原位激发微生物成矿加固钙质砂的剪切与压缩特性研究

钙质砂广泛分布于热带海岸地区,其抗剪强度较低,在较高应力条件下极易破碎。因此,对以钙质砂为主要原料的地基材料进行加固,是海洋岩土工程领域的研究热点。基于尿素水解过程的碳酸钙成矿技术（MICP）是近年来地基材料加固领域的一项新技术。目前广泛使用的生物强化法实现MICP存在成本昂贵及环境适应性差等问题,制约了其大规模工程应用。研究采用原位生物激发MICP法对钙质砂进行加固,并对加固后试样开展直剪和一维压缩试验。结果表明：原位生物激发MICP方法可以在钙质砂中形成有效胶结,胶结水平最大可达6.26%。采用高浓度胶结溶液或增加注射次数可提高胶结水平。同时,加固后钙质砂的最大应力比、最大剪胀角以及残余内摩擦角均随胶结水平增加而显著增大,但竖向应力水平增大会抑制这些力学指标的增大。随胶结水平升高,试样压缩性显著减小;压缩后的原位激发MICP加固钙质砂中,细颗粒与粗颗粒的比例均随胶结水平的增加而增大。     

An anionic biopolymer γ-polyglutamate enhanced the microbially induced carbonate precipitation for soil improvement: mechanical behaviors and underlying mechanism

The use of biopolymer to improve the performance of microbially induced carbonate precipitation (MICP)-treated sands is a novel and eco-friendly concept. This work found an anionic biopolymer, γ-polyglutamate (γ-PGA), could significantly improve the performance of MICP-treated sands. Comparing the control with absence of γ-PGA, the concentration of 0.1–9 g/L γ-PGA increased the compressive strength of MICP-treated sands by 1.54–3.96 times and significantly reduced the brittleness. The MICP process analysis and microstructural detection demonstrated that γ-PGA in the specimens provided many nucleation sites and templates for calcite generation, partially kept the bacterial urease activity by replacement of the bacteria as nucleation sites, thereby improving the calcite generation. The γ-PGA also cemented sand grains with calcite through the hydrogen bond-type intermolecular interactions. Both the calcite generation and the hydrogen bond-type intermolecular interactions by γ-PGA played vital roles in enhancing MICP for soil improvement. Additionally, γ-PGA, as a viscoelastic admixture between the crystals and sand grains, effectively dissipated the energy of stress and thus reduced the brittleness of MICP-treated sands. This is the first report on the application of anionic biopolymer to MICP technology. It provides a novel concept in promoting the efficiency and sustainability of MICP.

     

Kitchen waste for Sporosarcina pasteurii cultivation and its application in wind erosion control of desert soil via microbially induced carbonate precipitation

Kitchen waste and wind erosion are two worldwide environmental concerns. This study investigated the feasibility of using kitchen waste for Sporosarcina pasteurii cultivation and its application in wind erosion control of desert soil via microbially induced carbonate precipitation (MICP). Enzymatic hydrolysis was adopted to improve the release and recovery of protein in kitchen waste for subsequent microorganism production. After conditions optimized, the maximum biomass concentration (OD₆₀₀) and urease activity of Sporosarcina pasteurii in the kitchen waste-based medium reached 4.19, and 14.32 mM urea min^?1, respectively, which were comparable to those obtained in conventional standard media. The harvested Sporosarcina pasteurii was then used to catalyze the precipitation of calcium carbonate in the desert soil, and its performance in wind erosion control was evaluated through wind tunnel tests. The microbially mediated calcium carbonate could significantly decrease wind erosion loss of the desert soil even after 12 wet–dry or freeze–thaw cycles. Scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) confirmed the bridge effect of calcium carbonate crystals in the soil matrix. The kitchen waste, as a cost-effective alternative nutrient for bacterial cultivation and carbonate precipitation, showed great potential for large-scale applications in wind erosion control of desert soils.

