groundwater levels during excavation. The analysis of the monitoring data demonstrates the presence of pronounced ‘spatial effects’ and ‘temporal effects’ on the deformation of the support structure and surrounding structures. The deformation of the support structure and surrounding structures exhibits distinct spatial distribution characteristics at different locations along the excavation pit wall. Typically, more significant deformations are observed in the middle section of the pit wall, while deformations decrease as the distance from the pit corner decreases. The support structure’s and surrounding structures’ deformation characteristics vary during different construction stages. During the excavation phase, the rate of deformation increase in the support structure and surrounding structures is notably higher. In contrast, during the construction of the underground basement floor and the backfilling phase of the excavation pit, the rate of deformation increase in the support structure and surrounding structures is relatively lower. Throughout the entire construction period of the excavation pit, the groundwater level in the vicinity of the pit exhibits a fluctuating trend. Apart from the influence of rainfall, the overall variation in groundwater level is minimal, indicating the effective water-sealing performance of the combined Soil-Mixing Wall (SMW) support structure within the circular enclosure.

Application and Research of Soil Mixing Wall

Soil Mixing Wall can meet the needs of foundation pit support structures in various projects. Compared with other supporting structures, it has the advantages of good permeability resistance, short construction period, and less impact on the surrounding environment. It is a foundation pit supporting structure with great development potential[1].

A Practical Method for Calculating Soil Mixing Wall Retaining Structure by Means of a “Simple Beam Method”

SMW is the abbreviation of soil mixing wall. H‐type steel, also known as the new cement mixing pile wall, is inserted into the cement pile, which combines the bearing load with the impervious water retaining, and has the two functions of stress and impervious retaining wall of the supporting structure. In the design of conventional foundation pit engineering, the active Earth pressure calculated by Rankine’s theory is not consistent with the engineering practice because the soil behind the retaining structure has not reached the limit equilibrium state. The embedded depth and the horizontal supporting force of the retaining structure are usually calculated with the equivalent beam method, but the method is complicated. Taking the supporting structure of a foundation pit called “soil mixing wall retaining wall and bolt” as a case, in this paper, the lateral pressure is used to calculate the active Earth pressure at any depth, and the “simple beam method” is used to calculate the embedded depth, the horizontal supporting force, and the internal force of the SMW continuous wall, which intends to find out the first and second supporting points as the pivots of the “simple beam method” under the most unfavorable conditions. When the first pivot is used as the supporting point of the “simple beam method,” the soil pressure is ignored because it is within the critical depth of the Rankine active Earth pressure; while the second pivot is used as the supporting point of the “simple beam method,” the forces on it are balanced to the torque of the second pivot, only considering the moment balance of the active and passive Earth pressure on the isolation body under the second pivot point. The results are in good agreement with the results of the equivalent beam method and the measured values, and they are much closer to the measured values, which provides a practical method for designing SMW retaining structures.

Centrifuge performance of LCSM wall reinforced pile-supported wharf subjected to yard load-induced marine slope soil movement

Lattice cement soil mixing (LCSM) walls are constructed to relief the marine slope soil movement that will trigger failure of the pile-supported wharf, the structural performance and pile-soil interactions after the LCSM implementation are major concerns. This paper investigated motion modes, load-displacement relations, soil and pore pressures, and bending moments of pile-supported wharfs with LCSM walls subjected to yard load-induced slope soil movement via centrifuge modeling. Results showed that the LCSM wall tilted to compress the soil and pile, inducing the tilting of the wharf. The lateral structural displacement was effectively restricted by the LCSM wall compared with that of a nonreinforced wharf, but the LCSM wall was not superior to the other lattice wall type with legs in limiting the lateral structural displacement, and the deep LCSM wall worked better at larger soil movement. The rear piles were evidently affected by slope soil movement and were compressed in the middle part. Soil pressures generally increased with increasing yard loads, whereas their distributions were deeply affected by different LCSM wall depths. Pore pressures were greater around the tilting LCSM wall because of larger soil shear areas but dissipated when soil movement stopped. Bending moment distributions indicated evident waterside curvatures in rear piles, whereas waterside curvatures occurred in the upper part and landside curvatures occurred in the lower part in front and middle piles, the effects of LCSM wall types and depth on bending moment distributions were tremendous.