     

An elastoplastic mechanical constitutive model for microbially mediated cemented soils

Microbially induced calcite precipitation (MICP) is an innovative bio-mediated soil improvement technique that develops cementation within originally loose and potentially collapsible soils. This method utilizes biogeochemical processes with microbes. It has the advantage of being friendly to the environment and sustainable. In spite of the current interest in the MICP technique, the mechanical modeling of MICP-treated soils is still limited. In this paper, a constitutive model for MICP-treated sands is presented. The core components of the proposed approach include: a critical state yield surface, sub-loading concepts, a mechanism to account for the MICP-induced cementation enhancement, and an evolution law to consider bonding degradation effects during shearing. The mathematical framework is presented in detail. The model is then applied to analyze recently published experiments involving MICP-treated samples, with different calcite contents, and tested under different conditions (i.e., various confining pressure and loading paths). The model was able to properly capture the main features of MICP-treated sands behavior observed in the tests. It also assisted to interpret the response of this type of soil under different loading conditions.

     

Use of microfluidic experiments to optimize MICP treatment protocols for effective strength enhancement of MICP-treated sandy soils

Microbially induced calcium carbonate (CaCO₃) precipitation (MICP) has been extensively studied for soil improvement in geotechnical engineering. The quantity and size of calcium carbonate crystals affect the strength of MICP-treated soil. In this study, microfluidic chip experiments and soil column experiments were conducted to optimize MICP treatment protocols for effective strength enhancement of MICP-treated sandy soils. The microscale experiments reveal that, due to Ostwald ripening, longer injection intervals allow crystals to dissolve and reprecipitate into larger crystals regardless of the concentration of cementation solution. Even though a cementation solution input rate of 0.042 mol/l/h is sufficient to maintain a high chemical transformation efficiency, a further reduction in the input rate by about four times resulted in an increase in the size of crystals produced by the end of treatment from about 40 to 60 μm. These findings were applied in soil column experiments. Results showed that significantly larger crystals and higher soil strength were achieved when the normalized rate of cementation solution injection was reduced from 0.042 to 0.021 mol/l/h. Crystal size and soil strength increased slightly more when the normalized input rate was further reduced from 0.021 to 0.010 mol/l/h. This study demonstrates how data from microscale microfluidic experiments that examine the effects of injection intervals and concentration of cementation solution on the properties of calcium carbonate crystals can be used to optimize MICP treatment in macroscale sand soil column experiments for effective strength enhancement.

     

One-phase-low-pH enzyme induced carbonate precipitation (EICP) method for soil improvement

Enzyme induced carbonate precipitation (EICP) is an emerging soil improvement method using free urease enzyme for urea hydrolysis. This method has advantages over the commonly used microbially induced carbonate precipitation (MICP) process as it does not involve issues related to bio-safety. However, in terms of efficiency of calcium carbonate production, EICP is considered lower than that of MICP. In this paper, a high efficiency EICP method is proposed. The key of this new method is to adopt a one-phase injection of low pH solution strategy. In this so-called one-phase-low-pH method, EICP solution consisting of a mixture of urease solution of pH?=?6.5, urea and calcium chloride is injected into soil. The test results have shown that the one-phase-low-pH method can improve significantly the calcium conversion efficiency and the uniformity of calcium carbonate distribution in the sand samples as compared with the conventional two-phase EICP method. Furthermore, the unconfined compressive strength of sand treated using the one-phase-low-pH method is much higher than that using the two-phase method and the one-phase-low-pH method is also simpler and more efficient as it involves less number of injections.

     

A microbial pathway for the formation of gold-anomalous calcrete

The formation of pedogenic carbonate (calcrete) in terrestrial environments is commonly mediated by microorganisms. In Australia, Au-anomalous calcrete is an important sampling medium for geochemical exploration, but current models describing its formation do not include a confirmed microbial component. This study demonstrates that bacterial communities in calcareous sands from dunes overlying the Barns Gold Deposit in semi-arid South Australia, are capable of mediating the biomineralisation of Au-anomalous carbonates. Bacterial enrichment cultures obtained from calcareous sands at three depths (0.1, 0.64 and 2.1 m, plus abiotic control) were incubated in urea and Ca²⁺-containing growth media (pH 8), unamended and amended with Au (100 parts-per-billion, ppb) as Au–aspartic-acid complex. During the incubation of the enrichment cultures urea was turned over to NH₄⁺ within 96 h to 220 h. The solution pH increased concurrently by approximately 1.2 units, and Au-anomalous Ca-carbonate crystallites were precipitated on cells, which functioned as nucleation sites; no carbonate precipitation was observed in abiotic controls. Compared to the medium, Au was strongly enriched in these carbonates and appeared to be uniformly dispersed in the individual crystallites, as shown using LA-ICP-MS; a similar distribution is present in naturally occurring Au-anomalous calcrete. Phylogenetic 16S rRNA PCR DGGE analyses, shotgun cloning and functional microbial analyses (BioLog, ureC quantitative PCR) demonstrated that naturally occurring and culture-enriched bacterial communities were dominated by alkaliphylic, halotolerant Bacillus spp. The indigenous bacterial communities were capable of utilising amino acids (including l-aspartic acid) and urea, which appears to lead to the destabilisation of the Au–amino acid complexes and concomitant co-precipitation of Au in the Ca-carbonates. In conclusion, a model combining geomicrobial– with evapotranspiration– and plant-based components is likely to best describe the formation of (Au-anomalous) calcrete in semi-arid and arid zones.     

Retarding effect of concentration of cementation solution on biocementation of soil

Concentration of cementation solution (CCS) is one of the key factors influencing the cementation effect on soil improvement through the microbially induced carbonate precipitation (MICP) process. To precipitate more calcium carbonate per treatment, a higher CCS is needed. However, the MICP process may be retarded or even terminated with an increase in CCS. This retarding effect can be a major limitation for the MICP-based soil treatment and thus needs to be understood properly. This paper presents a systematic study on the conditions causing retarding and its effect on biocementation. The test results of this study have identified that there is retarding effect of CCS on the MICP process, showing that the calcium conversion efficiency, which represents the amount of calcium that has been converted into calcium carbonate in each treatment, reduces with the increase in CCS, and the concentration of calcium is the control factor. The retarding effect will dominate increasingly when CCS is higher than 1.0 M and the amount of calcium carbonate precipitation will reduce for the given amount and type of bacteria used in this study and become zero with CCS of 2.5 M. For the same calcium carbonate content, the unconfined compressive strength is greater for sand treated using a lower CCS as the contribution to the bonding strength by the calcium carbonate generated under a lower CCS is greater than that under a higher CCS.

     

Comparison of rates of ureolysis between Sporosarcina pasteurii and an indigenous groundwater community under conditions required to precipitate large volumes of calcite

Ureolysis-driven calcite precipitation has potential to seal porosity and fracture networks in rocks thus preventing groundwater flow and contaminant transport. In this study urea hydrolysis and calcite precipitation rates for the model bacterium Sporosarcina pasteurii were compared with those of indigenous groundwater communities under conditions required to precipitate large volumes of calcite (up to 50 g L⁻¹). We conducted microcosm experiments in oxic artificial and anoxic natural groundwaters (collected from the Permo-Triassic sandstone aquifer at Birmingham, UK) that were inoculated with aerobically grown S. pasteurii. The rate constants for urea hydrolysis, k_urea, ranged between 0.06 and 3.29 d⁻¹ and were only affected by inoculum density. Higher Ca²⁺ concentration (50-500 mM Ca²⁺) as well as differences in fO₂ did not inhibit the ureolytic activity of S. pasteurii and did not significantly impact k_urea. These results demonstrate that S. pasteurii has potential to improve calcite precipitation in both oxic and anoxic groundwaters, especially if indigenous communities lack ureolytic activity. Urea hydrolysis by indigenous groundwater communities was investigated in anoxic, natural groundwaters amended with urea and CaCl₂. A notable increase in ureolysis rates was measured only when these communities were stimulated with dilute nutrients (with best results from blackstrap molasses). Furthermore, there was a considerable lag time (12-20 days) before ureolysis and calcite precipitation began. Calculated ureolysis rate constants, k_urea, ranged between 0.03 and 0.05 d⁻¹ and were similar to k_urea values produced by S. pasteurii at low inoculum densities. Overall, this comparative study revealed that the growth of ureolytic microorganisms present within groundwaters can easily be stimulated to enhance rates of urea hydrolysis in the subsurface, and thus can be used to induce calcite precipitation in these environments. The time required for urea hydrolysis to begin is almost instantaneous if an inoculum of S. pasteurii is included, while it may take several weeks for ureolytic groundwater communities to grow and become ureolytically active.     