Site Measurement Study on Mechanical Properties of SMW Piles of Building Structures in Sandy Soil Areas

SMW (soil mixing wall) piles have been widely used in soft soil areas such as Jiangsu, Shanghai, Tianjin and so on, and they have many advantages, such as retaining the structures of foundation pits. In order to promote the application of SMW piles in sandy soil areas such as Henan province, SMW piles were used in a deep foundation pit project of a high-rise building in Zhengzhou. Three SMW piles in the middle area of the foundation pit were selected for site measurement to determine the mechanical properties of SMW piles in sandy soil areas. Several typical test sections were determined along the height of the pile. The vibrating string type of the reinforcement dynamometers were set on the H-shaped steel of each test section, and the stress distribution of the H-shaped steel along the depth of the pit was obtained via testing. The axial force, bending moment and shearing force of the H-shaped steel were further calculated, and the affecting factors and development laws of the internal force distribution of the H-shaped steel were analyzed in detail. The research shows that, at the stage of foundation pit excavation, the overall stress of H-shaped steel increases gradually. The axial force of H-shaped steel in an SMW pile is mainly affected by such factors as the weight of the H-shaped steel, the weight of the crown beam and the first support system, the weight of the breast beam and the second support system, and the frictional resistance of the cemented soil. The bending moment and shearing force of H-shaped steel are mainly affected by such factors as the lateral soil pressure and the concentrated forces of the two support systems. When the foundation pit was excavated to the base, the development of and changes in the law of internal force with regard to the H-shaped steel was analyzed. When the overall internal force of the H-shaped steel is at its maximum, the maximum absolute values in terms of the axial force, bending moment and shearing force are −481 KN, 371 KN·m and 123 KN. In the process of foundation pit excavation and backfilling, the point of contraflexure of the H-shaped steel moves down gradually, and the fixed end of corresponding SMW pile also moves down and stabilizes below the base. These results may provide a reference for the design and construction of SMW piles of building structures in sandy soil areas.

Application of TRD Hydraulic Soil Mixing Wall in the Reinforcement of Deep Foundation Pit Groove Wall in Soft Soil

Application of TRD Hydraulic Soil Mixing Wall in the Reinforcement of Deep Foundation Pit Groove Wall in Soft Soil

Displacement analysis of point cloud removed ground collapse effect in SMW by CANUPO machine learning algorithm

In this paper, a three-dimensional laser scanner was used to monitor the displacement of retaining structures for excavation, including a ring beam and a reinforced soil mixing wall (SMW) at an open excavation site. Eight scans of the retaining structures were taken before and after the excavation. Three-dimensional point clouds of the retaining structures produced with these scans are registered and analyzed to determine displacements of the retaining structures. Cloud to Mesh (C2M) method is used to identify displacement along the length of ring beam and depth of the SMW. The displacement obtained is then validated against displacement measured by the total station. The surface of the ring beam is flat so that the displacement of the ring beam can be estimated by the C2M. There was soil collapse and deposition on the surface of the SMW, which can affect the estimation of displacement in the cloud comparison. Therefore, a CANUPO machine-learning algorithm is applied to detect these areas and to remove the point clouds affected by soil collapse and deposition. The displacement is re-estimated based on the revised point clouds. The re-estimated displacement by the CANUPO method is more uniformly changed with the depth of the SMW than results without the CANUPO method, and the horizontal displacement due to excavation can be calculated.

Effects of deep soil mixing on existing shield tunnels in soft soil ground

To mitigate the impact of adjacent construction on existing shield tunnels, deep soil mixing (DSM) has been widely used to reinforce the soft soil ground around shield tunnels. However, the construction of DSM may cause the movement of existing shield tunnels under soft soil and sensitive ground conditions, and reasonable installation parameters will reduce the impact of DSM construction on the existing shield tunnels. Based on the field tests of DSM installation parameters and a program of field measurements of existing shield tunnels during the DSM construction in Suzhou, the reasonable installation parameters of DSM were selected, and the movement of soil behind the soil mixing walls (SMWs) during multirow DSM installation was investigated. The movement of the shield tunnels caused by DSM construction were discussed in detail. The field test results showed that the DSM columns installed at a higher speed and a lower water-cement ratio enlarged the movement of the surrounding soil. The DSM should be installed at a lower speed and a higher water-cement ratio to reduce the movement of the shield tunnels. The field measurement results showed that the displacement of the tunnel lining was primarily caused by the construction of DSM zones beside the shield tunnels, which led to vertical compression and horizontal expansion of the tunnel lining. The construction of DSM immediately above the shield tunnels caused uplift to the tunnels. In addition, the deformed shapes of the two shield tunnels were asymmetric, and the displacement of the spring lining was larger than that of the crown. By taking the reasonable installation parameters of DSM and under the protection of the SMWs, the deformation of the shield tunnels caused by the construction of DSM was effectively controlled, and the maximum displacement was within the control value of the shield tunnels in this study.

Mechanical Characteristics and Optimum Design of SMW Construction Method for a Comprehensive Pipe Gallery in a Water-Rich Weak Stratum

The K0+080-K0+275 bid section of the underground comprehensive pipe corridor on Wanxin Road in Binhai New City located in Fuzhou was considered in this work. The mechanical properties and optimal design of the soil mixing wall (SMW) construction method piles (steel-cement mixing piles) in the comprehensive pipe corridor in the water-rich, weak stratum were studied. In the K0+080-K0+275 bid section of the comprehensive pipe gallery, different construction parameters of the steel-cement-soil mixing piles were tested through pile tests. The construction parameters of the SMW construction piles were as follows: water-cement ratio of 1.3 and cement content of 20%. The finite element software MIDAS-GTS NX was used to establish a mechanical model of the SMW construction method piles. The variations in mechanical characteristics, such as the horizontal displacement of SMW construction method piles under different supporting pile diameters, steel layouts, steel sizes, and supporting axial forces, were analyzed. The optimal design of the SMW construction method piles was also determined. Results revealed that when the pile diameter of the SMW construction method increased from 0.55 m to 0.85 m, the horizontal displacement of the pile body decreased by 28.9%. The horizontal displacement of the pile body could be effectively controlled by increasing the pile diameter. Increasing the size of the flange and web of the section steel had little effect on the deformation of the foundation pit. The flange was sensitive to the deformation of the supporting structure because it was on the stressed side. The different layout forms of the steel section exerted a great influence on the deformation of the foundation pit. The maximum horizontal displacement of the pile body for the type of steel close insertion was 18.4% less than that for the plug-one-jump-one insertion type. Increasing the supporting pre-added axial force effectively reduced the deformation of the envelope structure, and adopting the value of 50%-80% of the designed axial force was reasonable. The K0+080-K0+275 bid section of the Wanxin Road underground comprehensive corridor was determined to be supported by φ650@450 cement-soil five-axis mixing pile interpolated with HM500×300×11×18 section steel, and the layout of the section steel adopts the plug-one-hop-one type. The on-site monitoring data of the optimal construction plan were in accordance with the change law of the numerical simulation and were successfully used in the underground comprehensive pipe corridor project. Ideal results were achieved.

Application and Research of Soil Mixing Wall

Soil Mixing Wall can meet the needs of foundation pit support structures in various projects. Compared with other supporting structures, it has the advantages of good permeability resistance, short construction period, and less impact on the surrounding environment. It is a foundation pit supporting structure with great development potential<sup>[1]</sup>.

Research on Quality Evaluation Method of TRD Cement-soil Continuous Wall Based on Analytic Hierarchy Process

In order to accurately evaluate the wall quality of cement-soil mixing wall by TRD method and reduce the risk of foundation pit excavation, this paper proposes a comprehensive evaluation method of wall quality. Based on strength analysis, impermeability analysis, borehole TV analysis and electromagnetic borehole radar analysis, the main influencing factors of TRD cement soil wall quality are analyzed and determined. Using the analytic hierarchy process, the hierarchical structure model of the wall quality evaluation index system is established and the evaluation factors are quantified. The fuzzy comprehensive evaluation method is used to evaluate the index factors. By analyzing the evaluation results, the evaluation grade standards of excellent, good, medium and poor reflecting the wall quality are established. The evaluation system and grade standard are used to evaluate the wall quality of waterproof curtain in a station foundation pit of Qingdao metro. The actual excavation of the foundation pit is basically consistent with the evaluation results. It has preliminarily realized a change from qualitative and empirical to scientific and half quantitative. The research results can be promoted and applied to the similar TRD cement soil mixing wall project in the future.