珊瑚砂微生物固化体三轴压缩试验及损伤本构模型研究

利用微生物诱导碳酸钙沉积（MICP）技术固化南海某岛礁的陆域吹填珊瑚砂,对珊瑚砂微生物固化体进行了三轴压缩试验,基于损伤力学理论建立了珊瑚砂微生物固化体的损伤本构模型。结果表明,利用MICP技术固化珊瑚砂效果好,强度高;固化体的三轴压缩应力–应变曲线可分为近似线弹性阶段、屈服阶段与延性流动阶段。将固化体划分为匀质微元进行损伤演化分析,根据连续介质损伤力学的有效应力理论与应变等效假说,定义了损伤变量,假定固化体强度服从双参数的Weibull分布及Druker-Prager准则,建立了损伤本构模型。模型参数包括固化体力学参数和Weibull分布参数,由三轴试验和线性回归法确定,并用试验资料初步验证了模型的合理性。     

Mechanical characteristics and particle breakage of coral sand under one-dimensional repeated loading

Coral sand, which is an important filler resource in coastal areas, is continuously subjected to repeated waves or traffic loading. In this study, a series of oedometer tests are conducted on coral sand and silica sand under repeated loading, and the results are compared. The influence of the initial density and number and amplitude of repeated loading on the volumetric deformation, soil stiffness, and particle breakage are investigated. The results reveal that the volumetric deformation and particle breakage of coral sand mainly occur in the first loading stage and increase by increasing loading amplitude and reducing initial density. Compared to silica sand, the soil stiffness is lower and volumetric deformation is greater in coral sand during the initial loading stage. However, the opposite trend is observed for the subsequent loading. Finally, three power functions are proposed to predict the volumetric deformation and particle breakage of coral sand under repeated loading.

     

Experimental investigation of cephapirin adsorption to quartz filter sands and dune sands

Batch experiments were performed to investigate cephapirin (a widely used veterinary antibiotic) adsorption on various size sands of low total organic carbon content (0.08–0.36 wt%). In the aqueous concentration range investigated (11–112 μmol/L cephapirin), adsorption to nearly pure quartz filter sands (0.50–3.35 mm diameter) is low. Isotherms are S-shaped and most display a region of minimum adsorption, where decreased adsorption occurs with increasing solution concentration, followed by increased adsorption at higher concentrations. Cephapirin adsorption to quartz-rich, feldspar-bearing dune sands (0.06–0.35 mm diameter), and the smallest quartz filter sand investigated (0.43–0.50 mm), can be described by linear sorption isotherms over the range of concentrations investigated. Distribution coefficients (K _d) range from 0.94 to 3.45 L/kg. No systematic relationship exists between grain size and amount of adsorption for any of the sands investigated. Cephapirin adsorption is positively correlated to the feldspar ratio (K-feldspar/(albite + Ca-plagioclase). Feldspar-ratio normalization of distribution coefficients was more effective than organic carbon normalization at reducing variability of K _d values in the dune sands investigated.     

东帝汶帝力市珊瑚砂地基的工程性质

珊瑚砂属珊瑚礁碎屑土,是一种特殊的地质体,具有典型的疏松多孔、硬度低、易碎的特点,由于珊瑚礁仅分布在热带海域,往往位于远离大陆的礁岛,当前对珊瑚礁岩土的勘察研究较少,相关规范也尚未涉及。以实际工程为对象,对东帝汶某珊瑚砂场地的工程性质进行了一些探讨,从标准贯人试验和钻孔剪切波速试验等原位试验结果进行分析,借鉴了目前石英砂工程性质的评价方法作为对珊瑚砂工程性质判断的参考,对珊瑚砂的强度特性和地震液化特性进行了讨论。相对石英砂的一般性质而言,珊瑚砂的标贯击数较低而相应的剪切波速相对较大,珊瑚砂在地震作用下液化的可能性较大。     

MICP联合纤维加筋改性钙质砂的动力特性研究

为了提高我国南海钙质砂地基的抗液化性能,提出利用微生物诱导碳酸钙沉积（MICP）技术联合纤维加筋技术对钙质砂进行改性处理。通过开展动三轴试验,对比分析了改性前后钙质砂试样的动应变、动孔压、应力−应变滞回曲线以及动弹性模量的发展规律和演化特征,并结合扫描电镜（SEM）试验探究了MICP和纤维加筋技术对钙质砂的联合改性机制。研究结果表明：（1）MICP技术可以明显改善钙质砂试样的抗变形与抗液化性能,相比于未胶结处理试样,仅MICP处理试样的动应变和动孔压分别降低了95.74% 和 92.46%;（2）纤维的掺入进一步提升了MICP的改性效果,相比于仅MICP处理试样,MICP和纤维加筋联合处理试样的动应变和动孔压分别降低了 74.32%和 74.18%;（3）MICP 和纤维加筋技术通过减轻试样在循环荷载作用下的循环活动强度和能量耗散、提高试样的动弹性模量和减小动弹性模量的衰减速率,从而实现试样抗变形与抗液化性能的显著提高;（4）SEM 试验分析结果表明,MICP 与纤维对钙质砂动力特性的改善具有协同作用。纤维的掺入为细菌提供了更多的附着场所,促进了碳酸钙晶体的生成量,该部分碳酸钙不仅增加了颗粒间的胶结强度,同时也将纤维固定在砂颗粒上增强了纤维网的约束作用。     

生物固土用于防风固沙的研究进展

文章对近年来基于生物固土技术的防风固沙研究进行了回顾和分析。常用于防风固沙的生物过程包括基于微生物或酶诱导碳酸钙沉积（MICP或EICP）的矿化固土技术,加入黄原胶等生物高聚物作为辅助剂,可获得更好的固土效果。土壤风蚀过程中,除了风力本身,风携带的跃移颗粒对土的撞击,也是侵蚀破坏的重要因素,这在生物固化土风蚀试验中体现明显。生物固化防风固沙的处理过程简单易行,以尿素和钙盐作为处理材料,用细菌或脲酶作为催化诱导媒介,对土体进行单遍喷洒处理即可获得很好的抗风效果。室内抗风试验中,将风蚀速率与临界起动风速两个指标结合是较为合理的评估方法。在室内和现场条件下,表面贯入强度测试可用来快速测定处理效果和抗风性能。目前的现场试验研究表明,生物固化土中植物可以生长,但是极端条件下生长受限。为了将该方法推向实用,需要从多重侵蚀因子作用下的抗风力侵蚀能力、生态恢复能力和现场施工技术等方面进一步研究探索。     

降雨条件下微生物技术治理崩岗侵蚀

崩岗是中国花岗岩地区危害最大的一种土壤侵蚀方式,坡面防护是崩岗侵蚀治理的重要措施。为研究微生物诱导碳酸钙沉淀（MICP）技术在花岗岩崩岗侵蚀区冲刷防护中应用的可行性,以福建省崩岗最为发育的安溪县官桥镇花岗岩土质覆盖层为研究对象,进行降雨条件下微生物治理崩岗的模型试验研究。采用喷洒加固法对崩岗坡面进行处理,然后利用降雨模拟系统冲刷坡面,最后分析了MICP加固技术对泥沙产量及坡面侵蚀深度的影响。结果表明：与未加固边坡相比,MICP固化边坡泥沙产量由未加固的7648.43 g下降至266.61 g,较加固之前降低了96.51%;最大侵蚀深度由未加固的60 mm下降至除个别侵蚀坑外边坡表面基本未发生侵蚀。     

Mound‐forming cold‐water corals and bryozoans in the Early Palaeocene of Denmark

The Faxe Quarry in south‐east Denmark offers excellent exposures of Early Palaeocene, Danian deep‐water intercalated coral and bryozoan mounds that form complexes at least 40 m thick and a few kilometres wide along and over submarine highs. The coexisting coral and bryozoan mounds represent two different biogenic carbonate factories with a highly dynamic interplay during growth. The sedimentary facies, mound geometries and the density, diversity and palaeoecology of the associated benthic invertebrates and nannofossils allow recognition of six successive growth units. Unit 1 represents an outer shelf bryozoan mound belt characterized by an oligotrophic cool‐water nannofossil assemblage. Unit 2 comprises a mixed faunal assemblage of bryozoans and octocorals with an initial sparse colonization of hexacorals. The nannofossil assemblage records a decrease in diversity and an increase in warm water forms. Unit 3 marks the onset of dense colonization of the scleractinian coral Dendrophyllia candelabrum with associated low‐diversity macrofauna and nannofossil assemblages. Unit 4 represents the main coral build‐up phase with frame‐building hexacorals of Dendrophyllia and Faxephyllia associated with a high‐diversity invertebrate fauna, and relatively low‐diversity nannofossil assemblages. Unit 5 represents the late coral mound phase showing extensive lateral distribution and finally death and erosion of the coral mounds. This event was contemporaneous with a warming trend in the pelagic environment. The succeeding Unit 6 marks the burial and overgrowth of the coral mound complex by bryozoan‐rich sediments. The coral mound complex in the Faxe Quarry initiated and terminated in global nannofossil zone NP 3 and regional nannofossil zones NNT p2G–3 suggesting a mound growth duration of ca 300 kyr and a mean vertical accretion of the coral mound of 13 cm kyr⁻¹. The mound complex probably serves as the best‐exposed analogue to modern deep and cold‐water coral mounds in the North Atlantic.     