Effect of ground improvement on the lateral resistance of closed-end steel pipe piles in a coal ash pond

This study assessed the effect of configuration of the ground-improved body to improve the lateral resistance of piles driven into a coal ash pond. Nine closed-end steel pipe piles were studied by lateral load tests in the investigation, which included four test piles and five reaction piles. While TP1 pile was carried out without the reinforcement, TP2, TP3, and TP4 piles were tested with various reinforcements, including grid-type, block-type, and cross-type. The lateral load test results showed that the ultimate lateral loading capacity, pile-head stiffness, and soil resistance of the reinforced piles compared with TP1 pile were increased by 26%–39%, 54%–238%, and 33%–128%, respectively. Conversely, the maximum bending moments of the reinforced piles were reduced by 48%–73%, respectively. Soil-mixing wall reinforcement was found to increase effectively the lateral resistance of the closed-end steel pipe piles in a coal ash pond. However, because a variety of ground-improved body configurations can increase the lateral resistance of piles, the choice of the type of reinforcement must be considered for reliable design, construction feasibility, and economic benefits of engineering practice.

Deformation Characteristics of Retaining Structures and Nearby Buildings for Different Propped Retaining Walls in Soft Soil

Abstract This article reports the field performance of deep excavations of two subway station cases, including the lateral wall deflection behavior and settlement trends of the surrounding soil and nearby buildings. The retaining structures employed in these cases were contiguous pile walls (CPW), soil-mixing walls, and diaphragm walls (DW), all of which were embedded in soft clay. The measured wall deflection profiles exhibited typical bulging behavior at the end of the excavation. The ratios of the measured maximum wall deflection to the excavation depth were found to be similar for all three types of retaining wall. Furthermore, the maximum and minimum corner effects on the wall deflection development were obtained for the DW and CPW, respectively. The measured ground surface settlement increased linearly with increased maximum lateral wall deflection, while the settlement magnitude became extraordinarily large because of the presence of sludgy soil. A concave pattern was proposed for the surface settlement profiles for all three types of retaining wall. The building settlement was quantified, with the value lying between those of the surface settlement and soil settlement at 10-m depth. The soil displacement field induced changes in the side and end resistance behaviors of the loaded piles, along with additional settlement of pile-foundation buildings. In addition, the pile-foundation building settlement was influenced by the corner effect. These research results will enhance our understanding of the deformation characteristics of the retaining structure and nearby buildings. Meanwhile, the findings will provide guidance for the optimal design of the retaining structure in soft soil.

Experimental Study on Mitigations of Seismic Settlement and Tilting of Structures by Adopting Improved Soil Slab and Soil Mixing Walls

Settlement of surface structures due to subsoil liquefaction is a big issue in geotechnical engineering. It has been happening during earthquakes in liquefaction-prone areas for many years. Mitigations have been proposed for this problem. The improved soil slabs and vertical mixing soil walls combined with lowering ground water levels (GWLs) were proposed in this study. Experiments were carried out by adopting a 1-g shaking table test. Two different soil densities with uniform and eccentric loads were included. Combined with lowering GWLs, three different soil slabs with a length of 40, 60 and 80 cm and two different mixing walls with soil and plastic were studied and compared. Results show that the horizontal soil slabs have good performance to reduce the settlement of structures. On the other hand, the vertical soil mixing walls did not reduce the settlement effectively, but its performance could be improved by lowering of GWLs.

Soil-cement mixture properties and design considerations for reinforced excavation

soil-cement is a mixture produced by grouting or mixing cement with soils. This paper reviews and discusses the general classifications of grouting techniques and the suitability of their applications. The mechanical properties of soil-cement mixture and the influence of sodium silicate added are discussed. Design considerations for deep soil mixed wall (DSMW) for excavation support and vault arch for tunnelling stabilisation are presented. Parameters for the numerical analysis of soil-cement mixture are evaluated and recommended.