Acoustic emission characteristics of a dry sandy soil subjected to drained triaxial compression

Acoustic emission (AE) technique that is capable of diagnosing the failure process of stressed materials has rarely reported its application to sandy soils subjected to triaxial compression. In this paper, drained triaxial compression tests incorporating with a high-performance AE measurement system were conducted for dry sands with different confining stresses and initial relative densities. Generally, an increased confining stress or initial relative density generates more acoustic emissions, while there also exist exceptions due to different failure patterns. A good resemblance between stress–strain and AE hit rate–strain relations was observed, and power functions between the mechanical parameters and AE hit rate were well established regardless of different confining stresses and initial relative densities. Besides, the behavioral state of yield and peak during compression could be also evaluated by AE hit rate, compared with conventional stress–strain determination. Particularly, the peak AE hit rate is found not always synchronous to but fluctuating at around the peak stress depending on different failure patterns, which might provide beneficial insights into the incipient failure of sands. The present good consistencies suggest that AE characteristics could be used as alternative parameters to evaluate and even predict the mechanical behavior of dry sands.

     

Temporal and Spatial Variabilities of Chemical and Physical Parameters on the Heron Island Coral Reef Platform

Globally, coral reefs are threatened by ocean warming and acidification. The degree to which acidification will impact reefs is dependent on the local hydrodynamics, benthic community composition, and biogeochemical processes, all of which vary on different temporal and spatial scales. Characterizing the natural spatiotemporal variability of seawater carbonate chemistry across different reefs is critical for elucidating future impacts on coral reefs. To date, most studies have focused on select habitats, whereas fewer studies have focused on reef scale variability. Here, we investigate the temporal and spatial seawater physicochemical variability across the entire Heron Island coral reef platform, Great Barrier Reef, Australia, for a limited duration of six days. Autonomous sensor measurements at three sites across the platform were complemented by reef-wide boat surveys and discrete sampling of seawater carbonate chemistry during the morning and evening. Variability in both temporal and spatial physicochemical properties were predominantly driven by solar irradiance (and its effect on biological activity) and the semidiurnal tidal cycles but were influenced by the local geomorphology resulting in isolation of the platform during low tide and rapid flooding during rising tides. As a result, seawater from previous tidal cycles was sometimes trapped in different parts of the reef leading to unexpected biogeochemical trends in space and time. This study illustrates the differences and limitations of data obtained from high-frequency measurements in a few locations compared to low-frequency measurements at high spatial resolution and coverage, showing the need for a combined approach to develop predictive capability of seawater physicochemical properties on coral reefs.

     

珊瑚砂振冲密实加固响应室内模型试验研究

随着海洋岛礁工程的大力推进,吹填珊瑚砂地基的密实加固问题开始备受关注。利用自主研发的室内振冲器开展了珊瑚砂饱和砂土地基的室内振冲模型试验研究,深入分析了振冲过程中动孔隙水压力、水平动土压力等动参量的响应规律,探讨了振冲后沉降变形、相对密实度的变化特征。结果表明：松散珊瑚砂地基的密实度在经过两次双点振冲反复加固后均提升至中密。其中相对密实度在振冲点位处的提升效果较其余位置更为明显,并且中层或深层区域的加固效果优于表层区域。在超孔隙水压力方面,其最大值出现在振冲珊瑚砂地基过程中的贯入阶段,并且在留振开始时出现衰减现象。珊瑚砂地基在振冲器上拔过程中超孔隙水压力发生断崖式下跌。在第2次贯入时,超孔隙水压力比的峰值较首次出现显著下降。超孔隙水压力比等值线云图表明,振冲过程中的超孔隙水压力比等值线呈现平行分布。珊瑚砂浅层水平土压力随振冲器的贯入与拔出均呈现增加态势,深层水平土压力则呈现减少态势。