구벽안정성을 위한 SMW 최적배합비 및 현장적용 사례에 관한 연구

The purpose of this study is to investigate experimentally the optimum mix design and site application case of soil mixing wall (SMW) method which is cost-effective technique for construction of walls for cutoff wall and excavation support as well as for ground improvement before constructing LNG storage tank typed under-ground. Considering native soil condition in site, main materials are selected ordinary portland cement, bentonite as a binder slurry and also it is applied 1,833 kg/m 3 as an unit volume weight of native soil, Variations for soil mixing wall are as followings ; (1) water-cement ratio 4cases (2) mixing velocity (rpm) 3levels (3) bleeding capacity and ratio, compressive strength in laboratory and site application test. As test results, bleeding capacity and ratio are decreased in case of decreasing water-cement ratio and increasing mixing velocity. Required compressive strength (1.5 MPa) considering safety factors in site is satisfied with the range of water-cement ratio 150% below, and test results of core strength are higher than those of specimen strength in the range of 8~23% by actual application of element members including outside and inside in site construction work. Therefore, optimum mix design of soil mixing wall is proposed in the range of unit cement 280 kg/m 3 , unit bentonite 10 kg/m 3 , water-cement ratio 150% and mixing velocity 90rpm and test results of site application case are satisfied

Field Response of High Speed Rail Box Tunnel During Horizontal Grouting

Abstract The construction of two bored tunnels passing underneath an existing high speed rail (HSR) box tunnel needed to traverse obliquely through the diaphragm wall originally used for excavation and lateral support during construction of the HSR box tunnel. An access lift shaft was constructed adjacent to the HSR box tunnel diaphragm wall to provide access for the horizontal grouting equipment used to modify the surrounding soil to have sufficient water tightness and shear strength for safe tunnel eye creation and removal of steel H-beams left within the soil mixing wall. The grout block behind the tunnel eye was constructed first, followed by a long distance (up to 52 m) horizontal grouting (LDHG) program to form the other grout block around the steel H-beams. Since the grouted area was confined by a box tunnel on top and diaphragm walls on both sides, inappropriate grouting pressure could cause significant vertical movement of the HSR box tunnel above and potentially endanger the safety of the HSR service within. The grouting program was adjusted in accordance to real time box tunnel motion as detected by electronic beam sensors along the side walls of the box tunnel. Our strategies for overcoming the challenges associated with long distance horizontal wash boring through diaphragm walls, scattered with steel H-beams, and accompanying grouting strategy will be presented in this paper. The vertical movement of the HSR box tunnel during the LDHG program was well controlled to less than 4 mm, while the maximum lateral displacement of the shaft diaphragm wall was maintained below 9 mm.

Design of Structure and its Enclosure for Subaqueous Tunnel to Cross River in Urban Highway Line

This paper summarizes the design of reinforced concrete structure and its enclosure for a subaqueous tunnel used to cross a river in urban highway line. The tunnel mainly consists of open-cut section on river bank and cut-cover section under river bed. Their structure and enclosure are both illustrated in the paper according to site geology and general layout of urban highway line. The use of rotary bored pile and soil mixing wall to preserve the stability of open-cut foundation pit are summarized in the paper.

Wall and Ground Movements due to Deep Excavations in Shanghai Soft Soils

An extensive database of 300 case histories of wall displacements and ground settlements due to deep excavations in Shanghai soft soils were collected and analyzed. The mean values of the maximum lateral displacements of walls constructed by the top-down method, walls constructed by the bottom-up method (including diaphragm walls, contiguous pile walls, and compound deep soil mixing walls), sheet pile walls, compound soil nail walls, and deep soil mixing walls are 0.27%H, 0.4%H, 1.5%H, 0.55%H, and 0.91%H, respectively, where H is the excavation depth. The mean value of the maximum ground surface settlement is 0.42%H. The settlement influence zone reaches to a distance of about 1.5H to 3.5H from the excavation. The ratio between the maximum ground surface settlement and the maximum lateral displacement of a wall generally ranges from 0.4 to 2.0, with an average value of 0.9. The factors affecting the deformation of the wall were analyzed. It shows that there is a slight evidence of a trend for decreasing wall displacement with increasing system stiffness and the factor of safety against basal heave. Wall and ground movements were also compared with that observed in worldwide case histories.